20085_Arbor_East_Groundwater_Report_20120620

REPORT FOR GROUNDWATER MONITORING
FORMER LEEWAY SERVICE CENTER
10141 U.S. 70 BUSINESS HIGHWAY WEST
CLAYTON, JOHNSTON COUNTY, NORTH CAROLINA
NCDENR-DWM GROUNDWATER INCIDENT NUMBER# 10178
FACILITY ID # 0-014051
SITE RISK CLASSIFICATION: HIGH
LAND USE CATEGORY: INDUSTRIAL/COMMERCIAL
June 20, 2012
Responsible Party:
A.G. Lee Oil Company
P.O. Box 237
Smithfield, North Carolina 27577
[phone]
Current Property Owner:
A.G. Lee Oil Company
P.O. Box 237
Smithfield, North Carolina 27577
[phone]
Consultant:
East Coast Environmental, P.A.
3815 Junction Blvd.
Raleigh, North Carolina 27603
[phone]
Release Discovery Date: 07/20/93
Cause of Release: Leaking Commercial Gasoline UST System(s)
Quantity of Release: Undetermined
UST Sizes and Contents: (1) 6,000-gallon gasoline, (1) 8,000-gallon gasoline,
Report for Annual Groundwater Monitoring
Leeway Service Center
Clayton, North Carolina
(1) 10,000-gallon gasoline, (2) 4,000-gallon diesel fuel USTs
Latitude: 37°07’00” N, Longitude: 78° 26’49” W
East Coast Environmental, P.A.
3815 Junction Blvd.
Raleigh, North Carolina 27603
[phone] Fax: [phone]
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Report for Annual Groundwater Monitoring
Leeway Service Center
Clayton, North Carolina
Table of Contents
1.0 DISCUSSION OF SAMPLING RESULTS ............................................................................................ 5
1.1 INTRODUCTION ................................................................................................................................................ 5
1.2 SUMMARY OF GROUNDWATER ANALYTICAL RESULTS ........................................................................................... 7
1.2.1 Affected Groundwater Classification .................................................................................................. 7
1.2.2 Free Product ....................................................................................................................................... 7
1.2.3 Groundwater Sampling Event – May 9, 2012 ..................................................................................... 7
1.2.3.1 Groundwater Level Measurements .............................................................................................................. 7
1.2.3.2 Well Purging ............................................................................................................................................... 8
1.2.3.3 Groundwater Sample Collection ................................................................................................................. 8
1.2.3.4 Sample Storage and Transport .................................................................................................................... 9
1.2.3.5 Analytical Methodology ............................................................................................................................. 9
1.2.4 Analytical Results – Groundwater Samples ...................................................................................... 10
1.2.4.1 EPA Method 6200B ................................................................................................................................ 10
1.3 CURRENT PLUME INFORMATION ...................................................................................................................... 12
1.4 SUMMARY OF REMEDIAL ACTIVITIES ................................................................................................................ 13
1.4.1 Groundwater Remediation ................................................................................................................ 13
1.4.1.1 Overview/General Description ................................................................................................................... 13
1.4.1.2 System Operation ....................................................................................................................................... 15
1.4.1.3 System Effluent Sampling .......................................................................................................................... 15
1.4.1.4 Monthly Operation Maintenance Costs ...................................................................................................... 16
1.4.1.5 Future Remediation Activities ................................................................................................................... 16
NPDES Information ............................................................................................................................................... 17
1.5 GROUNDWATER CONDITIONS ........................................................................................................................... 17
1.5.1 Proximity to Potential Receptors ...................................................................................................... 17
EPA Method 6200b (Supply Well Analytical Results) – June 19, 2012 ..................................................... 18
1.5.3 Groundwater Flow ............................................................................................................................ 18
2.0 CONCLUSIONS AND RECOMMENDATIONS ............................................................................... 20
East Coast Environmental, P.A.
