NCD079044426_20000719_General Electric Co. Shepherd Farm_FRBCERCLA RD_Response to Agency Comments Final Design for Groundwater - May 2000-OCR

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION 4.
4WD-NSMB
Ms. Janet Boyer
EHS Manager
GE Lighting Systems, Inc
3010 Spartanburg Highway
Hendersonville, NC 28792
ATLANTA FEDERAL CENTER
61 FORSYTH STREET
ATLANTA, GEORGIA 30303-8960
July 19, 2000
SUBJ: GE/Shepherd Farm NPL Site
East Flat Rock, NC
Dear Ms. Boyer:
RECEIVED
JUL 21200JJ
SIJPERFUND.SECT/ON
Enclosed are the Agency's comments on the Final Remedial Design (RD) and
Remedial Action Work Plan for Groundwater dated June 29, 2000. All comments must be
incorporated before approval of the RD can be given. Please submit revised documents
or replacement pages no later than August 9, 2000.
If you have any questions, please do not hesitate to give me a call at 404/562-8824.
cc: Dave Mattison, NC DENR
iezelle S. Bennett
Remedial Project Manager
Todd Hagemeyer, HSI GeoTrans
Jim LaForest, COM
Internet Address (URL)• http:llwww.epa.gov
Recycled/Recyclable • Printed with Vegetable Oil Based lnKs on Recycled Paper (Minimum 30% Postconsumer)
•cs'.•.:,. •
General
•
REVISED FINAL DESIGN FOR GROUNDWATER
COMMENTS
1. During the development of the proposed groundwater extraction scheme, It was
pointed out that a more rigorous surface water, sediment and residential well
sampling strategy would be required due to the reduction in contaminant
containment. However, the Revised Final Design for Groundwater does not reflect
this point. Therefore, the following must be incorporated into the Revised Final
Design for Groundwater:
Surface Water & Sediment Monitoring Stations
In addition to the currently proposed three (3) surface water and sediment monitoring
stations, please include an additional three (3) surface water and sediment monitoring
stations to be located as follows:
1. At the intersection of Bat Fork Creek and Spartanburg Highway
(US Highway 176).
2. Approximately fifty (50) feet upstream of the confluence of Bat
Fork Creek and the Unnamed Tributary that intersects Bat Fork
Creek south of the Large Pond at the General Electric (GE)
Subsite.
3. Along Bat Fork Creek at a point immediately upstream of the
bend where Bat Fork Creek changes from a northwesterly
direction to northeasterly direction. This point is located
approximately 250 feet south of groundwater monitoring well
MW-27.
Residential Well Monitoring Network
In addition to the currently proposed residential well monitoring network, please include
the following additional residential wells to the residential well monitoring network: WW-
28 and WW-33.
Sampling Frequency
The current sampling scheme proposes annual surface water, sediment and residential
well sampling frequency. However, due to the reduced contaminant containment and
the fact that steady-state conditions will not be reached for three years (see Appendix E
-Numerical Groundwater Model Report), the surface water, sediment and residential
monitoring network must be sampled on a quarterly basis for three years. GE may then
seek authorization from the United States Environmental Protection Agency (US EPA)
and the North Carolina Department of Environment and Natural Resources (NC DENA)
to reduce the sampling frequency of the surface water, sediment and residential
monitoring network to a semi-annual basis for the subsequent four (4) events. Upon
completion of semi-annual sampling, GE may then seek authorization from the US EPA
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and the NC DENR to reduce the sampling frequency of the surface water, sediment
and residential monitoring network to an annual basis thereafter.
Every attempt has been made by the reviewer to identify the locations in the Revised
Final_,Design for Groundwater that the above comments need to be inserted. However,
this does not relieve GE and their consultant, HSI Geo Trans, of the responsibility to
review the Revised Final Design for Groundwater and incorporate the above comments
in all of the appropriate sections.
2. It was noted during the review of the Revised Final Design for Groundwater that the
performance monitoring well network for the GE Subsite is once again inconsistently
identified. Table 4-3 of the Final Design Report, Table 2-1 of the Remediation Goal
Verification Plan (Appendix F) and Table 2-2 of the Field Sampling and Analysis Plan
(Attachment 1 of Appendix F) indicate that GE Subsite performance monitoring wells
are MW-3, 8, 12, 12A, 128, 13, 13A, 14, 14A, 15, 16, 16A, 22A, 27, 27A and 29.
However, Figure 2-1 of the Remediation Goal Verification Plan (Appendix F) and Figure
2-1 of the Field Sampling and Analysis Plan (Attachment 1 of Appendix F) indicates
that the GE Subsite performance monitoring wells are MW-3, 8, 12, 12A, 128, 13, 13A,
14, 14A, 148, 15, 16, 22A, 27, 27 A and 29. Obviously, the two figures include the ·
. additional monitoring well MW-148 and omit monitoring well MW-16A. The inclusion of
a deep bedrock monitoring well at MW-148 would be advantageous as contamination
has been observed historically at this location and there are is only one proposed deep
bedrock performance monitoring wells (MW-128). However, the omission of shallow
bedrock monitoring well MW-16A does provide a fairly significant data gap between
performance monitoring well MW-8 and the MW-14 performance well cluster (although
. it is impossible to determine the extent of contamination noted at monitoring well MW-
16A as MW-16A was not sampled during the 1997 baseline sampling event and all the
data regarding remediation goal exceedances in the Revised Final Design for
Groundwater is based upon the 1997 baseline sampling event). Therefore, please
revise the Final Design Report for Groundwater to indicate that the GE Subsite
performance monitoring wells are MW-3, 8, 12, 12A, 128, 13, 13A, 14, 14A, 148, 15,
16, 16A, 22A, 27, 27A and 29. Every attempt has been made by the reviewer to
identify the locations in the Revised Final Design for Groundwater that the above
comments need to be inserted. However, this does not relieve GE and their consultant,
HSI Geo Trans, of the responsibility to review the Revised Final Design for Groundwater
and incorporate the above comments in all of the appropriate sections.
FINAL DESIGN REPORT
Table of Contents
/3_ Several discrepancies were noted during the review of the Table of Contents. Please
correct these oversights.
a. The title for Figure 4-1 should be given as "Balanced Removal at the GE
Subsite with 15 gpm Extraction at 5 Wells" in the List of Figures.
b. The title for Figure 4-2 should be given as "Simulated Water Table
Drawdown from 15 gpm Extraction at GES and 17 gpm Extraction at
SFS" in the List of Figures.
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c. The title for Table 2-5 should be given as "Remediation Goal Exceedances
for Baseline Groundwater Conditions (July 1997) at the Shepherd Farm
Subsite" in the List of Tables.
d. The title for Table 4-1 should be given as "Calculation of a Representative
Influent Concentration" in the List of Tables.
Acronyms for the Remedial Design
/ 4. Please correct the definition of the acronym "NPDES" to state, "National Pollutant
Discharge Elimination System."
Section 1.2.1 Remedial Objectives
/ 5. Please revise the end of the first paragraph of Section 1.2.1 to include the statement,
"Consequently, the remedial objectives also include the avoidance of adverse impacts to
wetlands, including a wetland containing the federally endangered plant species known
as the bunched arrowhead."
Section 1.2.3 System Operation
di-I 7.
In accordance with General Comment #2, please revise the second sentence of
Section 1.2.3 to state, "A total of twenty-one performance wells will be sampled on a
quarterly basis for the first three years, semi-annually for two years, and annually
thereafter until Exit Monitoring and Closure Monitoring are initiated."
In accordance with General Comment #1, please revise the fourth sentence of Section
1.2.3 to state, "In addition, seven residential wells, six surface water and sediment
samples will be sampled on a quarterly basis for the first three years, semi-annually
for the following two years, and annually thereafter until Exit Monitoring and
Closure Monitoring are initiated."
Section 2.7 Extent of Contamination in Surface Water and Sediment
:JI I 8. In accordance with General Comment #1, please revise the last sentence of Section
2.7 to state, "To ensure that the remediation objectives with the surface water and
sediment are being met, the quality of Bat Fork Creek will be monitored on a
quarterly basis for the first three years, semi-annually for the following two years,
and annually thereafter until Exit Monitoring and Closure Monitoring are initiated."
Section 3.2.4.2 Groundwater
JI I 9. In accordance with General Comment #1, please revise the last sentence of the second
paragraph of Section 3.2.4.2 to state, "Water quality of the groundwater will continue to
be monitored from seven residential wells (W'~-2 WW-5, WW-17, WW-33, WW-34,
WW-73, and WW-82)." tJw-tB
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Section 4.7 Remediation Start-Up and Shakedown
.Ao. Please revise the last sentence of the fourth bullet item in Section 4.7 to state, "At least
three samples per week will be analyzed for VOCs and SVOCs by an off-site laboratory."
Section 6 Schedule and Estimated Cost
-11. In accordance with Table 6-1, please revise the first sentence of the second paragraph
of Section 6 to state, ''The estimated cost to construct the groundwater remediation
system is $482,230, as shown in Table 6-1."
Figure 2-5 Location of Residential Wells
/12. Please revise Figure 2-5 to identify the GE and Shepherd Farm Subsites, as originally
submitted. I
Figure 2-10 Extent of TVOC in Groundwater for Baseline Conditions
/13. Please revise Figure 2-10 to include the roads and structures, as originally submitted.
Figure 2-11 Extent of PCE in Groundwater for Baseline Conditions
A 4. Please revise Figure 2-11 to include the roads and structures, as originally submitted.
Figure 2-13 Location of Surface Water and Sediment Sampling Station! .
l
:Ji r 15. In accordance with General Comment #1, please revise Figure 2-13 to include the
additional three surface water and sediment monitoring locations.
Table 3-4 Monthly AGRS Effluent Monitoring Data for Metals
✓ 16. Please revise Table 3-4 to include the monthly Accelerated Ground\'fater Remediation
System (AGRS) effluent monitoring data for metals for the period of May 1998 through
October 1999, as originally submitted. l .
Table 4-1 Calculation of Representative Influent Concentrations and Design Effluent
Concentrations I
/17. Please revise Table 4-1 to indicate that the performance goal for trans-1, 2-dichloroethene
is 70 micrograms per liter (mg/L).
Table 4-3 System Performance Monitoring
4/ /18. In accordance with General Comment #1, please revise Table 4-3 to indicate that the
surface water and sediment sampling program will consist of six locatibns along Bat Fork
Creek and will be sampled, at a minimum, quarterly for first three years, semi-annually
for the following two years, and annually thereafter.
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;ll I 19.
/21.
. I •
'
In accordance with General Comment #1, please revise Table 4-3 to indicate that the
residential monitoring well network will consist of seven residential' wells and will be
sampled, at a minimum, quarterly for first three years, semi-annually for the following
two years, and annually thereafter. ·
'
In accordance with General Comment #2, please revise Note 2 to ~tale, "GE Subsite
performance monitoring wells are MW-3, 8, 12, 12A, 12B, 13, 13A, 14) 14A, 14B, 15, 16,
16A, 22A, 27, 27A and 29.".
Please revise Note 4 of Table 4.3 to state, "At least three voe and svbc samples will be
collected and analyzed during start-up (estimated to be two weeks)." 1
Table 6·2 Summary of Estimated Annual Operation and Maintenance Costs
,!/ f2-22.
I
Please revise Table 6-2 to include the additional sampling to be conducted in
accordance with General Comments #1 and #2.
Table 6-3 Detailed Estimate of Annual Operation and Maintenance Costs
JI/ t 'I. 23. Please revise Table 6-3 to include the additional sampling to be conducted in
accordance with General Comments #1 and #2.
_--, I..,• r,._.} ~ < 9 t,.)t,\I >
REMEDIAL ACTION WORK PLAN FOR GROUNDWATER
Table of Contents
/ 24. Please correct the Table of Contents to indicate that Section 1.4 is located on page 1·6.
Acronyms for the Remedial Design
'
/ 25. Please correct the definition of the acronym "NP DES" to state, "National Pollutant
Discharge Elimination System."
Section 1.3 Remedial Action Objectives
I
✓26. Please revise the second paragraph of Section 1.3 to include the statement,
"Consequently, the remedial objectives also include the avoidance of ·adverse impacts to
wetlands, including a wetland containing the federally endangered plant species known
as the bunched arrowhead."" I
Section 3.2.2 Recovery System at the GE Subsite
I 27.
I
Please revise the last sentence of the fourth bullet item of Section 3.2.2 to state, "At least
three samples per week will be analyzed for voes and SVOCs by an;off-site laboratory."
Please insert the following bullet item into Section 3.2.2: "Air samples will be collected
from the GAG air stream influent and effluent to ensure that the system is operating
properly. The first set of samples will be analyzed for voes by an off-site laboratory. If
VOCs are not detected in the influent, no additional air samples will be collected.
Otherwise, one sample per week will be analyzed for voes by an off-site laboratory."
.5.
• •
Section 3.2.3 Performance Monitoring
I
In accordance with General Comments #1 and #2, please revise the second sentence of
Section 3.2.3 to state, "Performance monitoring activities will include hydraulic head
surveys, well pumping rate measurements, chemical analyses at twenty~one performance
wells, six surface water and sediment stations, and seven residential wells."
Section 4.7 Permits
✓ 30. Please delete the last sentence of the first paragraph of Section 4.7.
Section 4.8.2 Construction Activities Waste
/ 31. Section 02222 of the Technical Specifications does not include any specifications for the
handling and disposal of waste generated during the course of this project. Please revise
the Technical Specifications to include a separate section that detail the handling and
disposal requirements for all waste generated. Please make the appropriate references
to the new section. :
APPENDIX F REMEDIATION GOAL VERIFICATION PLAN
List of Tables
/ 32. Please correct the indention for Table 1-2 in the List of Tables.
Acronyms for the Remediation Goal Verification Plan
/33. Please correct the definition of the acronym "NPDES" to state, "Natioilal Pollutant
Discharge Elimination System."
Section 1.1.1 Site Features and History
I
Please correct the last sentence of the second paragraph of Section 1.1.1 to state,
"Water is occasionally discharged from the large pond to Bat Fork Creek under a
National Pollutant Discharge Elimination System (NPDES) permit."
Section 2.1 Performance Monitoring Network
.Jf z._ 35.
di I 36.
In accordance with General Comment #2, please revise the third sentence of Section
2.1 to state, "Seventeen performance monitoring wells are located at the GE Subsite."
In accordance with General Comment #1, please revise the fifth, sixth and seventh
sentences of Section 2.1 to state, "Six surface water and sediment locations and
seven residential wells will be monitored. Figure 2-3 depicts the six :surface water and
sediment monitoring stations. Figure 2-4 depicts the seven residential wells that make
up the residential well sampling network." ;
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Section 2.1.2 Surface Water and Sediment Monitoring Stations
JI 37.
JI I 38.
/39.
In accordance with General Comment #1, please revise the first sentence of Section
2.1.2 to state, "In addition to the groundwater monitoring points described above, six
surface water and sediment stations are also proposed for sampling and analysis (See
Figure 2-3)." · !
Please revise the second paragraph of Section 2.1.2 in accordance with General
Comment #1.
As the proposed groundwater extraction system has less contaminanr,containment
than the currently operating AGRS, the last sentence of Section 2.1.2 is incorrect.
Please delete the last sentence of Section 2.1.2.
Section 2.1.3 Residential Wells
;, I 40.
Jl I 41.
In accordance with General Comment #1, please revise the first sentence of the
Section 2.1.3 to state, "In addition to the performance monitoring wells previously
described, seven residential wells will be sampled (See Figure 2-4)." 1
Please revise the second paragraph of Section 2.1.3 in accordance with General
Comment #1.
Section 2.3.1 Performance Monitoring
jl / 42. In accordance with General Comment #1, please revise the last sentence of Section 2.3.1
to state, "Surface water and sediment stations and the residential well network will be
sampled on a quarterly basis for three years. GE may then seek authorization from
the US EPA and the NC DENA to reduce the sampling frequency of the surface water,
sediment and residential monitoring network to a semi-annual basis for the
subsequent four (4) events. Upon completion of semi-annual sampling, GE may then
seek authorization from the US EPA and the NC DENA to reduce the sampling
frequency of the surface water, sediment and residential monitori'ng network to an
annual basis thereafter."
./ 43. Please revise the last sentence of Section 2.3.1 to state, "In addition to the sampling
requirements for the GE facility process water, groundwater treatment influent and
effluent water will be sampled for all RTCs on a quarterly basis."
Section 2.4 Monitoring Parameters
/ 44. Please revise the last sentence of the first paragraph of Section 2.4 to state, "Under such
a condition, GE will submit a request to the Agency that the monitoring frequency for the
targeted RTC be reduced to an annual basis for that particular groundwater
monitoring well or residential well. However, in the event that the RTC is detected
above the ROD remediation goal during annual sampling of the groundwater
monitoring well or residential well, quarterly groundwater monitoring for the RTC
must be re-initiated at that groundwater monitoring well or residential well."
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✓ 45.
•
Please revise the second paragraph of Section 2.4 to state, "However, at a minimum,
annual samples shall be collected from all surface water and sediment sampling
locations for analyses of all RTCs."
✓ 46. Please revise the first and second sentences of Section 2.4 to state, "During annual
sampling intervals, collected samples will be analyzed for the entire RTC list. In the case
that the annual sampling event detects a previously removed param(lter, the parameter
will be added to the analysis performed on performance monitoring wells within the
affected subsite or zone." ' ' I
/ 47. Please revise the fourth paragraph of Section 2.4 to include provisions for the quarterly
sampling of the treatment system influent and effluent, in addition to those to demonstrate
compliance with the publicly owned treatment works (POTW) requirements. Please
include provisions for the analysis of the influent and effluent samples ·1or analyses for all
remediation target compounds (RTCs) .
../ 48. Please revise Section 2.3 to describe the treatment system air emission monitoring
parameters.
Figure 2-1 GE Subsite Monitoring Points
:Ji i-50.
Please revise Figure 2-1 to correctly identily the recovery well RW-7 (currently identified
as recovery well RW-11) and to provide a notation indicating that the existing piping
connecting recovery wells RW-3 and RW-4 will not be used for the proposed groundwater
extraction system.
1
In accordance with General Comment #2, please revise Figure 2-1 to indicate that the GE
Subsite performance monitoring wells are MW-3, 8, 12, 12A, 128, 13, 13A, 14, 14A, 148,
15, 16, 16A, 22A, 27, 27A and 29.
Figure 2-3 · Location of Surface Water and Sediment Sampling Stations
J',/ 51. In accordance with General Comment #1, please revise Figure 2-3 to include the additional
three surface water and ~ediment monitoring locations.
Figure 2-4 Location of Residential Well Monitoring Network
;Ji ( 52. In accordance with General Comment #1, please revise Figure 2-4 to include the additional
two residential well locations. '
Figure 2-5 Decision Process for Requesting Removal of RTC Analyte~
✓ 53. Please revise Figure 2-5 to include a note that in the event that the RTC is detected above.
the ROD remediation goal during annual monitoring of the sampling location, quarterly
monitoring for the RTC must be re-initiated. '
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Table 2-1 Performance Well Network
.I\ 1-54. In accordance with General Comment #2, please revise Table 2-1 to indicate that the GE
Subsite performance monitoring wells are MW-3, 8, 12, 12A, 12B, 13, 13A, 14, 14A, 14B,
15, 16, 16A, 22A, 27, 27A and 29. . ,.
Table 2-2 Residential Well Monitoring Network
:11 I 55. In accordance with General Comment #1, please revise Table 2-2 to include the
appropriate information regarding the additional two residential well locations.
Table 2-3 Proposed Sample Collection Schedule
:J:11 56. In accordance with General Comment #1, please revise Table 2-3 to include provisions for
the collection of residential well samples, surface water samples and sediment samples
on a quarterly basis for the first three years; semi-annually for the following two
years, and annually thereafter. ·
Attachment 1 Field Sampling and Analysis Plan
Section 1 Introduction
' /57. Please revise the third sentence of the third paragraph of Section 1 to state, ''The
proposed final system consists of nine recovery wells pumping at 32 gallons per
minute (gpm) and is described in the Final Design Report (HSI GeoTrans, 2000)."
I
Section 2.1 Performance Well Sampling
JJ z_ 58. In accordance with General Comment #2, please revise the second sentence of
Section 2.1 to state, "Seventeen performance wells are located at the GE Subsite."
Section 2.2 Surface Water and Sediment Sampling
Ji I 59. Please revise the second paragraph of Section 2.2 in accordance with General Comment
#1.
Section 2.3 Residential Well Sampling
J:l I 60.
/61.
Please revise the first paragraph of Section 2.3 in accordance with General Comment #1.
Please revise the last sentence of Section 2.3 to state, "Attachme,nt 4 contains the
Sampling Standard Operating Procedures."
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Section 3.2.1 Monitoring Schedule
/62. Please revise the first paragraph of Section 3.2.1 to include the statement, "However, all
changes in monitoring frequency shall require prior approval from the appropriate
regulatory agencies prior to implementation."
Section 4.1 Sample Identification
JI-I 63. Please revise the last paragraph of Section 4.1 in accordance with General Comment #1.
Figure 2.1 GE Subsite Monitoring Points
✓54_
,:Jlz,65.
'
Please revise Figure 2-1 to correctly identify the recovery well RW-7 (currently identified
as recovery well RW-11) and to provide a notation indicating that the existing piping
connecting recovery wells RW-3 and RW-4 will not be used for the proposed groundwater
extraction system. '
In accordance with General Comment #2, please revise Figure 2-1 to indicate that the GE
Subsite performance monitoring wells are MW-3, 8, 12, 12A, 128, 13, 13A, 14, 14A, 148,
15, 16, 16A, 22A, 27, 27A and 29.
Figure 2-3 Location of Surface Water and Sediment Sampling Stations
JI I 66. In accordance with General Comment #1, please revise Figure 2-3 to include the additional
three surface water and sediment monitoring locations.
Figure 2-4 Location of Residential Well Monitoring Network
JI I 67. In accordance with General Comment #1, please revise Figure 2-4 to include the additional
two residential well locations. · ' ·
Table 1-2 Summary of Field RA Activities
j. / 68. In accordance with General Comment #1, please revise Table 1-2 to indicate that the
residential well network, surface water sampling stations, and sediment sampling stations
will be sampled, at a minimum, quarterly for first three years, semi-annually for the
following two years, and annually thereafter.
Table 1-3 Estimated Numbers of Samples
,ti I 69. In accordance with General Comment #1, please revise Table 1-3 to indicate that the
residential well network, surface water sampling stations, and sediment sampling stations
will be sampled, at a minimum, quarterly for first three years, semi-annually for the
following two years, and annually thereafter.
Table 2-1 Proposed Sample Collection Schedule
Ii/ 70. In accordance with General Comment #1, please revise Table 2-1 to indicate that the
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' residential well network, surface water sampling stations, and sediment sampling stations
will be sampled, at a minimum, quarterly for first three years, semi-annually for the
following two years, and annually thereafter. '
Table 2-2 Performance Well Network
JI Z,, 71. In accordance with General Comment #2, please revise Table 2-2 to indicate that the GE
Subsite performance monitoring wells are MW-3, 8, 12, 12A, 128, 13, 13A, 14, 14A, 14B,
15, 16, 16A, 22A, 27, 27A and 29.
Table 2-3 Residential WeU Monitoring Network
)JI 72. In accordance with General Comment #1, please revise Table 2-3 to include the
appropriate information regarding the additional two residential well locations.
Attachment 2 Quality Assurance Project Plan
Section 1.1 Site Description and History
✓ 73. Please correct the last sentence of the third paragraph of Section 1.1·to state, Water is
occasionally discharged from the large pond to Bat Fork Creek under,a National
Pollutant Discharge Elimination System (NPDES) permit."
Figure 1-1 Project Organization Chart
Please revise Figure 1-1 to account for Jason West's replacement for the task of Periodic
~n~~~-,
Table 1-2 Remediation Goals/POTW Effluent Limitations and Monitoring Requirements
./75_ Please revise Table 4-1 to indicate that the performance goal fortrans-1, 2-dichloroethene
is 70 mg/L.
Table 3-1 Summary of RA Field Activities
JI 76. In accordance with General Comment #1, please revise Table 3-1 to indicate that the
residential well network, surface water sampling stations, and sediment sampling stations
will be sampled, at a minimum, quarterly for first three years, semi-annually for the
following two years, and annually thereafter. '
Attachment 3 Ecological Evaluation of the Potential Effects of Remedial Groundwater
Extraction on Wetlands and Streams
Section 1.0 Introduction
I
Please revise the last sentence of the third paragraph of Section 1.0 to state, "At this
time, the proposed groundwater extraction at the GE Subsite is 15 gpm; the proposed
groundwater extraction at the Shepherd Farm Subsite is 17 gpm."
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Section 2.1.4 Hydrology
di 7778. Please revise the second paragraph of Section 2.1.4 to account for the revised
groundwater extraction system as proposed in the Final Design Report.
Section 2.1.6 Monitoring and Management Needs
JJJ179. Please revise the second item of the first paragraph of Section 2.1.6 to account for the
revised groundwater extraction system as proposed in the Final Design Report.
Section 2.2.3 Hydrology
,J,11 80. Please revise Section 2.2.3 to account for the revised groundwater extraction system
as proposed in the Final Design Report. ·
Section 4.0 Contingency Actions
Please revise Section 4.0, Section 4.1, Section 4.2, Section 4.3 and Section 4.4 to
account for the revised groundwater extraction system as proposed in the Final Design
Report. ; ·
'
Section 4.2 Reduced Flows in Bat Fork Creek or Impacts to Downstream wetlands Reliant
for Hydration or Water from Bat Fork Creek ·
;:1 71 82. Please restate the third sentence of .Section 4,2 to make serise.
Section 5.0 Summary
'
Please revise Section 5.0 to account for the revised groundwater extraction system as
proposed in the Final Design Report. '
APPENDIX G DESIGN CALCULATIONS AND MANUFACTURERS EQUIPMENT
INFORMATION
/ 84. Please revise Appendix G to include the letter regarding the capacity of the secondary
containment for the two 30,000 gallon tanks to be used for effluent storage prior to use
within the plant.
/ 85. Please revise Appendix G to include the air stripper program results, accounting for all
voes at the design influent concentrations (including a 150% factor of safety) as specified
in Table 4-1 of the Final Design Report.
✓ 86. Please include a copy of the cut sheets for the QED EZ-16.4 Low Profile Air Stripper in
Appendix G, however, pleas·e leave the copy of the cut sheets for the QED EZ-16.4 Low
Profile Air Stripper in Appendix C.
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,./87. Please include a copy of the cut sheets for the TetraSolv VF-3000 vapor treatment unit in
Appendix G, however, please leave the copy of the cut sheets for the TetraSolv VF-500
vapor treatment unit in Appendix C.
APPENDIX I
General
CONSTRUCTION SPECIFICATIONS AND DESIGN DRAWINGS
/ 88. A number of the pages of the Construction Specifications were inadvertently omitted as
shown in the table below. Please correct this oversight.
Construction Omitted Page(s)
Specification
Section Number
Section O 1440 Pace10of10 '
Section 01500 Pace 2 of 5
Section 02205 Paoes 1 and 3 of 4
Section 02222 Paoes 1, 5, 6, 8 and 9 of 9 1
Section 02223 Pages 2, 5, 7 and 8 of 8 '
Section 02250 Paces 2 and 4 of 5 '
Section 02270 Paoes 2 and 4 of 4
Section 02275 Page 1 of 2
Section 02500 Page 1 of 1
Section 02607 Paces 2, 3 and 4 of 4
Section 02671 Paoes 4, 5 and 6 of 12
Section 05503 Paoes 2 and 5 of 7
Section 09900 Page 6 of 9
Section 16010 Pages 2 and 5 of 6
Section 16111 Paces 3 and 4 of 5
Section 16123 Paoes 2 and 4 of 5
Section 16130 Paoes 1 and 4 of 6
Section 16170 Pace 2 of 3
Section 16180 Paces 1 and 3 of 3
Section 16190 Pace 2 of 3
Section 16720 Paoe 3 of 3
Section 15105 Combination Air and Vacuum Valves
/as. Please revise Paragraph 3.4.A of Section 15105 to account for the revised design as
submitted in the Final Design Report.
Drawing No. 3D 1 "=40' General Site and Piping Layout Plan
✓so. Please revise Drawing No. 3D to include a notation that recovery wells RW-3 and RW-4
are not to be used in the revised groundwater extraction system and that recovery wells
RW-3 and RW-4 should be valved shut, although not permanently disconnected.
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Drawing No. 4 Pipeline Right-of-Way Crossings, Profile
' ✓91. Please revise Detail 2 on Drawing No. 4 to include Section B, as shown in Detail Bon
Drawing No. 4.
APPENDIX J CONSTRUCTION QUALITY ASSURANCE PLAN
Figure 1-1 Project Organization Chart
/92. Please revise Figure 1-1 to account for Jason West's replacement for the task of Periodic
Monitoring.
APPENDIX K HEAL TH AND SAFETY PLAN
Acronyms for the Health and Safety Plan
,/ 93. Please correct the definition of the acronym "NPDES" to state, "National Pollutant
Discharge Elimination System."
Table 11-1 Emergency Response Contacts and Resources
./94_ Please revise Table 11-1 to account for Jason West's replacement as Site
Coordinator/SE RC.
Attachment 1
Section 3.1
Cold Stress Prevention Program
Hypothermia
/ 95. Please correct the numbering scheme provided for the numbered item.s in Section 3.1.
APPENDIX L OPERATION AND MAINTENANCE MANUAL
Section 1 Introduction
/95_ Please revise Section 1 to account for the revised final design as submitted in the Final
·oesign Report. ''
Section 4 Air Stripper O&M Manual
✓ 97. The Air Stripper O&M Manual was inadvertently omitted from Section '4. Please correct
this oversight.
-14-
, • • UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
4WD-NSMB
Ms. Janet Boyer
EHS Manager
GE Lighting Systems, Inc
3010 Spartanburg Highway
Hendersonville, NC 28792
REGION 4
ATLANTA FEDERAL CENTER
61 FORSYTH STREET□c:CEIVED
ATLANTA, GEORGIA 303031llll6e
Mfi.Y 2 2 2000
May 18, 2000
SUBJ: GE/Shepherd Farm NPL Site
East Flat Rock, NC
Dear Ms. Boyer:
Enclosed are the Agency's comments on the Response to Agency Comments on
Final Design for Groundwater dated May 3, 2000. Please make sure that all comments
are incorporated before submittal of the final documents. Please submit revised
documents no later than June. 8, 2000.
If you have any questions, please do not hesitate to give me a call at 404/562-
8824.
cc: Dave Mattison, NC DENR
Sincerely,
o<!-11d191A
G~: S. Bennett
Remedial Project Manager
Todd Hagemeyer, HSI Geo Trans
Lynn France, COM
Tom Augspurger, US F&W
Internet Address (URL)• http://www.epa.gov
Recycled/Recyclable • Printed with Vegetable Oil Based Inks on Recycled Paper (Minimum 30% Postconsumer)
•
COMMENTS ON THE MAY 3, 2000
RESPONSE TO AGENCY COMMENTS ON
FINAL DESIGN FOR GROUNDWATER
1. The Response to North Carolina Department of Environment and Natural
Resources (NC DENR) Comment 23 states that a withdrawal permit is not
required. However, conversations with Mr. Kenneth Ash, NC DENR Water
Resources Division (919-715-5443), indicate that a state withdrawal permit is
required if the recovery well systems exceed a capacity of 100,000 gallons per
day (approximately 70 gallons per minute continuously). Therefore, please
revise Section 4.6.3 of the Final Design Report accordingly. ·
2. The Response to NC DENR Comments 44, 96, 109, 136, 143, and 158 states:
"Please refer to EPA Comment 182 on the Pre-Final (90%) Remedial Design
and Remedial Action Work Plan for Groundwater which stated, "we
recommend that this RGVP be revised to include the schedule originally
proposed for performance sampling. In particular:
All performance monitor wells should be sampled quarterly for the
first three years, semiannually for the next two years, and annually
thereafter."
No direc\ion was initially given requiring Agency or NC DENR approval to
adhere to the originally proposed schedule. Agency and NC DENR approval
will be sought to enter Exit Monitoring and Closure Monitoring."
' However, this response is unacceptable. Although the proposed schedule is
acceptable for the purpose of completing the remedial design, please revise the
sections referenced by the above mentioned comments to indicate that General
Electric (GE) shall seek written authorization from the United States Environmental
Protection Agency (US EPA) and the NC DENR for all changes in groundwater
monitoring frequency and that the proposed schedule is subject to US EPA and NC
DENR approval. This is consistent with remedial actions conducted at other sites
under the authority of the US EPA and the NC DENR, and is consistent with the
information provided in the Response to NC DENR Comments 85:and 87.
3. The Response to NC DENR Comments 99, 100 and 101 indicate t.hat clarification
of the NC DENR site closure protocols is required. The second paragraph of
Chapter 11.0 -Site Closure of the guidance document, Groundwater Section
Guidelines for the Investigation and Remediation of Soil and Groundwater, Volume
1 -Sources Other Than Petroleum Underground Storage Tanks, NC DENR Division
of Water Quality, May 1998, states:
-1-
• •
"Sites that have been undergoing active remediation must show that
groundwater has been remediated to below groundwater standards. Four
consecutive quarters of data documenting no contamination above the 15A
NCAC 2L standards or interim standards while the remediation system is
operational, and four consecutive quarters of data documenting no
contamination above 15A NCAC 2L standards or interim standards after the
remediation system has been shut down are required."
Please revise the sections referenced by NC DENR Comments 9~, 100 and 101
accordingly.
4. The Response to NC DENR comment 102 states, "Per EPA Comment 69,
references to recovery well operation status have been deleted in the Annual
Monitoring Reports; and therefore wi!I not be included in the Quarterly Monitoring
Reports." Although other reviewers may differ, NC DENR finds this information is
useful in determining the success/failure of the extraction system and is useful in
developing system modifications and system improvements. Therefore, please
revise Section 3.1 and Section 3.2 of Appendix F -Remediation Goal Verification
Plan to include the submittal of the recovery well operation status in the Quarterly
Monitoring Reports and the Annual Monitoring Reports.
5. The response to EPA Comment 104 completely misses the point of the comment.
This action is being conducted by Superfund and not the POTW. Hence, if a
treatment goal is not achieved, it would be a violation of the requirements of the
Consent Decree in which GE agreed to clean up the groundwater to the
remediation goals. This also must be clearly understood.
6. Written comments on Attachment 1, Groundwater Modeling Results will not be
given due to the May 22, 2000 upcoming meeting on more extensive groundwater
modeling results.
-2-
H~
G·ROTRANS
A TETRA TECH COMPANY
Ms. Giezelle Bennett
Remedial Project Manager
U.S. EPA Region 4
6 I Forsyth Street
Atlanta, Georgia 30303-8960
• 1080 Holcomb Bridge Road
Building 100, Suite 190
Roswell, Georgia
30076
770-642-1000 FAX [phone]
May 3, 2000
'
RECEIVED
MAY 04 2000
SUPER!iUNO SEC1ION
Reference: Response to Agency Comments on Final Design for Groundwater
GE/Shepherd Farm Superfund Site, East Flat Rock, NC l
HSI Geo Trans Project No. N754-034
Dear Ms. Bennett:
On behalf on General Electric (GE), enclosed please find the response to
Agency comments on the Final Remedial Design and Remedial Action Work Plan
for Groundwater for the GE/Shepherd Farm Site in East Flat Rock, North ,
Carolina dated March I 0, 2000. Comments addressed in this response include
written comments from EPA, Fish & Wildlife Service, and NCDENR dated April
14, as well as, verbal comments received during a April 20 teleconference.
Each response enclosed includes the Agency's comment on the Final
Design, as well as, the Pre-Final Design' for completeness and continuity. Many
topics are covered in the responses. Response highlights are presented below.
I
METALS TREATMENT OF GROUNDWATER
The Agency requested clarification on the requirement and methodology
for metals treatment of the groundwater. Metals treatment is not expectedjto be
necessary to meet POTW or any other permit requirements. However, GE agrees
to discharge treated groundwater from the air stripper to the existing, on-site
metals pre-treatment facility, which is currently used for process water, before
final discharge to the POTW. A metals recovery assessment was performed on
the pre-treatment facility as part of this response. The assessment demonstrates a
high degree of metals removal efficiency from the pre-treatment facility .. The five
target metals were treated to below detection limits which were all below the
remediation goals. Sludge from the lime treatment process is a delisted w~ste.
P:\GEIDOCS\EPA~Pll 73.wpd
GE also agrees to sample pre-treatment influent and effluent on a quarterly basis
for target metals and reporting the results to the Agency.