3815 Junction Blvd.
Raleigh, North Carolina 27603
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Report for Annual Groundwater Monitoring
Leeway Service Center
Clayton, North Carolina
APPENDICES
Section A Figures
Section B Tables and Historical Analytical Data Charts - Total BTEX (ug/l)
Section C Analytical Data- May 9, 2012 Groundwater Sampling Event
LIST OF FIGURES
Figure 1 Topographic Site Location Map
Figure 1a Topographic Site Map with Updated Receptor Survey
Figure 2 Site Map With Monitoring Well Locations
Figure 3 Groundwater Hydraulic Gradient Map – May 9, 2012
Figure 4 Benzene Isoconcentration Map – May 9, 2012
Figure 5 Ethylbenzene Isoconcentration Map – May 9, 2012
Figure 6 MTBE Isoconcentration Map – May 9, 2012
LIST OF TABLES
Table 1 Summary of Analytical Data-Groundwater (ug/l) – May 9, 2012
Table 2 Historical Analytical Data, Groundwater (ug/l)
Table 3 Groundwater Level Measurements (ft.) – May 9, 2012
Table 4 Historical Groundwater Level Measurements (ft)
Table 5 Monitoring Well Construction Data
LIST OF CHARTS
Chart 1 Total BTEX Concentrations – MW-4
Chart 2 Total BTEX Concentrations – MW-14
Chart 3 Total BTEX Concentrations – MW-27
Chart 4 Total BTEX Concentrations – MW-33
Chart 5 Total BTEX Concentrations – MW-36
Chart 6 Total BTEX Concentrations – MW-39
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3815 Junction Blvd.
Raleigh, North Carolina 27603
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Report for Annual Groundwater Monitoring
Leeway Service Center
Clayton, North Carolina
1.0 DISCUSSION OF SAMPLING RESULTS
1.1 Introduction
At the request of A.G. Lee Oil Company (LEE), and in accordance with the provisions of
North Carolina Administrative Code, Title 15A, Subchapter 2L, Section .0110
(Monitoring), East Coast Environmental, P.A. (ECE), of Raleigh, Wake County, North
Carolina, has prepared this Report for Groundwater Monitoring for petroleum
contaminated groundwater on and adjacent to the (Former) Leeway Service Center
(Facility ID # 0-014051), hereinafter referred to as the “Site”, located at 10141 U.S. 70
Business Highway West within the corporate limits of Clayton, Johnston County, North
Carolina. See Section A, Figure 1 for a map showing Site location and local topography.
This report has been developed in response to a directive issued by the North Carolina
Department of Environment and Natural Resources (NCDENR), Division of Waste
Management (DWM) for groundwater sampling in accordance with the provisions of the
Corrective Action Plan (CAP) submitted by ECE on October 12, 1994. A Site Map
(Section A, Figure 2) shows the location of the Site and the locations of all monitoring
wells associated with the Site.
Since the CAP was originally approved several groundwater monitoring wells that were
to be included in subsequent monitoring events became unavailable for sampling.
Monitoring well MW-4 was destroyed by a landscape contractor, but has since been
replaced by a second well also named MW-4. Monitoring wells MW-15, 16, 19, 21, 23,
24, 28, and 30 have been destroyed in the past by activities on the former Peele property
located across U.S. Highway 70 from the Site. MW-11 was also destroyed during road
construction activities related to the moving of NC Highway 42 in this area.
Monitoring well MW-9 was destroyed during the construction of a Quick-10 oil change
facility on the property located west of the Site. Monitoring wells MW-5 and MW-26
were destroyed during soil excavation activities conducted on the Site while monitoring
wells MW-6, MW-25, and VMW-25 were destroyed during the construction of a
convenience store also on the Site. Monitoring well DW-1 was constructed in order to
replace VMW-25.
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Raleigh, North Carolina 27603
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More recently monitoring wells MW-17, MW-18, MW-20, MW-22 and MW-29 could
not be located for the August 2008 monitoring event. The areas where some of these
wells were located have recently been paved or redeveloped and it is believed they may
have been destroyed during these activities. Monitoring wells MW-17, MW-18, MW-20,
MW-22 and MW-29 were needed in order to define the extent of the dissolved phase
contaminant plume west of the Site in the direction of the receptor area. In response,
ECE installed replacement wells MW-36, MW-37, MW-38 and MW-39 during March
2009 so that groundwater monitoring could resume in these areas.
Up to ten homes located off Pecan Lane as close as 800-feet north of the Site are supplied
water either by private water supply wells or the available Town of Clayton water supply.
However, an updated well survey completed during May of 2010 revealed that the homes
closest to the Site have now either hooked onto the available Town of Clayton water
supply or onto a water supply well located further from the Site. This updated well
survey revealed that the nearest in-use water supply well is now located 1,050 feet
northeast of the Site and source area while the next closest in-use water supply well is
located 1,190 feet northeast of the Site. Alternate water supplies are readily available
from the Town of Clayton should these homes require a change in their water supply.