INFLUENT/EFFLUENT SAMPLING
GE agrees to sample the air stripper influent and effluent on a quarterly
basis. GE further agrees to contemporaneously sample the composite sample port
that incorporated all Shepherd Farm recover wells so that the mass removed can
be calculated for each subsite.
EXTRACTION AND MONITORING AT RECOVERY WELL RWSF-1
The Agency requested the need for additional groundwater extr~ction near
proposed recovery well RWSF-1 at the Shepherd Farm Subsite be evahiated.
After further discussions, GE, HSI GeoTrans (HSIG) and the Agency agreed that
no additional groundwater extraction would be necessary in this area. GE has
agreed to evaluate the need for additional pumping near RWSF-1 at the five-year
review. If the five-year review indicates that an increase in extraction in this area
would significantly improve the contaminant mass removal rate, additional
extraction will be implemented. GE further agreed to not use lack of groundwater
extraction near RWSF-1 as support for a Technical Impracticability wajver.
The Agency requested that RWSF-1 be replaced by a new monitor well in
the performance monitoring network. After further discussions, GE, HSIG, and
the Agency agreed that no change in the monitoring network at the Shepherd
Farm Subsite was necessary.
IMPACTS TO THE BUNCHED ARROWHEAD HABITAT
The Agency expressed concern that the presented design, may
inadequately protect the bunched arrowhead habitat. At the request of the
Agency, numerous additional groundwater model simulations were performed to
develop alternative groundwater extraction scenarios that causes no impact to the
bunched arrowhead (defined by the Agency in a teleconference as less than 0.1
foot of drawdown and less than 25 % reduction in groundwater baseflow into the
habitat). The results of-three alternative scenarios are presented in Attachment I.
The degree ofVOC mass containment at the GE Subsite ranges from 29',to 72%
for the three alternatives presented. The preferred design, referred to as the
balanced design, contains 59% of the total VOCs at the GE Subsite. This
balanced design strikes a balance between source removal (at existing recovery
wells) and plume containment while honoring the stipulated drawdown and
baseflow reduction constraints.
P:'GE\OOCS\EPA\Epa73.wpCI 2
'4
HSIGEOTRANS
• PERFORMANCE MONITORING NETWORK AND SAMPLE :.
FREQUENCY
No changes to the performance monitoring network are propoied. During
the April 20 teleconference, GE, HSIG, EPA and NCDENR agreed that the
proposed monitoring at the Shepherd Farm Subsite was adequate. It .,,;,as also
agreed that the sampling requirements (e.g., frequency and parameters) may differ
between the two subsites. '
PERFORMANCE MONITORING METHODS (LOW-FLOW SA:MPLING)
GE agrees to provide greater detail on the low-flow sampling methods in
the Field Sampling Plan. The methodology will follow EPA guidance'.from Puls
and Barcelona (1996) (see Attachment 2 of the enclosed response). The low-flow
sampling technique specifies that the groundwater sample is collected after field
parameters, such as pH, conductivity, Eh turbidity and dissolved oxyg~n, have
stabilized and is independent of the volume of water removed. The purging of
three well volumes is not required for low-flow sampling. Diane Guthrie, P.E.,
Environmental Engineer of the EPA Office of Quality Assurance in Athens (706-
355-8622) was contacted for guidance with the use of low-flow sampling in
Region IV. Ms Guthrie offered to be available to answer any questions but
opined that the use of dedicated bladder pumps for performance monitor wells of
groundwater remediation systems, as proposed, is an ideal application.
j
I hope that these responses and proposed design changes meet your
approval. Please feel free to call Janet Boyer at 828-693-2505 or me if you have
any remaining questions or comments.
cc:
P:IGEIOOCS'EPA.'Epa73 wpd
Tom Augspurger, FWS
Janet Boyer, GELS
Lynne France, CDM
David Mattison, NC DENR
Peter Rich, HSIG
3
Sincerely,
-r o&.Y--~•'-'JU~
Todd Hagemeyer, P.G.
Hydrogeologist
Associate
HSIGEOTRANS
•
RESPONSE TO AGENCY COMMENTS DATED APRIL 14, 2000
ON THE FINAL REMEDIAL DESIGN (RD) AND REMEDIAL ACTION WORK PLAN
FOR GROUNDWATER DATED MARCH 2000. '
General Comments
/I) Comment: Many previous review comments have been addressed, and the Final
Remedial Design and Remedial Action Work Plan for Groundwater has been improved.
However, there are stm some areas of disagreement, some comments that have not been
addressed, and some issues that will need careful attention and monitoring as the
Remedial Action is implemented. These are covered in the following General and
Specific Comments. If these areas of concern are addressed, there does not appear to be
any reason to delay implementation of the Remedial Action.
Response: Substantial efforts have been made to adequately address all Agency
comments and incorporate the pertinent changes into the final design package.
/ 2) Comment: In numerous instances, the Response stated that a specific change had been
made in the text; however, an examination of the text indicated that no change had been
made. This made verification of the desired changes very frustrating and decreased
confidence in the content of the reviewed documents. It is recommended that the authors
be much more careful in the future in all aspects' of report preparation.
Response: Thorough review of each comment has been made. Care has been exercised
to not respond Text revised as requested in instances when text has been revised in a
manner different than the request.
/ 3) Comment: This final design document is in much better shape than the pre-final design
document. However, there are still some significant concerns that have hot been
addressed adequately. There are also a few inconsistencies in the document which still
need to be corrected for the sake of clarity. These concerns and inconsistencies are
discussed below. Additional comments on new material are also provided below.
Response: Comment is noted. Inconsistencies discussed in following comments have
been clarified in the revised final design package.
/4) Comment: The treatment or lack of treatment of metals is one major point of contention.
The position of HSI Geo Trans and GE Lighting Systems appears to be that no treatment
of extracted ground water for metals is necessary because the POTW does not require it
or does not have standards for certain metals. However, there are also RQD-Specified
Remediation Goals, which appears to mean that the ground water must be remediated to
below those goals. It is not clear if these goals apply to ground water only while it is in
I
•
the ground or also to water that has been extracted. This point of contention must be
reconciled.
Response: General Electric (GE), HSI GeoTrans (HSIG), the Environmental Protection
Agency (EPA), the North Carolina Department of the Environment and Natural
Resources (NC DENR), Biological Research Associates (BRA) (ecologist), and COM
Federal (EPA subcontractor) dialogued together on Thursday, April 20, 2000. GE
committed to treating extracted groundwater with their existing lime tre'atment system
before discharging the extracted groundwater to the POTW. Quarterly effluent samples
for the seven target VOCs and the one target SVOC will be collected after extracted
groundwater has been treated with the air stripper. Quarterly effluent sJmples for the five
target metals will be collected before and after water has been treated with the lime
treatment. Residual sludge from the lime treatment is a delisted waste and disposed of at
the Henderson County landfill.
The POTW Industrial User Permit between GE and the POTW requires,daily flow
measurements; four samples per month for BOD, TSS, temperature, pH, COD,
ammonia(N), and oil/grease; monthly samples for cadmium, chromium,·copper, cyanide,
lead, mercury, nickel, silver, and zinc; quarterly samples for aluminum, arsenic,
molybdenum, and selenium; and bi-annual sampling for total toxic org~ics (TTO) which
includes VOCs (EPA 624), SVOCs(EPA 625), and PCBs/pesticides(EPA 608). The
Agency will be copied on all reporting between GE and the POTW regarding the listed
discharge sampling.
/5) Comment: Monitoring of head in the wetlands is critical. The MODFLOW modeling
results are interesting and appear to indicate that there will be no adverse drawdown in
the various wetlands. However, as with all computer models, there are 11umerous
assumptions. The modeling results should be used as a guide rather than being assumed
to be completely accurate. It is recommended that careful attention be paid to monitoring
the ground water levels throughout the site and adjoining areas, especially in the
wetlands, as the ground water pumping occurs. The Ecological Evaluatipn of the
Potential Effects of Remedial Groundwater Extraction on Wetlands and Streams at the
General Electric/Shepherd Farm Superfund Site, prepared for HSI Geo Trans, Inc.,
represents a good step towards such actions. This new report is the best discussion yet of
the wetlands, potential effects of pumping, and monitoring needs. Recommendations
presented in this report should be followed.
Response: Comment is noted.
Specific Comments
Comment 3. The response indicates that additional QA/QC was performed to minimize ,,
inconsistencies. This additional QA/QC was apparently very faulty, as evidenced
2
• •
throughout this Response. The response to numerous comments is that the text has been
revised as suggested; however, the claimed change does not appear in the text. It is
recommended that the very basic QA/QC of verifying the changes that ~re claimed
should be followed. The person who writes the response should read the text of the
document.
90% Design Comment 3: Inconsistency: Many regulatory comments'have been issued
due to inconsistencies in information and details provided by the various
documents/appendices. Although it is recognized that many individuals have contributed
a great amount of effort in drafting this document, there is an apparent lack of
communication regarding the intent of the groundwater remedial design as well as the
specifications for the groundwater remediation system's construction, operation and
maintenance. No where was this more apparent than in regards to the actual monitoring
points used to assess the groundwater remediation system's adequacy in containing the
contaminant plume and extracting and treating the contaminant plume in an efficient
manner. l
90% Design Response 3: Additional QA/QC was performed to minimize
inconsistencies.
Response: Comment is noted. Additional QA/QC was performed to minimize
inconsistencies throughout the revised final design package and the accompanying
appendices. To facilitate review of the Agency comments, the original Agency comment I on the 90% design, the original response, and the current response with the associated
change in text are provided for completeness and continuity.
/ 7) Comment 9 -Instead of having only one recovery well located in the "hot zone"
pumping at half the rate as the other recovery wells, the PRPs now have :no recovery
wells in the hot zone area and the only upgradient well is pumping at 40% of the rate of
the other recovery wells. Thus, the majority of the contaminant mass must travel a longer
distance before it is removed. Although the PRPs have increased the amount of
contaminant mass contained from 85% to 96% with this new design, the1 removal is less
efficient. A much greater portion of the contaminant mass in the "hot zone" needs to be
captured sooner, and to achieve this objective, a series of vertical recovery wells ( or one
horizontal recovery well) needs to be located in the hot zone down the ce_nterline of the
plume. In addition, due to the limited drawdown available in the saprolite in this area, the
design of the vertical wells (if used instead of a horizontal extraction well) needs to be
revised to allow for more flow from the well. Instead of placing the pump 10 feet above
the bottom of the well, the recovery well should be constructed with a 5-foot sump (5 feet
into the bedrock) at the bottom of the well for placement of the pump. By lowering the
pump, additional drawdown is available so that the flow may be increased.
90% Design Comment 9: Unlike at the GE subsite, the proposed groundwater recovery
3
•
system at the Shepherd Farm subsite does not appear to provide a good balance between
containing the contaminant plume and removing the contaminant mass'. The proposed
system has only one extraction well located in the "hot spot" area and it is pumping at
half the rate of the other wells. Thus, the capture zone of this well is small and a
significant portion of the contaminant mass must travel a long distance ,to the
downgradient interceptor wells before it is removed. This is an inefficient design. A
much greater portion of the contaminant mass in the "hot spot" area ne~ds to be captured
sooner, and to achieve this objective, either the pumping rate at the lonb "hot spot" area
well needs to be increased or additional recovery wells need to be located in the "hot
spot" area. In addition, the PRPs should investigate redesigning the recovery well system
at this subsite to capture a greater portion of the contaminant mass than,85%. As far as
we know, there are no wetlands to be impacted by greater drawdown in_ this area.
90% Design Response 9: The layout of the recovery wells at the Shepherd Farm Subsite
has been revised. The resulting contaminant mass containment for the revised design is
approximately 96%.
Response: After discussing this comment with the Agency on April 20, it was mutually
agreed between EPA, NCDENR, GE and HSIG that no changes to the well locations,
extraction rates, or construction details at the Shepherd Farm Subsite ar~ necessary. The
number of wells and rate of extraction is appropriate for the nature and extent of
contamination at the site. If the five year review indicates that an increase in extraction in
the area ofRWSF-1 would significantly improve the contaminant mass ~emoval rate,
additional extraction will be implemented.
/8) Comment 12. The response indicates that all treated ground water will be used as
process water and then discharged to the POTW. However, this ignores the treated
ground water stored in the storage tank that is discharged directly to the POTW during
times of plant shutdown (as shown on the Water Flow Diagram of Appe\ldix G). Thus, it
cannot be said that all treated ground water will be used as process water. In addition, if
the POTW standard for metals content in water is less stringent than the remedial goals
for the ground water, the currently proposed system appears to be merely a way to bypass
more stringent ground water remedial goals.
90% Design Comment 12: Although there appears to be a plausible potential need for
treatment of the recovered groundwater to remove metals, the proposed design does not
include any metals treatment unit. The PRPs indicate that if needed, a reyerse osmosis
(RO) unit may be added to the treatment system, but no design is presented. To avoid
future delays in adding this treatment unit to the system, this design should include the
design of a reverse osmosis unit with the stipulation that it may be added 'in the future, if
needed.
90% Design Response 12: See response to comment 5. All treated groµndwater will be
transferred to storage tanks, used as process water in GE manufacturing facility and then
'
4
• •
discharged to the POTW. All water from the air stripper will meet the POTW
requirements. Therefore, metals treatment prior to the groundwater entering the GE
process water system is not necessary. The manufacturing facility can use all of the water
from the air stripper or it can be discharged directly to the POTW. Any polishing or
additional treatment performed by GE in the manufacturing process will not constrain the
continuous and full operation of the groundwater pump-and-treat system. Therefore, any
polishing or additional treatment is relevant to the manufacturing process, not the
remedial action.
Response: All treated water will be discharged to the POTW. The first priority for the
treated groundwater is to reuse it in the manufacturing process. However, if groundwater
production exceeds demand, it will be discharged to the POTW witho~t reuse.
/9) Comment 17. All the changes do not appear to have been made, even:though the
response says they were.
90% Design Comment 17: Table of Contents -Several discrepancies were noted during
the review of the Table of Contents. Please correct these oversights.
a The title for Section 5 should be given as "Groundwater Remedial Action at the
Shepherd Farm Subsite."
b The title of Appendix C should be given as "AGRS Equipment."
c The title for Appendix E should be given as "Numerical Groundwater Flow Model."
d The title for Table 3-3 should be given as "Quarterly AGRS effluent monitoring data
for VOCs" in the List of Tables.
90% Design Response 17: The Table of Contents revised as requested'.
Response: The reviewer is correct in stating that the above italicized words were left out
of the table of contents. The table of contents will be updated so that we remove
ambiguity and do not refer to such things as Appendix C -Numerical Gr.oundwater Flow
Model as Appendix C -Numerical Groundwater Model Report.
/10) Comment 22. The text was not revised as claimed in the response.
90% Design Comment 22: Section 1.1.1 GE/Shepherd Farm Subsite Features and
History -Please revise the sixth paragraph of Section 1.1.1 to include the entire sixth
paragraph of Section I. I. I of the Intermediate (60%) Design for Groundwater.
90% Design Response 22: Text added as requested.
Response: The portion of the paragraph that was not kept in the Final Design "This
wetland is referred to as the East Flat Rock Bog Remnant. It is considered to be of
5
• •
national significance (NCDENR, 1995)." was left out because the statement is incorrect.
The East Flat Rock Bog Remnant covers an area much larger than the wetlands discussed
in this section and it is misleading to keep this sentence. '
/11) Comment 39. The recommendation was not followed to add a statement regarding
manganese being found in on-site wells at an order of magnitude greater than the
remediation goal.
90% Design Comment 39: Pg. 2-9, Section 2.6.1.2 -The second paragraph is confusing
and needs to be divided into two separate paragraphs. If it is pointed out that manganese
was found in the background wells, it should also be noted that the levels found in onsite
wells is at least an order of magnitude above the remediation goal.
90% Design Response 39: Text revised as requested.
Response: The text was revised to state, "Manganese is ubiquitous and is typically found
at concentrations at least two times the remediation goal (50 parts per billion (ppb)) in
background wells (e.g., MW-32, MW-57, MW-59, and MW 60A). In on-site wells, the
manganese concentrations range from 12 to 7,380 ppb. The concentrations appear to
decrease with depth (see Figures 34-36 in Appendix B)." ·
./i 2) Comment 40. The text was not revised as claimed in the response.
/13)
90% Design Comment 40: Pg. 2-10, Section 2.6.1.2 -In the paragraph that begins "In
summary ... ", in the sentence that begins "Manganese is also pervasive .. :", the text needs
to add appropriate language between the words "excess" and "in" (the second "in").
'
90% Design Response 40: Text revised as requested.
Response: The text was revised to state, "Manganese is also pervasive; but found in
concentrations significantly in excess of remediation goals in backgrouri~ wells."
Comment 41. Instead of including a brief explanation of how the bedrock thicknesses
were determined, the text merely changed the wording from "was calculated as" to "was
assigned''. This is a meaningless change. An explanation of why these thicknesses were
"assigned" is needed.
90% Design Comment 41: Pg. 2-11, Section 2.6.1.2, voe Mass -Please explain how
the thicknesses of the two bedrock units were determined as well as their.effective
porosities.
90% Design Response 41: Text revised to explain how the estimated thickness of the
bedrock and the estimated effective porosities were used to determine voe mass.
6
•
Response: The following text will be added to Section 2.6.1.2:
' voe mass is considered to be significant in the saprolite and upper 100 feet of bedrock
and insignificant below the upper 100 feet of bedrock. This assumption is based on the
reduced volume of water, or porosity, expected with depth (see description of the
conceptual groundwater model presented in Section 2.3.1) and the observed reduction in
voe concentration with depth (presented in Appendix BJ.
A hydro geologic distinction is made between the shallow and deep bedrock zones. Site
bedrock monitor wells screened in the shallow bedrock (wells with an ''A" designation)
monitor generally the upper 40 feet of bedrock while site bedrock monitor wells screened
in the deep bedrock (wells with an "B" designation) monitor generally 60feet of bedrock
below the shallow bedrock. Hydro graphs (presented in Appendix A) illustrate that a
hydraulic gradient exists between the shallow and deep bedrock and thus define two
distinct hydrogeologic units.
Porosity values were assigned for the geologic units using published literature as a
guide. According to EPA (1985), the porosity of the saprolite is about 20 to 30 percent
and the porosity of the bedrock is about 0.01 to 2 percent in this physiographic region.
The porosity generally decreases with depth in the bedrock as the degree of weathering
and fracturing diminishes. The combination of a porosity and concentr~tion reduction
with depth causes mass to become relatively insignificant below a bedrock depth of
approximately 100 feet.
Reference: EPA, 1985, Protection of Public Water Supplies from Ground-water
Contamination, EP A/625/4-85/016.
7
/14)
•
Comment 47. The requested explanation was not added to the text, although Drawing 5
was changed (in addition, it is not clear where Drawing 5 is). ·
90% Design Comment 47: Pg. 3-2, Section 3.2.2, Operational Discharge Rate -Six
months (May 1999 to November 1999) is a long time for a groundwater recovery system
not to be operating as designed ( I 6 gpm vs. 25 gpm). Please explain why replacing a
failed pump was such a problem and what safeguards are being planned such that future
pump failures/replacements will not cause this proposed remedial action to be operating
at less than full capacity for such a long period.
90% Design Response 47: A reserve discharge pump is being added at the air stripper
discharge. See Drawing 5.
Response: Drawing 5 is a D-size drawing located in the set of bound drawings. The
following text was added to Section 3.2.2 to further explain the reduction in the AGRS
flow rates: In this 6 month period 2 pumps were replaced and the system was temporarily
shut down so that a water softener could be added to the treatment train in an attempt to
pass the NPDES chronic toxicity test.
J 15) Comment 51. The cause of the mixing and homogenization was briefly discussed;
however, the implications of the non-decreasing concentrations in MW-12A and MW-
12B were not discussed. Do these concentrations in MW-12A and MW-12B mean that
there is significant contamination in the bedrock, the saprolite, or both? What effects
does this have on the remedial plans? '
90% Design Comment 51: Section 3.2.4.2, Groundwater -The Design Report suggests
that stable voe concentrations that do not decrease at monitor wells MW-l 2A and MW-
12B are due to mixing and homogenization of saprolite and bedrock wat~r near the
recovery wells. This implies that the recovery wells are impacting water having relatively
higher concentrations, and which is drawn into MW-12A and MW-12B. It is possible
that this concentration behavior provides clues as to the location of the contamination
being in either or both of the saprolite and bedrock. Successful clean up of the ground
water will require that the impact and effectiveness of the ground water recovery system
on water in the saprolite and in the bedrock be understood. It is recommended that the
causes and implications of this mixing and homogenization be further discussed in the
Design Report. 1
90% Design Response'51: The text was revised to state that the mixing and
homogenization caused by induced downward flow toward the pump, which is located in
the bedrock.
Response: The observed voe concentrations at monitor wells MW-12, '12A, and 12B
8
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are consistent with the expected response from pumping from a well that is completed in
the saprolite and shallow bedrock. Locally, in areas near the extraction wells, VOC mass
will be pulled down from the saprolite into the bedrock. This phenomenon has no
bearing on the groundwater design because the area of homogenization would not be
expected to extend significantly below the extraction wells and would be expected to be
captured by the extraction wells.
✓i 6) Comment 54. Table 3-5 does not include a note that SWW9 is not used for drinking
water, although the response says it does. In addition, the note should indicate that
SWWI O is not used for drinking water purposes as well.
90% Design Comment 54: Pg. 3-5, Section 3.2.4.2, Groundwater -Private well WW34
shows a lead concentration of 85 ppb. This well needs to be resampled. as soon as
possible. A note should be added to the table that SWW9 is not being used for drinking
water purposes. What was the rationale behind the decision to choose the three
residential "sentinel" wells? Others that should also continue to be sampled are 34 and 2.
90% Design Response 54: The residents at WW-34 have been contacted about the 1999
results. The well is scheduled to be re-sampled in March 2000. A note was added to the
table indicating that SWW9 is not used for drinking water purposes.
Most of the residents around the site have city water because GE has offered to have them
connected. Per the CD, some residential wells will be sampled periodically. The
proposed monitoring program includes five residential wells around the GE Subsite
(WW3, WWI 7, WW34, WW73, and WW82). These wells will be sampled annually.
Wells WW-34 and WW-3 have been added to the residential well sampling program.
Response: The following note was added to Table 3-5: The following wells are not
used for drinking water purposes: SWW-9, SWW-10, WW-34.
Ji 7) Comment 55. The text was not revised as claimed in the response.
90% Design Comment 55: Pg. 3-5, Section 3 .2.4.2, Groundwater -In the last
paragraph, delete the remainder of the sentence after the word "AGRS". As mentioned in
previous comments, to state that requirements have not been exceeded when there are no
requirements is misleading.
90% Design Response 55: Text revised as requested.
Response: The portion of the sentence after the word "operation" will be deleted from
the revised Final Design.
9
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✓I 8) Comment 56. The text was not revised as claimed in the response.
90% Design Comment 56: Pg. 3-5, Section 3.2.4.3, Surface Water and Sediment -
Contrary to what the text states, there was more than one detection of o,rganic compounds
in surface water and sediment. The following organic compound detections are indicated
in Tables 3-6 through 3-8:
• In September 1999, tetrachloroethane was detected at 1.4 ug/1 in surface water at the
Stream-2 sample location
• In July 1997, PCBs were detected at 0.063 mg/kg in sediment at the Stream-2 sample
location
• In September 1998, PCBs were detected at 0.047 mg/kg in sedime,it at the Stream-2
sample location
• In September 1999, PCBs were detected at 283.5 mg/kg in sediment at the Stream-2
sample location
This section needs to be revised accordingly. An evaluation of the significance of these
detections is also needed.
90% Design Response 56: Text requested has been revised. Also, Table 3-8 has been
corrected to state that in September 1999, PCBs were detected at 0.2835 mg/kg in
sediment at the Stream-2 sample location.
Response: The text was revised to address the reviewer's comment as follows.
"No volatile organic compounds have been detected in the surface water.or sediment with
one exception. In September 1999, PCE was detected at Stream-2 at an estimated
concentration of 1.4 ug/1. This value is below the NC surface water standard of 8.85
ug/1."
A discussion of trace amounts of PCBs below state and federal standards is not
appropriate. Only exceedances are discussed in this section of the report. Tables 3-6 and
3-7 present the results for all collected stream samples and are referenced in this section
for completeness. Again, please note that Table 3-8 has been corrected to state that in
September 1999, PCBs were detected at 0.2835 mg/kg in sediment at the' Stream-2
sample location.
j19) Comment 60. The text was not revised as claimed in the response.
90% Design Comment 60: Pg. 3-6, Section 3.3 -In the fourth paragraph, delete the
word "close" in the first sentence. The plume extends to the site boundary.
10
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90% Design Response 60: Text deleted as requested in comment 59.
Response: The third paragraph of Section 3-3 now reads, "The contaminant plume at the
GE Subsite consists of a central portion with high contaminant concentrations and an
exterior portion with lower concentrations that extends to the site boundary. The
groundwater within the central region of the plume is relatively depleted of oxygen,
indicating the presence of biological activity. This activity appears to diminish with
depth and with distance away from the central region."
)20) Comment 62. The text was not revised as claimed in the response.
90% Design Comment 62: Pg. 4-1, Section 4, Groundwater Remedial Action at the GE
Subsite -' Add the words "majority of the" in front of"VOC plume" in the first sentence
of this section.
90% De~ign Response 62: Text revised as requested.
Response: Pending implementation of final groundwater modeling results in conjunction
with assessment of impacts on the bunched arrowhead, text will be added to the first
sentence:of Section 4 as requested. The revised sentence will read "The existing
groundwater extraction and treatment system, referred to as the AGRS, will be modified
to hydraulically contain the majority of the VOC plume at the GE Subsite and treat
extracted groundwater."
/ 21) Comment 64. To address the concern about a gap between R W-IO and R W-1 I, it appears
that R W" I I was moved northward, but R W-10 was also moved northward, but to a greater
degree. There now appears to be an even greater gap between R W-10 and R W-1 I .
90% Design Comment 64: Pg. 4-1, Section 4.1, Groundwater Extraction -GE Subsite -
While the proposed extraction well layout provides a fairly good balance between
containing the contaminant plume and removing the contaminant mass in an efficient
manner, we believe that a few small modifications will improve this balance. There is an
area around MW-14 which has consistently had high concentrations ofVOCs. With the
proposed layout, this area is located midway between recovery wells R W-10 and R W-1 I
which will become an area of stagnation once pumping is initiated. Thus, the VOC
contamination in this area will sit for a long period of time until the pumping arrangement
changes. To remove this "hot spot" of contamination in a more efficient manner, we
recommend that an additional recovery well be located in this "hot spot" area, and that
the other recovery wells located along Bat Fork Creek be moved slightly to provide a
more uniform spacing with this change. In addition, to be more efficient, we recommend
that an additional recovery well be located in the area of MW-23 so that the high levels of
contamination found in the southern part of the GE plant area do not have to travel all the
way to the recovery wells located along Bat Fork Creek before being·'removed.
11
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90% Design Response 64: The proposed location of the recovery wells has been
revised.' A recovery well is now proposed near MW-14 as requested. A recovery well is
now proposed near MW-23 as requested.
Response: After further discussions, and on the April 20 conference call it was agreed
that no change to the location of proposed recovery wells in this area is warranted based
on this comment.
/22) Comme.nt 65. It is unclear if the discussion with the POTW regarding acceptance of the
treated ground water included the fact that the ground water would not be treated for
metals.
90% Design Comment 65: Pg. 4-2, Section 4.2, Design Influent Concentrations and
Effluent Discharge Requirements -Please indicate whether the POTW has been notified
and agn,ed to accepting the plant process water under the existing site POTW
pretreatment agreement, given this potential change in the source of the plant process
water.
90% Design Response 65: The POTW was notified on October 28, 1999 and February
25, 2000 by Mr. Lee Humphrey of GE. POTW representative Mr. Wayne Cooper stated
that they would accept the plant process water from the treated groundwater source under
the exist_ing agreement with GE.
Response: See response to EPA general comment 4.
✓ 23) Comment 67. Table 4-1 indicates that the ROD-Specified Remediation Goals for
manganese and lead are exceeded by the design influent concentration. Further, these
metals will not be treated before being released to the POTW. Regardless of whether or
not the POTW cares about the concentrations of these, this proposal appears to be merely
a way to ignore the ROD-Specified Remediation Goals. Apparently these Remediations
Goals are meaningless once the ground water is extracted. This issue must be resolved.
90% Design Comment 67: Please revise the third sentence of the fourth paragraph of
Section 4.2 to state, "The VOCs, SVOCs and metals in groundwater will be treated to
drinking. water MCL standards prior to discharge for use in the plant or to Bat Fork
Creek."·
90% Design Response 67: Refer to response to comment 11. The sentence in question
will not be revised. The groundwater treatment system is designed to remove VOCs. No
SVOCs or metals in the calculated influent concentrations exceed effluent design
standards (see Table 4.1 ). As the effluent is used as nonpotable process water in the GE
Facility,'acceptance of iron and manganese levels above secondary MC Ls is based on
GE's water quality needs.
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Response: A corrected version of Table 4-1 will be included that accounts for the revised
pumping scenario and addresses the calculated groundwater influent concentrations. All
groundwater will be treated for metals. '
/24) Comment 68. The response to this comment should actually refer back to the response
for comment 7, instead of 6.
90% Design Comment 68: Pg. 4-2, Section 4.3, Groundwater Remediation System
Components -Nothing is mentioned in this Remedial Design about "nonoperating"
recovery wells, as is indicated in Appendix F.
90% Design Response 68: Refer to response to comment 6.
Response: Reviewer is correct.
/ 25) Comment 82. The suggested change does not appear to have been made as claimed in
the respc:mse.
90% Design Comment 82: Pg. 5-l, Section 5. l -In the second paragraph, delete the
I
sentence after "PCE".
90% Design Response 82: Text revised as requested.
Response: The text was changed from the 90% design, removing the subjective term
"low." The sentence was revised in the Final Design to state " The predominant
contaminant at the Shepherd Farm Subsite is PCE, which is currently present at
concentrations <JOO ppb." As EPA Comment 54 correctly points out, SWW-9 recorded
a PCE concentration of I 12 ppb in September of l 999. Therefore, the sentence in
question:will be revised to state "The predominant contaminant at the Shepherd Farm
Subsite i_s PCE, which is currently present at concentrations less than l 20 ppb."
I 26) Comment 83. The response is non-responsive.
90% Design Comment 83: Pg. 5-1, Section 5.1.1, Recovery System -The proposed
layout for the pipeline conveying effluent from the Shepherd Farm subsite to the GE
subsite comes very close (i.e., within 30 feet) to the bunched arrowhead wetland. Is not
construction so close to this endangered specie's habitat a risky venture with respect to
harming ,the plant community? In addition, could not rupture of the pipeline in this area
lead to contaminated water being discharged to this habitat? We recommend that the
pipeline layout be revised such that dangers from construction and pipeline rupture to the
bunched 'arrowhead habitat are minimized.
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90% Design Response 83: Biological Research Associates has been consulted on the
piping layout.
Response: The piping layout has been revised. The proposed route has been moved
approxiipately 240 feet to the south.
J 27) Comment 84. Please explain how a regular visual inspection along the pipeline route
will detect a leak if the pipeline is underground. In addition, regularly visually inspecting
the pipeline route is not included in the operation and maintenance plan. This plan
should be revised accordingly.
90% Design Comment 84: Pg. 5-2, Section 5.4, Operation and Maintenance -Please
indicate how flow through the pipeline will be monitored to determine if there are any
leaks. The pipeline travels through some sensitive areas and 3,000 feet is a long distance
for contaminated water to travel without any leak monitoring.
90% Design Response 84: The pipeline is HOPE which will be heat fused and pressure
tested prior to backfill. System operation will include monitoring totalized flow at each
well for comparison with the system total. Any unlikely significant leak will be found by
this method or regular visual inspection along the pipeline route. The total PCE conveyed
from Shepherd Farm Subsite to the GE Subsite is 0.009 pounds per day.
Response: The reviewer is correct in ascertaining that a regular visual inspection along
the pipeline route would not be an effective means of leak detection unless the leak was
' substantial enough to cause some sort of surface erosion or surface flow. Any unlikely
significant leak will be indicated by a discrepancy between totalized flow and individual
well flows.
Comment 86. Please elaborate on what is meant by "discussions are ongoing". At what
stage are the discussions? Has access at least been verbally agreed upon? These
agreements are critical to the success of this design. Without these agreements, major
design revisions will be required. In addition, obtaining access agreements for railroad
crossings or working within railroad easements is often a long process, and a significant
delay in starting the remedial action could occur if the PRPs have only recently initiated
' the process.
90% Design Comment 86: Pg. 5-2, Section 5.5, Permit Requirements -GE's objection
to this approach at the ROD stage was access from the railroad. Has this access been
obtained or even discussed with the railroad? This should be considered now, instead of
later, as with the power poles.
'
90% Design Response 86: Applications for pipeline crossings have been submitted to
I
both Norfolk Southern and NC DOT. Discussions are ongoing.
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Response: Applications have been submitted to both NCDOT and Norfolk Southern.
These applications are being reviewed at multiple levels within NCDOT and Norfolk
Southern. Although final approval has not been granted, both organizations have
indicated in phone conversations that the time frame for application review and approval
will not interfere with the proposed remedial action.
/29) Comment 92. The new sampling location (Stream 4) proposed to monitor surface
water/sediment during the remedial action does not meet the objective stated in EPA's
comment. The station should be located immediately downgradient of the area where the
Shepherd Farm plume discharges into Bat Fork Creek to see ifthis discharge may be
impacting the ecosystem in Bat Fork Creek. The proposed location is over 1500 feet
downstream of the plume discharge. At this distance, any stream contamination would
likely be susceptible to the effects of dilution and volatilization prior to reaching the
sampling point.
In addition, adding the proposed surface water/sediment sample location to Figure 2-13 as
the PRPs have done has made the document less clear. Section 2. 7 refers to three
historical sampling locations "as shown in Figure 2-13 ", but Figure 2-13 now has four
sampling locations. Either the text or the figure ( or both) needs to be revised to indicate
which sampling locations Section 2. 7 is referring to.
90% Design Comment 92: Figure 2-13, Surface Water and Sediment Sampling
Locations -Figure 2-13 indicates that there is no surface water or sediment sampling
location immediately downstream of the Shepherd Farm Subsite. Groundwater modeling
performed by GE indicates that the groundwater contamination existing at the Shepherd
Farm Subsite discharges into Bat Fork Creek. However, GE cannot document that
immediately downstream of the Shepherd Farm Subsite surface water and sediment
contamination does not.exist at levels that exceed North Carolina or Federal sediment and
surface water standards. Previous sampling activities do indicate that stream
contamination has not been detected at the downstream sampling point that is located
downstream of the GE Subsite. However, this sampling point (Stream-2) is located
approximately one mile downstream of the Shepherd Farm Subsite. Any stream
contamination existing at the Shepherd Farm Subsite would be susceptible to the effects
of dilution and volatilization prior to reaching sampling point Stream-2. Please revise
Figure 2-13 to include an additional surface water and sediment sampling location
immediately downstream of the Shepherd Farm Subsite.
90% Design Response 92: A proposed surface water/sediment sample location has been
placed between the Shepherd Farm and GE Subsites. Figure 2-13 has been revised.
Response: The 90% Design Comment requested an additional sample location
immediately downstream of the Shepherd Farm Subsite. The area label as the Shepherd
Farm Subsite on Figure 2-13 encompasses a large area and extends to within 250 feet of
the proposed sample location (Stream 4). The proposed location is sited in a location to
15
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measure the cumulative effects, if any, that the Shepherd Farm Subsite imposes to Bat
Fork Creek. The reviewer has changed their wording to now state that the sample
location be immediately downstream of the plume rather than the subsite boundary. This
location is acceptable, however, the terms downgradient or immediately downgradient are
a subject continuum. The revised proposed sample location was moved immediately
downgradient of the area where the Shepherd Farm plume discharges into Bat Fork
Creek. For clarity, a note was added to Figure 2-13 as follows:
Note: Upon EPA approval, STREAM 4 will be added as a monitored sample
location and STREAM 3 will be no longer be monitored.
/30) Comment 89. · The change was not made as claimed in the response.
)31)
90% Design Comment 89: Section 8, References -Please revise the reference to
Schrauf et al. (1994) to state, "Schrauf, T. W., P. J. Sheehan, and L. H. Pennington, 1994,
Alternative method of groundwater sparging for petroleum hydrocarbon remediation,
Remediation, Vo. 4, No. I."
90% Design Response. 89: Text revised as requested.
Response: In the Final Design, the reference was revised and listed as "Schrauf, T. W.,
P. J. Sheehan, and L. H. Pennington, 1994, Alternative method of groundwater sparging
for petroleum hydrocarbon remediation." The journal name, volume, and number will be
added.
Comment 96. The method a software program uses to make tables of schedules does not
affect a requirement that report submittals are due in 30 calendar days. The use of an old-
fashioned paper calendar is recommended if that is what it takes to understand the
concept of 30 calendar days.
90% Design Comment 96: Figure 6-1 -Submittal of reports following comments
should be 30 calendar days, not 30 working days. Please revise this schedule
accordingly.
90% Design Response 96: The scheduling software used, Microsoft Project, calculates
the duration of a task by counting the amount of active working time between the
scheduled start and end of the task. This is generally the time from task start to finish,
not counting time between split tasks or non-working time. The duration format was not
changed on the schedule.
Response: The intent of90% Design Comment 96 was misunderstood. The Proposed
Project Schedule will be corrected to indicate that responses to EPA will occur within 30
calendar days. Duration will still reflect working days. Figure 6-1 will be updated to
reflect the current proposed schedule as the task referenced by 90% Design Comment 96
16
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has already been completed and is a moot point.
/32) Comment 97. Table 1-1 was not revised as claimed in the response.
90% Design Comment 97: Table 1-1, Remediation Goals for Groundwater - Please
revise Table 1-1 to include the cis-1, 2-dichloroethene and trans-I, 2-dichloroethene
isomers of 1,2-dichloroethene.
90% Design Response 97: Table 1-1 revised as requested.
Response: A note has been added to Table 1-1. Remediation Goals for Groundwater to
include the cis-I, 2-dichloroethene and trans-I, 2-dichloroethene isomers of 1,2-
dichloroethene. The isomers were not added to the body of the table to avoid confosion
when the text references seven VOCs, one SVOC, and five metals.
/33) Comment 104. The statement is made that " ... any treatment goals beyond the GE
Facility and POTW requirements are arbitrary". The relationship of the GE Facility and
POTW requirements to the ROD-Specified Remediation Goals for ground water must be
clarified in order to address this statement and this issue, and to determine what goals are
to be followed.
90% Design Comment I 04: Table 4-1, Calculation of Representative Influent
Concentrations and Design Effluent Concentrations -The third sentence of the fourth
paragraph of Section 4.2 states, "The VOCs in groundwater will be treated to drinking
water MCL standards prior to discharge for use in the plant or to Bat Fork Creek."
However, the design effluent concentrations given in Table 4-1 are incorrect in many cases
(i.e., the incorrect Maximum Contaminant Level (MCL) is provided). Furthermore, in the
event that the remediation system effluent is discharged to Bat Fork Creek, the North
Carolina surface water standards are more stringent than the MCL in many cases. Please
revise Table 4-1 to include the more stringent of the MCL or the North Carolina surface
water standard as the design effluent concentration for each individual contaminant. Lastly,
many of the contaminants listed in Table 4-1 do not have an effluent design criterion
because there is no Federal MCL for the contaminant. Please develop criterion for each
contaminant being monitored using some drinking water or surface water standard, so as to
have some measure as to whether proper treatment of the effluent is occurring.
90% Design Response 104: The design effluent column in Table 4-1 reflects the USEPA
MCLs that the air stripper was designed to meet for the AGRS. The air stripper treatment
efficiency is discussed in the response to comment 4. Monitoring of the air stripper effluent
will be conducted as described in Appendix F. As the treated water will be used for non-
potable process water in the GE Facility and monitored per the pretreatment agreement with
the POTW, any treatment goals beyond the GE Facility and POTW requirements are
arbitrary.
17
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Response: The groundwater treatment goals are the Federal MCLs. These are goals. It
must be clearly understood that failure to achieve a treatment goal is not a violation of
any regulation or standard unless it exceeds a POTW requirement.
/34) Comments 105 and 106. Manganese has a ROD-Specified Remediation Goal. See
comment I 04 regarding clarification of what goals are applicable.
90% Design Comment 105: Table 4-2 -Please add manganese to the list of metals to be
sampled in the effluent.
90% Design Response 105: Manganese was required for NPDES discharge to Bat Fork
Creek but is not a required parameter for the proposed POTW discharge.
90% Design Comment 106: Table 4-2 -Groundwater Treatment System Effluent
Compliance Monitoring -Please revise Table 4-2 to include effluent analyses for the
target compounds cis-1, 2-dichloroethene, nitrobenzene, barium and manganese.
90% Design Response 106: cis-1, 2-dichloroethene and nitrobenzene are included as a
part of the total toxic organics measurement. Barium and manganese were required for
NPDES discharge to Bat Fork Creek but are not a required parameter for the proposed
POTW discharge.
Response: Please see responses to EPA Comment 33 and EPA Comment 4.
/35) Comment 108. Collection of groundwater samples from the recovery wells was not
added to Table 4-3.
90% Design Comment 108: Table 4-3, System Performance Monitoring Program -
Please revise Table 4-3 to include the collection of groundwater samples from recovery
wells RW-1, RW-2, RW-3, RW-4 and RWSF-1 for groundwater quality assessment in
accordance with the Remediation Goal Verification Plan included as Appendix F.
Additionally, please revise Table 4-3 to include the collection of composite recovery well
groundwater samples from composite sampling ports PSP-1, PSP-2, PSP-3 and PSP-4 for
groundwater quality assessment in accordance with the Remediation Goal Verification
Plan included as Appendix F.
90% Design Response 108: Table 4-3 has been revised to be consistent with the
Remediation Goal Verification Plan included as Appendix F.
Response: Quarterly influent groundwater samples will be collected (I) as a composite
from the Shepherd Farm Subsite and (2) prior to treatment by the air stripper.
Calculations based upon flow rates will allow computation of recovery from each subsite.
18
/36)
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Quarterly effluent samples will also be collected. No other recovery well water quality
information will be collected as a part of the performance monitoring program.
Comment 109. Well MW-2 was not added to Table 4-3.
90% Design Comment 109: Table 4-3, System Performance Monitoring Program -As
previous comments have indicated, there does not appear to be any usefulness of
including upgradient background monitor wells in the performance monitor well network.
Sampling of these wells will not help monitor how well the extraction system is achieving
the remedial action objectives (i.e., containing the plume and reducing contaminant
concentrations). Therefore, please replace groundwater monitoring wells MW-21 and
MW-58 with downgradient monitor wells MW-2 and MW-29 as part of the performance
monitor well network. In addition as minimizing the impacts on the environment is also
a remedial action objective, a monitoring program for the wetland areas should also be
prepared and implemented as part of the remedial action to make sure that these areas are
not unduly impacted by the groundwater extraction system.
90% Design Response 109: Table 4-3 has been revised to be consistent with the
Remediation Goal Verification Plan included as Appendix F.
Response: After discussing this comment with the Agency on April 20, it was mutually
agreed between EPA, NCDENR, GE and HSIG that no additional wells would be added
to the performance monitoring network.
/37) Comment 129. Well SWW-9 was not added to the text.
/38)
90% Design Comment 129: Section 3.3.4, Performance Monitoring -Please revise the
third sentence of Section 3.3.4 to state, "The groundwater will be monitored periodically
at monitor wells MW-64, MW-64A and MW-66, residential well SWW-9, and recovery
• well SFRW-1."
90% Design Response 129: Section 3.3.4 has been revised to be consistent with the
Remedial Goals Verification Plan included as Appendix F.
Response: After discussing this comment with the Agency on April 20, it was mutually
agreed between EPA, NCDENR, GE and HSIG that no additional wells would be added
to the performance monitoring network.
Comment 131. Table 4-3 of the Design Report indicates that hydraulic head
measurements will be made in all monitor and recovery wells on a weekly, then monthly
to quarterly basis. It appears that these data will be provided in the quarterly and annual
monitoring reports specified in the Remedial Goal Verification Plan. These data are
important and must be presented in some form.
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/39)
•
90% Design Comment 131: Section 8.3.4, Reporting -It is not explicitly specified that
monitoring data on ground water head, gradient, and flow direction will be included in
the Remedial Action Report. These data will be necessary to determine the impact of the
remedy on the wetlands. It is recommended that these data be included along with all
ground water quality data specified under "Sampling results.for groundwaler".
90% Design Response 131: The Remedial Action Report will not include measurements
of ground water head, gradient, and flow direction. The Remedial Goal Verification Plan,
included as Appendix F, details the biological monitoring and reporting that will
determine the impact of the remedy on the wetlands.
Response: Comment is noted and data will be presented in some form.
Comment 134. Table 4-3 indicates that MW-128 is a performance monitoring well, yet
this is not listed in Appendix A or in the response to the comment.
90% Design Comment 134: The performance monitoring wells given in Appendix A do
not agree with the performance monitoring wells given in Table 4-3. Please clarify this
discrepancy.
90% Design Response 134: Performance monitor wells include MW-3, 8, 12, 12A, 13,
13A, 14, 14A, 15, 16, 16A, 22A, 27, 27A, and 29 at the GE Subsite and MW-64, 64A,
and 66 at the Shepherd Farm Subsite. Table 4-3 and Appendix A have been corrected.
Response: MW-128 is a performance monitoring well.
J40) Comment 138. The use of the Drain Package in MODFLOW does not allow for
recharge of the ground water from a wetlands. While it is true that the wetlands are a
discharge area in the initial situation at the site, if the ground water level falls below the
wetlands, the wetlands could recharge ground water (perhaps "drying up" in the process).
A conceptual model of the physical conditions has not been presented in the modeling
report, so what is actually happening cannot be verified. For example, it is unclear if the
wetlands have a subsurface or surface hydraulic connection with Bat Fork Creek and if
the Creek is supplying water to the wetlands. In that case, it is conceivable that the
wetlands could be a recharge area if the water table drops enough. Use of the River
Package could address that case. The use of the Drain Package based on the
recommendation for wetlands that is found in Applied Groundwaler Modeling (Anderson
and Woessner, 1992) has to be reexamined in light of the more complex physical
situation at the site, in which the wetlands are immediately adjacent to the creek, and
where there are pumping wells very close to the wetlands. Those situations are not
addressed in Applied Groundwaler Modeling. it is recommended that the modeling
report completely discuss the physical situation to verify that the model scenario actually
represents physical reality. A better understanding by the modeler of the physical
20
/ 41)
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situation, or a better description of it in the text, would increase confidence in the results
of the model.
90% Design Comment 138: Section 2.2.3.2, Wetlands -The specification of the
wetlands as internal boundaries using the Drain Package of MODFLOW in the modeling
needs to be reevaluated or defended. The Drain Package sets the height of the wetlands at
a fixed height, with the ·wetlands capable of removing water from the aquifer (if the water
table is above the height of the wetlands) but not capable of adding water to the aquifer (if
the water table is below the height of the wetlands). This specification of the wetlands at
a fixed height appears to be 'forcing' the head in the wetland to be at a constant head, i.e.,
the head in the wetland will not decrease despite the pumping occurring next to the
wetland. Thus, the simulated water table drawdown, as shown in Figure 4-3, would be
incorrectly constrained so as to not affect the wetlands. This figure shows that drawdown
would not occur in the large wetland to the west of Bat Fork Creek. The improper use of
the Drain Package for wetlands occurs too frequently in modeling, and its use here must
be defended (the River Package is often more proper to use). It is recommended that
justification be included for the use of the Drain Package, the accuracy of the resulting
head values in the large wetland, and the conclusion that drawdown will not occur in the
wetland.
90% Design Response 138: The reviewer has a misunderstanding of head-dependent
boundaries in MODFLOW. No change to the model or model report was made.
Wetlands are a head-dependent boundary and are typically simulated in MOD FLOW
using the Drain Package or Evapotranspiration Package, not the River Package as stated
by the reviewer. The wetlands at the site are discharge wetlands. As noted in Applied
Groundwater Modeling (Anderson and Woessner, 1992) springs and seeps are normally
simulated with the Drain Package. When the water table intersects or rises above the land
surface, groundwater discharges into the wetland and the water is removed from the
system. When the water table is below land surface, no water is removed from the
system. Discharge wetlands can only remove water, not provide water, and therefore
cannot "constrain" heads in stressed conditions. Contrary to the reviewer's opinion, it is
the River Package, not the Drain Package that has the ability to"constrain" the magnitude
or extent of drawdown because it can add water to the system. All things being equal, a
simulation with the Drain Package would show more drawdown than a simulation with
the River Package.
Response: The physical setting of the discharge wetlands is simple. The wetlands are
wet for one reason -groundwater discharges into them. The groundwater modeling
report will be revised to clearly state that there is no significant surface water component
associated with the discharge wetlands.
Comment 144. It is now stated that there will be a 51 % reduction in flow to the bunched
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arrowhead wetlands and to the wetlands just west of Bat Fork Creek, with no significant
effect on head in these wetlands. Variations in saturated thickness and hydraulic
conductivity do affect or cause variations in drawdown, but many assumptions have been
made in the model about assigning values to saturated thickness and hydraulic
conductivity. The head and conditions in the wetlands will need to be monitored to verify
the predictions of the model, since reducing the flow into the wetlands by half could have
negative effects. The Ecological Evaluation of the Potential Effects of Remedial
Groundwater Extraction on Wetlands and Streams at the General Electric/Shepherd
Farm Superfund Site indicates that the proposed rate of ground water extraction ( causing
a 51 % reduction in flow to the bunched arrowhead wetlands) "may cause irreparable
harm to the population of bunched arrowhead' (p. 14 of that report).
90% Design Comment 144: Section 4, Proposed Remedial Design -The text and Table
4-1 indicate that the simulated flow reductions at the wetlands are 3% to 65%, with the
greatest impact in the large wetland (to the west of Bat Fork Creek). However, Figure 4-3
appears to indicate that little drawdown (less than I foot) will occur in most of this large
wetland, even though there are greater drawdowns immediately adjacent to the wetland.
Physically, the wetland might serve as a discharge area for a larger portion of the drainage
basin than that affected by the pumping wells, and it would be expected that head
gradients would be steep between the wetland and the region around the pumping wells
as water from the wetland is drawn into the extraction wells. However, a large reduction
in flow into the wetland (because of interception of the discharging ground water by the
AGRS) could decrease the hydraulic heads in the wetland. It is recommended to discuss
why the large reduction in flow into the wetland has a minimal effect on hydraulic heads
in this wetland. It is also recommended to include a discussion of the potential impacts of
decreased flow into the wetlands on their overall status. In addition, the use of the Drain
Package in MODFLOW does not allow for the movement of water from the wetland
towards the extraction wells, thus the numerical model cannot match the physical model
of what happens in the wetlands. It is recommended to clarify this potential discrepancy.
90% Design Response 144: The drawdown variation is strongly influenced by the
transmissivity of the aquifer which is a function of the saturated thickness and hydraulic
conductivity, both of which vary across the site. This will be stated in the report.
Appendix H covers the effect of the drawdown on the wetlands. A biological assessment
has been completed and is included in Appendix F. Refer to response to comment 138
for a discussion of the use of the Drain Package in MODFLOW.
Response: The groundwater conditions in the bunched arrowhead habitat are, and will
continue to be, monitored. In addition, the remedial design presents a long-term
biological monitoring program.
/42) Comment 147. The response indicates that in the future, simulation results may be
compared to monitoring data to improve the understanding of the hydrogeologic system.
This is strongly encouraged; periodic monitoring reports should include comparison of
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observations to what has been predicted by the modeling. Any discrepancies will need to
be explained.
90% Design Comment 147: Section 5, Transient Response -It is unclear why an
extraction rate of 25 gpm was used to model the longer-term transient response rather
than the 65 gpm that is proposed as the selected design extraction rate. The reasons and
implications of this should be discussed.
90% Design Response 147: The purposes of the transient simulations were(!) to gain a
general understanding of the aquifer system dynamics, (2) to determine the amount of
potential AGRS drawdown that has been realized at the time of the Final RD, and (3) to
determine the rate at which drawdown will be realized in the future with the proposed
RD.
The analysis shows that 90% of the AGRS steady-state drawdown is realized after three
years of pumping. This type of analysis shows that most of the AGRS drawdown has
been realized at this point in time. This conclusion is important in evaluating the current
and potential future impact of groundwater extraction on the bunched arrowhead habitat
which is discussed in Appendix H.
An additional transient simulation has been completed and is included in the report. The
new simulation assumes that the proposed final system is installed in September 2000. In
the future, the results of this simulation may be compared to monitoring data to expand
on the understanding of the hydrogeologic system.
Response: Groundwater model predictions of drawdown will be compared to observed
conditions as part of the five year review process. Significant differences will be
described.
/43) Comment 161. We recommend that sampling of the five composite sampling ports
shown in the design drawings be retained as part of the performance monitoring network
and be sampled at the same frequency as the performance monitor wells. This is
especially important considering that no influent sampling is to be conducted during the
remedial action. Not only can the composite port sampling provide information on the
average concentrations recovered from large portions of the plume, they can provide
estimates of contaminant mass removal from these regions. This information can then be
used to better assess how well remediation is progressing in these particular regions and
whether revisions to the recovery well pumping scheme may be advantageous. Sampling
from just the performance monitor wells will not provide this information as the
performance well network only provides representative data, not comprehensive data, for
the site. In addition, without any influent sampling or composite port sampling, we will
have no data indicating the characteristics of the water going into the treatment plant.
Given this composite port sampling, we also recommend that SWW9 (or a new monitor
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well located in its place) replace R WSF 1 in the performance well network, especially
considering the proposed location ofRWSFl. First, a performance monitor well is
needed in the "hot zone" of the Shepherd Farm plume and SWW9 is the "hottest" well.
Second, with the water from R WSF 1 being included in a composite sampling port
sample, sampling of the this well individually is no longer needed.
90% Design Comment 161: The designation of the composite sampling point to
monitor RW-5, RW-6 and RW-7 needs to be corrected.
90% Design Response 161: The discussion on the composite sample ports has been
deleted; the sample ports are not pertinent to the periodic performance monitoring.
Response: Influent samples will be collected quarterly to determine VOC mass removal
from each subsite. This information will be used to assess how well remediation is
progressing at each subsite.
After discussing the comment to sample additional wells at the Shepherd Farm Subsite
with the Agency on April 20, it was mutually agreed between EPA, NCDENR, GE and
HSIG that no adaitional wells would be added to the performance sampling network.
/44) Comment 180. As commented previously, contaminants will not be eliminated from
the RTC list for any performance monitoring well until it is shown that the contaminant is
below its corresponding ROD remediation goal throughout the whole subsite. Because
groundwater contaminants will be continuously moving toward the recovery wells, it is
quite possible that a particular contaminant may not show up in a particular performance
monitor well for a year or more. Likewise, it is possible that a particular contaminant
may disappear from a monitor well for a year or more and then reappear later. As long as
a contaminant is a concern at a subsite, all the performance monitor wells should be
monitored for this contaminant. It should also be noted that to show that a contaminant is
below its corresponding ROD remediation goal throughout a whole subsite, extensively
monitoring beyond just the performance monitor wells will be needed.
90% Design Comment 180: Section 2.3, Monitoring Parameters -Please revise Section
2.3 to be consistent with NC DENR Division of Water Quality, Groundwater Section
protocols. In summary, quarterly sampling of all performance wells shall continue until
four co_nsecutive quarterly groundwater sampling events indicate that the remediation
target compounds (RTCs) meet the corresponding ROD remediation goals. If an
individual groundwater monitoring well achieves the specified ROD remediation goals
prior to the other groundwater monitoring wells, annual sampling of the groundwater
monitoring well shall commence until such time as all performance monitoring wells
achieve the specified ROD remediation goals for four consecutive quarterly groundwater
sampling events. Upon achieving the specified ROD remediation goals at all
performance monitoring wells, GE shall seek written approval from the US EPA and the
NC DENR to discontinue the groundwater extraction system. Once written approval has
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been received from the US EPA and the NC DENR, GE may discontinue the groundwater
extraction system. At this point, quarterly groundwater sampling shall resume at all
performance monitoring wells until GE can demonstrate that the specified ROD
remediation goals have been maintained for four consecutive quarterly groundwater
sampling events. If GE cannot make this demonstration to the satisfaction of the US EPA
and the NC DENR, GE shall evaluate additional groundwater treatment options in order
to meet the specified ROD remediation goals.
90% Design Response 180: The text has been revised to state the following.
Performance wells at both the GE and Shepherd Farm Subsites will be sampled quarterly
for the first three years, semi-annually for the subsequent two years, and annually
thereafter. Surface water and sediment stations and the residential well network will be
sampled annually. Treated water that is being used as process water at the GE facility is
subject to the testing requirements of the POTW. The POTW Industrial User Permit
requires daily flow measurements; four samples per month for BOD, TSS, temperature,
pH, COD, ammonia(N), and oil/grease; monthly samples for cadmium, chromium,
copper, cyanide, lead, mercury, nickel, silver, and zinc; quarterly samples for aluminum,
arsenic, molybdenum, and selenium; and bi-annual sampling for total toxic organics
(TTO) which includes VOCs (EPA 624), SVOCs(EPA 625), and PCBs/pesticides(EPA
608). Effluent air from the groundwater treatment process will be sampled at the same
frequency as the performance network. Recovery wells and composite sampling ports
will be sampled at the discretion of GE and at five year intervals.
Additionally, the text states that the Remediation Target Compounds will be sampled for
at least four consecutive temporal measurements. If monitoring points within a subsite or
a distinct zone of a subsite indicate a given RTC is consistently below its corresponding
ROD Remediation Goal, GE will submit a request to the Agency that the targeted RTC be
removed from the list of monitored parameters in subsequent periodic sampling and
analysis efforts for those applicable monitoring points.
During the 5-year sampling intervals, collected samples will be analyzed for the entire
RTC list. In the case that the 5-year sampling event detects a previously removed
parameter, the parameter will be added to the analysis performed on performance
monitoring wells within the affected zone.
Response: It is agreed that the sample frequency for a particular target compound may
differ at the two subsites. GE proposes to sample quarterly for all parameters for the first
year at all performance monitor wells. If a parameter is not detected above the
remediation goal at a subsite for four consecutive quarters within the first three years of
operation, thenthe frequency for that parameter will be changed to annual. Otherwise,
the sample frequency will follow the plan presented in Table 2-3 of Appendix F. GE
acknowledges that any proposed change in the performance monitoring plan must be
approved in advance by the Agency.
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✓ 45)
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The final design comment describes the process of eliminating a parameter from the RTC
list. A distinction must be made between performance monitoring and exit monitoring.
The change in sample frequency proposed in the remedial design is only applicable to the
performance monitoring, not the exit monitoring. GE is not requesting that a parameter
be eliminated from the RTC list, only a change in the sample frequency on an individual
parameter basis and individual well basis. Exit monitoring would include the same 13
target compounds that will be analyzed quarterly during the first year of operation.
Comment 182. Contrary to the response, the RSVP still does not discuss, nor does it
provide a schedule for, water level measurements and recovery well flow measurements.
This plan should be revised accordingly.
90% Design Comment 182: Pg. 2-7, Section 2.4.1, Performance Monitoring -Because
of the long time needed to achieve groundwater flow equilibrium at this site (three years),
we recommend that this RGVP be revised to include the schedule originally proposed for
performance sampling. In particular:
• All performance monitor wells should be sampled quarterly for the first three years,
semiannually for the next two years, and annually thereafter.
• All surface water/sediment sampling should be conducted at the s_ame frequency as
the performance monitor wells.
• Hydraulic head measurements should be collected from all recovery wells and all the
monitor wells at the site (not just performance monitor wells) at the same time
groundwater samples are collected from the performance monitoring wells.
• Treatment system performance monitoring should be conducted as indicated in Table
4-3 in the main report.
• Flow measurements should be collected at the same time effluent samples are
collected.
In addition, please explain what is meant by "non-operating Recovery Wells." All the
recovery wells will be operating from the start.
90% Design Response 182: Section 2.3 of the RGVP has been revised to address these
comments. Additionally, please refer to the response to comment 180.
Response: A new Section 2.2.2 Site-wide Monitoring has been added to incorporate
these comments. The previous Section 2.2.2 Ecological Monitoring is now Section 2.2.3.
)46) Comment 192. Report still states 90 days instead of 60 as the response indicates.
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90% Design Comment 192: Pg. 3-l, Section 3, RGVP Deliverables and Submission
Schedule - A report will be submitted after any sampling event occurs. A year is a long
time to go without reporting how well a system is performing, especially if there are any
performance problems.· These reports do not have to be elaborate. A letter report
presenting the measurement results and any conclusions reached based on the results
should suffice. Elaborate reports providing detailed analyses of all the performance
monitoring results collected during any particular year can then be submitted annually.
These would be due within 60, not 90 days, after the completion of the last groundwater
sampling event for the year.
90% Design Response 192: The text has been revised to include quarterly reports
submitted within 60 days after the completion of the last groundwater sampling event.
Response: Reporting of third-party validated sample results is not feasible within 60
days. If measurement results are due within 60 days, GE will report non-validated
results. The subsequent report will then present the previous validated results and the
current non-validated results.
/ 47) Comment 195. Attachment I (Sampling and Analysis Plan) to the Remedial Goal
Verification Plan does contain a Table 1-5 and a Table 3-1. The revisions still need to be
made.
90% Design Comment 195: Figure 2-2, Shepherd Farm Subsite Monitoring Points -
Please revise Figure 2-2 to include all groundwater-monitoring points, including those to
be added as a result of revisions to Table 2-2.
90% Design Response 195: The figure has been revised.
Response: No response can be given for this unclear comment. The listed Comment
195 does not reference Attachment I, Table 1-5, or Table 3-1. Comment 196 did refer to
a Table 1-5 and Table 3-1. However, both of these tables that occur in the Final Design
for Groundwater -Appendix F -Attachment I have been updated since the 90% Design.
Comment 205. The text was not revised as claimed in the response.
90% Design Comment 205: Section 1.1, Objectives -Please revise the second sentence
of Section I. I to state, "The SAP is consistent with the content criteria specified in the
Consent Decree Statement of Work (SOW) and includes sampling objectives, locations,
frequency, equipment and procedures, handling, and analyses."
90% Design Response 205: Text revised as requested.
Response: The acronym used in the attachment to the appendix to the main report will be
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spelled out as requested.
/49) Comment 206. The text was not revised as claimed in the response.
90% Design Comment 206: Section 1.1, Objectives -Please revise the first and second
sentences of the second paragraph of Section 1.1 to state, "Remedial action (RA) field
sampling will be performed as a part of the Remediation Goal Verification Plan (RGVP)
and to assess containment of the contaminated groundwater. Additionally, treatment
system effluent sampling will be performed to monitor system performance and meet
publicly operated treatment works (POTW) and National Pollutant Discharge
Elimination System (NP DES) requirements."
90% Design Response 206: Text revised as requested.
Response: Text requires no revision. The acronym RA was defined in the first
paragraph of Section 1.1. The acronym POTW is defined in the listed text. The reference
to National Pollutant Discharge Elimination System requirements was removed because
it is no longer applicable.
/50) Comments 217 to 219. No response is given for these comments.
90% Design Comment 217: Table 1-2, Summary of Field Activities for Remedial
Action Activities -Please revise the RGVP Sample Design entry for Effluent to state,
"Quarterly when discharging except metals which are monthly." Additionally, please
revise the Purpose entry for Effluent to state, "Assess treatment system performance and
POTWINPDES compliance."
90% Design Comment 218: Table 1-3, Estimated Numbers of Samples -Please revise
the heading in Table 1-3 to state "Periodic RGVP Monitoring" and the effluent location to
state, "POTWINPDES Outfall."
90% Design Comment 219: Table 1-3, Estimated Numbers of Samples -Please revise
Table 1-3 to indicate that the periodic and five year monitoring events will consist of
sampJe.s from twenty GE Subsite wells, four Shepherd Farm wells, five recovery wells,
four composite recovery wells, three residential wells, three surface water sample
locations and three sediment sample locations. Additionally, please revise Table 1-3 to
include the collection of semiannual air emission samples.
90% Design Response: None provided.
Response: Tables 1-2 and 1-3 were updated in the I 00% Design to incorporate changes
in the RGVP and process train methodology. Not all aspects of each 90% Design
Comment are still applicable.
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./51)
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Comment 263. The replacement sentence is an incomplete sentence. Please revise.
90% Design Comment 263: Pg. 1-1, Section I. I -The last sentence on this page states
that "The only remaining natural location in North Carolina that contains the bunched
arrowhead is near the site." Yet, in Section 2.1 -three are indicated. Which is correct?
90% Design Response 263: The text has been revised to state that the only natural
locations in North Carolin\! are in Henderson County. It is not clear at this time, exactly
where all locations are in Henderson County. The Asheville office of the US F&W was
contacted for clarification, but could not be reached at the time of this response.
Response: The comment is unclear. The text in Section 1.1 of Appendix H in the 90%
Design stated, "The only remaining natural location in North Carolina that contains the
bunched arrowhead is near the site. A significant population exists on GE property
situated between the GE and Shepherd Farm Subsites (see Figures 1-1, 1-2, and 1-3)."
The text in Section I. I of Appendix Hin the 100% Design was revised to state, "A
natural bunched arrowhead population exists on GE property situated between the GE
and Shepherd Farm Subsites (see Figures 1-1, 1-2, and 1-3)." This sentence is not an
incomplete sentence.
SPECIFIC COMMENTS -Main Report
Note: The following references to "text revised as requested" refer to the pending revised final
design.
/52) Comment: pg. 3-5, Section 3.2.4.2 Groundwater -Contrary to what the text states,
VOCs were detected in two of the ten residential wells sampled (SWW9 and SWWI0) in
1998 and 1999. Please revise accordingly.
Response: The paragraph has been revised to state, "Water quality of the groundwater
from IO residential wells is monitored on an annual basis. Table 3-5 lists the results of
the annual residential well sampling. Similar to 1997, the 1998 and 1999 data shows that
no VOCs or SVOC were detected in any of the 8 offsite wells. PCE has been found in
SWW-9 and SWW-10 at the Shepherd Farm Subsite. These wells are not currently used
by the residents. Note that quantitation limits of some compounds are above the
respective remediation goal for that compound. Water quality of the groundwater will
continue to be monitored from five residential wells (WW3, WWI 7, WW34, WW73, and
WW82).
/23) Comment: pg. 4-1, Section 4.1 Groundwater Extraction -The extraction rate proposed
is 60 gpm, not 65 gpm as indicated in this section. Please revise.
Response: Text revised as requested pending final results of groundwater modeling.
29
/54)
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Comment: pg. 5-1, Section 5.1 Groundwater Extraction and Treatment at the Shepherd
Farm Subsite -Contrary to what the text states, the PCE concentration is not currently
<I 00 ppb. The most recent sampling (September 1999) at SWW9 indicated a PCE
concentration of 112 ppb. Please revise accordingly.
Response: Text has been revised as indicated in the response to EPA Comment 25.
/ 55) Comment: pg. 5-1, Section 5.1.1 Recovery System -Contrary to what the text states,
the recovery wells at the Shepherd Farm Subsite will not be similar to the GE Subsite
recovery wells. The GE Subsite wells will be screened 20 feet into bedrock whereas the
Shepherd Farm Subsite wells will only be screened to the bottom of the saprolite. This is
an important distinction which needs to be better presented, especially in the design
specifications and drawings. In addition, it is recommended that the recovery wells at
the Shepherd Farm Subsite be constructed with a sump so that the pump may be placed
lower in the well as discussed previously.
I 56)
Response: As the reviewer has discerned, Shepherd Farm Subsite recovery wells will be
similar to the GE Subsite recovery wells ( e.g. stainless steel casings, constructed in a
similar manner) but the Shepherd Farm Subsite recovery wells will not be screened into
the bedrock. This is the identical text that appeared in the Pre-Final (90%) Design for
Groundwater with no comment given. Additonal text has been included in Section 5.1.1
to add clarity. Please refer to response to EPA Comment 7 for a discussion of the sump.
Comment: pg. 6-1, Section 6 Schedule And Estimated Cost -Tables 6-1, 6-2, and 6-3
are absent from the document. Please revise accordingly.
Response: Tables 6-1, 6-2, an 6-3 have been included to the document.
}57) Comment: Table 4-1 -The ROD remediation goals for PCE and chloroform are missing
from this table. Please revise accordingly.
Response: Table 4-1 was revised to include the remediation goals for chloroform and
PCE.
SPECIFIC COMMENTS -RA Work Plan
/58) Comment: Table 4-3 -In addition, to be complete, a reference to Appendix F should be
provided in this table to indicate all the other performance monitoring activities to be
conducted (i.e., biological monitoring activities).
Response: Table 4-3 will include a reference to Appendix F.
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/59) Comment: pg. 2-1, Section 2.1.1 Nature and Extent of Contamination -The reference
to Table 2-4 should reference Table 2-1. Please revise.
Response: The reference was changed as requested.
/ 60) Comment: pg. 2-2, Section 2.1.2 Nature and Extent of Contamination -There are two
Tables 2-2 in this work plan. The second one is from the Pre-Final RA Work Plan and
should be removed. In addition, according to the design report, the dissolved PCE mass
was estimated to be 2.2 pounds, not 6.5 pounds. Please revise.
Response: The second Table 2-2 was removed from the work plan. In addition, there is
no reference to PCE mass in Section 2.1.2. The first sentence of the second paragraph in
Section 2.2.1 was changed to state, " In July 1997, the dissolved VOC mass was
estimated to be 2.2 pounds where PCE comprises 100% of the total VOC mass."
SPECIFIC COMMENTS -Appendix E: Numerical Groundwater Model Report
161) Comment: There are remaining concerns with the Numerical Groundwater Flow Model
MODFLOW regarding: (I) use of the Drain package for the wetlands; (2) use and
placement of the No-flow boundaries, which results in the model domain being a
"bathtub" (i.e., the "bathtub" means that there is no flow in or out the model boundaries:
the only inflow is from recharge and the river, and the only outflow is to the river, drains,
and wells. This is often not the case when boundaries are assumed to mimic surface
topography); (3) the thoroughness of the sensitivity analysis (especially with respect to
the high conductivity values assumed for the wetlands region); (4) whether enough head
values were determined throughout most of the model domain for calibration; and (5) the
high conductivity values used in much of the river and wetland areas. In any case, the
model results should be verified by sufficient monitoring of head throughout critical areas
such as the Bunched Arrowhead wetlands and the wetlands immediately to the west of
Bat Fork Creek.
Response: As stated previously, the groundwater and biological conditions at the
bunched arrowhead habitat will be monitored.
J 62) Comment: pg. 6-2, Section 6 Conclusions -Please delete the last two sentences in this
section. Monitoring should continue until the most extreme conditions possible have
been encountered, and the habitat still was able to survive without any mitigation.
Response: The sentence will be deleted as requested.
/63) Comment: Section 4. PROPOSED REMEDIAL DESIGN (Second paragraph, third
sentence). The sentence should read " ... eight additionally proposed extraction wells."
31
/ 64)
•
Response: The text will be revised pending final groundwater modeling results.
Comment: Figure 3-3. The title of Figure 3-3 is given as simulated head in saprolite
(model layer 2). The title should refer to the shallow bedrock instead of the saprolite.
Response: The title of Figure 3-3 was revised as requested.
SPECIFIC COMMENTS -Appendix F: Remediation Goal Verification Plan
j 65) Comment: pg. 2-1, Section 2.1 Performance Monitoring Network -Figure 2-3 shows
four surface water/sediment sampling locations and needs to be revised to indicate the
three stations to be included in the performance monitoring network.
Response: Please refer to EPA Comment 29.
/66) Comment: pg. 2-3, Section 2.1.2 Surface Water and Sediment Monitoring Stations -
The last sentence of this section is confusing. Please explain what is meant by the
statement that the surface water and sediment stations "are mainly targeted for contingent
sampling of surface water and sediment". It is our understanding that monitoring at these
stations is to be on a regular schedule. What contingency?
Response: The last sentence of this paragraph has been deleted.
f67) Comment: pg. 2-7; Section 2.4.1 Performance Monitoring; Table 2-4-The treated
effiuent water will be analyzed for the RTCs to ensure performance of the treatment
system and reported to the Agencies. The POTW required monitoring does not need to
be reported.
Response: Comment noted. This comment is in apparent contradiction to NC DENR
Comment 40. Performance monitoring will be consistent to the response to EPA
Comment 4.
/68) Comment: pg. 3-1, Section 3.1 Quarterly Monitoring Reports -How is TVOC mass
removed going to be estimated if no influent sampling is conducted? Add influent
sampling to Table 2-3 and associated text.