Section A, Figure 1A is an updated receptor map identifying the two in-use wells located
closest to the Site and contaminant source area. The solid circle on this figure represents
a 1,000 foot radius of the Site source area while the dashed circle indicated a 1,000 foot
radius of the leading edge of the contaminant plume which is located off-Site and north of
US 70. There is one water supply located within a 1,000 foot radius of the leading edge
of the contaminant plume. These two closest potable supply wells were last sampled on
May 23, 2011.
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3815 Junction Blvd.
Raleigh, North Carolina 27603
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Report for Annual Groundwater Monitoring
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1.2 Summary of Groundwater Analytical Results
1.2.1 Affected Groundwater Classification
Classification of the groundwater located on and adjacent to the Site has been identified
as GA.1 The best use for this classification of groundwater is as an existing or potential
source of drinking water for humans. This classification is intended for those
groundwaters in which chloride concentrations are equal to or less than 250 mg/l, and
which are considered suitable for drinking in their natural state, but which may also
require treatment to improve their quality relative to natural conditions.
1.2.2 Free Product
Free product was not discovered in any wells during this sampling event and therefore
will not be addressed further in this report.
1.2.3 Groundwater Sampling Event – May 9, 2012
1.2.3.1 Groundwater Level Measurements
Groundwater level measurements were obtained from all wells targeted for sampling
during this event, utilizing a water level indicator capable of measuring the water level
within each well to the nearest 0.01-foot. Wells were gauged to a reference mark on the
top of each well casing which has been surveyed to the nearest 0.01-foot both
horizontally and vertically. This data is necessary for the calculation of groundwater
hydraulic gradient. Groundwater level measurements are also necessary in determining
the proper purge volume(s) for each well targeted for sampling. Levels within the wells
targeted for sampling during this event were measured for the purpose of calculating
groundwater gradient for the May 2012 monitoring event. Groundwater level
measurements collected for the gauging event are presented in Section B, Table 3.
Section A, Figure 3 displays groundwater gradient as interpreted from this measuring
event.
1Reference:NCAC Title 15A, Chapter 2, Subchapter 2L, Section .0201 (Groundwater Classifications)
East Coast Environmental, P.A.
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Raleigh, North Carolina 27603
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1.2.3.2 Well Purging
The groundwater within each well targeted for sampling was purged of a pre-determined
volume of water to allow for infiltration of representative groundwater, and thus
collection of representative groundwater samples. Each well was purged of a minimum
of three well volumes of water prior to sampling. Subsequent to purging, the
groundwater level within each well was allowed to recharge to within 80% of the static
level initially observed. Purging of each well was accomplished through the use of
separate disposable bailers.
1.2.3.3 Groundwater Sample Collection
Representative groundwater samples were collected from each well subsequent to their
purging and recharge. The collection of groundwater samples was performed in
accordance with established EPA and NC-DWQ protocols for the collection of
groundwater samples. ECE modeled its sampling procedures after the procedures noted
in the “Guidelines for Assessment and Corrective Action for UST Releases, Effective
July 15, 2008”, (hereinafter referred to as the “Guidelines” published by the NCDENR-
DWM, Underground Storage Tank Section.
Groundwater samples were collected from monitoring wells MW-1, 2, 3, 4, 7, 8, 10, 12,
13, 14, 27, 32, 33, 34, 35, 36, 37, 38, 39, DW-1, and DW-2. Samples collected from each
well were submitted for chemical analysis by EPA method 6200b in accordance with
monitoring requirements established for the Site by the NCDENR-DWM, Raleigh
Regional Office. A description of specific analytical methods for this sampling event is
presented in Section 1.2.3.4. Analytical results for these samples are discussed in
Section 1.2.4.
As stated previously, monitoring wells MW-5, 6, 9, 11, 15, 16, 17, 19, 21, 22, 23, 24, 25,
26, 28, 30 and 31 have also either been destroyed or rendered unusable at some time since
their installation and therefore were not sampled during this event.
East Coast Environmental, P.A.
3815 Junction Blvd.
Raleigh, North Carolina 27603
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Report for Annual Groundwater Monitoring
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1.2.3.4 Sample Storage and Transport
All samples collected during this monitoring event were properly contained in pre-
washed sample containers. The sample containers utilized in this sampling event were
provided by Environmental Conservation Laboratories, Inc., (ENCO) (NCDENR-DWQ
analytical license # 591) located in Cary, NC.
Samples collected for volatile organic analysis (EPA Method 6200b) were properly
contained in 40-ml "VOAs", pre-preserved with 1:1 hydrochloric acid. All headspace
was removed from the sample bottles during the collection of these samples bottles and
prior to capping.
Subsequent to sample collection all sample containers were properly labeled with the
sample designation, sample date and time, and analysis requested. Each sample was
recorded on a chain-of-custody form, providing sample identification, and the analysis (or
analyses) requested for the sample(s). The samples were then placed in a cooler on ice
pending delivery to ENCO.
The samples were transported to ENCO with all appropriate chain-of-custody
documentation accompanying the samples. The samples collected during May 9, 2012
were relinquished to ENCO on May 11, 2012.
1.2.3.5 Analytical Methodology
Groundwater samples collected from the monitoring wells located on and adjacent to the
Site were analyzed for petroleum hydrocarbons and related petroleum additives. Samples
collected during the March 2011 event were analyzed by EPA Method 6200B. EPA
Method 6200B targets low-boiling-point petroleum hydrocarbons, such as those typical of
gasoline.
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3815 Junction Blvd.
Raleigh, North Carolina 27603
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1.2.4 Analytical Results – Groundwater Samples
1.2.4.1 EPA Method 6200B
Results of chemical testing of groundwater samples collected from monitoring wells
located on and adjacent to the Site indicated the presence of targeted petroleum
hydrocarbons in numerous samples submitted for analysis.
Analytical data for EPA Method 6200B indicated the presence of targeted compounds in
samples collected from wells DW-1, MW-4, 7, 14, 27, 33, 37, 38 and 39. One or more
compounds detected in samples from wells MW-4, 7, 14, 27, 33, and 39 were in excess of
the maximum allowable concentrations defined by NCAC Title 15A, Subchapter 2L,
Section .0202 (Water Quality Standards for Class GA Waters) hereinafter referred to as
the “2L Standards”.
Benzene contaminant levels were present in wells MW-27 (3,900 ug/l), MW-14 (740
ug/l), MW-33 (85 ug/l), MW-4 (49 ug/l), MW-7 (13 ug/l), and MW-39 (5.4 ug/l). This
data is included on Figure 4 which displays the benzene groundwater contaminant plume.
The lateral extent of the benzene contamination related to the Site covers an area of
approximately 5.5 acres. Although levels detected in wells at the Site showed decreases
in benzene, the overall area of benzene contamination appears to have remained virtually
the same, with only minor plume migration further north and west when compared to the
March 2011, March 2010 and April 2009 data. All six of these wells were found to
contain levels in excess of their maximum allowable standard of 1 ug/l as defined by the
2L Standards.
Ethylbenzene contaminant levels were present in well MW-14 (1,500 ug/l), MW-27 (450
ug/l), MW-4 (110 ug/l), MW-39 (61 ug/l), and MW-7 (1.9 ug/l). This data is plotted on
Figure 5. The level in MW-14 was found in excess of their maximum allowable 2L
standard of 600 ug/l.
MTBE contaminant levels were present in wells MW-27 (990 ug/l), MW-14 (640 ug/l),
MW-4 (310 ug/l), MW-33 (83 ug/l), MW-7 (9.9 ug/l), MW-38 (4.6 ug/l), MW-37 (2.9
ug/l), and DW-1 (2.7 ug/l). This data is plotted on Figure 6. The lateral extent of MTBE
contamination related to the Site covers an area of approximately 4 acres. Overall, the
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Report for Annual Groundwater Monitoring
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Clayton, North Carolina
area of MTBE contamination appears to remain unchanged since the last sampling event.
Only the concentrations detected in wells MW-4, 14, 27, and 33 were in excess of their
2L Standard of 20 ug/l.
Naphthalene contaminant levels were present in wells MW-14 (470 ug/l), MW-27 (140
ug/l), MW-4 (130 ug/l), MW-39 (29 ug/l), MW-7 (7.6 ug/l), and MW-33 (1.2 ug/l). This
data is plotted on Figure 7. The lateral extent of naphthalene contamination related to the
Site covers an area of approximately 4 acres. Overall, the area of naphthalene
contamination appears to remain unchanged since the last sampling event. Only the
concentrations detected in wells MW-4, 14, 27 and 39 were found in excess of their 2L
Standard of 6 ug/l.
Toluene contaminant levels were present in wells MW-14 (370 ug/l) and MW-39 (1.0
ug/l). Both samples show toluene levels in less than the 2L Standard of 600 ug/l.