Response: Influent sampling will be added to the RGVP. Please refer to EPA Comment
35.
/49) Comment: pg. 3-1, Section 3.2 Annual Monitoring Reports -Delete the bullet referring
to recovery well operation status.
Response: Text has been revised as requested.
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✓70) Comment: This report contains many good recommendations for monitoring the
hydrologic conditions in the various wetlands. It is recommended that these monitoring
efforts be implemented (it is good that ~hey do appear to have been added to the Remedial
Goal Verification Plan Sampling and Analysis Plan, i.e., Attachment 1 ).
Response: Comment is noted.
SPECIFIC COMMENTS -Appendix F Attachment l: Remediation Goal Verification Field
Sampling and Analysis Plan
✓71) Comment: pg. 3-3, Section 3.2.1 Monitoring Schedule -Monitoring of hydrological
parameters is to be conducted semi-monthly as indicated in Table 3-2, not bi-monthly as
the text states. Please revise .
. Response: According to Webster's Dictionary, a definition ofbi-monthly is occurring
twice a month. Also according to Webster's Dictionary, a definition of semi-monthly is
occurring or issued twice a month. Monitoring of hydrological will be conducted twice a
month as stated in Section 3.2.1 and in Table 3-2. There is not an inconsistency and the
text will not be changed.
/72) Comment: pg. 3-3, Section 3.2.1 Monitoring Schedule -Does GE have a basis of
comparison for Figure 3-1? Will future· monitoring be compared to the initial baseline to
be conducted following RA start-up?
Response: No basis of comparison exists. The AGRS system has been pumping since
1998 therefore an initial baseline ecological monitoring is not possible unless pumpage is
temporarily halted. The ecological monitoring will only be able to document changes in
vegetation.
/13) Comment: pg. 3-3, Section 3.2.2 Hydrology -This section and all subsequent sections
referring to activities to be included in the ecological monitoring plan need to be revised
to be more definitive with respect to the proposed monitoring plan. For instance, all
statements indicating things that "should" be conducted should be revised to indicate that
they "will" be conducted. In addition, the number and locations of all piezometers and
staff gages should be specified.
Response: Text has been revised to be more definitive. Number and locations of
piezometers and staff gauges is listed.
-/74) Comment: pg. 3-12, Section 3.2.7.5 Creek-It appears that the only location at which
flow will be monitored is the weir location. This weir is located south of the Large
Settlement Pond (which provides recharge to groundwater) and likely will show very
little impact from the groundwater reco".'ery system. We recommend that two additional
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stations be established for flow monitoring. One station should be located near the
middle of the large wetland located east of Bat Fork Creek to monitor the reduction in
flow in the area most sensitive to a reduction in groundwater recharge. The other station
should be located just downstream of the GE subsite, where the Stream 2 surface
water/sediment sampling is conducted, to monitor the total reduction in flow to Bat Fork
Creek created by the recovery well system.
Response: The existing weir has been selected as the measurement point for flow in Bat
Fork Creek because of the accuracy and precision of its measurements. HSI GeoTrans
has collected historical .data from this point so that changes in flow can be measured.
Without installation of additional weirs 'or Parshall flumes, the precision of flow
measurements at the two proposed locations would not allow for accurate interpretations
of impacts from the groundwater recovery system. We do not propose to include any
additional flow measurement locations as the permitting and costs are not justified by the
quality of the possible data. Additionally, please note that as EPA Comments 139 and
148 on the Pre-Final (90%) Design for Groundwater stated, "the large wetland on the
'east side of Bat Fork Creek' is actually' on the west side of Bat Fork Creek." This
oversight should be corrected in future correspondence.
SPECIFIC COMMENTS -Appendix F Attachment 2: Ecological Evaluation of the
Potential Effects of ... Streams
/75) Comment: This evaluation appears to be a critique of Dr. Newberry's latest study. On
page 14 and throughout the remainder of the report, the evaluation indicates that the
proposed rate of groundwater extraction may cause irreparable harm to the population of
bunched arrowhead. If the groundwater design was based, in part, on this study, then
why is the 77 gpm pumping rate still being proposed?
Response: Please refer to the response to the Fish and Wildlife Comments.
SPECIFIC COMMENTS -Appendix G: Design Calculations
/76) Comment: Effluent Transfer Pump Design Calculations -For the sake of consistency
and clarity, these calculations should be revised using the actual design flow (presently 77
gpm), not 82.5 gpm.
Response: For the sake of consistency and clarity, these calculations will be revised once
the actual design flow has been determined. It is unlikely that a 6. 7% reduction in flow
(from 82.5 gpm to 77 gpm) will change the design of this pump.
Comment: The supporting information for the design (calculations, vendor info, etc.)
supports the selection of the equipment specified. Comments on the discharge were
34
• •
related to how the potential RO system would be implemented (triggers, design criteria,
etc.) and how the storage tanks would be used in the discharge scenario. To address these
concerns a significant change has been made in that the system will now have no direct
surface water discharge. A flow diagram provided in Appendix G shows that water from
the treatment system will be directed to the existing storage tanks. From the storage
tanks the water would either be used for processing or discharged to the POTW. Actually
this is a much better option than before because it will be more reliable in the long-term.
Below are some comments related to this plan:
a) Since the remediation system will not have a surface water discharge, one could
assume that an NPDES permit is no longer needed. In the permitting
requirements section of the report an NPDES permit is not identified, however,
hasn't GE been discharging under an NPDES permit and don't they still have one
in place. Please confirm the status of the permit, if one exists, and if so, does GE
plan on keeping it. If GE plans on keeping it, why?
b) Drawing number 5 (and others) continue to show a surface water outfall.
Drawing 5 shows a locked valve which would prevent discharge to the outfall,
directing the flow to the tanks. EPA may consider that an option would be to put
in a blind flange instead of the valve, making it very difficult to discharge to the
outfall.
c) In response number 4 it states the storage tanks are 30,000 gallons each and gives
the tank dimensions as 12 feet in diameter and 5 feet high. These dimensions
would result in a 4,227 gallon tank. The dimensions appear to be incorrect
because the drawings, and other references show two 30,000 gallon tanks. It is
not critical that we know the exact dimensions, but it is important to understand if
the tanks are 4,200 or 30,000 gallon capacity. If the tanks have a 4200 gallon
capacity, this could result in problems managing the flow rates from the treatment
system, depending on the tank piping sizes and configurations.
d) The tanks have not been sized using any design criteria related to the treatment
system. They are existing tanks that are being put into service for this purpose.
As long as the 30,000 gailon capacity is correct, they would be sufficient.
Response:
a) GE will maintain its NPDES permit for other non-Superfund related discharges to
Bat Fork Creek.
b) Comment noted.
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•
c) Tanks are 30,000 gallon tanks. Detailed information regarding the tanks will be
included in Appendix G.
d) Tanks are 30,000 gallon tanks.
SPECIFIC COMMENTS -Appendix H: Hydrologic Study of the Bunched Arrowhead
Habitat
J78) Comment: Please correct the table of contents.
Response: Text has been revised.
36
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Fish and Wildlife Service Comments: /
Despite Service and USEPA efforts to convey the importance of the remedial objective of
avoiding impacts to habitat supporting the federally listed endangered bunched
arrowhead, Sagittaria fascicu/ata, the documents and appendices fail to present a design
to meet this objective. In fact, the proposed design is predicted to impact the head and
flow to wetlands supporting this endangered plant; this is not acceptable.
Along with extracting/treating contaminated groundwater (a remedial objective the
Service has previously endorsed), the overall remedy includes an objective, as stated on
page 1-5 of the May I 999 60% Design Report, of" ... avoidance of adverse impacts to
wetlands, including a wetland containing the Federally-endangered plant species known
as the bunched arrowhead." While much work on the bunched arrowhead has been
incorporated, the explicit objective of protecting the bunched arrowhead does not appear
in the current document's listing of remedial objectives (absent from page 1-5 and 1-6); it
should be added and re-emphasized.
Despite the absence of the stated objective, the project consultants have clearly done
groundwater monitoring, groundwater modeling, a hydro logic assessment of the bunched
arrowhead habitat and proposed a bunched arrowhead habitat monitoring plan in an
attempt to work toward this goal. While the model development appears sound, its
applications are incomplete. The model predicts impacts to wetlands upon startup, and
predicts that steady state impacts will not be known for three years. This information
should have led to a redesign of the proposed extraction system. We suggest three
significant modifications of model application. First, the model should be run with a
condition of zero predicted drawdown rather than 0.5 feet; it should also seek to minimize
any reductions in flow. By definition, the 0.5 feet drawdown is a level considered to put
· the species at risk, which is wha\ we are striving to avoid. Model scenarios for zero
predicted drawdown are a necessary part of remedial action planning for this site.
Second, the model should be run to predict ultimate drawdown through longer modeling
runs (i.e., if modeling indicates three years to steady state, then run the model out three
years to predict the full impacts. Third, and most significantly, the model should be used
to fit various potential extraction designs to model runs that predict no impact to
wetlands, either through lower pumping rates, seasonally-variable pumping rates, or
alternate extraction well locations. There are myriad extraction designs that could be
developed and tested; the model projections indicate a need to revisit other designs.
With the inherent uncertainties in models and the limited model fitting to varying stress
periods in this case, the proposed biological monitoring of the habitat is an appropriate
safeguard. It should not, however, replace a design that is envisioned to be protective
from the outset.
We previously forwarded a US Geological Survey recommendation for use of
37
• •
telemetered wells to facilitate verification monitoring. We believe the telemetered wells
would help with monitoring as well as an adaptive extraction schedule, whereby
withdrawals for treatment were directed by a robust understanding of the near-real-time
water budget. This approach should be re-evaluated.
Response: The Fish and Wildlife Service has stated that the predicted impact to the
groundwater flow system in the bunched arrowhead habitat is unacceptable. Numerous
additional groundwater model simulations have been performed, at the direction of the
Agency, to develop an alternative groundwater extraction scenario that causes no impact
to the bunched arrowhead ( defined by the Agency as less than O. l foot of drawdown and
less than 25 % reduction in groundwater baseflow into the habitat). Alternative
groundwater remediation designs are presented in Attachment l. Note that all model
predictions are steady-state not transient, thus the full drawdown and baseflow reduction
for that particular scenario are presented.
The explicit objective of protecting the bunched arrowhead will be added to Section
l.2. l. Text will added that states "the remedy must be protective of the bunched
arrowhead, an endangered species, to be consistent with the endangered species act, an
ARAR."
The usefulness of telemetered wells was reevaluated. After additional consideration, it
was determined that it would be impractical to use real-time data to manage groundwater
extraction schedules. Basic hydraulic principles, such as the Theis equation, demonstrate
that there will be a time lag between a change in pumping conditions at the site and the
water level in an observation well by the bunched arrowhead habitat. Groundwater
modeling results indicate that the time lag could be as much as three years. Water levels
respond more quickly to changes in rainfall conditions, as demonstrated in Figure 5-3 of
Appendix H. The transient overlap of responses due to well extraction, rainfall, and other
stresses results in a system that would be impractical to manage on a real-time basis.
Alternatively, a detailed hydrologic and biologic monitoring plan has been proposed.
The results will be provided on a regular basis to the Agency. Any change in the
extraction rate would be approved by the Agency.
38
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North Carolina Department of Environment and Natural Resources Comments
FINAL DESIGN FOR GROUNDWATER
Table of Contents
/comment 1:
Response:
Several discrepancies were noted during the review of the Table of Contents.
Please correct these oversights.
a. The title for Section 5 should be given as "Groundwater Remedial Action
at the Shepherd Farm Subsite."
b.
C.
d.
e.
f.
g.
The title of Appendix C should be given as "AGRS Equipment."
The title for Appendix E should be given as "Numerical Groundwater
Flow Model."
' The title for Figure 1-3 should be given as "Location of the Shepherd
Farm Subsite" in the List of Figures.
The title for Figure 4-2 should be given as "Simulated Water Table
Drawdown from 60 gpm Extraction at GE Subsite and 17 gpm Extraction
at the Shepherd Farm Subsite" in the List of Figures.
The title for Table 1-1 should be given as "Remediation Goals for RTC's
in Groundwater" in the List of Tables.
The title for Table 3-4 should be given as "Monthly AGRS Effluent
Monitoring Data for Metals" in the List of Tables.
Comment la, I b, and le are redundant to EPA Comment 9. The Table of
Contents has been revised as requested. To maintain consistency Figure 1-3 has
been renamed Shepherd Farm Subsite Features.
Section 1.2.1 Remedial Objectives
/comment 2: Please revise item 6 of the first paragraph to state, "Reduce the
concentration of hazardous substances, pollutants, and contaminants in
surface water, groundwater, and surface and subsurface soil within the
site to levels specified by the remediation goals."
90% Design Stated: Reduce the concentration of hazardous substances, pollutants, and
contaminants in groundwater (in-situ) to levels specified by the
remediation goals (Table 1-1) and in the discharge of the treated
groundwater to the limitations stated by the NPDES.
I 00% Design Stated: Reduce the concentration of hazardous substances, pollutants, and
contaminants in groundwater (in-situ) to levels specified by the
remediation goals (Table 1-1) and in the discharge of the treated
groundwater to the limitations stated by the NPDES.
39
•
Response: The text was revised as requested.
✓ Comment 3: Please revise the end of the first paragraph of Section 1.2.1 to include the
statement, "Consequently, the remedial objectives also include the
avoidance of adverse impacts to wetlands, including a wetland containing
the federally endangered plant species know as the bunched arrowhead."
90% Design Stated: The goai of the remedial action is to restore groundwater to its beneficial
use. The remedial action must be protective of human health and the
environment, must comply with all federal, state, and local applicable or
relevant and appropriate requirements (ARARs), and must be technically
practicable. Objectives of the remedial action at the site were defined in
the SOW of the CD and consist of the following:
100% Design Stated: Remedial goals were established in ROD were for five VOCs, one semi-
volatile compound (SVOC) and seven metals. Table 1-1 lists the
remediation goals for these contaminants.
Response: The requested text was added to Section 1.2.1.
Section 1.2.2 Selected Remedy
/ Comment 4:
Response:
Please revise the last sentence of Section 1.2.2 to state, "Treatment for the
contaminated extracted groundwater from the GE and Shepherd Farm
Subsites will take place at the GE Subsite and is to consist of air stripping
to remove organic compounds and granular activated carbon (GAC) to
treat the vapor effluent."
The text has been revised to change the word activate to activated.
Section 2.3.2 Site Groundwater Flow Directions
/comment 5: Please revise the first sentence of Section 2.3.2 to state, "Site
hydrogeology data has been collected from 70 monitor wells and four
recovery wells (see Table 2-1 for well construction details)." Furthermore,
please revise the last sentence of the first paragraph of Section 2.3 .2 to
state, "A total of 47 active monitor wells are screened in the saprolite and
17 active monitor wells are screened in or open to the bedrock."
90% Design Stated: Site hydrogeology data has been collected from 72 monitor wells and four
recovery wells (see Table 2-1 for well construction details). The well
names with an "A" indicate that the well is screened or open in the shallow
bedrock. The well names with a "B" indicate that the well is screened or
40
•
open in the deep bedrock. The exceptions to this naming convention are
monitor wells 5, 6, and 8 which have no letter designation but are shallow
bedrock wells Some of the wells have been abandoned for various
reasons. A total of 49 active monitor wells are screened in the saprolite
and 17 active monitor wells are screened in or open to the bedrock.
100% Design Stated: Site hydrogeology data has been collected from 68 monitor wells and four
recovery wells (see Table 2-1 for well construction details). The well
names with an "A" indicate that the well is screened or open in the shallow
bedrock. The well names with a "B" indicate that the well is screened or
open in the deep bedrock. The exceptions to this naming convention are
monitor wells 5, 6, and 8 which have no letter designation but are shallow
bedrock wells Some of the wells have been abandoned for various
reasons. A total of 49 active monitor wells are screened in the saprolite
and 17 active monitor wells are screened in or open to the bedrock.
Response: The text was revised as follows, "Site hydrogeology data has been
collected from 70 monitor wells and four recovery wells (see Table 2-1
for well construction details). The well names with an "A" indicate that
the well is screened or open in the shallow bedrock. The well names with
a "B" indicate that the well is screened or open in the deep bedrock. The
exceptions to this naming convention are monitor wells 5, 6, and 8 which
have no letter designation but are shallow bedrock wells Some of the
wells have been abandoned for various reasons. A total of 4 7 active
monitor wells are screened in the saprolite and 17 active monitor wells are
screened in or open to the bedrock."
Section 2.6.1.2 Extent of Contamination
/ Comment 6: Please insert the following sentence between the first and last sentences of
the third paragraph of Section 2.6.1.1, "However, manganese is present in
onsite monitor wells at levels exceeding one order of magnitude above the
remediation goal."
90% Design Stated: Data show that PeE is the principle voe present in the groundwater at the
site. The source of the voe contamination is believed to be a failed drain
line which, prior to 1985, conveyed floor drainage and sink wash water
from the manufacturing area to the Large Pond. The water passing
through the drain line at times contained small amounts of PeE and
possibly other voes as employees rinsed spent containers of degreasers in
the sink. The drain line was replaced in 1984-85.
100% Design Stated: Data show that PeE is the principle voe present in the groundwater at the
41
Response:
Section 2.6.1.3
leommcnt7:
Response:
komment8:
Response:
Section 2.6.2.3
/comment 9:
Response:
site. The source of the VOC contamination is believed to be a failed drain
line which, prior to 1985, conveyed floor drainage and sink wash water
from the manufacturing area to the Large Pond. The water passing
through the drain line at times contained small amounts of PCE and
possibly other VOCs as employees rinsed spent containers of degreasers in
the sink. The drain line was replaced in 1984-85.
The comment should reference Section 2.6.1.2. This comment was
addressed in response to EPA Comment 11. The text has been revised to
state, "Manganese is ubiquitous, and is found at concentrations at least two
times the remediation goal ( 50 parts per billion (ppb)) in background
wells (e.g., MW-32, MW-57, MW-59, and MW 60A). In on-site wells,
the manganese concentrations range from 12 to 7,380 ppb. The
concentrations appears to be diminished with depth (see Figures 34-36 in
Appendix B)."
VOe Mass
Please revise the seventh sentence of the second paragraph of Section
2.6.1.3 to_ state, "Representative effective porosities of 20%, 5% and I%
were used for the saprolite, shallow bedrock, and deep bedrock,
respectively."
Text has been revised as requested.
Please revise the last paragraph of Section 2.6.1.3 to include a basis or
reference for the selection of the values used for the uniform thickness of
the shallow bedrock, the uniform thickness of the deep bedrock, the
effective porosity of the saprolite, the effective porosity of the shallow
bedrock, and the effective porosity of the deep bedrock.
Please refer to response to EPA Comment 13.
VOe Mass
Please revise the last sentence of the first paragraph of Section 2.6.2.3 to
state, "The estimate of contaminant mass-in-place was calculated as
described in Section 2.6.1.3." Furthermore, please revise the fifth
sentence of the second paragraph of Section 2.6.2.3 to state, "An effective
porosity of 20% was used for the saprolite."
Text revised as requested.
42
/Comment 10:
Response:
Section 3.2.4.3
/comment 11:
Response:
• •
Please revise the last paragraph of Section 2.6.2.3 to include a basis or
reference for the value used for the effective porosity of the saprolite.
Please refer to response to EPA Comment 13.
Surface Water and Sediment
Please revise Section 3.2.4.3 to address the significance of the
polychlorinated biphenyl (PCB) detections in sediments located at the
STREAM-2 sampling location.
Please refer to response to EPA Comment 18.
Section 3.2.6 Environmental Impacts
/comment 12: Please revise the last sentence of Section 3.2.6 to state, "More detailed
information on the impacts of the AGRS on the bunched arrowhead
habitat can be found in the Hydro logic Study of the Bunched
Arrowhead Habitat (Appendix H) (HIS GeoTrans, 2000a) and in
Attachment 3 of the RGVP (Appendix F) (HIS GeoTrans, 2000b)."
90% Design Stated: The effect of the AGRS extraction on the Bunched arrowhead habitat has
not been determined at this time due to the relatively short duration of
pumpage and below average precipitation in 1999. More detailed
information on the impacts of the AGRS on the Bunched arrowhead
habitat can be found in Section 2.5 and Appendix H.
I 00% Design Stated: The effect of the AGRS extraction on the bunched arrowhead habitat has
not been determined at this time due to the relatively short duration of
pumpage and below average precipitation in I 999. More detailed
information on the impacts of the AGRS on the bunched arrowhead
habitat can be found in Section 2.5 of the Bunched Arrowhead Hydrology
Report (Appendix H) (HSI Geo Trans, 2000a) and in Attachment 3 of the
RGVP (Appendix F) (HSI GeoTrans, 2000b).
Response: Microsoft Word's automatic spell correction will change HSI to HIS.
Please correct this oversight in future correspondence. The text Bunched
Arrowhead Hydrology Report (Appendix H) (HSI GeoTrans, 2000a) will
be corrected to state Hydro logic Study of the Bunched Arrowhead Habitat
(Appendix H) (HSI GeoTrans, 2000a).
Section 3.3 Enhanced In-Situ Bioremediation
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•
Jcomment 13: Please revise the first sentence of the third paragraph of Section 3.3 to
state, "The contaminant plume at the GE Subsite consists of a central
portion with high contaminant concentrations and an exterior portion with
lower concentrations that extends to the site boundary."
Response: Please refer to response to EPA Comment 19.
Section 4 Groundwater Remedial Action at the GE Subsite
J Comment 14: Please revise the fourth sentence of Section 4 to state, "Capture is not
designed to extend to the creek so that the flow of groundwater to surface
water is not stopped, although the proposed groundwater extraction
system will significantly reduce the flow of groundwater to surface
water."
90% Design Stated: The groundwater extraction and treatment system designed for the GE
Subsite is based on several investigations and studies including site
characterization results (Section 2), and the performance and operation of
the AGRS (described in Section 3.2). A groundwater model has been
developed (see Appendix E) to provide recommended recovery well
locations and rates to hydraulically contain the groundwater plume. The
proposed system contains approximately 90% ofVOC plume by area with
interpolated concentrations greater than I µg/L and over 98% of VOC
mass. Capture is not designed to extend to the creek so that the flow of
groundwater to surface water is not stopped. The design of the
groundwater treatment system is based upon model predicted estimates of
combined flow to the treatment system, historic groundwater quality data
from monitoring wells and existing recovery wells, and treated effluent
discharge standards. The groundwater extraction and treatment system
design for the GE Subsite is presented below. Design calculations and
model input information are provided in Appendix G. Appendix I
contains the construction specifications and drawings for modifications to
the GE Subsite extraction system and the installation of the Shepherd
Farm recovery system.
I 00% Design Stated: The groundwater extraction and treatment system designed for the GE
Subsite is based on several investigations and studies including site
characterization results (Section 2), and the performance and operation of
the AGRS (described in Section 3.2). A groundwater model has been
developed (see Appendix E) to provide recommended recovery well
locations and rates to hydraulically contain the groundwater plume. The
proposed system contains 99% of VOC mass. Capture is not designed to
extend to the creek so that the flow of groundwater to surface water is not
44
•
, stopped. The design of the groundwater treatment system is based upon
model predicted estimates of combined flow to the treatment system,
historic groundwater quality data from monitoring wells and existing
recovery wells, and treated effluent discharge standards. The groundwater
extraction and treatment system design for the GE Subsite is presented
below. Design calculations and model input information are provided in
Appendix G. Appendix I contains the construction specifications and
drawings for modifications to the GE Subsite extraction system and the
installation of the Shepherd Farm recovery system.
Response: The requested text stating that baseflow is reduced was added.
Section 4.1 Groundwater Extraction
A::omment 15: Please revise the first sentence of Section 4.1 to state, "The existing
groundwater extraction and treatment system, referred to as the AGRS,
will be modified to hydraulically contain the majority of the VOC plume
at the GE Subsite and treat extracted groundwater."
Response: Please refer to response to EPA Comment 20.
/comment 16: In accordance with Figure 4-1, please revise the first sentence of the
second paragraph of Section 4.1 to state, "The proposed groundwater
extraction recovery well locations and simulated extent of capture using a
total extraction rate of 60 gpm for the GE Subsite are shown on Figure
4-1.
90% Design Stated: The proposed groundwater extraction recovery well locations and
simulated extent of capture using a total extraction rate of 65 gpm are
shown on Figure 4-1.
I 00% Design Stated: The proposed groundwater extraction recovery well locations and
simulated extent of capture using a total extraction rate of 65 gpm are
shown on Figure 4-1 for the GE Subsite.
Response: The text was revised to state, "The proposed groundwater extraction
recovery well locations and simulated extent of capture using a total
extraction rate of 60 gpm are shown on Figure 4-1 for the GE Subsite."
Section 4.2 Design Influent Concentrations and Effluent Discharge Requirements
J Comment 17: Please revise the first sentence of the fourth paragraph of Section 4.2 to
state, "The groundwater treatment system design effluent standards are
45
•
· summarized in Table 4-1."
90% Design Stated: The groundwater treatment system design effluent standards are
summarized in Table 4-1.
I 00% Design Stated: The groundwater treatment system design effluent standards are
summarized in Table 4-2.
Response: The text was revised to state, "The groundwater treatment system design
effluent standards are summarized in Table 4-1."
Section 4.3.4 Effluent Discharge
/comment 18:
90% Design Stated:
Please revise the second sentence of Section 4.3.4 to state, "Treated
groundwater will be discharge to two 30,000 gallon storage tanks for use
as plant cooling and process water and then discharged to the POTW."
The existing AGRS outfall line will be valved and locked to prevent
discharge through the existing outfall structure. Treated groundwater will
be discharged to two 30,000 gallons storage tanks for use as plant cooling
and process water and then discharged to the POTW.
I 00% Design Stated: The existing AGRS outfall line will be valved and locked to prevent
discharge through the existing outfall structure. Treated groundwater will
be discharged to two 30,000 gallons storage tanks for use as plant cooling
and process water and then discharged to the POTW.
Response: As requested, gallons will be changed to gallon. Discharged was not
changed to discharge because we assumed that this was merely a
typographical error.
Section 4.4 Performance Monitoring
/ Comment 19: Please revise the fourth sentence of the second paragraph of Section 4.4 to
state, "Additionally, biological monitoring will be performed to protect
against overpumping, which could adversely impact the site wetlands."
90% Design Stated: Other performance monitoring activities will include hydraulic head
surveys, well pumping rate measurements, chemical analyses at select
wells, and air emission monitoring. The initial projection of performance
monitoring for the GE Subsite is summarized in Table 4-3. Refer to
Appendix F for a more detailed discussion of the performance monitoring
of the groundwater, surface water, and sediment.
46
• •
I 00% Design Stated: Other performance monitoring activities will include hydraulic head
surveys, well pumping rate measurements, chemical analyses at
performance wells, surface water and sediment stations, and residential
wells. The initial projection of performance monitoring for the GE
Subsite is summarized in Table 4-3. Refer to Appendix F for a more
detailed discussion of the performance monitoring of the groundwater,
surface water, and sediment. Additionally, the biological monitoring will
be performed to protect against overppumping, which could adversely
impact the site wetlands. The proposed biological monitoring is provided
in Appendix F.
Response: The word "the" was removed as requested and the spelling of the word
overpuniping was corrected.
Section 4.5 Operation and Maintenance
(Comment 20: Please revise the third sentence of the third paragraph of Section 4.5 to
state, "Readings from each well flow totalizer should be made on a
monthly basis."
90% Design Stated: Operational requirements for the groundwater extraction and treatment
system include: inspection of each well vault, bag filter unit, air stripper
and blower, air filter, duct work, and all above-ground piping. The
recovery system will require periodic adjustment of individual well flow
rates using a throttle valve and variable area flow meter located at each
well vault. Readings from each well flow totalizer should be made on
monthly to quarterly basis. Flow totalizing measurements should also be
made monthly at the treatment system and submitted as part of the NP DES
compliance reporting.
I 00% Design Stated: Operational requirements for the groundwater extraction and treatment
system include: inspection of each well vault, bag filter unit, air stripper
and blower, air filter, duct work, and all above-ground piping. The
recovery system will require periodic adjustment of individual well flow
rates using a throttle valve and variable area flow meter located at each
well vault. Readings from each well flow totalizer should be made on
monthly to quarterly basis. Flow totalizing measurements should also be
made monthly.
Response: The text has been revised as requested.
Section 4.6.2 Air Permit and Emission Controls
/ Comment 21: Please revise Section 4.6.2 to include the statement, "Projected air
47
•
emission design calculations are included in Appendix G."
90% Design Stated: An air permit to discharge treated air stripper off-gas was not required for
the AGRS off-gas and is not anticipated to be required for the full scale
system. However, the AGRS emissions have been run through granular
activated carbon (GAC) as the full scale system's will be.
I 00% Design Stated: An air permit to discharge treated air stripper off-gas was not required for
the AGRS off-gas and is not anticipated to be required for the full scale
system. However, the AGRS emissions have been run through a granular
activated carbon (GAC) unit. Likewise, the full scale system emissions
will be run through a GAC unit. Additionally, NC DENR, Division of Air
Quality, Asheville Regional Office was notified in February 2000 about
the expected air stripper emissions for the proposed final system.
Response:
Section 4.6.3
/comment 22:
The text has been revised as requested.
Other Permits and Applicable Controls
Please revise the second sentence of Section 4.6.3 to state, "These may
include but are not limited to: recovery well permits, grading permits,
wetland permits, an approved sediment and erosion control plan, railroad
and highway crossing agreements, private property access
agreements, electrical permits and inspections, and plumbing and
mechanical permits and inspections."
90% Design Stated: Other permitting and inspections for construction and operation of the
groundwater extraction and treatment systems will be required from state
and local authorities. These may include but are not limited to: grading
permits, wetland permits, railroad and highway crossing agreements, an
approved sediment and erosion control plan, electrical inspections, and
permits, and plumbing and mechanical permits and inspections. A state
withdrawal permit may be required if the recovery well systems exceed a
capacity of 100,000 gallons per day (approximately 70 gpm continuously).
I 00% Design Stated: Other permitting and inspections for construction and operation of the
groundwater extraction and treatment systems will be required from state
and local authorities. These may include but are not limited to: well
permits, grading permits, wetland permits, an approved sediment and
erosion control plan, electrical inspections, and permits, and plumbing and
mechanical permits and inspections. A state withdrawal permit may be
required if the recovery well system exceeds a capacity of 100,000 gallons
per day (approximately 70 gpm continuously).
Response: The text now states, "These may include but are not limited to: recovery
48
•
well permits, grading permits, wetland permits, an approved sediment and
erosion control plan, railroad and highway crossing agreements, private
property access agreements, electrical permits and inspections, and
plumbing and mechanical permits and inspections."
/comment 23: The last sentence of Section 4.6.3 states that "A state withdrawal permit
may be required if the recovery well systems exceed a capacity of 100,000
gallons per day (approximately 70 gpm continuously)." Numerous
comments have been generated regarding this point. GE has previously
stated that conversations with the North Carolina Department of
Environment and Natural Resources (NC DENR) Division of Water
Quality, Groundwater Section, Asheville Regional Office, have indicated
that a withdrawal permit is not required for a pump-and-treat system, but
that a permit application must be filed to construct a recovery well system.
If the state withdrawal permit is not required, please provide written
documentation from the NC DENR that the state withdrawal permit is not
required and revise Section 4.6.3 accordingly. If the state withdrawal
permit is required, please delete the last sentence of Section 4.6.3.
90% Design Stated: Other permitting and inspections for construction and operation of the
groundwater extraction and treatment systems will be required from state
and local authorities. These may include but are not limited to: grading
permits, wetland permits, railroad and highway crossing agreements, an
approved sediment and erosion control plan, electrical inspections, and
permits, and plumbing and mechanical permits and inspections. A state
withdrawal permit may be required if the recovery well systems exceed a
capacity of I 00,000 gallons per day (approximately 70 gpm continuously).
I 00% Design Stated: Other permitting and inspections for construction and operation of the
groundwater extraction and treatment systems will be required from state
and local authorities. These may include but are not limited to: well
permits, grading permits, wetland permits, an approved sediment and
erosion control plan, electrical inspections, and permits, and plumbing and
mechanical permits and inspections. A state withdrawal permit may be
required if the recovery well system exceeds a capacity of 100,000 gallons
per day (approximately 70 gpm continuously).
Response: A withdrawal permit is not required. The sentence was removed. The
new paragraph states, "Other permitting and inspections for construction
and operation of the groundwater extraction and treatment systems will be
required from state and local authorities. These may include but are not
limited to: recovery well permits, grading permits, wetland permits, an
approved sediment and erosion control plan, railroad and highway
crossing agreements, private property access agreements, electrical permits
49
•
and inspections, and plumbing and mechanical permits and inspections."
Landon Davidson of Ne DENR (828-251-6208) can be contacted to verify
necessity of permits.
Section 4.7 Remediation Start-Up and Shakedown
/comment 24: Please revise last sentence of the fourth item in Section 4.7 to state, "At
least three samples per week will be analyzed for voes, SVOCs and
metals by an off-site laboratory."
90% Design Stated: Water samples will be collected from the treatment system influent and
effluent to ensure that the treatment system is operating properly, and
effluent samples are in conformance with permit limitations. These
samples will be analyzed daily with a field-Ge or off-site laboratory. At
least three samples per week will be analyzed for voes and metals by an
off-site laboratory.
100% Design Stated: Water samples will be collected from the treatment system influent and
effluent to ensure that the treatment system is operating properly. These
samples will be analyzed daily with a field-Ge or off-site laboratory. At
least three samples per week will be analyzed for voes and metals by an
off-site laboratory.
Response: Samples will be analyzed during the start-up and shake-down period for
the target voes in order to optimize the treatment system. SVOes were
not analyzed for in the initial AGRS start-up/shake-down and are not
present in quantities great enough to warrant using SVOe data to optimize
the system. Additionally, metals sampling was removed from the start-
up/shake-down section because the air stripper is not proposed to be and
will not be treating for metals. Samples will be taken by GE and analyzed
.for metals before discharging the water to the POTW.
/comment 25:
Response:
The paragraph in the final design will state, "Water samples will be
collected from the treatment system influent and effluent to ensure that the
treatment system is operating properly. These samples will be analyzed
daily with a field-Ge or off-site laboratory. At least three samples per
week will be analyzed for voes by an off-site laboratory."
Please revise Section 4.7 to include provisions for the collection and
analysis of air emission samples.
Additional text was added to state, "Air samples will be collected from the
GAe air stream influent and effluent to ensure that the system is operating
properly. The first set of samples will be analyzed for voes by an off-site
50
•
laboratory. lfVOCs are not detected in the influent, no additional air
samples will be collected. Otherwise, at least three samples per week will
be analyzed for VOCs by an off-site laboratory."
Section 5.1.1 Recovery System
/ Comment 26: The response to US EPA comment #83 stated that Biological Research
Associates has been consulted on the piping layout. However, no mention
of the piping layout was made in their report submitted as Attachment 3 of
Appendix F. Please address the issue of the piping layout, its close
proximity to the wetlands, and special construction procedures to be
implemented to protect these sensitive environments.
Response: Please refer to response to EPA Comment 26.
Section 5.4 Operation and Maintenance
/ Comment 27: Please revise the last sentence of Section 5.4 to state, "Readings from each
well flow totalizer should be made on a monthly basis."
90% Design Stated: Due to the nature of the system design, operation and maintenance of the
proposed Shepherd Farm Subsite extraction system will be minimal.
Operational requirements for the groundwater extraction system include:
inspection of each well vault and all exposed piping. The recovery system
will require periodic adjustment of individual well flow rates using a
throttle valve and a flow meter located at each vault. Readings from each
well flow totalizer should be made on a monthly to quarterly basis.
I 00% Design Stated: Due to the nature of the system design, operation and maintenance of the
proposed Shepherd Farm Subsite extraction system will be minimal.
Operational requirements for the groundwater extraction system include:
inspection of each well vault and all exposed piping. The recovery system
will require periodic adjustment of individual well flow rates using a
throttle valve and a flow meter located at each vault. Readings from each
well flow totalizer should be made on a monthly to quarterly basis.
Response: Text was revised as requested.
Section 7.3 Pulsed Pumping
j Comment 28: Please revise the first sentence of Section 7.3 to state, "Pulsed pumping
can sometimes be used to increase the ratio of contaminant mass removed
to pumped groundwater volume where mass transfer limitations restrict
dissolved concentrations (USEPA, 1994)."
51
•
90% Design Stated: Pulsed pumping can sometimes be used to increase the ratio of
contaminant mass removed to pumped groundwater volume where mass
transfer imitations restrict dissolved concentrations (USEPA, 1994).
I 00% Design Stated: Pulsed pumping can sometimes be used to increase the ratio of
contaminant mass removed to pumped groundwater volume where mass
transfer imitations restrict dissolved concentrations (USEPA, 1994).
Response: Text was revised as requested.
Figure 2-5
/comment 29:
Response:
Location of Residential Wells
Please revise Figure 2-5 to identify the GE and Shepherd Farm Subsites,
as originally submitted.
Figure 2-5 was revised as requested.
Figure 2-13 Location of Surface Water and Sediment Sampling Stations
/comment 30: Please revise Figure 2-13 to include a note that states, "Upon approval of
the Final Design Report, surface water and sediment sampling station
STREAM-3 will be abandoned in favor of surface water and sediment
sampling station STREAM-4."
Response:
Table 1-1
/comment 31:
Response:
Table 2-4
/comment 32:
Response:
Please refer to EPA Comment 29 ..
Remediation Goals for RTC's in Groundwater
Please revise Table 1-1 to include the cis-1, 2-dichloroethene and trans-I,
2-dichloroethene isomers of 1,2-dichloroethene.
Please refer to EPA Comment 103.
Remediation Goal Exceedances for Baseline Gronndwater Conditions (July
1997) at the GE Subsite
Please revise the title of Table 2-4 to state, "Remediation Goal
Exceedances for Baseline Groundwater Conditions (July 1997) at the GE
Subsite."
The July 1997 reference was removed from this and other baseline
conditions data tables in the final report because some of the data that is
being called baseline conditions is from a different time frame.
52
• •
Table 2-5 Remediation Goal Exceedances for Baseline Groundwater Conditions (.July
1997) at the Shepherd Farm Subsite
✓Comment 33: Please revise the title of Table 2-5 to state, "Remediation Goal
Exceedances for Baseline Groundwater Conditions (July 1997) at the
Shepherd Farm Subsite."
Response: Please refer to response to Comment 32, above.
J Comment 34: Please revise Table 2-5 to include the results for Shepherd Farm
Geoprobe™ sample location SFGP-15.
Response: Table has been revised as requested to include location SFGP-15.
Table 3-3 Quarterly AGRS Effluent Monitoring Data for VOCs in 1998
/comment 35: Please revise Table 3-3 to include quarterly Accelerated Groundwater
Remediation System (AGRS) effluent monitoring data for volatile organic
compounds (VOCs) from the first quarter of 1998 to the present.
Additionally, please revise the title located on Table 3-3 and as given in
the List of Tables accordingly.
Response: Table has been revised as requested.
/ Comment 36: Please revise Table 3-3 such that the names of the parameters
bromodichloromethane, trans-I, 2-dichloroethene, and I, 1,2,2-
tetrachloroethane are not truncated.
Response: Table has been revised as requested.
Table 3-5 Annual Residential Well Data
/comment 37: Please revise Table 3-5 to include a note that residential well SWW-9 is
not being used for drinking water purposes.
Response: Table has been revised as requested.
Table 3-7 Annual Surface Water Monitoring Data for Metals and PCBs
komment 38: Please revise the title of Table 3-7 to state, "Annual Surface Water
Monitoring Data for Metals and PCBs."
Response: Table has been revised as requested.
53
Table 4-1
/comment 39:
Response:
Table 4-2
/comment 40:
Response:
/comment 41:
Response:
Table 4-3
/comment 42:
Response:
•
Calculation of Representative Influent Concentrations and Design Effluent
Concentrations
Please revise Table 4-1 to include the table as previously submitted in the
Prefinal (90%) Remedial Design and Remedial Action Work Plan for
Groundwater. However, please correct the former Table 4-1 to include the
correct Maximum Contaminant Levels (MCLs). Additionally, please
include a 150% factor of safety for the design influent. These values
should then be used in the air stripper program and vapor treatment
calculations included in Appendix G to verify the adequacy of treatment
by the proposed system.
Please refer to response to EPA Comment 23.
Groundwater Treatment System Effluent Compliance Monitoring
Please revise Table 4-2 to include provisions for four samples per month
for biological oxygen demand (BOD), total suspended solids (TSS),
temperature, chemical oxygen demand (COD), ammonia (as nitrogen
(N)), and oil/grease.
Comment is noted. This comment is in apparent contradiction to EPA
Comment 67. Please refer to response to EPA Comment 4.
Please revise Table 4-2 to include provisions for quarterly groundwater
treatment system influent and effluent monitoring for all remediation
target compounds (RTCs).
Text revised as requested.
System Performance Monitoring
Please revise Table 4-3 to indicate that the residential monitoring well
network will follow the sampling conventions of the groundwater at the
GE and Shepherd Farm Subsites ( quarterly sampling for first three years,
semi-annual sampling for two years, and annually thereafter).
The residential monitoring program wells will continue to be sampled on
an annual basis. With the existing AGRS system pumping at
approximately 25 gallons per minute, residential wells have been sampled
annually. Since the inception of the residential monitoring program, only
one exceedance at the GE Subsite has occurred. This exceedance involved
lead, a metal that is common in background wells. Subsequent sampling
of this residential well, WW34, showed levels of lead below the
54
.r Comment 43:
Response:
-Comment 44:
Response:
Table 6-1
/ Comment 45:
Response:
Table 6-2
/comment 46:
Response:
Table 6-3
J C~mment 47:
Response:
•
remediation goals .
Please revise Table 4-3 to include provisions for quarterly groundwater
treatment system influent and effluent monitoring for all RTCs.
Text revised as requested.
Please revise Table 4-3 to include a note that all changes in monitoring
frequency are subject to US EPA and NC DENR approval.
Please refer to EPA Comment 182 on the Pre-Final (90%) Remedial
Design and Remedial Action Work Plan for Groundwater which stated,
"we recommend that this RGVP be revised to include the schedule
originally proposed for performance sampling. In particular:
• All performance monitor wells should be sampled quarterly
for the first three years, semiannually for the next two
years, and annually thereafter."
No direction was initially given requiring Agency or NC DENR approval
to adhere to the originally proposed schedule. Agency and NC DENR
approval will be sought to enter Exit Monitoring and Closure Monitoring.
Estimate of Capital Costs
Table 6-1 was inadvertently omitted. Please correct this oversight.
Table 6-1 has been included.
Summary of Estimated Annual Operation and Maintenance Costs
Table 6-2 was inadvertently omitted. Please correct this oversight.
Table 6-2 has been included.
Detailed Estimate of Annual Operation and Maintenance Costs
Table 6-3 was inadvertently omitted. Please correct this oversight.
Table 6-3 has been included.
55
•
REMEDIAL ACTION WORK PLAN FOR GROUNDWATER
Table of Contents
✓Comment 48:
Response:
Several discrepancies were noted during the review of the Table of
Contents. Please correct these oversights.
I) The title for Section 3.3.1 should be given as "Groundwater
Extraction at the Shepherd Farm Subsite."
2) The title of Figure 1-2 should be given as "GE Subsite Features."
.3) The title for Figure 1-3 should be given as "Shepherd Farm
Subsite Features."
4) The title for Appendix L should be given as "Operation and
Maintenance Manual."
The Table of Contents has been revised as requested.
Section 1.3 Remedial Action Objectives
/comment 49: Please revise item 6 of the first paragraph to state, "Reduce the
concentration of hazardous substances, pollutants, and contaminants in
surface water, groundwater, and surface and subsurface soil within the
site to levels specified by the remediation goals."
Response: Text has been revised as requested.
/Comment 50: Please revise the second paragraph of Section 1.3 to include the statement,
"Consequently, the remedial objectives also include the avoidance of
adverse impacts to wetlands, including a wetland containing the federally
endangered plant species know as the bunched arrowhead."
Response: Text has been revised to repeat text from the Section 1.2.1 of the Final
Design for Groundwater.
Section 3.1 Existing Accelerated Groundwater Remediation System (AGRS)
/ Comment 51: Please revise the last sentence of the first paragraph of Section 3 .1 to state,
"Underground piping has been installed to use the treated water at the
manufacturing facility as process water."
90% Design Stated: A groundwater pump-and-treat system, referred to as the Accelerated
Groundwater Remediation System (AGRS), was constructed as an initial
groundwater remediation step using pre-existing, unutilized, recovery
wells. The AGRS was constructed per the CD according the specifications
56
•
contained in the Remedial Design Work Plan (HSI GeoTrans, 1997). The
AGRS consists of four recovery wells (RW-1 through RW-4), a treatment
building, a constructed outfall, and associated pumps, piping and controls.
The groundwater is treated for VOCs (principally PCE) using a low-
profile, tray-type air stripper and discharged into Bat Fork Creek under a
NPDES permit. The treatment system is equipped with an oil/water
separator and a sediment bag filter. Off gases from the air stripper are
treated using a vapor phase granulated activated carbon (GAC) system.
Underground piping has been installed to use a portion of the treated water
at the manufacturing facility as process water.
I 00% Design Stated: A groundwater pump-and-treat system, referred to as the Accelerated
Groundwater Remediation System (AGRS), was constructed as an initial
groundwater remediation step using pre-existing, unutilized, recovery
wells. The AGRS was constructed per the CD according the specifications
contained in the Remedial Design Work Plan (HSI GeoTrans, 1997). The
AGRS consists of four recovery wells (RW-1 through RW-4), a treatment
building, a constructed outfall, and associated pumps, piping and controls.
The groundwater is treated for VOCs (principally PCE) using a low-
profile, tray-type air stripper and was discharged into Bat Fork Creek
under a NPDES permit until October 1999 at which time GE began using
100% of the water in the plant process .. The treatment system is equipped
with an oil/water separator and a sediment bag filter. Off gases from the
air stripper are treated using a vapor phase granulated activated carbon
(GAC) system. Underground piping has been installed to use a portion of
the treated water at the manufacturing facility as process water.
Response: The text_was revised as requested.
Section 3.2.1 Modification of the Existing AGRS
/comment 52: Please revise the first sentence of Section 3.2.1 to state, "The main
modification to the existing AGRS will be the following: removal of the
phase separation system, replacement of the simplex bag filter by a duplex
bag filter assembly, re-plumbing of the treatment system conveyance with
a 3-inch diameter (dia.) PVC schedule 80 piping, and installation of
fittings, connections, etc., as appropriate."
90% Design Stated: The main modification to the existing AGRS will be the following:
removal of the phase separation system, replacement of the simplex bag
filter by a duplex bag filter assembly, re-plumbing of the treatment system
conveyance with a 3-inch diameter (dia.) PVC schedule 80, and
installation of fittings, connections, etc., as appropriate.
57
•
I 00% Design Stated: The main modification to the existing AGRS will be the following:
removal of the phase separation system, replacement of the simplex bag
filter by a duplex bag filter assembly, re-plumbing of the treatment system
conveyance with a 3-inch diameter (dia.) PVC schedule 80, and
installation of fittings, connections, etc., as appropriate.
Response: The word 'piping' was added to the first sentence of Section 3.2.1 as
requested.
Section 3.2.2 Recovery System at the GE Subsite
/ Comment 53: Please revise the first and second sentences of Section 3 .2.2 to state, "The
proposed GE Subsite recovery well system will consist of the four existing
recovery wells (RW-1 through RW-4) and eight additional recovery wells
(RW-5 through RW-12) with a pumping rate of 5 gpm each. One-half
horsepower (hp) pumps will be used for all recovery wells."
90% Design Stated: The proposed GE Subsite recovery well system will consist of the four
existing recovery wells (RW-1 through RW-4) and nine additional
recovery wells (RW-5 through RW-13) with a pumping rate of 5 gpm
each. One-half HP pumps will be used for all recovery wells. The total
pumping rate, for the GE Subsite if 65 gpm. Extracted groundwater wifr
flow from each well via subsurface piping to the modified treatment
system.
100% Design Stated: The proposed GE Subsite recovery well system will consist of the four
existing recovery wells (RW-1 through RW-4) and nine additional
recovery wells (RW-5 through RW-12) with a pumping rate of5 gpm
each. One-half HP pumps will be used for all recovery wells. The total
pumping rate, for the GE Subsite if 60 gpm. Extracted groundwater will
flow from each well via subsurface piping to the modified treatment
system.
Response:
Section 3.2.2.2
/comment 54:
Text revised as requested. Additionally, gpm was defined as gallons per
minute.
Pumps, Piping and Level Controls
Please revise Section 3.2.2.2 to include the following statements as
included in the PreFinal (90%) Remedial Design and Remedial Action
Work Plan for Groundwater: "The minimum depth to provide frost
protection is 18 inches (Means, I 996, Site Work and Landscape Cost
Data). Piping will be exposed only at the well head. Due to the burial
depth and connection to the subsurface, freeze problems at the wells heads
58
•
are not expected."
Response: Text has been revised as requested.
Section 3.3.1 Groundwater Extraction at the Shepherd Farm Subsite
komment 55: The title for Section 3.3.1 should be given as "Groundwater Extraction
at the Shepherd Farm Subsite."
90% Design Stated: Groundwater Extraction and at the Shepherd Farm Subsite
I 00% Design Stated: Groundwater Extraction and at the Shepherd Farm Subsite
Response: The word 'and' was removed from the title of Section 3.3.1 as requested.
Section 3.3.3 Treatment System
!comment 56: Please revise Section 3.3.3 to state, "There will be no separate treatment
system at the Shepherd Farm Subsite, the extracted groundwater will be
connected via underground piping to a header pipe, which will transport
the flow to the treatment system building located at the GE Subsite."
90% Design Stated: There will be no separate treatment system at the Shepherd Farm Subsite,
the extracted groundwater will be connected via underground piping to a
header piping, which will transport the flow to the treatment system
building located at the GE Subsite.
I 00% Design Stated: There will be no separate treatment system at the Shepherd Farm Subsite,
the extracted groundwater will be connected via underground piping to a
header piping, which will transport the flow to the treatment system
building located at the GE Subsite.
Response: The word 'piping' has been changed to 'pipe' as requested.
Section 4.8.2 Construction Activities Waste
/ Comment 57: Section 02222 of the Technical Specifications does not include any
specifications for the handling and disposal of waste generated during the
course of this project. Please revise the Technical Specifications to
include a separate section that detail the handling and disposal
requirements for all waste generated. Please make the appropriate
references to the new section.
59
Response:
•
Comment is understood to state, "Please revise the Technical
Specifications to include a separate section that details the handling and
disposal requirements for all waste generated." Appropriate reference to
the handling and disposal of waste generated during course of this project
will be added.
Section 8.3.2 Progress Reports
/comment 58:
Response:
Please correct the spelling of the word "Manager" in the first sentence of
Section 8.3.2.
Text has been revised as requested.
Section 8.3.3 Community Relations
/comment 59: Please place a period(.) at the end of the second sentence of Section 8.3.3.
Response:
Section 9
/comment 60:
Text has been revised as requested.
References
Please revise the eleventh entry of Section 9 to state, "NCDC, 1998,
National Climatic Data Center Database Retrieval."
90% Design Stated: NCDC, 1998. National Climactical Data Center Database Retriveal.
I 00% Design Stated: NCDC, 1998. National Climactical Data Center Database Retriveal.
Response: Text has been revised to correctly spell the word 'retrieval' in the list of
references.
Table 2-1 Remediation Goal Exceedances for Baseline Groundwater Conditions (.July
1997) at the GE Subsite
/comment 61: Please revise the title of Table 2-1 to state, "Remediation Goal
Exceedances for Baseline Groundwater Conditions (July 1997) at the GE
Subsite."
Response: See response to NC DENR Comment 32.
Table 2-2 Remediation Goal Exceedances for Baseline Groundwater Conditions (July
1997) at the Shepherd Farm Subsite
./ Comment 62: Please revise the title of Table 2-2 to state, "Remediation Goal
60
Response:
/Comment 63:
Response:
APPENDIX A
/4omment 64:
Response:
APPENDIXB
/comment 65:
Response:
APPENDIXC
/eomment 66:
Response:
/comment 67:
Response:
APPENDIXE
List of Figures
komment68:
• •
Exceedances for Baseline Groundwater Conditions (July 1997) at the
Shepherd Farm Subsite."
See response to NC DENR Comment 32.
Please revise Table 2-2 to include the results for Shepherd Farm
Geoprobe™ sample location SFGP-15.
Table has been revised as requested to include location SFGP-15.
HYDROGRAPHS
Please revise the first page of Appendix A to include groundwater
monitoring well MW-12B as a performance monitoring well.
Text has been revised as requested.
DISTRIBUTION OF REMEDIATION TARGET COMPOUNDS IN
GROUNDWATER
Please revise Figure 10 of Appendix B such that the locations where the
1,2-dichloroethene concentrations exceeded the remediation goal follow
the nomenclature given in the legend.
Figure has been revised as requested.
AGRS EQUIPMENT
Please revise Appendix C to include the specifications for the granular
activated carbon (GAC) treatment of the air stripper emissions.
Specifications for the granular activated carbon treatment of air will be
provided as requested.
Please revise Appendix C to include the cut sheets for the conducting level
sensor and oil water separator as originally submitted.
The oil water separator will be taken off line when the final system is
being installed. Cut sheet for the conducting level sensor will be included.
NUMERICAL GROUNDWATER MODEL REPORT
Several discrepancies were noted during the review of the List of Figures.
61
Response:
List of Tables
/comment 69:
Response:
Section 2.2.3.2
/tomment70:
Response:
Please correct these oversights.
1) The title for Figure 3-2 should be given as "Simulated Head in
Saprolite (Model Layer I) for Baseline Conditions.
2) The title for Figure 3-3 should be given as "Simulated Head in
Shallow Bedrock (Model Layer 2) for Baseline Conditions."
3) The title for Figure 3-4 should be given as "Simulated Head in
Deep Bedrock (Model Layer 3) for Baseline Conditions."
4) Please delete the entry for Figure 3-9 .
. 5) The title for Figure 4-1 should be given as "Simulated Capture
Zone at the GE Subsite with 60 gpm Extraction at 12 Wells."
6) The title for Figure 4-2 should be given as "Simulated Capture
Zone at the SF Subsite with 17 gpm Extraction at 4 Wells."
7) The title for Figure 4-3 should be given as "4-3. Simulated
Water Table Drawdown from 60 gpm Extraction at GES and 17
gpm Extraction at SFS."
8) Please include an entry for Figure 5-3 -Simulated Remediation
System Drawdown (in ft) for Years 0-10.
Text has been revised as requested but is subject to change based upon
revised modeling results.
Several discrepancies were noted during the review of the List of Tables.
Please correct these oversights.
1) The title for Table 4-1 should be given as "Simulated Base flow
Reduction to Wetlands Due to Pumping 60 gpm at the GE Subsite
and 17 gpm at the Shepherd Farm Subsite."
2) The title for Table 4-2 should be given as "Simulated Drawdown al
the Bunched Arrowhead Wetland for the Proposed Design."
Text has been revised as requested but is subject to change based upon
revised modeling results.
Wetlands
Please revise the second sentence of the third paragraph of Section 2.2.3 .2
to state, "The biology and hydrology of the bunched arrowhead is being
studied as part of the RD/RA (sec Appendix H)."
Text has been revised as requested.
62
•
Section 3.5 Sensitivity Analysis
,/Comment 71: Please revise the.first sentence of the second paragraph of Section 3.5 to
state, "A summary of the residual statistics is shown on Table 3-6."
Furthermore, please delete the second and third sentences of the second
paragraph of Section 3.5.
Response: Residual statistics will be correctly referenced in the revised report.
Section 4 Proposed Design
./Comment 72: The last sentence of the second paragraph of Section 4 indicates that
approximately 98 percent of the total voe mass is captured by the
proposed groundwater extraction system. However, the Final Design
Report, the Remedial Action Work Plan, and Section 6 of this Numerical
Groundwater Model Report indicate that approximately 99 percent of the
total voe mass is captured by the proposed groundwater extraction
system. Please clarify this discrepancy.
Response: The text was revised to state that the capture zone hydraulically contains
99 percent of the total voe mass, however, this may change based upon
revised groundwater modeling.
Section 5.3.1 AGRS Simulation
/Comment 73: Please revise the third sentence of Section 5.3.1 to state, "The first stress
period is four months in length (August through November 1997) and
uses a total AGRS extraction rate of 5 gpm."
90% Design Stated: The transient simulation of the AGRS begins in August 1997 when AGRS
extraction was initiated. Two stress periods were simulated. The first
stress period is four month in length (August though November 1997) and
uses a total AGRS extraction rate of 5 gpm. This is the initial period of
time when the AGRS was not operating at full capacity. A second stress
period starts in December 1997 and continues to July 2007. During this
period, the AGRS is assigned a total extraction rate of 25 gpm. The first
stress period uses IO times steps and the second stress period uses 15 time
steps. A time step multiplier of 1.1 is used for both stress periods.
I 00% Design Stated: The transient simulation of the AGRS begins in August 1997 when AGRS
extraction was initiated. Two stress periods were simulated. The first
stress period is four month in length (August though November 1997) and
uses a total AGRS extraction rate of 5 gpm. This is the initial period of
time when the AGRS was not operating at full capacity. A second stress
63
Response:
/comment 74:
90% Design Stated:
I 00% Design Stated:
Response:
komment75:
90% Design Stated:
•
period starts in December 1997 and continues to July 2007. During this
period, the AGRS is assigned a total extraction rate of 25 gpm. The first
stress period uses IO times steps and the second stress period uses 15 time
steps. A time step multiplier of 1.1 is used for both stress periods.
An "s" was added to the word "month" in the third sentence of Section
5.3.1 as requested.
Please revise the seventh sentence of Section 5.3.1 to state, "The first
stress period uses IO time steps and the second stress period uses 15 time
steps."
The transient simulation of the AGRS begins in August 1997 when AGRS
extraction was initiated. Two stress periods were simulated. The first
stress period is four month in length (August though November 1997) and
uses a total AGRS extraction rate of 5 gpm. This is the initial period of
time when the AGRS was not operating at full capacity. A second stress
period starts in December I 997 and continues to July 2007. During this
period, the AGRS is assigned a total extraction rate of25 gpm. The first
stress period uses IO times steps and the second stress period uses 15 time
steps. A time step multiplier of 1.1 is used for both stress periods.
The transient simulation of the AGRS begins in August 1997 when AGRS
extraction was initiated. Two stress periods were simulated. The first
stress period is four month in length (August though November 1997) and
uses a total AGRS extraction rate of 5 gpm. This is the initial period of
time when the AGRS was not operating at full capacity. A second stress
period starts in December 1997 and continues to July 2007. During this
period, the AGRS is assigned a total extraction rate of 25 gpm. The first
stress period uses IO times steps and the second stress period uses 15 time
steps. A time step multiplier of 1.1 is used for both stress periods.
The letter "s" was removed from the word "times" in the seventh sentence
of Section 5.3.1 as requested.
In accordance with the graph for groundwater monitoring well MW-12A
as shown in Figure 5-2, please revise the third sentence of the third
paragraph of Section 5.3.1 to state, "Simulated steady-state drawdowns at
the nine performance monitor wells ranged from 4.6 to 13.3 feet."
Figure 5-2 shows the simulated AGRS drawdown at the nine performance
monitor wells over the entire I 0-year simulation. Drawdown in the wells
asymptotically approach steady-state conditions. Simulated steady-state
drawdowns at the nine performance monitor wells ranged from 4.6 to 14.3
64
• •
feet. Using an average response from all nine performance wells, 90% of
the steady-state drawdown is realized after three years and 99 % of the
steady-state drawdown is realized after six years. These results indicate
that nearly all of the expected drawdown from the AGRS has been realized
at the time of the completion of the Final RD.
I 00% Design Stated: Figure 5-2 shows the simulated AGRS drawdown at the nine performance
monitor wells over the entire I 0-year simulation. Drawdown in the wells
asymptotically approach steady-state conditions. Simulated steady-state
drawdowns at the nine performance monitor wells ranged from 4.6 to 14.3
feet. Using an average response from all nine performance wells, 90% of
the steady-state drawdown is realized after three years and 99 % of the
steady-state drawdown is realized after six years. These results indicate
that nearly all of the expected drawdown from the AGRS has been realized
at the time of the completion of the Final RD.
Response: Text revised as requested.
Section 5.3.2 Proposed Final Groundwater Remedy
/comment 76: Please revise the seventh sentence of Section 5.3.2 to state, "The first
stress period uses IO time steps, the second stress period uses 15 time
steps, and the third stress period uses 20 time steps."
90% Design Stated: The transient simulation of the proposed final groundwater remedy also
begins in August 1997 when AGRS extraction was initiated. Three stress
periods were simulated. Like the AGRS transient simulation, the first
stress period is four month in length (August though November 1997) and
uses a total AGRS extraction rate of 5 gpm for the initial period when the
AGRS was not operating at full capacity. The second stress period starts
in December 1997 and continues to August 2000. During this period, the
AGRS is assigned a total extraction rate of25 gpm. The third stress
period starts in September 2000 and continues to July 2007 to represent
the proposed final groundwater remedy. The first stress period uses I 0
times steps, the second stress period uses 15 time steps, and the third stress
period uses 20 time steps. A time step multiplier of 1.1 is used for all
stress periods.
I 00% Design Stated: The transient simulation of the proposed final groundwater remedy also
begins in August 1997 when AGRS extraction was initiated. Three stress
periods were simulated. Like the AGRS transient simulation, the first
stress period is four month in length (August though November 1997) and
uses a total AGRS extraction rate of 5 gpm for the initial period when the
AGRS was not operating at full capacity. The second stress period starts
65
Response:
Table 3-2
/comment 77:
Response:
•
in December 1997 and continues to August 2000. During this period, the
AGRS is assigned a total extraction rate of25 gpm. The third stress
period starts in September 2000 and continues to July 2007 to represent
the proposed final groundwater remedy. The first stress period uses IO
times steps, the second stress period uses 15 time steps, and the third stress
period uses 20 time steps. A time step multiplier of 1.1 is used for all
stress periods.
The "s" was again removed from the word "times" as requested.
Goodness of Fit for Baseline Model
Please revise the title of Table 3-2 to state, "Goodness of Fit for Baseline
Model."
The word "new" was removed from the title of Table 3-2 in Appendix E as
requested.
Table 3-4 Summary of Water Budget for Baseline Model with AGRS
/comment 78: Please revise the title of Table 3-4 to state, "Summary of Water Budget for
Baseline Model with AGRS at 25 gpm."
Response:
APPENDIXF
"At 25 gpm" was added to the title of Table 3-4 in Appendix E as
requested.
REMEDIATION GOAL VERIFICATION PLAN
Section 2. 1.2 Surface Water and Sediment Monitoring Locations
komment 79: Please delete the last sentence of the first paragraph of Section 2.1.2.
90% Design Stated: In addition to the recovery wells, sixteen monitoring wells will be used to
assess the site-wide fate ofRTCs at the site and down-gradient of the site.
These wells will be monitored periodically to assess long-term progress of
the RA toward meeting the ROD groundwater Remediation Goals across
the site and to evaluate the fate ofRTCs in the groundwater. The location
and rationale for the selected monitoring wells, as well as their associated
recovery wells, are listed in Table 2-1.
100% Design Stated: In addition to the groundwater monitoring points described above, three
surface water and sediment stations are also proposed for sampling and
analysis (See Figure 2-3). These sites will be monitored to evaluate the
extent of any adverse effects of groundwater contamination on surface
66
•
water and sediment, if any. During the soil remediation, surface water and
sediment samples were analyzed for PCBs.
Response: Text will be revised.
/comment 80: Please delete the last sentence of Section 2.1.2.
90% Design Stated: In addition to the recovery wells, sixteen monitoring wells will be used to
assess the site-wide fate ofRTCs at the site and down-gradient of the site.
These wells will be monitored periodically to assess long-term progress of
the RA toward meeting the ROD groundwater Remediation Goals across
the site and to evaluate the fate ofRTCs in the groundwater. The location
and rationale for the selected monitoring wells, as well as their associated
recovery wells, are listed in Table 2-1.
100% Design Stated: Three consecutive annual surface water and sediment sampling events
have already been performed at STREAM! - 3 beginning in I 997. To
date, neither the surface water or sediment samples have exceeded North
Carolina State Standards for the RTCs. With the implementation of a
larger scale pump-and-treat system and the completion of soil excavation
at both sites, increasing levels of contamination in the surface water or
sediment is unlikely. Given the consistent nature of the surface water and
sediment data results, these stations are mainly targeted for contingent
sampling of surface water and sediment.
Response: Please refer to EPA Comment 66.
Section 2.2.1 Treatment System Effluent Monitoring
/comment 81: Based on the information provided in Table 4-1 of the Final Design
Report, please revise the second sentence of the second paragraph of
Section 2.2.1 to state, "The estimated TVOC concentration of
approximately 1,500 µg/1 with a design flow rate of 77 gpm yields
approximately 1.4 pounds per day ofVOCs."
Response: Table 4-1 is being revised based upon groundwater modeling to limit any
impacts to the bunched arrowhead habitat. The text in Section 2.2.1 will
be consistent with the revised Table 4-1.
/ Comment 82: Please delete the third sentence of the second paragraph of Section 2.2.1.
90% Design Stated: Not Applicable (NI A)
I 00% Design Stated: Estimated initial groundwater concentrations at the beginning of operation
67
Response:
/comment 83:
90% Design Stated:
100% Design Stated:
Response:
komment84:
90% Design Stated:
• •
are shown in Table 4-1 of the Final Design for Groundwater Report (HSI
Geo Trans, 2000). The estimated TVOC concentration of approximately
500 ug/1 with a design flow rate of 77 gpm yields approximately 0.5
pounds per day ofVOCs. The AGRS groundwater, with TVOC
concentrations nearly three time greater than the estimated concentration
for the final system, has consistently been treated to less than 5 ug/1 total
VOCs (with one exception in March 1998). The process has been
designed to treat the extracted groundwater to Federal MCLs. The
treatment system effluent water will be sampled during start up and during
operations to ensure proper function of the air stripper and to ensure
POTW requirements are met.
The referenced sentence will be modified, not deleted, based upon the
revised Table 4-1.
Please revise the first sentence of the third paragraph of Section 2.2.1 to
state, "The design air stream of 850 cubic feet per minute through the air
stripper, prior to any air treatment, will contain approximately_
mg/cubic meter of VOCs or_ parts per billion." Additionally, please
reevaluate the methodologies used to derive all results given in Section
2.2.1 and include a separate figure/table that describes the rationale,
assumptions, calculations (including dimensional analysis), and results.
NIA
The designed air stream of 850 cubic feet per minute through the air
stripper, prior to any air treatment, will contain approximately 5 mg/cubic
meter ofVOCs (0.5 lbs/day ofVOCs divided by 850 cfm of air (1440
min/day)(lb-mol/359cf)(29mw for air)) which is equivalent to less than 1
ppm. OSHA's allowable occupational exposure is 100 ppm (time-
weighted average) for an 8 hour work day. Regulatory limits 15A NCAC
2H.0610(h) specifies a maximum yearly discharge of 13,000 pounds and
4,000 pounds of PCE and TCE, respectively. These exposure limits and
maximum annual discharges are orders of magnitude greater than the
expected average untreated air stream concentrations.
Text will be revised to clearly state calculated amounts ofVQCs expected
in the air stream.
Please revise the second sentence of the third paragraph of Section 2.2.1 to
include the compound(s) that the Occupational Safety and Health
Administration (OSHA) allowable occupational exposure applies to.
NIA
68
•
I 00% Design Stated: The designed air stream of 850 cubic feet per minute through the air
stripper, prior to any air treatment, will contain approximately 5 mg/cubic
meter of VOCs (0.5 lbs/day of VOCs divided by 850 cfm of air ( 1440
min/day)(lb-mol/359ct)(29mw for air)) which is equivalent to less than 1
ppm. OSHA's allowable occupational exposure is 100 ppm (time-
weighted average) for an 8 hour work day. Regulatory limits 15A NCAC
2H.061 0(h) specifies a maximum yearly discharge of 13,000 pounds and
4,000 pounds of PCE and TCE, respectively. These exposure limits and
maximum annual discharges are orders of magnitude greater than the
expected average untreated air stream concentrations.
Response: The second sentence of the third paragraph of Section 2.2.1 will be
revised.
Section 2.2.2 Ecological Monitoring
,'. /Comment 85: Please delete the last three sentences of the third paragraph of Section
2.2.2.
90% Design Stated: N/ A
I 00% Design Stated: Monitoring will be conducted during the period of groundwater extraction
at the GE/Shepherd Farm Superfund site. In wetlands that have been
monitored in other areas, onset of groundwater extraction sufficient to
cause impacts to wetland physiognomy has resulted in rapid reduction in
wetland condition. It is therefore likely that any impacts will manifest
themselves within the first several years after increase in groundwater
extraction. If significant impacts to the abundance and geographical extent
of bunched arrowhead, or major changes to wetlands condition are not
observed within 3 years, monitoring could be reduced to once per year. If
no significant impacts are observed within 10 years and the bunched
arrowhead is healthy, monitoring could appropriately be ceased.
Monitoring of bunched arrowhead habitat should be ceased if at any time
the species is extirpated from this site.
Response: Note: A new Section 2.2.2 Site-wide Monitoring has been added.
/ Comment 86:
Ecological Monitoring is now Section 2.2.3. Text can be modified to state
that changes in monitoring frequency will be made pending EPA and NC
DENR approval. Quarterly monitoring is not prudent for the entire
duration of this remedial action nor if the species is extirpated from this
site.
Please revise the second sentence of the fourth paragraph of Section 2.2.2
to state, "Monitoring of vegetation at these locations will occur monthly
69
•
for the first three years of groundwater extraction."
90% Design Stated: N/ A
I 00% Design Stated: Monitoring of hydrological parameters will be conducted once every two
weeks during the first three years of groundwater extraction at the bunched
arrowhead habitat and at the large wetland at the GE Subsite. Monitoring
of vegetation at these locations will occur three times per year -spring
(March), summer (June), and fall (September). A photographic log from
selected points will be compiled during each vegetative monitoring event.
Additional monitoring at the bunched arrowhead habitat will include
identifying the extent of habitat, noting the density of plants, and
identifying any competitive species. Specific monitoring for hydrological
parameters and vegetation are included in Attachment I (RGVP Field
Sampling and Analysis Plan)
Response: Note: A new Section 2.2.2 Site-wide Monitoring has been added.
Ecological Monitoring is now Section 2.2.3. Since GE will be monitoring
hydraulic parameter once every two weeks during the first three years of
groundwater extraction and at the large wetland at the GE Subsite, GE
does not propose to monitor vegetation more than three times per year. To
date, there has been no regularly scheduled vegetation monitoring while
the AGRS has extracted groundwater at a rate of 25 gallons per minute.
/ Comment 87: Please revise the fourth paragraph of Section 2.2.2 to include the
statement, "GE may seek authorization from the appropriate regulatory
agencies to reduce hydrological and vegetative monitoring to a quarterly
basis after three years if major changes to wetlands condition and
significant impacts to the abundance and geographical extent of the
bunched arrowhead habitat are not observed."
90% Design Stated: NIA
100% Design Stated: Monitoring of hydrological parameters will be conducted once every two
weeks during the first three years of groundwater extraction at the bunched
arrowhead habitat and at the large wetland at the GE Subsite. Monitoring
of vegetation at these locations will occur three times per year -spring
(March), summer (June), and fall (September). A photographic log from
selected points will be compiled during each vegetative monitoring event.
Additional monitoring at the bunched arrowhead habitat will include
identifying the extent of habitat, noting the density of plants, and
identifying any competitive species. Specific monitoring for hydrological
parameters and vegetation are included in Attachment I (RGVP Field
Sampling and Analysis Plan)
70
•
Response: Please refer to response to Comments 85 and 86.
/ Comment 88: Please rc;vise the last sentence of Section 2.2.2 to state, "Specific
monitoring for hydrological parameters and vegetation are included in
Attachment I (Field Sampling and Analysis Plan)."
90% Design Stated: NI A
I 00% Design Stated: Monitoring of hydrological parameters will be conducted once every two
weeks during the first three years of groundwater extraction at the bunched
arrowhead habitat and at the large wetland at the GE Subsite. Monitoring
of vegetation at these locations will occur three times per year -spring
(March), summer (June), and fall (September). A photographic log from
selected points will be compiled during each vegetative monitoring event.
Additional monitoring at the bunched arrowhead habitat will include
identifying the extent of habitat, noting the density of plants, and
identifying any competitive species. Specific monitoring for hydrological
parameters and vegetation are included in Attachment 1 (RGVP Field
Sampling and Analysis Plan)
Response: Note: A new Section 2.2.2 Site-wide Monitoring has been added.
Ecological Monitoring is now Section 2.2.3. The Field Sampling and
Analysis Plan will no longer be referred to as the RGVP Field Sampling
and Analysis Plan.
Section 2.3 Monitoring Parameters
/comment 89: Please revise the first and third paragraphs of Section 2.3 to state that in
the event that a RTC is consistently below its corresponding Record of
Decision (ROD) remediation goal for four consecutive quarterly
monitoring events at a particular groundwater monitoring well or
residential well, GE may seek authorization from the US EPA and the NC
DENR to reduce groundwater monitoring for the RTC to annual
monitoring for that groundwater monitoring well or residential well.
However, in the event that the RTC is detected above the ROD
remediation goal during annual sampling of the groundwater monitoring
well or residential well, quarterly groundwater monitoring for the RTC
must be re-initiated at that groundwater monitoring well or residential
well.
Response:
j Comment 90:
Please refer to response to EPA Comment 44.
Please revise the first and second sentences of the second paragraph of
Section 2.3 to state, "Surface water and sediment samples will also be
71
90% Design Stated:
100% Design Stated:
Response:
./comment 91:
Response:
/comment 92:
90% Design Stated:
I 00% Design Stated:
Response:
/ Comment 93:
• •
sampled for the RTC list of parameters. In the event that a parameter has
been removed from the list of monitored parameters for all groundwater
monitoring well and residential well samples, GE may seek
authorization from the US EPA and the NC DENR to remove that
parameter from the list for surface water and sediment samples.
However, five year samples shall be collected from all surface water
and sediment sampling locations for analyses of all RTCs."
NIA
Surface water, sediment, and residential well samples will also be sampled
for the RTC list of parameters. In the event that a parameter has been
removed from the list of monitored parameters for groundwater samples,
that parameter will also be removed from the list for surface water,
sediment, and residential well samples. Anticipated parameters for which
GE will request removal, after four consecutive temporal measurements
are obtained, include SVOCs at the Shepherd Farm subsite and PCBs at
both sites.
Text will be revised. Please refer to response to EPA Comment 44 .
Please detail how GE proposes to eliminate PCBs from the list of RTCs as
PCBs are not a target groundwater contaminant.
GE is not proposing to eliminate PCBs from surface water and sediment
monitoring. PCBs are not a target groundwater contaminant but will be
monitored as a part of the site wide soil remediation efforts.
Please revise the fourth paragraph of Section 2.3 to include provisions for
the quarterly sampling of the treatment system influent and effluent, in
addition-to those to demonstrate compliance with the publicly owned
treatment works (POTW) requirements. Please include provisions for the
analysis of the influent and effluent samples for analyses for all RTCs.
NIA
In addition to the groundwater RTC parameters, treatment system water
effluent monitoring parameters (target compounds) are listed in Table 1-2.
POTW discharge requires the sampling of these parameters.
Text will be consistent with responses to EPA Comment 35 and EPA
Comment 4.
Please revise Section 2.3 to describe the treatment system air emission
72
•
monitoring parameters and frequency.
Response: Text will be revised.
Section 2.4 Monitoring Schedule
/comment 94: Please revise the first item in the first paragraph of Section 2.4 to state,
"Performance Monitoring."
90% Design Stated: • Perfomance Monitoring: Performed to evaluate progress toward
achievement of Remediation Goals; and
100% Design Stated: • Perfomance Monitoring: Performed to evaluate progress toward
achievement of remediation goals; and
Response:
/comment 95:
90% Design Stated:
The letter "r" was added to the first item of Section 2.4 as requested.
Please delete the last two sentences in the second paragraph of Section 2.4.
NIA
I 00% Design Stated: Figure 2-6 shows a monitoring schedule time period schematic with
hypothetical concentrations and assumes attainment of remediation goals
in September 2008. This schematic is shown for illustrative purposes only
to depict the progression from Performance Monitoring, to Exit
Monitoring, to Closure Monitoring. Performance Monitoring will be
performed as long as recovery wells are operating at a subsite and RTC
concentrations are above remediation goals. Exit Monitoring will begin
when RTC concentrations are below remediation goals. Upon termination
of recovery well operations in any subsite, Closure Monitoring will begin
in the given subsite.
Response: Text will be revised.
Section 2.4.1 Performance Monitoring
/comment 96: Please revise the second and third sentences of Section 2.4.1 to state,
"Performance wells and residential wells at both the GE and
Shepherd Farm Subsites will be sampled quarterly for the first 12
quarters. GE may then seek authorization from the US EPA and the
NC DENR to reduce the sampling frequency of performance wells
and residential wells to a semi-annually basis for the subsequent four
events. Upon completion of semiannual sampling, GE may seek
73
Response:
•
authorization from the US EPA and the NC DENR to reduce the
sampling frequency of performance wells and residential wells to an
annual basis thereafter. Surface water and sediment stations will be
sampled annually."
Please refer to EPA Comment 182 on the Pre-Final (90%) Remedial
Design and Remedial Action Work Plan for Groundwater which stated,
"we recommend that this RGVP be revised to include the schedule
originally proposed for performance sampling. In particular:
• All performance monitor wells should be sampled quarterly
for the first three years, semiannually for the next two
years, and annually thereafter."
No direction was initially given requiring Agency or NC DENR approval
to adhere to the originally proposed schedule. Agency and NC DENR
approval will be sought to enter Exit Monitoring and Closure Monitoring.
/comment 97: Please revise the last sentence of Section 2.4.1 to state, "In addition to
POTW effluent monitoring requirements, groundwater treatment
system influent and effluent will be sampled for all RTCs on a
quarterly basis."
90% Design Stated: NIA
I 00% Design Stated: Treated water that is being used as process water at the GE facility is
subject to the testing requirements of the POTW. Table 2-4 depicts the
proposed sampling for treated effluent water, both as the water exits the
groundwater treatment process and as the water exits the GE facility. The
POTW Industrial User Permit requires daily flow measurements; four
samples per month for BOD, TSS, temperature, pH, COD, ammonia(N),
and oil/grease; monthly samples for cadmium, chromium, copper, cyanide,
lead, mercury, nickel, silver, and zinc; quarterly samples for aluminum,
arsenic, molybdenum, and selenium; and bi-annual sampling for total toxic
organics (TTO) which includes VOCs (EPA 624), SVOCs (EPA 625), and
PCBs/pesticides (EPA 608). In addition to the sampling requirements for
the GE facility effluent water, groundwater treatment process water will be
sampled quarterly.
Response: Text will be revised to be consistent with responses to EPA Comment 35
and EPA Comment 4.
Section 2.4.2 Exit Monitoring
74
• •
/ Comment 98: Please delete the word "statistically" from the second sentence of Section
2.4.2.
90% Design Stated: The Exit Monitoring Period is intended to cover the period when RAPM
data indicate that operations of all recovery wells should cease. The Exit
Monitoring will be initiated by EPA approval of a Groundwater Recovery
Termination Report (GRTR). A GRTR may be submitted for one or both
of the subsites. The Exit Monitoring may consist of a combination of the
following options depending on the observed data characteristics over
different zones of the subsites:
I 00% Design Stated: The Exit Monitoring Period is intended to cover the period when RAPM
data indicate that operations of particular recovery wells should cease. At
such time as sample data indicate that remediation goals have been
attained, quarterly sampling will occur for four consecutive quarterly
events to statistically support the achievement of remediation goals. The
mean of the four consecutive quarterly events will be the yearly average,
adjusted for seasonality. The mean of the yearly averages will be
compared to the remediation goals for assessing attainment. In the case
Response:
Comment 99:
· that the first four consecutive quarterly sampling events result in a yearly
average that is less than the remediation goals, the mean of the yearly
averages will be equal to the one yearly average. The Exit Monitoring will
be followed by a request to EPA for approval of a Groundwater Recovery
Termination Report (GRTR). A GRTR may be submitted for one or both
of the subsites.
The word statistically was removed as requested.
Please revise the third, fourth and fifth sentences of Section 2.4.2 to state,
"Upon achieving the specified ROD remediation goals for all RTCs at
all performance monitoring wells and residential wells at a particular
subsite, GE shall seek written approval from the US EPA and the NC
DENR to discontinue the groundwater extraction system for that
subsite. Once written approval has been received from the US EPA
and the NC DENR, GE may discontinue the groundwater extraction
system for that subsite. At this point, quarterly groundwater
monitoring for all RTCs shall resume at all performance monitoring
wells and residential wells at that subsite until GE can demonstrate
that the specified ROD remediation goals for all RTCs have been
maintained for four consecutive quarterly groundwater sampling
events at that subsite. If GE cannot make this demonstration to the
satisfaction of the US EPA and the NC DENR, GE shall evaluate
additional groundwater treatment options in order to meet the
specified ROD remediation goals at that subsite."
75
•
90% Design Stated: The Exit Monitoring Period is intended to cover the period when RAPM
data indicate that operations of all recovery wells should cease. The Exit
Monitoring will be initiated by EPA approval of a Groundwater Recovery
Termination Report (GRTR). A GRTR may be submitted for one or both
of the subsites. The Exit Monitoring may consist of a combination of the
following options depending on the observed data characteristics over
different zones of the subsites:
I 00% Design Stated: The Exit Monitoring Period is intended to cover the period when RAPM
data indicate that operations of particular recovery wells should cease. At
such time as sample data indicate that remediation goals have been
attained, quarterly sampling will occur for four consecutive quarterly
events to statistically support the achievement ofremediation goals. The
mean of the four consecutive quarterly events will be the yearly average,
adjuste1 for seasonality. The mean of the yearly averages will be
compared to the remediation goals for assessing attainment. In the case
that the first four consecutive quarterly sampling events result in a yearly
average that is less than the remediation goals, the mean of the yearly
averages will be equal to the one yearly average. The Exit Monitoring will
be followed by a request to EPA for approval of a Groundwater Recovery
Termination Report (GRTR). A GRTR may be su_bmitted for one or both
of the subsites. ·
Response: Text can be revised if specific wording is provided from the Agency and
NC DENR that defines "maintaining the specified ROD remediation goals
for all RTCs for four consecutive quarterly groundwater sampling events"
and "the satisfaction of the US EPA and the NC DENR."
Section 2.4.3 Closure Monitoring
Comment 100: Please replace the first seven sentences of Section 2.4.3 with the following
statements: "Upon achieving the specified ROD remediation goals for
all RTCs at all performance monitoring wells and residential wells at
a particular subsite, GE shall seek written approval from the US EPA
and the NC DENR to discontinue the groundwater extraction system
for that subsite. Once written approval has been received from the
US EPA and the NC DENR, GE may discontinue the groundwater
extraction system for that subsite. At this point, quarterly
groundwater monitoring for all RTCs shall resume at all performance
monitoring wells and residential wells at that subsite until GE can
demonstrate that the specified ROD remediation goals for all RTCs
have been maintained for four consecutive quarterly groundwater
sampling events at that subsite. If GE cannot make this
demonstration to the satisfaction of the US EPA and the NC DENR,
GE shall evaluate additional groundwater treatment options in order
76
• •
to meet the specified ROD remediation goals at that subsite."
90% Design Stated: lfRTC concentrations over a zone ofa subsite display stable or decreasing
trends below ROD Remediation Goals, Closure Monitoring will be
pursued. The Closure Monitoring will consist of two rounds of annual
confirmatory sampling, where attainment of cleanup will be evaluated
consistent with EPA Guidance, Methods for Evaluating the Attainment of
Cleanup Standards (USEP A, 1992a). Upon completion of confirmatory
sampling and analysis, a subsite or zone Closure Report will be submitted
for EPA review and approval.
I 00% Design Stated: If RTC concentrations over a zone of a subsite display stable or decreasing
trends below ROD remediation goals during Exit Monitoring, Closure
Monitoring will be pursued. Upon achieving the specified remediation
goals at all performance monitoring wells at a subsite, GE will seek
written approval from the Agency to discontinue the groundwater
extraction system. Once written approval is received, GE will discontinue
the groundwater extraction system. At this point Closure Monitoring will
begin and consist of four consecutive quarterly groundwater sampling
events from all performance monitoring wells. The mean of the four
consecutive quarterly events will be the yearly average, adjusted for
seasonality. The mean of the yearly averages will be compared to the
remediation goals for assessing attainment. In the case that the first four
consecutive quarterly sampling events result in a yearly average that is less
than the remediation goals, the mean of the yearly averages will be equal
to the one yearly average. Upon completion of confirmatory sampling and
analysis, a subsite or zone Closure Report will be submitted for EPA
review and approval.
Response: Text can be revised if specific wording is provided from the Agency and
NC DENR that defines "maintaining the specified ROD remediation goals
for all RTCs for four consecutive quarterly groundwater sampling events"
and "the satisfaction of the US EPA and the NC DENR."
Section 2.5 Statistical Procedures
Comment 101:
Response:
Although the information presented in Section 2.5 may provide interesting
details regarding contaminant trend analysis, please note that the statistical
procedures as described in Section 2.4.2, Section 2.4.3 and Section 2.5 are
not acceptable for exit or closure monitoring.
In Comment 180 from the Agency's comments on the Pre-Final (90%)
Remedial Design and Remedial Action Work Plan for Groundwater, the
NC DENR Division of Water Quality, Groundwater Section protocols for
77
•
exit and closure monitoring are presented as follows. "If an individual
groundwater monitoring well achieves the specified ROD remediation
goals prior to the other groundwater monitoring wells, annual sampling of
the groundwater monitoring well shall commence until such time as all
performance monitoring wells achieve the specified ROD remediation
goals for four consecutive quarterly groundwater sampling events. Upon
achieving the specified ROD remediation goals at all performance
monitoring wells, GE shall seek written approval from the US EPA and
the NC DENR to discontinue the groundwater extraction system. Once
written approval has been received from the US EPA and the NC DENR,
GE may discontinue the groundwater extraction system. At this point,
quarterly groundwater sampling shall resume at all performance
monitoring wells until GE can demonstrate that the specified ROD
remediation goals have been maintained for four consecutive quarterly
groundwater sampling events. If GE cannot make this demonstration to
the satisfaction of the US EPA and the NC DENR, GE shall evaluate
additional groundwater treatment options in order to meet the specified
ROD remediation goals."
Section 2.5 states that analysis ofRTC data will include the use of
statistical procedures, consistent with EPA Guidance, including:
• EPA, Methods for Evaluating the Attainment of Cleanup
Standards, Volume 2: Ground Water, EPA 230-R-92-14, July
1992a;
• EPA, Statistical Analysis of Ground-Water Monitoring Data at
RCRA Facilities, Interim Final Guidance, EPA/530-SW-89-026,
1989.
• EPA, Statistical Analysis of Ground-Water Monitoring Data at
RCRA Facilities, Addendum to Interim Final Guidance, July
1992b.
If the cited EPA references are merely interesting and not acceptable for
exit or closure monitoring, please provide reference for the appropriate
guidance document and define the following phrases that were
summarized: "achieves the specified ROD remediation goals",
"demonstrate that the specified ROD remediation goals have been
maintained for four consecutive quarterly groundwater sampling events",
and "demonstration to the satisfaction of the US EPA and the NC DENR."
Section 3.1 Quarterly Monitoring Reports
/ Comment 102: Please revise Section 3.1 to include provisions for the submittal of a
summation of decisions regarding recovery well and groundwater
78
Response:
•
treatment system operation and an appendix consisting oflaboratory and
quality assurance/quality control (QA/QC) reports.
Per EPA Comment 69, references to recovery well operation status have
been deleted in the Annual Monitoring Reports; and therefore will not be
included in the Quarterly Monitoring Reports. Text will be revised to
include an appendix consisting of laboratory and quality assurance/quality
control (QA/QC) reports.
Figure 2-3 Location of Surface Water and Sediment Sampling Stations
Jeomment 103:
Response:
Please revise Figure 2-3 to include a note that states, "Upon approval of
the Final Design Report, surface water and sediment sampling station
STREAM-3 will be abandoned in favor of surface water and sediment
sampling station STREAM-4."
The figure was revised as described in EPA comment 29.
Figure 2-5 Decision Process for Requesting Removal of RTC Analytes
/comment 104:
Response:
/comment 105:
Response:
/Comment 106:
Response:
Please revise the title of Figure 2-5 to state, "Decision Process for
Requesting Removal ofRTC Analytes."
Text in Figure 2-5 will be revised.
Please revise Figure 2-5 to indicate that in the event that a RTC is
consistently below its corresponding ROD remediation goal for four
consecutive quarterly monitoring events at a particular sampling location,
GE may seek authorization from the US EPA and the NC DENR to reduce
subsequent monitoring for the RTC to annually for that particular
sampling location. However, in the event that the RTC is detected above
the ROD remediation goal during annual monitoring of the sampling
location, quarterly monitoring for the RTC must be re-initiated at that
particular sampling location.
Text in Figure 2-5 will be revised.
Please revise Figure 2-5 to include provision for receiving Agency
approval for removal of analytes before conducting future analyses for the
particular analyte on an annual basis
Text in Figure 2-5 will be revised.
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• •
Table 1-2 POTW Effluent Limitations and Monitoring Requirements
/ Comment 107:
Response:
Please revise Table 1-2 to include provisions for continual flow
measurements and four samples per week for BOD, TSS, temperature, pH,
COD, ammonia (as N), and oil/grease.
Table 1-2 will be revised to be consistent with the response to EPA
Comment 4.
Table 2-3 Proposed Sample Collection Schedule
/ Comment 108:
Response:
Comment 109:
Response:
Please revise Table 2-3 to include provisions for the collection of
residential well samples on a quarterly basis for the first two years, on a
semi-annual basis for the following two years, and on an annual basis
thereafter.
Please refer to response to NC DENR Comment 42.
Please revise Table 2-3 to include a note that all changes in monitoring
frequency are subject to US EPA and NC DENR approval.
Please refer to response to NC DENR Comment 96.
Table 2-4 Groundwater Treatment System Effluent Compliance Monitoring
!comment 110: Please revise Table 2-4 to include provisions for POTW effluent
compliance monitoring for four samples per week for BOD, TSS,
temperature, COD, ammonia (as N), and oil/grease.
Response: Text wili be revised to be consistent with response to EPA Comment 4.
j Comment 111: Please revise Table 2-4 to include provisions for quarterly groundwater
treatment system influent and effluent analyses for all RTCs.
Response: Text will be revised to be consistent with responses to EPA Comment 35
and EPA Comment 4.
Attachment 1 Field Sampling and Analysis Plan
/comment 112: Please revise the title of Attachment I to state, "Field Sampling and
Analysis Plan."
90% Design Stated: Remediation Goal Verification Field Sampling and Analysis Plan
80
•
I 00% Design Stated: Remediation Goal Verification Field Sampling and Analysis Plan
Response:
Table of Contents
/comment 113:
The title of Attachment I was revised as requested.
Several discrepancies were noted during the review of the Table of
Contents. Please correct these oversights.
I) The entry for Section 3.2.5.3 should indicate that Section 3.2.5.3 is
on page 3-10.
2) The entry for Section 3.2.7 should indicate that Section 3.2.7 is on
page 3-11.
3) Please delete the dotted line beneath the entry for Section 3.2.7.3 in
the Table of Contents.
Response: The Table of Contents was revised as requested.
Section 1.1 Objectives
/comment 114: Please revise the second sentence of Section I. I to state, "The SAP is
consistent with the content criteria specified in the Consent Decree
Statement of Work (SOW) and includes sampling objectives, locations,
frequency, equipment and procedures, handling, and analyses."
90% Design Stated: The General Electric/Shepherd Farm Superfund Site consists of two non-
contiguous areas in East Flat Rock, Henderson County, North Carolina
(Figure 1-1). These subsites include the GE facility (Figure 1-2) and the
Shepherd Farm property (Figure 1-3), referred to as the GE Subsite and
Shepherd Farm Subsite, respectively.
I 00% Design Stated:
Response:
/~omment 115:
The General Electric/Shepherd Farm Superfund Site consists of two non-
contiguous areas in East Flat Rock, Henderson County, North Carolina
(Figure 1-1 ). These subsites include the GE facility (Figure 1-2) and the
Shepherd Farm property (Figure 1-3), referred to as the GE Subsite and
Shepherd Farm Subsite, respectively.
Text was revised as requested.
Please revise the second sentence of the second paragraph of Section 1.1
to state, "Additionally, treatment system effluent sampling will be
perf01med to monitor system performance and meet publicly operated
treatment works (POTW) requirements."
81
• •
90% Design Stated: Remediation goals were established in the Record of Decision (ROD)
(USEPA, 1995) for seven VOCs, one semi-volatile compound (SVOC), and
five metals. Table 1-1 lists the remediation goals for these remediation
target compounds (RTCs). To attain the stated Remediation Goals, a
groundwater remedy has been selected, as described in the Pre-Final (90%)
Design for Groundwater (HSI Geo Trans, 1999). This remedy was initiated
in 1997 with the Accelerated Groundwater Remediation System (AGRS).
The AGRS consists of.four recovery wells (RW-1 though RW-4), a
treatment system, an outfall, and associated pumps, piping and controls.
I 00% Design Stated: Remediation goals were established in the Record of Decision (ROD)
(USEPA, 1995) for seven volatile organic compounds (VOCs), one semi-
volatile compound (SVOC), and five metals. Table 1-1 lists the remediation
goals for these remediation target compounds (RTCs). To attain the stated
Remediation Goals, a groundwater pump-and-treat system will be operated.
This remedy was initiated in 1997 with the Accelerated Groundwater
Remediation System (AGRS).
Response: Text was revised as requested.
Section 1.2 Overview of Field Activities
/comment I 16: Please revise the last sentence of the first paragraph of Section 1.2 to state,
"Periodic sampling, as described in the RGVP, will be performed to
monitor the performance of the RA."
90% Design Stated: RA sampling activities will be performed at both the GE Subsite and the
Shepherd Farm Subsite. Media to be sampled will include groundwater,
surface water, and surface water sediment. An initial round of baseline
data was collected during the summer of 1997. Periodic sampling, as
described in the RGVP, and annual monitoring of the surface water,
sediment, and residential wells will be collected to monitor the
performance of the RA.
I 00% Design Stated: RA sampling activities will be performed at both the GE Subsite and the
Shepherd Farm Subsite for the following three activities:
• Performance monitoring
• Exit monitoring
• Closure monitoring
Media to be sampled will include groundwater, surface water, sediment,
treated effluent groundwater, and treated effluent air from the air stripping
process. An initial round of baseline groundwater, surface water, and
82
Response:
• •
sediment data was collected during the summer of 1997, prior to AGRS
start-up. Periodic sampling, as described in the RGVP, and annual
monitoring of the surface water, sediment, and residential wells will be
performed to monitor the performance of the RA.
The following text was removed as requested, "and annual monitoring of
the surface water, sediment, and residential wells"
Section 2.1 Performance Well Sampling
/comment 117: Please append the second paragraph of Section 2.1 with the statement, "At
a minimum, groundwater sampling protocols will comply with the
requirements given in the United States Environmental Protection Agency
(US EPA) Environmental Investigation Standard Operating Procedures
and Quality Assurance Manual (EISOPQAM)."
90% Design Stated:
I 00% Design Stated:
Response:
/comment ll8:
Response:
NIA
Groundwater samples are proposed to be collected using dedicated low
flow sampling pumps. Sampling procedures will follow the guidelines
published in Low-Flow (Minimal Drawdown) Ground-water Sampling
Procedures (Puls and Barcelona, 1996). Field parameters such as pH,
temperature, conductivity, and turbidity will be measured at the time of
sample collection using a Horiba U-10 or equivalent water meter.
Groundwater sampling information and field parameter measurements will
be recorded on groundwater sampling forms. Groundwater samples will
be collected from dedicated tubing and ports.
Text will be revised as requested.
Please revise Section 2.1 to include specific details regarding all aspects of
groundwater sampling. Such items include, but are not limited to,
groundwater sampling, field parameter measurement procedures,
equipment calibration procedures, decontamination procedures, the
collection of QA/QC samples, etc. Simple reference to published
guidelines or the US EPA Region IV EISOPQAM is inadequate.
Section 2.1 will be revised.
Section 2.2 Surface Water and Sediment Sampling
/comment 119: Please revise the last sentence of the first paragraph of Section 2.2 to state,
"Surface water samples will be analyzed for seven VOCs, one SVOC, five
metals and PCBs."
83
90% Design Stated:
I 00% Design Stated:
Response:
/comment 120:
90% Design Stated:
•
Surface water and sediment sample locations are depicted on Figure 2-3.
Surface water and sediment samples were collected prior AGRS start-up to
establish baseline conditions for evaluating the performance of the
remedial activities. Samples will be collected along Bat Fork Creek by
wading in the shallow stream. Samples will be collected while facing
upstream. Samples will be collected in order from downstream to
upstream sampling locations. Surface water samples will be analyzed for
seven VOCs, one SVOC, and five metals.
Surface water and sediment sample locations are depicted on Figure 2-3.
Surface water and sediment samples were collected prior AGRS start-up to
establish baseline conditions for evaluating the performance of the
remedial activities. Samples will be collected along Bat Fork Creek by
wading in the shallow stream. Samples will be collected while facing
upstream. Samples will be collected in order from downstream to
upstream sampling locations. Surface water samples will be analyzed for
seven VOCs, one SVOC, and five metals.
Please see response to NC DENR Comment 91.
Please revise the last sentence of Section 2.2 to state, "A sample may be
homogenized in a bowl using circular stirring with occasional reverse
direction stirring."
The sediment sample at each station will be collected after the surface
water sample has been collected. A representative portion of the
streambed will first be identified. A sample will be collected using a
stainless steel scoop. Aliquots of the sediment sample will be placed in a
stainless steel bowl. The VOC sample will be collected directly from the
bowl using a stainless steel spoon. The sample for VOC analysis will not
be homogenized because of the high likelihood for release ofVOCs during
homogenization. The sediment material in the bowl will then be
homogenized for the metal and PCB samples. A bowl may be
homogenized using circular stirring with occasional reverse direction
stirring.
I 00% Design Stated: The sediment sample at each station will be collected after the surface
water sample has been collected. A representative portion of the
streambed will first be identified. A sample will be collected using a
stainless steel scoop. Aliquots of the sediment sample will be placed in a
stainless steel bowl. The VOC sample will be collected directly from the
bowl using a stainless steel spoon. The sample for VOC analysis will not
be homogenized because of the high likelihood for release of VOCs during
homogenization. The sediment material in the bowl will then be
84
•
homogenized for the metal and PCB samples. A bowl may be
homogenize_d using circular stirring with occasional reverse direction
stirring.
Response: Text revised as requested.
Section 2.3 Residential Well Sampling
./comment 121:
Response:
/Comment 122:
Response:
Please revise Section 2.3 to include specific details regarding all aspects of
residential well sampling. Such items include, but are not limited to,
residential well sampling, field parameter measurement procedures,
equipment calibration procedures, decontamination procedures, the
collection of QA/QC samples, etc. Simple reference to published
guidelines or the US EPA Region IV EISOPQAM is inadequate.
Further detail on residential well sampling will be provided as requested.
Please provide justification for the collection of residential well samples
using single-use Teflon hailers. The use of Low-Flow (Minimal
Drawdown) Groundwater Sampling Procedures as used in performance
well sampling is much more appropriate and preferred.
Residential wells already contain their original, dedicated, water-well
pumps. Residential well samples have been and are proposed to be
collected from the water spigot.
Section 2.4 Recovery Well Sampling
komment 123:
Response:
Please revise Section 2.4 to include provisions for collecting groundwater
samples from all new recovery wells at least two weeks following the
completion of their initial development and analyses for all RTCs.
Groundwater samples from all new recovery wells will be collected within
two weeks following the completion of their initial development and
analyzed for all RTCs.
Section 3.1.1 Treatment System Effluent Water
komment 124: Please revise the fourth sentence of Section 3.1.1 to state, "In addition to
POTW effluent monitoring requirements, groundwater treatment
system influent and effluent will be sampled for all RTCs on a
quarterly basis."
Response: Please refer to the response to EPA Comment 35.
85
•
Section 3.2.1 Monitoring Schedule
.komment 125: Please delete the last three sentences of the first paragraph of Section
3.2.1.
90% Design Stated:
I 00% Design Stated:
Response:
/comment 126:
90% Design Stated:
NIA
Monitoring will be conducted during the period of groundwater extraction
at the GE/Shepherd Farm Superfund site. In wetlands that have been
monitored in the southeastern United States, onset of groundwater
extraction sufficient to cause impacts to wetland physiognomy has resulted
in rapid reduction in wetland condition. It is therefore likely that any
impacts will manifest themselves within the first several years after an
increase in groundwater extraction. If significant impacts to the
abundance and geographical extent of bunched arrowhead, or major
changes to wetlands condition are not observed within 3 years, monitoring
could be reduced to once per year. If no significant impacts are observed
within 10 years and the bunched arrowhead is healthy, monitoring could
appropriately be ceased. Monitoring of bunched arrowhead habitat should
be ceased if at any time the species is extirpated from this site.
Please refer to response to NC DENR Comment 85.
Please revise the second sentence of the second paragraph of Section 3 .2.1
to state, "Monitoring of vegetation at these locations will occur monthly
for the first three years of groundwater extraction."
NIA
100% Design Stated: Monitoring of hydrological parameters will be conducted bi-monthly
during the first three years of groundwater extraction at the bunched
arrowhead habitat and at the large wetland at the GE Subsite. Monitoring
of vegetation at these locations will occur three times per year -spring
(March), summer (June), and fall (September). A photographic log from
selected points will be compiled during each vegetative monitoring event.
Additional monitoring at the bunched arrowhead habitat will include
identifying the extent of habitat, noting the density of plants, and
identifying any competitive species. Table 3-2 provides the proposed
schedule for biological evaluation monitoring. Figure 3-1 provides the
vegetation monitoring data form.
Response:
/Comment 127:
Please refer to response to NC DENR Comment 86.
Please revise the second paragraph of Section 3.2.1 to include the
86
• •
statement, "GE may seek authorization from the appropriate regulatory
agencies to reduce hydrological and vegetative monitoring to a quarterly
basis after three years if major changes to wetlands condition and
significant impacts to the abundance and geographical extent of the
bunched arrowhead habitat are not observed."
90% Design Stated: NIA
I 00% Design Stated: Monitoring of hydrological parameters will be conducted bi-monthly
during the first three years of groundwater extraction at the bunched
arrowhead habitat and at the large wetland at the GE Subsite. Monitoring
of vegetation at these locations will occur three times per year -spring
(March), summer (June), and fall (September). A photographic log from
selected points will be compiled during each vegetative monitoring event.
Additional monitoring at the bunched arrowhead habitat will include
identifying the extent of habitat, noting the density of plants, and
identifying any competitive species. Table 3-2 provides the proposed
schedule for biological evaluation monitoring. Figure 3-1 provides the
vegetation monitoring data form.
Response: Please refer to response to NC DENR Comments 85 and 86.
Section 3.2.4.4.1 Composition
/comment 128: Please revise the third item given in Section 3 .2.4.4.1 to indicate a score of
2 for the category, >80% cover ofOBL and/or FACW species.
90% Design Stated: NIA
I 00% Design Stated: Trees are defined as woody species> 4 cm DBH and> 1.0 m in height.
Response:
Tree species composition, based on estimated cover by species, will be
ranked based on the scale which follows:
0 <50% cover of OBL and/or F ACW species
I 50-80% cover of OBL and/or F ACW species
6 >80% cover of OBL and/or F ACW species
Text ·was revised as requested.
Figure 2-3 Location of Surface Water and Sediment Sampling Stations
komment 129: Please revise Figure 2-3 to include a note that states, "Upon approval of
the Final Design Report, surface water and sediment sampling station
STREAM-3 will be abandoned in favor of surface water and sediment
87
•
sampling station STREAM-4."
Response: The note was added to Figure 2-3 as requested.
Figure 3-1 Vegetative Monitoring Data Form
/comment 130:
Response:
/Comment 131:
Response:
(Figure 3-1) Please revise the second item given in the section for
Vegetation Zonation to state, "Somewhat abnormal zonation -some signs
of abnormal ground cover zonation mainly limited to the wetland edge."
The letters "g" and "r" were added to the second item for Vegetation
Zonation of Figure 3-1 in Attachment! to Appendix Fas requested.
(Figure 3-1) Please revise the second item given in the section for Shrub
Zonation to state, "Somewhat abnormal zonation -some signs of
abnormal shrub zonation mainly limited to the wetland edge."
The letter "m" was added to the second item for Shrub Zonation of Figure
3-1 in Attachment! to Appendix Fas requested.
Table 1-2 Summary of Field RA Activities
/comment 132:
Response:
/comment 133:
Response:
/ Comment 134:
Response:
Please revise Table 1-2 to indicate that the residential monitoring well
network will follow the sampling conventions of the groundwater at the
GE and Shepherd Farm Subsites (quarterly sampling for first three years,
semi-annual sampling for two years, and annually thereafter).
Table 1-2 will be revised to be consistent with response to NC DENR
Comment 42.
Please revise Table 1-2 to include provisions for quarterly groundwater
treatment system influent and effluent monitoring for all RTCs.
Text will be revised to be consistent with responses to EPA Comment 35
and EPA Comment 4.
Please revise Table 1-2 to include provisions for continual flow
measurements; four samples per week for BOD, TSS, temperature, pH,
COD, ammonia (as N), and oil/grease; monthly samples for cadmium,
chromium, copper, cyanide, lead, mercury, nickel, silver, and zinc;
quarterly samples for aluminum, arsenic, molybdenum, and selenium; and,
bi-annual sampling for total toxic organics (TTO) which
Table 1-2 will be revised to be consistent with the response to EPA
88
/ Comment 135:
Response:
Comment 136:
Response:
Comment 4.
Please delete the reference to the sampling of composite sampling ports in
Table 1-2.
Text will be deleted.
Please revise Table 1-2 to include a note that all changes in monitoring
frequency are subject to US EPA and NC DENR approval.
Text will be revised to be consistent with response to NC DENR
Comment44
Table 1-3 Estimated Numbers of Samples
/comment 137:
Response:
/comment 138:
Response:
/comment 139:
Response:
~omment 140:
Response:
Please revise Table 1-3 to include provisions for quarterly residential well
sampling.
Please refer to response to NC DENR Comment 42.
Please revise Table 1-3 to include provisions for quarterly groundwater
treatment system influent and effluent monitoring for all RTCs.
Table 1-3 will be revised to be consistent with responses to EPA Comment
35 and EPA Comment 4.
Please revise Table 1-3 to include provisions for continual flow
measurements; four samples per week for BOD, TSS, temperature, pH,
COD, ammonia (as N), and oil/grease; monthly samples for cadmium,
chromium, copper, cyanide, lead, mercury, nickel, silver, and zinc;
quarterly samples for aluminum, arsenic, molybdenum, and selenium; and,
bi-annual sampling for TIO which includes VOCs, SVOCs, and
PCBs/pesticides.
Table 1-3 will be revised to be consistent with responses to EPA Comment
35 and EPA Comment 4.
Please revise Table 1-3 to include provisions for semi-annual air emission
sampling.
Table 1-3 will be revised.
Table 1-5 Summary of Analytical Methods for Groundwater Treatment System
Effluent POTW Compliance Monitoring
89
_,,,Comment 141:
Response:
•
Please revise Table 1-5 to include the analytical methods to be used for
BOD, TSS, temperature, pH, COD, ammonia (as N), oil/grease, cadmium,
copper, cyanide, silver, aluminum, arsenic, molybdenum, and selenium
analyses. Furthermore, please delete the references to beryllium, cobalt
and iron analyses.
Table 1-5 will be revised to be consistent with responses to EPA Comment
35 and EPA Comment 4.
Table 2-1 Proposed Sample Collection Schedule
/comment 142: Please revise Table 2-1 to include provisions for the collection of
residential well samples on a quarterly basis for the first two years, on a
semi-annual basis for the following two years, and on an annual basis
thereafter.
Response:
Comment 143:
Response:
Please refer to response to NC DENR Comment 42.
Please revise Table 2-1 to include a note that all changes in monitoring
frequency are subject to US EPA and NC DENR approval.
Please refer to response to NC DENR Comment 96.
Table 3-1 Groundwater Treatment System Effluent Compliance Monitoring
/comment 144:
Response:
komment 145:
Response:
Please revise Table 3-1 to include provisions for POTW effluent
compliance monitoring for four samples per week for BOD, TSS,
temperature, COD, ammonia (as N), and oil/grease.
Table 1-3 will be revised to be consistent with responses to EPA Comment
35 and EPA Comment 4.
Please revise Table 3-1 to include provisions for quarterly groundwater
treatment system influent and effluent analyses for all RTCs.
Table 1-3 will be revised to be consistent with responses to EPA Comment
3 5 and EPA Comment 4.
Table 3-2 Schedule for Biological Evaluation Monitoring
/comment 146: Please revise Table 3-2 to include provisions for monthly vegetative,
muck, and photographic monitoring.
Response: Please refer to response to NC DENR Comment 86.
90
•
Attachment 2 Quality Assurance Project Plan
/Comment 147: Please revise the title of Attachment 2 to state, "Quality Assurance Project
Plan."
90% Design Stated: Remediation Goal Verification Quality Assurance Project Plan
100% Design Stated: Remediation Goal Verification Quality Assurance Project Plan
Response:
List of Tables
/comment 148:
Response:
Text revised as requested.
Several discrepancies were noted during the review of the List of Tables.
Please correct these oversights.
• The title for Table 1-2 should state, "POTW Effluent Limitations
and Monitoring Requirements.
• The title for Table 3-1 should state, "Summary of RA Field
Activities."
• The title for Table 7-2 should state, "Summary of Analytical
Methods for Groundwater Treatment System Effluent POTW
Compliance Monitoring."
Text was revised as requested
Section 1.4 Purpose and Organization of the QAPP
/ Comment 149: Please revise the first item of the second paragraph of Section I .4 to state,
"Performance Monitoring."
Response:
komment 150:
90% Design Stated:
Text was revised as requested.
Please revise the second sentence of the third paragraph of Section l.4 to
state, "Exit Monitoring will begin when RTC concentrations for all
performance monitoring wells and residential wells at a given subsite
are below remediation goals."
NIA
!00% Design Stated: Performance Monitoring will be performed as long as recovery wells are
operating at a subsite and RTC concentrations are above remediation
goals. Exit Monitoring will begin when RTC concentrations are below
91
•
remediation goals. Upon termination of recovery well operations in any
subsite, Closure Monitoring will begin in the given subsite.
Response: Text was revised as requested.
Section 4.6 Record Keeping
/eomment 151:
Response:
Please submit examples of all sample data sheets ( e.g., monitor well
sampling data sheet) as exhibits to Section 4.6.
The requested sample data sheets will be added to Section 4.6.
Section 8.1 Data Reduction
Jcomment 152: Please revise the third sentence of Section 8.1 to state, "More detailed
explanations of these data reduction procedures are described in
Accutest's QAPP."
90% Design Stated: Data reduction is the production of the analytical result summaries from
the original instrumental information. Data reduction involves the
mathematical and/or statistical calculations used by the laboratory to
convert raw data to the reported data. More detailed explanations of these
data reduction procedures are described in the QAPP. Wherever possible,
electronic means will be used to transmit, reduce and present analytical
results in order to minimize errors due to transcription, calculation, or data
entry.
I 00% Design Stated: Data reduction is the production of the analytical result summaries from
the original instrumental information. Data reduction involves the
mathematical and/or statistical calculations used by the laboratory to
convert raw data to the reported data. More detailed explanations of these
data reduction procedures are described in the Accutest's QAPP.
Wherever possible, electronic means will be used to transmit, reduce and
present analytical results in order to minimize errors due to transcription,
calculation, or data entry.
Response: The word "the" was removed as requested.
Table 1-2 POTW Effluent Limitations and Monitoring Requirements
/comment 153: Please revise Table 1-2 to include provisions for continual flow
measurements and four samples per week for BOD, TSS, temperature, pH,
COD, ammonia (as N), and oil/grease.
92
Response:
•
Table 1-2 will be revised to be consistent with responses to EPA Comment
35 and EPA Comment 4.
Table 3-1 Summary of RA Field Activities
/comment 154: Please revise Table 3-1 to indicate that the residential monitoring well
network will follow the sampling conventions of the groundwater at the
GE and Shepherd Farm Subsites ( quarterly sampling for first three years,
semi-annual sampling for two years, and annually thereafter).
Response:
komment 155:
Response:
/comment 156:
Response:
/comment 157:
Response:
Comment 158:
Response:
Please refer to response to NC DENR Comment 42.
Please revise Table 3-1 to include provisions for quarterly groundwater
treatment system influent and effluent monitoring for all RTCs.
Table 3-1 will be revised to be consistent with responses to EPA Comment
35 and EPA Comment 4.
Please revise Table 3-1 to include provisions for continual flow
measurements; four samples per week for BOD, TSS, temperature, pH,
COD, ammonia (as N), and oil/grease; monthly samples for cadmium,
chromium, copper, cyanide, lead, mercury, nickel, silver, and zinc;
quarterly samples for aluminum, arsenic, molybdenum, and selenium; and,
bi-annual sampling for TIO which includes VOCs, SVOCs, and
PCBs/pesticides.
Table 3-1 will be revised to be consistent with responses to EPA Comment
35 and EPA Comment 4.
Please delete the reference to the sampling of composite sampling ports in
Table 3-1.
Text will be deleted.
Please revise Table 3-1 to include a note that all changes in monitoring
frequency are subject to US EPA and NC DENR approval.
Please refer to response to NC DENR Comment 96.
Table 3-3 DQO Levels for Analyses and Measurements
/comment 159: Please revise Table 3-3 to include provisions for the collection and
analyses of quarterly groundwater treatment system influent samples for
analyses of all RTCs.
93
Response:
vk:omment 160:
Response:
•
Table 3-3 will be revised.
Please revise Table 3-3 to include data quality objective (DQO) level IV
analyses for all effluent analyses.
Table 3-3 will be revised.
Table 7-2 Summary of Analytical Methods for Groundwater Treatment System
Effluent POTW Compliance Monitoring
/comment 161:
Response:
Attachment 3
Table of Contents
Please revise Table 7-2 to include the analytical methods to be used for
BOD, TSS, temperature, pH, COD, ammonia (as N), oil/grease, cadmium,
copper, cyanide, silver, aluminum, arsenic, molybdenum, and selenium
analyses. Furthermore, please delete the references to beryllium, cobalt
and iron analyses.
Table 7-2 will be revised to be consistent with the responses to EPA
Comment 4 and EPA Comment 35
Ecological Evaluation of the Potential Effects of Remedial
Groundwater Extraction on Wetlands and Streams
/comment 162: Please revise the Table of Contents to reflect that Section 3.4.4.3 is on
page 26.
Response: The Table of Contents has been revised.
Section 2.1.2 Physiographic Setting
/comment 163: Please revise the second paragraph of Section 2.1.2 to state,
"Physiographically it is located in an area where there is an apparent
discontinuity between the slope of the water table and the ground surface
(Figure 2-3)."
90% Design Stated: NIA
I 00% Design Stated: The physiographic setting has been disturbed by human activities with
recontouring of nearby land surfaces during the railway and roadway
construction. The extent to which these alterations may have been altered
groundwater flows is not known.
Response: The second paragraph of Section 2.1.2 does not contain the above
94
• •
referenced sentence. The first paragraph of Section 2.1.2 does contain
such a sentence and the wording 'discontinuity between in the slope' has
been change to 'discontinuity between the slope.'
Section 3.0 Monitoring
/comment 164: Please delete the last three sentences of the third paragraph of Section 3.0.
90% Design Stated: NIA
I 00% Design Stated: In wetlands that have been monitored elsewhere in the southeastern United
States, onset of groundwater extraction sufficient to cause impacts to
wetland physiognomy has resulted in rapid reduction in wetland condition.
It is therefore likely that any impacts will manifest themselves within the
first several years after full implementation of the full groundwater
extraction system. If significant impacts to the abundance and
geographical extent of bunched arrowhead, or major changes to wetland
condition are not observed within 3 years, monitoring could be reduced to
once per year. If no significant impacts are observed within IO years and
the bunched arrowhead is healthy, monitoring could appropriately be
ceased. Monitoring of bunched arrowhead habitat should be ceased if at
any time the species is extirpated from this site.
Response: The last three sentences of the paragraph represent the opinion of a
biological expert. The text will not be changed.
Section 3.1 Monitoring Schedule
/Comment 165: Please revise the third and fourth sentences of Section 3.1 to state,
"Monitoring of vegetation will occur monthly for the first three years of
groundwater extraction. GE may seek authorization from the
appropriate regulatory agencies to reduce hydrological and vegetative
monitoring to a quarterly basis after three years if major changes to
wetlands condition and significant impacts to the abundance and
geographical extent of the bunched arrowhead habitat are not
observed."
90% Design Stated: NIA
I 00% Design Stated: Monitoring should be conducted during the period of water production at
the GE/Shepherd Farm Superfund site. Monitoring of hydrological
parameters should be conducted at least twice per month. Monitoring of
vegetation can appropriately occur three times per year -spring (March),
summer (June), and fall (September). The spring event should be
95
Response:
f Comment 166:
Response:
•
conducted during a period of active growth. If growth is not evident at the
time of the spring event, the event should be delayed, perhaps until late
April. Table 3.1 provides an overview of the suggested monitoring
schedule.
The recommendations and opinions stated in Attachment 3 Ecological
Evaluation of the Potential Effects of Remedial Groundwater Extraction
on Wetlands and Streams at the General Electric/Shepherd Farm
Superfund Site represent the opinion of a biological expert. The text will
not be changed.
Please revise Table 3.1 -Monitoring Schedule to reflect monthly
vegetative, muck and photographic monitoring of the bunched arrowhead
habitat.
The recommendations and opinions stated in Attachment 3 Ecological
Evaluation of the Potential Effects of Remedial Groundwater Extraction
on Wetlands and Streams at the General Electric/Shepherd Farm
Superfund Site represent the opinion of a biological expert. The text will
not be changed.
Section 4.0 Contingency Actions
/comment 167: Section 4.0, Section 4.1, Section 4.2, Section 4.3 and Section 4.4 indicate
that the adverse impacts due to groundwater extraction are anticipated to
occur in the wetlands and, in particular, the bunched arrowhead habitat.
The objective of the groundwater remedial design was to utilize
groundwater models and the recommendations from Dr. Newberry and
Biological Research Associates to define a groundwater system that
contains and treats the maximum amount of the groundwater plume
without harming the bunched arrowhead plant. It appears that this was
done; yet, Section 4.0, Section 4.1, Section 4.2, Section 4.3 and Section
4.4 indicate that the groundwater extraction may or already has caused
damage to the bunched arrowhead habitat. This is not consistent. Either
the design has achieved its objectives or it has not. If the design has not
achieved its objectives, then the design should not have been presented to
the Agencies until it had met the above criteria.
Response: Please refer to the response the Fish and Wildlife Service Comments.
96
• •
Section 4.2 Reduced Flows in Bat Fork Creek or Impacts to Downstream wetlands
Reliant for Hydration or Water from Bat Fork Creek
f Comment 168: Please restate the third sentence of Section 4.2 to make sense.
90% Design Stated: NIA
I 00% Design Stated: GE has need for water as part of its manufacturing process. As of
December 1999, GE had repiped the AGRS groundwater extraction
Response:
system so that all water can be routed for use by GE as process water.
Discharge after use, per GE's POTW pretreatment agreement is
preferentially to the municipal sewage system, and alternatively, to Bat
Fork Creek via its NPDES permit. If changes to the creek prove to cause
unacceptable ecological impacts, then through a NPDES permit, treated
water, either reused or not, could be routed to the creek at a rate adequate
to make up for the reduction due to pumping. Quantity of discharged
water could be estimated based on estimated flow reductions due to
quantities of water pumped within the previous month, and that quantity of
water could then be released into the stream instead of into the municipal
sewer system. If appropriate measures are used at the release point, there
is no reason why discharge into the creek would cause erosion or other
problems. Unless substantial changes to water chemistry are made,
excluding removal of contaminants, there is no reason to think that
addition of water to the stream would not successfully replace water lost
due to groundwater reductions.
Text will be revised.
Section 5.0 Summary
j Comment 169: Section 5.0 indicates that the adverse impacts due to groundwater
extraction are anticipated to occur in the wetlands and, in particular, the
bunched arrowhead habitat. The objective of the groundwater remedial
design was to utilize groundwater models and the recommendations from
Dr. Newberry and Biological Research Associates to define a groundwater
system that contains and treats the maximum amount of the groundwater
plume without harming the bunched arrowhead plant. It appears that this
was done; yet, Section 5.0 indicates that the groundwater extraction may
or already has caused damage to the bunched arrowhead habitat. This is
not consistent. Either the design has achieved its objectives or it has not.
If the design has not achieved its objectives, then the design should not
have been presented to the Agencies until it had met the above criteria.
Response: Please refer to the response to Fish and Wildlife Service Comments.
97
•
Appendix A Field Monitoring Form
JComment 170:
Response:
/ Comment 171:
Response:
APPENDIXG
!comment 172:
Response:
/ Comment 173:
Response:
/ Comment 174:
(Field monitoring fom1) Please revise the second item given in the section
for Vegetation Zonation to state, "Somewhat abnormal zonation -some
signs of abnormal groundcover zonation mainly limited to the wetland
edge."
The text 'oundcover' will be changed to 'groundcover.'
(Field monitoring form) Please revise the second item given in the section
for Shrub Zonation to state, "Somewhat abnormal zonation -some signs
of abnormal shrub zonation mainly limited to the wetland edge."
Text will be revised.
DESIGN CALCULATIONS AND MANUFACTURERS
EQUIPMENT INFORMATION
The response to US EPA comment #4 indicates that each tank to be used
for effluent storage is I 2 feet in diameter and 5 feet high. A tank of this
size has approximately 4,230 gallons capacity. The tank specified has
30,000 gallons capacity. Please clarify this discrepancy.
Please refer to response to EPA Comment 77. Please note that in NC
DENR Comment 18, the State has requested that the singular and plural
forms of the word gallon be correctly used. The use of the plural form of
the word gallon in the above comment is inconsistent with the singular
form of the word gallon in EPA Comment 77.
Please revise Appendix G to include the cut sheets for the two 30,000
gallon tanks to be used for effluent storage prior to use within the plant.
The cut sheets should include all dimensions, tank capacity, materials of
construction, and all necessary appurtenances for tank operation.
Additionally, please include cut sheets of the secondary containment as
well as the necessary calculations to demonstrate adequate secondary
containment capacity.
Cut sheets will be provided.
Please revise the vapor GAC usage calculations included in Appendix G to
account for all VOCs at the design influent concentrations (including the
150% factor of safety) as specified in Table 4-1 of the Final Design
Report.
98
Response:
./"Comment 175:
Response:
/comment 176:
Response:
komment 177:
Response:
/comment 178:
Response:
APPENDIXH
•
GAC usage calculations will be revised.
Please revise the air stripper program results include in Appendix G to
account for all VOCs at the design influent concentrations (including the
150% factor of safety) as specified in Table 4-1 of the Final Design
Report.
Comment is assumed to state, "Please revise the air stripper program
results included in Appendix G to account for all VOCs at the design
influent concentrations ... " Air stripper program results will be revised.
Detail No. 4 -NCDOT R/W Crossing at US 176 (Spartanburg Highway)
on Drawing No. 3F indicates that the proposed piping will have a +0.90%
slope. Please provide the justification for crossing Spartanburg Highway
with a positive slope, as opposed to using gravity to the advantage.
Furthermore, please detail whether this positive slope is to be used solely
for crossing Spartanburg Highway or if additional sections of this
particular pipe run are to be constructed with a positive slope. Lastly,
please detail whether the positive slope was considered in the pipeline
calculations included in Appendix G.
RWSF-4 is at an elevation of2165 ft, ms!. The treatment building is at an
elevation of 2174 ft, ms!. It is not possible to get the water from this well
to the treatment building without a positive slope. All head loss was
considered in the design calculations.
Please include a copy of the cut sheets for the QED EZ-16.4 Low Profile
Air Stripper in Appendix G, however, please leave the copy of the cut
sheets for the QED EZ-16.4 Low Profile Air Stripper in Appendix C.
Cut sheet will be included in Appendix G as requested.
Please include a copy of the cut sheets for the TetraSolv VF-3000 vapor
treatment unit in Appendix G, however, please leave the copy of the cut
sheets for the TetraSolv VF-500 vapor treatment unit in Appendix C.
Cut sheet will be included in Appendix G as requested.
HYDROLOGIC STUDY OF THE BUNCHED ARROWHEAD
HABITAT
Section 1.1 Background
/Comment 179: Please revise the fourth sentence of the fifth paragraph of Section I.I to
99
•
state, "A hydrogeologic study of the bunched arrowhead conducted by
Snipes et al. (1986) concluded that a small amount of groundwater
extraction, as little as IO gpm, could cause the plant to perish at a 50-acre
habitat in South Carolina."
90% Design Stated: The primary factor for the rarity of the Bunched arrowhead is the rarity of
the proper habitat. The plant grows in unique conditions; mucky seeps
located in gently sloping bogs with slow, continuous, cool, clean water.
The Bunched arrowhead is very susceptible to small fluctuations in the
water table elevation (U.S. Fish and Wildlife, 1983). A hydrogeologic
study of the Bunched Arrowhead conducted by Snipes et al. (1986)
concluded that a small amount of groundwater extraction, a little as 10
gpm, could cause the plant to perish at a 50-acre habitat in South Carolina.
Impacts to the Bunched arrowhead habitat should be avoided to comply
with the location-specific Applicable or Relevant and Appropriate
Requirements (ARARs) on wetlands (Executive Order 11990) and
endangered species (Endangered Species Act) as noted in Table 18 of the
ROD.
I 00% Design Stated: The primary factor for the rarity of the bunched arrowhead is the rarity of
the proper habitat. The plant grows in unique conditions; mucky seeps
located in gently sloping bogs with slow, continuous, cool, clean water.
The bunched arrowhead is very susceptible to small fluctuations in the
water table elevation (U.S. Fish and Wildlife, 1983). A hydrogeologic
study of the bunched arrowhead conducted by Snipes et al. (1986)
concluded that a small amount of groundwater extraction, a little as l 0
gpm, could cause the plant to perish at a 50-acre habitat in South Carolina.
Impacts to the bunched arrowhead habitat should be avoided to comply
with the location-specific Applicable or Relevant and Appropriate
Requirements (ARARs) on wetlands (Executive Order 11990) and
endangered species (Endangered Species Act) as noted in Table 18 of the
ROD.
Response: The text has been revised to state "as little as IO gpm" instead of
incorrectly stating "a little as 10 gpm."
Section 3.5 Hydrogeology
/comment 180: Please revise the second sentence of the last paragraph of Section 3.5 to
state, "AGRS extraction represents 4.2% of net groundwater recharge for
the entire basin."
90% Design Stated: AGRS extraction was added to the baseline model using a groundwater
extraction rate of25 gpm (or 4,813 ft3/day). AGRS extraction represents
100
•
4.4% of net groundwater recharge for the entire basin.
I 00% Design Stated: The groundwater budget for baseline conditions (without the AGRS)
includes inflow from recharge (96.7% or 110,277 ft3/day), Bat Fork Creek
(2.3%), and settlement ponds (I.I%) and outflow to Bat Fork Creek
(92.1 % or I 05,104 ft3/day), wetlands (6.5%), residential pumpage (0.8%),
and settlement ponds (0.6%). Modeled outflow to the three wetlands in
and around the bunched arrowhead habitat was 7,373 f't3/day.
AGRS extraction was added to the baseline model using a groundwater
extraction rate of25 gpm (or 4,813 ft3/day). AGRS extraction represents
4.4% of net groundwater recharge for the entire basin. The model shows
that the AGRS causes a 3 7% reduction to the outflow in the three wetlands
in and around the bunched arrowhead habitat outflow (790 to 497 ft3/day).
Note that it would take a period of time for the system to reach steady state
and therefore for the drawdowns and impacts to be fully realized.
Groundwater modeling of the AGRS indicated that 90% of the steady-
state drawdown would be realized after 3 years (in August 2000) and 99%
after 6 years (in August 2003).
Response: Inflow from recharge (i.e., net groundwater recharge) is indicated to be 110,277
ft3/day and AGRS groundwater extraction is indicated to be 4,813 ft3/day in the
100% Design. 4,813 divided by 110,277 is equal to 0.043644364 which is
equivalent to 4.4%. Therefore it is correct to state that AGRS extraction
represents 4.4% of net groundwater recharge for the entire basin.
Section 4.2 Groundwater
/comment 181: Please revise the second sentence of the last paragraph of Section 4.2 to
state, "Rounds of water-level measurements were collected from the
piezometers and all existing site monitor wells on June 7, September 13
and December 7, 1999."
90% Design Stated: The location and top of casing elevations of the piezometers were
surveyed by a licensed surveyor. Rounds of water-level measurements
were collected from the piezometers and all existing site monitor wells on
June 7 and September 13, 1999. A digital water-level recorder was
installed in piezometer BAPZ-3 which is located at the southern and
upgradient edge of the Bunched arrowhead habitat. Water-level
measurements are automatically recorded hourly and stored with a battery-
powered, digital water-level recorder. Water-level data may be
downloaded periodically to a computer for processing.
I 00% Design Stated: The location and top of casing elevations of the piezometers were
IO I
• •
surveyed by a licensed surveyor. Rounds of water-level measurements
were collected from the piezometers and all existing site monitor wells on
June 7 and September 13, 1999. A digital water-level recorder was
installed in piezometer BAPZ-3 which is located at the southern and
upgradient edge of the bunched arrowhead habitat. Water-level
measurements are automatically recorded hourly and stored with a battery-
powered, digital water-level recorder. Water-level data may be
downloaded periodically to a computer for processing.
Response: Text has been revised to state that quarterly monitoring has occurred beginning
June 7, 1999.
Section 5.2 Groundwater
/comment 182: Please revise the last sentence of the fourth paragraph of Section 5.2 to
state, "Monitor wells MW-30 and MW-62 are included in Attachment 2
to show background conditions."
90% Design Stated: Quarterly water-level data have been collected from all site monitor wells
since AGRS start up in July 1997. Hydrographs for select wells (MW-12,
18, 25, 28, 42, and 63) are included in Attachment I to illustrate the
change in groundwater elevations from AGRS pumping center to the
Bunched arrowhead habitat. Monitor well MW-42 is closest to the AGRS
pumping center. Monitor well MW-28 is closest to the Bunched
arrowhead habitat. Monitor wells MW-18 and MW-25 are in between
MW-42 and MW-28. Monitor wells MW-30 and MW-63 are background
wells.
I 00% Design Stated: Quarterly water-level·data have been collected from all site monitor wells
since AGRS start up in July 1997. Hydrographs for select wells (MW-12,
18, 25, 28, and 42) are included in Attachment 2 to illustrate the change in
groundwater elevations from AGRS pumping center to the bunched
arrowhead habitat. Monitor well MW-42 is closest to the AGRS pumping
center. Monitor well MW-28 is closest to the bunched arrowhead habitat.
Monitor wells MW-18 and MW-25 are in between MW-42 and MW-28.
Monitor well MW-30 is included in Attachment 2 to show background
conditions.
Response: Text revised as requested.
/comment 183: Please revise the second sentence of the seventh paragraph of Section 5.2
to state, "Near the AGRS pumping center (e.g., MW-42), the water table
levels have been lowered 12 feet on average to one foot on average at
MW-25."
102
•
90% Design Stated: Figure 5-4 shows the observed AGRS drawdown in June and September
1999. Near the AGRS pumping center (e.g., MW-42), water levels have
been lowered over 14 feet. The magnitude of the drawdown decreases
with distance from the pumping center. Near the Bunched arrowhead
habitat (e.g., MW-25 and MW-28), measurable water level declines have
been observed. The drawdown increased from June to September 1999.
100% Design Stated: Figure 5-4 shows the observed AGRS drawdown in 1999. Near the AGRS
pumping center ( e.g., MW-42), the water table levels has been lowered 12
feet on averageto one foot on average at MW-25. The magnitude of the
drawdown decreases with distance from the pumping center. The
drawdown at the bunched arrowhead (MW-28) could not be deciphered.
Response: Text revised to use the correct verb tense and to add a space between the words
"average" and "to."
Section 6.0 Conclusions
!comment 184: Please revise the sixth sentence of the third paragraph of Section 6.0 to
state, "The site experienced a deficit in precipitation for 1999."
90% Design Stated: The AGRS, pumping approximately 25 gpm since July 1997, has caused
over 14 feet of drawdown in the pumping center at the GE Subsite. The
magnitude of the drawdown diminishes with distance from the pumping
center. Data indicate that drawdown may be occurring near the Bunched
arrowhead habitat (see MW-25 and MW-28 in Figure 5-4). The
magnitude of drawdown has increased from June to September 1999.
These conclusions are subject to some error introduced by changes in
natural conditions. Daily groundwater elevation data and rainfall
measurements clearly show the strong influence rainfall has on the water
table elevation. The site is experiencing a deficit in precipitation for 1999.
It is difficult to differentiate AGRS drawdown from any possible natural
water level declines due to below average precipitation.
I 00% Design Stated: The AGRS has caused approximately 14 feet of drawdown in the water
table elevation in the pumping center at the GE Subsite. The magnitude of
the drawdown diminishes with distance from the pumping center. Data
indicate that drawdown may be occurring near the bunched arrowhead
habitat (see MW-25 and MW-28 in Figure 5-4). Any conclusions about
the magnitude of drawdown at the bunched arrowhead habitat are subject
to some error introduced by changes in natural conditions, most
importantly rainfalL Daily groundwater elevation data and rainfall
measurements clearly show the strong influence rainfall has on the water
table elevation. The site is experienced a deficit in precipitation for 1999.
103
• •
It is difficult to differentiate AGRS drawdown from any possible natural
water level declines due to below average precipitation. Groundwater
modeling (HSI GeoTrans, 2000a) indicates that it takes approximately .. three years for the system to approach steady-state conditions (i.e., 90% of
the steady-state drawdown realized) after AGRS startup. This would
indicate that nearly all of the AGRS drawdown should be realized by
August 2000. Similarly, nearly all of the drawdown from the expanded,
final system should be realized three years after startup.
Response: The text has been revised to state: The site experienced a deficit in precipitation
for 1999 that has continued into the year 2000.
APPENDIX I CONSTRUCTION SPECIFICATIONS AND DESIGN DRAWINGS
Drawing No. 3A
/comment 185:
Response:
Drawing No. 7
/comment 186:
Response:
/comment 187:
Response:
APPENDIXK
1 "=40' General Site and Piping Layout Plan
Please revise Drawing No. 3a to indicate that the typical well completion
detail, as referenced on Drawing No. 3, is located on Drawing No. 6 as
Detail No. I.
The reference on Drawing 3 was revised as requested.
Metering Well Vault Detail
Please revise the Typical Meter Vault Section Detail on Drawing No. 7 to
reflect the specification in Section 4.3 .2 that indicates "The header pipe
and power supply electrical line will be placed in a trench at
approximately 36-inches and 24-inches below grade, respectively."
The detail and/or the specifications will be modified to remove any
inconsistencies.
Please revise Drawing No. 7 to include a detail of all electrical wiring
appurtenances, including electrical conduit enclosures, junction boxes and
pull boxes.
The requested detail was added to Drawing 9.
HEAL TH AND SAFETY PLAN
Section 6.5 PPE Inspection Checklist and Maintenance
!comment 188: Please revise the last sentence of Section 6.5 to state, "PPE inspection
procedures are outlined in Sections 6.5.1 through 6.5.3."
104
Response:
APPENDIXL
Table of Contents
/comment 189:
Response:
• •
The text has been changed to no longer state 'Section s6.5. l through 6.5.3'
but to correctly state 'Sections 6.5.1 through 6.5.3.'
OPERATION AND MAINTENANCE MANUAL
Please revise the Table of Contents to include Section 2.7 -
Documentation.
The Table of Contents has been revised.
105
•
ATTACHMENT 1
GROUNDWATER MODELING RES UL TS
HSIGEOTRANS
Table 1. Comparison of various low impact remediation scenarios at the GE Subsite using the groundwater model.
Current Source Area Balanced Containment
AGRS Focus Approach Focus
Scenario Number (Figure Number) 1 , .)
Total Extraction Rate (gpm) 25 7.5 14.5 23
Total Number of Extraction Wells 4 3 5 5
Water Table Bunched Arrowhead Habitat BAPZ-3 0.26 0.10 0.10 0.10 • Drawdown (ft) MW-28 0.21 0.08 0.07 0.08
Large Wetland Next to Bat Fork Creek MW-27 0.03 0.01 0.17 0.19
Baseflow Bunched Arrowhead Habitat 37 15 15 15
Reduction(%) Large Wetland Next to Bat Fork Creek 10 3 24 27
Capture of Total VOCs Mass(%) 77 29 59 72
Note: Model scenarios 1 -

3

additionally include 17 gpm extraction from the Shepherd Farm Subsite using 4 extraction wells .
•
~ -N-
I
0
RW-1 Recovery well
0 2-5 extraction rate (gpm)
Baseline PCE
concentration contour
500 1000
SCALE IN FEET
L.OCATIOH
Source removal at the GE Subsite
with 7 .5 gpm extraction at 3 wells
GE Subsite, East Flat Rock, NC
HSI CHEO<EDBY RTH
ORAfTEO BY TCL
,n 4'11 GEQTRANS ,,...... AGRSmod1.WOR
--A 1TI'RA TEO! COMPANY DATE 5/3/00
FIGURE:
1
0
RW-1 Recovery well
® 2 extraction rate (gpm)
Baseline PCE
concentration contour
500 1000
SCALE IN FEET
Balanced removal at the GE Subsite
with 14.5 gpm extraction at 5 wells
GE Subsite, East Flat Rock, NC
...
HSI CHECKEOBY RTH FIGURE:
CRAFTED BY TCL a ◄ GEOTRANS ........ AGRSmod2.WOR
A nnA TEOI COMPANY DATE 5/3/00
2
-
~ -N-
I
0
RW-S Recovery well
0 5 extraction rate (gpm)
Baseline PCE
concentration contour
500 1000
SCALE IN FEET
LOCATION
Containment removal at the GE Subsite
with 23 gpm extraction at 5 wells
GE Subsite, East Flat Rock, NC
HSI """"'8>0Y RTH
llRAFfEO av TCL
GEOTRANS "-'"""' AGRSmod2.WOR
FIGURE:
3
A TE1'llA not COMPANY CATI! 5/3/00
• •
ATTACHMENT 2
LOW-FLOW SAMPLING GUIDANCE
HSIGEOTRANS
Unite.tes
Environmental Protection
Agency
Office of
Research and
Development
Office .lid Waste
and Emergency
Response
EPA/540/S-95/504
April 1996
&EPA Ground Water Issue
LOW-FLOW (MINIMAL DRAWDOWN)
GROUND-WATER SAMPLING PROCEDURES
by Robert W. Puls' and Michael J. Barcelona'
Background
The Regional Superfund Ground Water Forum is a
group of ground-water scientists, representing EPA's
Regional Superfund Offices, organized to exchange
information related to ground-water remediation at Superfund
sites. One of the major concerns of the Forum is the
sampling of ground water to support site assessment and
remedial performance monitoring objectives. This paper is
intended to provide background information on the
development of low-flow sampling procedures and its
application under a variety of hydrogeologic settings. It is
hoped that the paper will support the production of standard
operating procedures for use by EPA Regional personnel and
other environmental professionals engaged in ground-water
sampling.
For further information contact: Robert Puls, 405-436-8543,
Subsurface Remediation and Protection Division, NRMRL,
Ada, Oklahoma.
I. Introduction
The methods and objectives of ground-water
sampling to assess water quality have evolved over time.
Initially the emphasis was on the assessment of water quality
of aquifers as sources of drinking water. Large water-bearing
units were identified and sampled in keeping with that
objective. These were highly productive aquifers that
supplied drinking water via private wells or through public
water supply systems. Gradually, with the increasing aware-
ness of subsurface pollution of these water resources, the
understanding of complex hydrogeochemical processes
which govern the fate and transport of contaminants in the
subsurface increased. This increase in understanding was
also due to advances in a number of scientific disciplines and
improvements in tools used for site characterization and
ground-water sampling. Ground-water quality investigations
where pollution was detected initially borrowed ideas,
methods, and materials for site characterization from the
water supply field and water analysis from public health
practices. This included the materials and manner in which
monitoring wells were installed and the way in which water
was brought to the surface, treated, preserved and analyzed.
The prevailing conceptual ideas included convenient generali-
zations of ground-water resources in terms of large and
relatively homogeneous hydrologic units. With time it became
apparent that conventional water supply generalizations of
homogeneity did not adequately represent field data regard-
ing pollution of these subsurface resources. The important
role of heterogeneity became increasingly clear not only in
geologic terms, but also in terms of complex physical,
'National Risk Management Research Laboratory, U.S. EPA
1University of Michigan
Superfund Technology Support Center for
Ground Water
National Risk Management Research Laboratory
Subsurface Protection and Remediation Division
Robert S. Kerr Environmental Research Center
Ada, Oklahoma
•
chemical and biological subsurface processes. With greater
appreciation of the role of heterogeneity, it became evident
that subsurface pollution was ubiquitous and encompassed
the unsaturated zone to the deep subsurface and included
unconsolidated sediments, fractured rock, and aquitards or
low-yielding or impermeable formations. Small-scale pro-
cesses and heterogeneities were shown to be important in
identifying contaminant distributions and in controlling water
and contaminant flow paths.
It is beyond the scope of this paper to summarize all
the advances in the field of ground-water quality investiga-
tions and remediation, but two particular issues have bearing
on ground-water sampling today: aquifer heterogeneity and
colloidal transport. Aquifer heterogeneities affect contaminant
flow paths and include variations in geology, geochemistry,
hydrology and microbiology. As methods and the tools
available for subsurface investigations have become increas-
ingly sophisticated and understanding of the subsurface
environment has advanced, there is an awareness that in
most cases a primary concern for site investigations is
characterization of contaminant flow paths rather than entire
aquifers. In fact, in many cases, plume thickness can be less
than well screen lengths (e.g., 3-6 m) typically installed at
hazardous waste sites to detect and monitor plume movement
over time. Small-scale differences have increasingly been
shown to be important and there is a general trend toward
smaller diameter wells and shorter screens.
The hydrogeochemical significance of colloidal-size
particles in subsurface systems has been realized during the
past several years (Gschwend and Reynolds, 1987; McCarthy
and Zachara, 1989; Puls, 1990; Ryan and Gschwend, 1990).
This realization resulted from both field and laboratory studies
that showed faster contaminant migration over greater
distances and at higher concentrations than flow and trans-
port model predictions would suggest (Buddemeier and Hunt,
1988; Enfield and Bengtsson, 1988; Penrose et al., 1990).
Such models typically account for interaction between the
mobile aqueous and immobile solid phases, but do not allow
for a mobile, reactive solid phase. It is recognition of this third
phase as a possible means of contaminant transport that has
brought increasing attention to the manner in which samples
are collected and processed for analysis (Puls et al., 1990;
McCarthy and Degueldre, 1993; Backhus et al., 1993; U.S.
EPA, 1995). If such a phase is present in sufficient mass,
possesses high sorption reactivity, large surface area, and
remains stable in suspension, it can serve as an important
mechanism to facilitate contaminant transport in many types
of subsurface systems.
Colloids are particles that are sufficiently small so
that the surface free energy of the particle dominates the bulk
free energy. Typically, in ground water, this includes particles
with diameters between 1 and 1000 nm. The most commonly
observed mobile particles include: secondary clay minerals;
hydrous iron, aluminum, and manganese oxides; dissolved
and particulate organic materials, and viruses and bacteria.
2
•
These reactive particles have been shown to be mobile under
a variety of conditions in both field studies and laboratory
column experiments, and as such need to be included in
monitoring programs where identification of the total mobile
contaminant loading (dissolved + naturally suspended
particles) at a site is an objective. To that end, sampling
methodologies must be used which do not artificially bias
naturally suspended particle concentrations.
Currently the most common ground-water purging
and sampling methodology is to purge a well using bailers or
high speed pumps to remove 3 to 5 casing volumes followed
by sample collection. This method can cause adverse impacts
on sample quality through collection of samples with high
levels of turbidity. This results in the inclusion of otherv,,,ise
immobile artifactual particles which produce an overestima-
tion of certain analytes of interest (e.g., metals or hydrophobic
organic compounds). Numerous documented problems
associated with filtration (Danielsson, 1982; Laxen and
Chandler, 1982; Horowitz et al., 1992) make this an undesir-
able method of rectifying the turbidity problem, and include
the removal of potentially mobile (contaminant-associated)
particles during filtration, thus artificially biasing contaminant
concentrations low. Sampling-induced turbidity problems can
often be mitigated by using low-flow purging and sampling
techniques.
Current subsurface conceptual models have under-
gone considerable refinement due to the recent development
and increased use of field screening tools. So-called
hydraulic push technologies (e.g., cone penetrometer,
Geoprobe®, QED HydroPunch®) enable relatively fast
screening site characterization which can then be used to
design and install a monitoring well network. Indeed,
alternatives to conventional monitoring wells are now being
considered for some hydrogeologic settings. The ultimate
design of any monitoring system should however be based
upon adequate site characterization and be consistent with
established monitoring objectives.
If the sampling program objectives include accurate
assessment of the magnitude and extent of subsurface
contamination over time and/or accurate assessment of
subsequent remedial performance, then some information
regarding plume delineation in three-dimensional space is
necessary prior to monitoring well network design and
installation. This can be accomplished with a variety of
different tools and equipment ranging from hand-operated
augers to screening tools mentioned above and large drilling
rigs. Detailed information on ground-water flow velocity,
direction, and horizontal and vertical variability are essential
baseline data requirements. Detailed soil and geologic data
are required prior to and during the installation of sampling
points. This includes historical as well as detailed soil and
geologic logs which accumulate during the site investigation.
The use of borehole geophysical techniques is also recom-
mended. With this information (together with other site
characterization data) and a clear understanding of sampling
•
objectives, then appropriate location, screen length, well
diameter, slot size, etc. for the monitoring well network can be
decided. This is especially critical for new in situ remedial
approaches or natural attenuation assessments at hazardous
waste sites.
In general, the overall goal of any ground-water
sampling program is to collect water samples with no alter-
ation in water chemistry; analytical data thus obtained may be
used for a variety of specific monitoring programs depending
on the regulatory requirements. The sampling methodology
described in this paper assumes that the monitoring goal is to
sample monitoring wells for the presence of contaminants and
it is applicable whether mobile colloids are a concern or not
and whether the analytes of concern are metals (and metal-
loids) or organic compounds.
II. Monitoring Objectives and Design
Considerations
The following issues are important to consider prior
to the design and implementation of any ground-water
monitoring program, including those which anticipate using
low-flow purging and sampling procedures.
A. Data Quality Objectives (DQOs)
Monitoring objectives include four main types:
detection, assessment, corrective-action evaluation and
resource evaluation, along with hybrid variations such as site-
assessments for property transfers and water availability
investigations. Monitoring objectives may change as contami-
nation or water quality problems are discovered. However,
there are a number of common components of monitoring
programs which should be recognized as important regard-
less of initial objectives. These components include:
1) Development of a conceptual model that incorporates
elements of the regional geology to the local geologic
framework. The conceptual model development also
includes initial site characterization efforts to identify
hydrostratigraphic units and likely flow-paths using a
minimum number of borings and well completions:
2) Cost-effective and well documented collection of high
quality data utilizing simple, accurate, and reproduc-
ible techniques; and
3) Refinement of the conceptual model based on
supplementary data collection and analysis.
These fundamental components serve many types of monitor-
ing programs and provide a basis for future efforts that evolve
in complexity and level of spatial detail as purposes and
objectives expand. High quality, reproducible data collection
is a common goal regardless of program objectives.
3
•
High quality data collection implies data of sufficient
accuracy, precision, and completeness (i.e., ratio of valid
analytical results to the minimum sample number called for by
the program design) to meet the program objectives. Accu-
racy depends on the correct choice of monitoring tools and
procedures to minimize sample and subsurface disturbance
from collection to analysis. Precision depends on the
repeatability of sampling and analytical protocols. It can be
assured or improved by replication of sample analyses
including· blanks, field/lab standards and reference standards.
B. Sample Representativeness
An important goal of any monitoring program is
collection of data that is truly representative of conditions at
the site. The term representativeness applies to chemical and
hydrogeologic data collected via wells, borings, piezometers,
geophysical and soil gas measurements, lysimeters, and
temporary sampling points. It involves a recognition of the
statistical variability of individual subsurface physical proper-
ties, and contaminant or major ion concentration levels, while
explaining extreme values. Subsurface temporal and spatial
variability are facts. Good professional practice seeks to
maximize representativeness by using proven accurate and
reproducible techniques to define limits on the distribution of
measurements collected at a site. However, measures of
representativeness are dynamic and are controlled by
evolving site characterization and monitoring objectives. An
evolutionary site characterization model, as shown in Fig-
ure 1, provides a systematic approach to the goal of consis-
tent data collection.
r'"' _.,. DenM Pro,g"'-"l aiJ,tcttv ..
~
e.uDIIVI Datll Quallry
-0,. 0oGl'III 8jplinQI Ind
Evolulion■,y Stt. An:alyllcai Protocolli
Ch1~n· '
Appl}> PTot--.
' Rm.,.PTGtoco6a4-_ -> lllab Sit. Oaeialo,.._
Figure 1. Evolutionary Site Characterization Model
The model emphasizes a recognition of the causes of the
variability (e.g., use of inappropriate technology such as using
bailers to purge wells; imprecise or operator-dependent
methods) and the need to control avoidable errors.
•
1) Questions of Scale
A sampling plan designed to collect representative
samples must take into account the potential scale of
changes in site conditions through space and time as well as
the chemical associations and behavior of the parameters
that are targeted for investigation. In subsurface systems,
physical (i.e., aquifer) and chemical properties over time or
space are not statistically independent. In fact, samples
taken in close proximity (i.e., within distances of a few meters)
or within short time periods (i.e., more frequently than
monthly) are highly auto-correlated. This means that designs
employing high-sampling frequency (e.g., monthly) or dense
spatial monitoring designs run the risk of redundant data
collection and misleading inferences regarding trends in ·
values that aren't statistically valid. In practice, contaminant
detection and assessment monitoring programs rarely suffer
these over-sampling concerns. In corrective-action evaluation
programs, it is also possible that too little data may be
collected over space or time. In these cases, false interpreta-
tion of the spatial extent of contamination or underestimation
of temporal concentration variability may result.
2) Target Parameters
Parameter selection in monitoring program design is
most often dictated by the regulatory status of the site.
However, background water quality constituents, purging
indicator parameters, and contaminants, ~II represent targets
for data collection programs. The tools and procedures used
in these programs should be equally rigorous and applicable
to all categories of data, since ail may be needed to deter-
mine or support regulatory action.
C. Sampling Point Design and Construction
Detailed site characterization is central to all
decision-making purposes and the basis for this characteriza-
tion resides in identification of the geologic framework and
major hydro-stratigraphic units. Fundamental data for sample
point location include: subsurface lithology, head-differences
and background geochemical conditions. Each sampling point
has a proper use or uses which should be documented at a
level which is appropriate for the program's data quality
objectives. Individual sampling points may not always be
able to fulfill multiple monitoring objectives (e.g., detection,
assessment, corrective action).
1) Compatibility with Monitoring Program and Data
Quality Objectives
Specifics of sampling point location and design will
be dictated by the complexity of subsurface lithology and
variability in contaminant and/or geochemical conditions. It
should be noted that, regardless of the gr9und-water sam-
pling approach, few sampling points (e.g., wells, drive-points,
screened augers) have zones of influence in excess of a few
4
feet. Therefore, the spatial frequency of sampling points
should be carefully selected and designed.
2) Flexibility of Sampling Point Design
In most cases well-point diameters in excess of 1 7/8
inches will permit the use of most types of submersible
pumping devices for low-flow (minimal drawdown) sampling.
It is suggested that short (e.g., less than 1.6 m) screens be
incorporated into the monitoring design where possible so
that comparable results from one device to another might be
expected. Short, of course, is relative to the degree of vertical
water quality variability expected at a site.
3) Equilibration of Sampling Point
Time should be allowed for equilibration of the well
or sampling point with the formation after installation. Place-
ment of well or sampling points in the subsurface produces
some disturbance of ambient conditions. Drilling techniques
(e.g., auger, rotary, etc.) are generally considered to cause
more disturbance than direct-push technologies. In either
case, there may be a period (i.e., days to months) during
which water quality near the point may be distinctly different
from that in the formation. Proper development of the sam-
pling point and adjacent formation to remove fines created
during emplacement will shorten this water quality recovery
period. ·
Ill. Definition of Low-Flow Purging and Sampling
It is generally accepted that water in the well casing
is non-representative of the formation water and needs to be
purged prior to collection of ground-water samples. However,
the water in the screened interval may indeed be representa-
tive of the formation, depending upon well construction and
site hydrogeology. Wells are purged to some extent for the
following reasons: the presence of the air interface at the top
of the water column resulting in an oxygen concentration
gradient with depth, loss of volatiles up the water column,
leaching from or sorption to the casing or filter pack, chemical
changes due to clay seals or backfill, and surface infiltration.
Low-fiow purging, whether using portable or dedi-
cated systems, should be done using pump-intake located in
the middle or slightly above the middle of the screened
interval. Placement of the pump too close to the bottom of the
well will cause increased entrainment of solids which have
collected in the well over time. These particles are present as
a result of well development, prior purging and sampling
events, and natural colloidal transport and deposition.
Therefore, placement of the pump in the middle or toward the
top of the screened interval is suggested. Placement of the
pump at the top of the water column for sampling is only
recommended in unconfined aquifers, screened across the
water table, where this is the desired sampling point. Low-
•
flow purging has the advantage of minimizing mixing between
the overlying stagnant casing water and water within the
screened interval.
A. Low-Flow Purging and Sampling
Low-flow refers to the velocity with which water
enters the pump intake and that is imparted to the formation
pore water in the immediate vicinity of the well screen. It
does not necessarily refer to the flow rate of water discharged
at the surface which can be affected by flow regulators or
restrictions. Water level drawdown provides the best indica-
tion of the stress imparted by a given flow-rate for a given
hydrological situation. The objective is to pump in a manner
that minimizes stress (drawdown) to the system to the extent
practical taking into account established site sampling
objectives. Typically, flow rates on the order of 0.1 -0.5 Umin
are used, however this is dependent on Site-specific
hydrogeology. Some extremely coarse-textured formations
have been successfully sampled in this manner at flow rates
to 1 Umin. The effectiveness of using low-flow purging is
intimately linked with proper screen location, screen length,
and well construction and development techniques. The
reestablishment of natural flow paths in both the vertical and
horizontal directions is important for correct interpretation of
the data. For high resolution sampling needs, screens less
than 1 m should be used. Most of the need for purging has
been found to be due to passing the sampling device through
the overlying casing water which causes mixing of these
stagnant waters and the dynamic waters within the screened
inteival. Additionally, there is disturbance to suspended
sediment collected in the bottom of the casing and the
displacement of water out into the formation immediately
adjacent to the well screen. These disturbances and impacts
can be avoided using dedicated sampling equipment, which
precludes the need to insert the sampling device prior to
purging and sampling.
Isolation of the screened interval water from the
overlying stagnant casing water may be accomplished using
low-flow minimal drawdown techniques. If the pump intake is
located within the screened inteival, most of the water
pumped will be drawn in directly from the formation with little
mixing of casing water or disturbance to the sampling zone.
However, if the wells are not constructed and developed
properly, zones other than those intended may be sampled.
At some sites where geologic heterogeneities are sufficiently
different within the screened intetval, higher conductivity
zones may be preferentially sampled. This is another reason
to use shorter screened intervals, especially where high
spatial resolution is a sampling objective.
B. Water Quality Indicator Parameters
It is recommended that water quality indicator
parameters be used to determine purging needs prior to
sample collection in each well. Stabilization of parameters
such as pH, specific conductance, dissolved oxygen, oxida-
5
•
lion-reduction potential, temperature and turbidity should be
used to determine when formation water is accessed during
purging. In general, the order of stabilization is pH, tempera-
ture, and specific conductance, followed by oxidation-
reduction potential, dissolved oxygen and turbidity. Tempera-
ture and pH, while commonly used as purging indicators, are
actually quite insensitive in distinguishing between formation
water and stagnant casing water; nevertheless, these are
important parameters for data interpretation purposes and
should also be measured. Performance criteria for determi•
nation of stabilization should be based on water-level draw-
down, pumping rate and equipment specifications for measur-
ing indicator parameters. Instruments are available which
utilize in-line flow cells to continuously measure the above
parameters.
It is important to establish specific well stabilization
criteria and then consistently follow the same methods
thereafter, particularly with respect to drawdown, flow rate
and sampling device. Generally, the time or purge volume
required for parameter stabilization is independent of well
depth or well volumes. Dependent variables are well diam-
eter, sampling device, hydrogeochemistry, pump flow rate,
and whether the devices are used in a portable or dedicated
manner. If the sampling device is already in place (i.e.,
dedicated sampling systems), then the time and purge
volume needed for stabilization is much shorter. Other
advantages of dedicated equipment include less purge water
for waste disposal, much less decontamination of equipment,
less time spent in preparation of sampling as well as time in
the field, and more consistency in the sampling approach
which probably will translate into less variability in sampling
results. The use of dedicated equipment is strongly recom-
mended at wells which will undergo routine sampling over
time.
If parameter stabilization criteria are too stringent,
then minor oscillations in indicator parameters may cause
purging operations to become unnecessarily protracted. It
should also be noted that turbidity is a very conseivative
parameter in terms of stabilization. Turbidity is always the
last parameter to stabilize. Excessive purge times are
invariably related to the establishment of too stringent turbidity
stabilization criteria. It should be noted that natural turbidity
levels in ground water may exceed 10 nephelometric turbidity
units (NTU).
C. Advantages and Disadvantages of Low-Flow
(Minimum Drawdown) Purging
In general, the advantages of low-flow purging
include:
samples which are representative of the mobile load of
contaminants present (dissolved and colloid-associ-
ated);
minimal disturbance of the sampling point thereby
minimizing sampling artifacts;
less operator variability, greater operator control;
------•'-----------"l•F-------
reduced stress on the formation (minimal drawdown);
less mixing of stagnant casing water with formation
water;
reduced need for filtration and, therefore, less time
required for sampling;
smaller purging volume which deCreases waste
disposal costs and sampl_ing time:
better sample consistency; reduced artificial sample
variability.
Some disadvantages of low-flow purging are:
higher initial capital costs,
greater set-up time in the field,
need to transport additional equipment to and from the
site,
increased training needs,
resistance to change on the part of sampling practitio-
ners,
concern that new data will indicate a change in
conditions and trigger an action.
IV. Low-Flow (Minimal Drawdown) Sampling
Protocols
The following ground-water sampling procedure has
evolved over many years of experience in ground-water
sampling for organic and inorganic compound determinations
and as such summarizes the authors' (and others) experi-
ences to date (Barcelona et al.. 1984. 1994; Barcelona and
Helfrich, 1986; Puls and Barcelona, 1989; Puls et. al. 1990,
1992; Puls and Powell, 1992; Puls and Paul, 1995). High-
quality chemical data collection is essential in ground-water
monitoring and site characterization. The primary limitations
to the collection of representative ground-water samples
include: mixing of the stagnant casing and fresh screen
waters during insertion of the sampling device or ground-
water level measurement device; disturbance and
resuspension of settled solids at the bottom of the well when
using high pumping rates or raising and lowering a pump or
bailer; introduction of atmospheric gases or degassing from
the water during sample handling and transfer, or inappropri-
ate use of vacuum sampling device, etc.
A. Sampling Recommendatio11s
Water samples should not be taken immediately
following well development. Sufficient time should be allowed
for the ground-water flow regime in the vicinity of the monitor-
ing well to stabilize and to approach chemical equilibrium with
the well construction materials. This lag time will depend on
site conditions and methods of installation but often exceeds
one week.
Well purging is nearly always necessary to obtain
samples of water flowing through the geologic formations in
the screened interval. Rather than using a general but
arbitrary guideline of purging three casing volumes prior to
6
sampling, it is recommended that an in-line water quality
measurement device (e.g., flow-through cell) be used to
establish the stabilization time for several parameters (e.g. ,
pH, specific conductance, redox, dissolved oxygen, turbidity)
on a well-specific basis. Data on pumping rate, drawdown,
and volume required for parameter stabilization can be used
as a guide for conducting subsequent sampling activities.
The following are recommendations to be considered
before, during and after sampling:
use low-flow rates (<0.5 Umin), during both purging
and sampling to maintain minimal drawdown in the
well;
maximize tubing wall thickness, minimize tubing
length;
place the sampling device intake at the desired
sampling point;
minimize disturbances of the stagnant water column
above the screened interval during water level
measurement and sampling device insertion;
make proper adjustments to stabilize the flow rate as
soon as possible;
monitor water quality indicators during purging;
collect unfiltered samples to estimate contaminant
loading and transport potential in the subsurface
system.
8. Equipment Calibration
Prior to sampling, all sampling device and monitoring
equipment should be calibrated according to manufacturer's
recommendations and the site Quality Assurance Project Plan
(QAPP) and Field Sampling Plan (FSP). Calibration of pH
should be performed with at least two buffers which bracket
the expected range. Dissolved oxygen calibration must be
corrected for local barometric pressure readings and eleva-
tion.
C. Water Level Measurement and Monitoring
It is recommended that a device be used which will
least disturb the water surface in the casing. Well depth
should be obtained from the well logs. Measuring to the
bottom of the well casing will only cause resuspension of
settled solids from the formation and require longer purging
times for turbidity equilibration. Measure well depth after
sampling is completed. The water level measurement should
be taken from a permanent reference point which is surveyed
relative to ground elevation.
D. Pump Type
The use of low-flow (e.g., 0.1-0.5 Umin) pumps is
suggested for purging and sampling all types of analytes. All
pumps have some limitation and these should be investigated
with respect to application at a particular site. Bailers are
inappropriate devices for low-flow sampling.
•
1) General Considerations
There are no unusual requirements for ground-water
sampling devices when using low-flow, minimal drawdown
techniques. The major concern is that the device give
consistent results and minimal disturbance of the sample
across a range of /ow flow rates (i.e.,< 0.5 Umin). Clearly,
pumping rates that cause minimal to no drawdown in one well
could easily cause significant drawdown in another well
finished in a less transmissive formation. In this sense, the
pump should not cause undue pressure or temperature
changes or physical disturbance on the water sample over a
reasonable sampling range. Consistency in operation is
critical to meet accuracy and precision goals.
2) Advantages and Disadvantages of Sampling Devices
A variety of sampling devices are available for low-
flow (minimal drawdown) purging and sampling and include
peristaltic pumps, bladder pumps, electrical submersible
pumps, and gas-driven pumps. Devices which lend them-
selves to both dedication and consistent operation at defin-
able low-flow rates are preferred. It is desirable that the pump
be easily adjustable and operate reliably at these lower flow
rates. The peristaltic pump is limited to shallow applications
and can cause degassing resulting in alteration of pH,
alkalinity, and some volatiles loss. Gas-driven pumps should
be of a type that does not allow the gas to be in direct contact
with the sampled fluid.
Clearly, bailers and other grab type samplers are ill-
suited for low-flow sampling since they will cause repeated
disturbance and mixing of stagnant water in the casing and
the dynamic water in the screened interval. Similarly, the use
of inertial lift foot-valve type samplers may cause too much
disturbance at the point of sampling. Use of these devices
also tends to introduce uncontrolled and unacceptable
operator variability.
Summaries of advantages and disadvantages of
various sampling devices are listed in Herzog et al. (1991),
U.S. EPA (1992), Parker (1994) and Thurnblad (1994).
E. Pump Installation
Dedicated sampling devices (left in the well) capable
of pumping and sampling are preferred over~ other type of
device. Any portable sampling device should be slowly and
carefully lowered to the middle of the screened interval or
slightly above the middle (e.g., 1-1.5 m below the top of a 3 m
screen). This is to minimize excessive mixing of the stagnant
water in the casing above the screen with the screened
interval zone water, and to minimize resuspension of solids
which will have collected at the bottom of the well. These two
disturbance effects have been shown to directly affect the
time required for purging. There also appears to be a direct
correlation between size of portable sampling devices relative
to the well bore and resulting purge volumes and times. The
key is to minimize disturbance of water and solids in the well
casing.
7
•
F. Filtration
Decisions to filter samples should be dictated by
sampling objectives rather than as a fix for poor sampling
practices, and field-filtering of certain constituents should not
be the default. Consideration should be given as to what the
application of field-filtration is trying to accomplish. For
assessment of truly dissolved (as opposed to operationally
dissolved [i.e., samples filtered with 0.45 µm filters]) concen-
trations of major ions and trace metals, 0.1 µm filters are
recommended although 0.45 µm filters are normally used for
most regulatory programs. Alkalinity samples must also be
filtered if significant particulate calcium carbonate is sus-
pected, since this material is likely to impact alkalinity titration
results (although filtration itself may alter the CO2 composition
of the sample and, therefore, affect the results).
Although filtration may be appropriate, filtration of a
sample may cause a number of unintended changes to occur
(e.g. oxidation, aeration) possibly leading to filtration-induced
artifacts during sample analysis and uncertainty in the results.
Some of these unintended changes may be unavoidable but
the factors leading to them must be recognized. Deleterious
effects can be minimized by consistent application of certain
filtration guidelines. Guidelines should address selection of
filter type, media, pore size, etc. in order to identify and
minimize potential sources of uncertainty when filtering
samples.
In-line filtration is recommended because it provides
better consistency through less sample handling, and
minimizes sample exposure to the atmosphere. In-line filters
are available in both disposable (barrel filters) and non-
disposable (in-line filter holder, flat membrane filters) formats
and various filter pore sizes (0.1-5.0 µm). Disposable filter
cartridges have the advantage of greater sediment handling
capacity when compared to traditional membrane filters.
Filters must be pre-rinsed following manufacturer's recom-
mendations. If there are no recommendations for rinsing,
pass through a minimum of 1 L of ground water following
purging and prior to sampling. Once filtration has begun, a
filter cake may develop as particles larger than the pore size
accumulate on the filter membrane. The result is that the
effective pore diameter of the membrane is reduced and
particles smaller than the stated pore size are excluded from
the filtrate. Possible corrective measures include prefiltering
(with larger pore size filters), minimizing particle loads to
begin with, and reducing sample volume.
G. Monitoring of Water Level and Water Quality
Indicator Parameters
Check water level periodically to monitor drawdown
in the well as a guide to flow rate adjustment. The goal is
minimal drawdown (<0.1 m) during purging. This goal may be
difficult to achieve under some circumstances due to ge0logic
heterogeneities within the screened interval, and may require
adjustment based on site-specific conditions and personal
experience. In-line water quality indicator parameters should
be contini.Jously monitored during purging. The water quality
----~•'--------_____.•--------
indicator parameters monitored can include pH, redox
potential, conductivity, dissolved oxygen (DO) and turbidity.
The last three parameters are often most sensitive. Pumping
rate, drawdown, and the time or volume required to obtain
stabilization of parameter readings can be used as a future
guide to purge the well. Measurements should be taken
every three to five minutes if the above suggested rates are
used. Stabilization ls achieved after all parameters have
stabilized for three successive readings. In lieu of measuring
all five parameters, a minimum subset would include pH,
conductivity, and turbidity or DO. Three successive readings
should be within± 0.1 for pH, ± 3% for conductivity, ± 10 mv
for redox potential, and± 10% for turbidity and DO. Stabilized
purge indicator parameter trends are generally obvious and
follow either an exponential or asymptotic change to stable
values during purging. Dissolved oxygen and turbidity usually
require the longest time for stabilization. The above stabiliza-
tion guidelines are provided for rough estimates based on
experience.
H. Sampling, Sample Containers, Preservation and
Decontamination
Upon parameter stabilization, sampling can be
initiated. If an in-line device is used to monitor water quality
parameters, it should be disconnected or bypassed during
sample collection. Sampling flow rate may remain at estab-
lished purge rate or may be adjusted slightly to minimize
aeration, bubble formation, turbulent filling of sample bottles,
or loss of volatiles due to extended residence time in tubing.
Typically, flow rates less than 0.5 Umin are appropriate. The
same device should be used for sampling as was used for
purging. Sampling should occur in a progression from least to
most contaminated well, if this is known. -Generally, volatile
(e.g., solvents and fuel constituents) and gas sensitive (e.g.,
Fe'', CH,, H2S/HS·, alkalinity) parameters should be sampled
first. The sequence in which samples for most inorganic
parameters are collected is immaterial unless filtered (dis-
solved) samples are desired. Filtering should be done last
and in-line filters should be used as discussed above. During
both well purging and sampling, proper protective clothing
and equipment must be used based upon the type and level
of contaminants present.
The appropriate sample container will be prepared in
advance of actual sample collection for the analytes of
interest and include sample preservative where necessary.
Water samples should be collected directly into this container
from the pump tubing.
Immediately after a sample bottle has been filled, it
must be preserved as specified in the site (QAPP). Sample
preservation requirements are based on the analyses being
performed (use site QAPP, FSP, RCRA guidance document
[U.S. EPA, 1992] or EPA SW-846 [U.S. EPA, 1982] ). It
may be advisable to add preservatives to sample bottles in a
controlled setting prior to _entering the field in order to reduce
the chances of improperly preserving sample bottles or
8
introducing field contaminants into a sample bottle while
adding the preservatives.
The preservatives should be transferred from the
chemical bottle to the sample container using a disposable
polyethylene pipe! and the disposable pipe! should be used
only once and then discarded.
After a sample container has been filled with ground
water, a Teflon™ (or tin)-lined cap is screwed on tightly to
prevent the container from leaking. A sample label is filled
out as specified in the FSP. The samples should be stored
inverted at 4°C.
Specific decontamination protocols for sampling
devices are dependent to some extent on the type of device
used and the type of contaminants encountered. Refer to the
site QAPP and FSP for specific requirements.
I. Blanks
The following blanks should be collected:
(1) field blank: one field blank should be collected from
each source water (distilled/deionized water} used for
sampling equipment decontamination or for assisting
well development procedures.
(2) equipment blank: one equipment blank should be
taken prior to the commencement of field work, from
each set of sampling equipment to be used for that
day. Refer to site QAPP or FSP for specific require-
ments.
(3) trip blank: a trip blank is required to accompany each
volatile sample shipment. These blanks are prepared
in the laboratory by filling a 40-ml volatile organic
analysis (VOA) bottle with distilled/deionized water.
V. Low-Permeability Formations and Fractured
Rock
The overall sampling program goals or sampling
objectives will drive how the sampling points are located,
installed, and choice of sampling device. Likewise, site-
specific hydroge_ologic factors will affect these decisions.
Sites with very low permeability formations or fractures
causing discrete flow channels may require a unique monitor-
ing approach. Unlike water supply wells, wells installed for
ground-water quality assessment and restoration programs
are often installed in low water-yielding settings (e.g., clays,
silts). Alternative types of sampling points and sampling
methods are often needed in these types of environments,
because low-permeability settings may require extremely low-
fiow purging ( <0.1 Umin) and may be technology-limited.
Where devices are not readily available to pump at such low
flow rates, the primary consideration is to avoid dewatering of
the well screen. This may require repeated recovery of the
water during purging while leaving the pump in place within
the well screen.
Use of low-flow techni_ques may be impractical in
these settings, depending upon the water recharge rates.
The sampler and the end-user of data collected from such
wells need to understand the limitations of the data collected;
i.e., a strong potential for underestimation of actual contami-
nant concentrations for volatile organics, potential false
negatives for filtered metals and potential false positives for
unfiltered metals. It is suggested that comparisons be made
between samples recovered using low-flow purging tech-
niques and samples recovered using passive sampling
techniques (i.e., two sets of samples). Passive sample
collection would essentially entail acquisition of the sample
with no or very little purging using a dedicated sampling
system installed within the screened interval or a passive
sample collection device.
A. Low-Permeability Formations (<0.1 Umin
recharge)
1. Low-Flow Purging and Sampling with Pumps
a. "portable or non-dedicated mode" -Lower the pump
(one capable of pumping at <0.1 Umin) to mid-screen
or slightly above and set in place for minimum of 48
hours (to lessen purge volume requirements). After 48
hours, use procedures listed in Part IV above regard-
ing monitoring water quality parameters for stabiliza-
tion, etc., but do not dewater the screen. lf excessive
drawdown and slow recovery is a problem, then
alternate approaches such as those listed below may
be better.
b. "dedicated mode" -Set the pump as above at least a
week prior to sampling; that is, operate in a dedicated
pump mode. With this approach significant reductions
in purge volume should be realized. Water quality
parameters should stabilize quite rapidly due to less
disturbance of the sampling zone.
2. Passive Sample Collection
Passive sampling collection requires insertion of the
device into the screened interval for a sufficient time period to
allow flow and sample equilibration before extraction for
analysis. Conceptually, the extraction of water from low
yielding formations seems more akin to the collection of water
from the unsaturated zone and passive sampling techniques
may be more appropriate in terms of obtaining "representa-
tive" samples. Satisfying usual sample volume requirements
is typically a problem with this approach and some latitude will
be needed on the part of regulatory entities to achieve
sampling objectives.
9
•
B. Fractured Rock
In fractured rock formations, a low-flow to zero
purging approach using pumps in conjunction with packers to
isolate the sampling zone in the borehole is suggested.
Passive multi-layer sampling devices may also provide the
most "representative" samples. It is imperative in these
settings to identify flow paths or water-producing fractures
prior to sampling using tools such as borehole flowmeters
and/or other geophysical tools.
After identification of water-bearing fractures, install
packer(s) and pump assembly for sample collection using
low-flow sampling in "dedicated mode" or use a passive
sampling device which can isolate the identified water-bearing
fractures.
VI. Documentation
The usual practices for documenting the sampling
event should be used for low-flow purging and sampling
techniques. This should include, at a minimum: information
on the conduct of purging operations (flow.rate, drawdown,
water-quality parameter values, volumes extracted and times
for measurements), field instrument calibration data, water
sampling forms and chain of custody forms. See Figures 2
and 3 and "Ground Water Sampling Workshop --A Workshop
Summary" (U.S. EPA, 1995) for example forms and other
documentation suggestions and information. This information
coupled with laboratory analytical data and validation data are
needed to judge the "useability" of the sampling data.
VII. Notice
The U.S. Environmental Protection Agency through its Office
of Research and Development funded and managed the
research described herein as part of its in-house research
program and under Contract No. 68-C4-0031 to Dynamac
Corporation. It has been subjected to the Agency's peer and
administrative review and has been approved for publication
as an EPA document. Mention of trade names or commercial
products does not constitute endorsement or recommenda-
tion for use.
VIII. References
Backhus, D.A, J.N. Ryan, D.M. Groher, J.K. McFarlane, and
P.M. Gschwend. 1993. Sampling Colloids and Colloid-
Associated Contaminants in Ground Water. Ground Water,
31(3):466-479.
Barcelona, M.J .. J.A. Helfrich, E.E. Garske, and J.P. Gibb.
1984. A laboratory evaluation of groundwater sampling
mechanisms. Ground Water Monitoring Review, 4(2):32-41.
I
Barcelona, M.J. and J.A. Helfrich. 1986. Well construction and
purging effects on ground-water samples. Environ. Sci.
Technof., 20(11):1179-1184.
Barcelona, M.J., H.A. Wehrmann, and M.D. Varljen. 1994.
Reproducible well purging procedures and VOC stabilization
criteria for ground-water sampling. Ground Water, 32(1):12-
22.
Buddemeier, R.W. and J.R Hunt. 1988. Transport of Colloidal
Contaminants in Ground Water: RadionuClide Migration at the
Nevada Test Site. Applied Geochemistry, 3: 535-548.
Danielsson, L.G. 1982. On the Use of Filters for Distinguish-
ing Between Dissolved and Particulate Fractions in Natural
Waters. Water Research, 16: 179. ·
Enfield, C.G. and G. Bengtsson. 1988. Macromolecular
Transport of Hydrophobic Contaminants in Aqueous Environ-
ments. Ground Water, 26(1): 64-70.
Gschwend, P.M. and M.D. Reynolds. 1987. Monodisperse
Ferrous Phosphate Colloids in an Anoxic Groundwater
Plume, J. of Contaminant Hydro/., 1: 309-327.
Herzog, B., J. Pennino, and G. Nielsen. 1991. Ground-Water
Sampling. In Practical Handbook of Ground-Water Moni-
toring (D.M. Nielsen, ed.). Lewis Publ., Chelsea, Ml, pp. 449-
499.
Horowitz, A.J., K.A. Elrick, and M.R Colberg. 1992. The effect
of membrane filtration artifacts on dissolved trace element
concentrations. Water Res., 26(6):753-763.
Laxen, D.P.H. and I.M. Chandler. 1982. Comparison of
Filtration Techniques for Size Distribution in Freshwaters.
Analytical Chemistry, 54(8): 1350.
McCarthy, J.F. and J.M. Zachara. 1989. Subsurface Transport
of Contaminants, Environ. Sci. Technol., 5(23):496-502.
McCarthy, J.F. and C. Degueldre. 1993. Sampling and
Characterization of Colloids and Ground Water for Studying
Their Role in Contaminant Transport. In: Environmental
Particles (J. Buffie and H.P. van Leeuwen, eds.), Lewis Publ.,
Chelsea, Ml, pp. 247-315.
Parker, L.V. 1994. The Effects of Ground Water Sampling
Devices on Water Quality: A Literature Review. Ground
Water Monitoring and Remediation, 14(2):130-141.
Penrose, W.R., W.L. Polzer, E.H. Essington, D.M. Nelson,
and K.A. Ortandini. 1990. Mobility of Plutonium and Ameri-
cium through a Shallow Aquifer in a Semiarid Region,
Environ. Sci. Techno/., 24:228-234.
Puls, RW. and M.J. Barcelona. 1989. Filtration of Ground
Water Samples for Metals Analyses. Hazardous Waste and
Hazardous Materials, 6(4):385-393.
•
Puls, RW., J.H. Eychaner, and RM. Powell. 1990. Colloidal-
Facilitated Transport of Inorganic Contaminants in Ground
Water: Part I. Sampling Considerations. EPA/600/M-90/023,
NTIS PB 91-168419.
Puls, R.W. 1990. Colloidal Considerations in Groundwater
Sampling and Contaminant Transport Predictions. Nuclear
Safety, 31(1):58-65.
Puls, R.W. and RM. Powell. 1992. Acquisition of Representa-
tive Ground Water Quality Samples for Metals. Ground Water
Monitoring Review, 12(3):167-176.
Puls, RW., D.A. Clark, B.Bledsoe, RM. Powell, and C.J.
Paul. 1992. Metals in Ground Water. Sampling Artifacts and
Reproducibility. Hazardous Waste and Hazardous Materials,
9(2): 149-162.
Puls, R.W. and C.J. Paul. 1995. Low-Flow Purging and
Sampling of Ground-Water Monitoring Wells with Dedicated
Systems. Ground Water Monitoring and Remediation,
15(1):116-123.
Ryan, J.N. and P.M. Gschwend. 1990. Colloid Mobilization in
Two Atlantic Coastal Plain Aquifers. Water Resour. Res., 26:
307-322.
Thumblad, T. 1994. Ground Water Sampling Guidance:
Development of Sampling Plans, Sampling Protocols, and
Sampling Reports. Minnesota Pollution Control Agency.
U.S. EPA. 1992. RCRA Ground-Water Monitoring: Draft
Technical Guidance. Office of Solid Waste, Washington, DC
EPA/530/R-93/001, NTIS PB 93-139350.
U.S. EPA. 1995. Ground Water Sampling Workshop --A
Workshop Summary, Dallas, TX, November 30 -December 2,
1993. EPA/600/R-94/205, NTIS PB 95-193249, 126 pp.
U.S. EPA. 1982. Test Methods for Evaluating Solid Waste,
. Physical/Chemical Methods, EPA SW-846. Office of Solid
Waste and Emergency Response, Washington, D.C.
10
• •
Figure 2. Ground Water Sampling Log
Project _______ Site _______ Well No. ______ Date ___________ _
Well Depth Screen Length _____ Well Diameter ____ Casing Type _____ _
Sampling Device Tubing type Water Level _______ _
Measuring Point Otherlnfor _____________________ _
Sampling Personnel----------------------------------
Time pH Temp Cond. Dis.02 Turb. [ ]Cone Notes
.
Type of Samples Collected
Information: 2 in = 617 ml/ft, 4 In = 2470 ml/ft: Voley1 = nr1h, Vol.p,_,. = 413n rl
11
r • •
1, Figure 3. Ground Water Sampling Log (with automatic data logging for most water quality
F parameters)
Project _______ Site _______ Well No. ______ Date __________ _
Well Depth Screen Length _____ Well Diameter ____ Casing Type ____ _
Sampling Device Tubing type Water Level _______ _
Measuring Point Other Infer _____________________ _
Sampling Personnel---------------------------------
Time Pump Rate Turbidity Alkalinity [ ] Cone Notes
.
Type of Samples Collected
lnfonnation: 2 in = 617 ml/ft, 4 in = 2470 ml/ft: Volcv1 = nr2h, Vol•P""•• = 4/Jrr r1
12