Xylenes (total) contaminant levels were present in wells MW-14 (1,800 ug/l), MW-4
(120 ug/l), MW-27 (72 ug/l), MW-39 (53 ug/l), and MW-7 (3.5 ug/l). Only the levels
detected in MW-14 was in excess of its 2L Standard of 500 ug/l.
Other compounds detected in the wells of the Site at levels in excess of their 2L
Standards included: isopropylbenzene, tert-butylbenzene, n-butylbenzene, n-
propylbenzene, 1,3,5-trimethylbenzene, and 1,2,4-trimethylbenzene. The samples that
were found to contain the highest concentrations of these parameters were collected from
monitoring wells MW-4, and 14 thereby defining the core of the plume. A compilation
of the data for samples obtained during this event is presented in Table 1.
Fluctuations in the extent and/or levels of contamination within the plume at the Site may
be related to several factors occurring in the subsurface of the areas in which the plume
exists. These factors may include fluctuations in groundwater hydraulic gradient, natural
attenuation of contaminants and the discharge of affected water to the surface of the
swampy area located northwest of the Leeway property. Conversely, these same factors
may have decreased spreading of contaminants through the surficial aquifer, as observed
during this most recent and subsequent sampling events.
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3815 Junction Blvd.
Raleigh, North Carolina 27603
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Report for Annual Groundwater Monitoring
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Clayton, North Carolina
Overall groundwater flow through the area remains consistent with data obtained in the
past for the Site, with flow trending generally to the north, northwest and southwest from
the Site location.
Historical analytical data for samples collected from the Site is presented in Section B,
Table 2. Laboratory analytical reports for the May 9, 2011 sampling event are presented
as an attachment in Section C.
In an effort to track the petroleum contaminated groundwater plume, ECE has constructed
a series of bar charts (Charts MW-4, MW-14, MW-27 and MW-33) comparing Total
BTEX concentrations vs. time for groundwater monitoring wells MW-4, MW-14, MW-
27 and MW-33. Historical total BTEX concentrations in all four monitoring wells for
which charts have been made show general declines in total BTEX contaminant
concentrations for this most recent sampling events. These charts can be found in
Section B.
1.3 Current Plume Information
Analytical data for EPA Method 6200b showed the presence of targeted compounds in
samples collected from wells DW-1, MW-4, 7, 14, 27, 33, 37, 38 and 39. One or more
compounds detected in samples from wells MW-4, 7, 14, 27, 33, and 39 were in excess of
the maximum allowable concentrations as defined in the 2L Standards.
This data suggest that the area(s) encompassed by the plume have remained nearly
constant when compared to the previous sampling events. However, newly installed
monitoring wells MW-36 and MW-39 provides additional information for the area
northwest of the Site and across Highway 70. Laboratory results from MW-36 and MW-
39 continues to indicate that the contaminant plume may have spread in this direction
further than was previously believed based on past data.
Further, contaminant levels have remained relatively consistent when compared to the
previous March 2011 sampling event. As with sampling events conducted at the Site in
the past, variations in contaminant levels may indicate influences such as seasonal water
table fluctuations, and natural attenuation of contaminants. Three wells which have
historically shown the highest levels of contamination (MW-4, MW-7 and MW-27) are
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showing much lower contaminant levels in the May 2012 monitoring event when
compared to previous monitoring events conducted over the past 10 years. It should also
be noted that for the first time in the over 10 years MW-27 has been sampled it did not
produce a groundwater sample containing benzene at a concentration in excess of its
Gross Contaminant Level of 5,000 ug/l (The benzene contaminant concentration for the
sample collected from MW-27 as part of the May 2012 sampling event was found to be
only 3,900 ug/l). This may indicate that the groundwater contaminant concentrations in
the areas where these wells are located are showing a decreasing trend. This decreasing
trend is also continuing in MW-14, MW-27, and MW-33 but at a much slower pace that
the other wells. This data may suggest that the contaminant plume is moving further into
the low lying wet area across Highway 70 and away from the original source area and that
contaminant levels in this area are also diminishing likely through a combination of
dilution, natural attenuation and biodegradation.
1.4 Summary of Remedial Activities
1.4.1 Groundwater Remediation
1.4.1.1 Overview/General Description
The groundwater treatment system consists of an interceptor subsurface trench
approximately 550-feet in length and 8-feet in depth, running parallel to the south side of
U.S. Highway 70 East. A sump pit and pump provides an extraction point for the
collected groundwater that is transported via closed piping to the treatment compound for
pre-treatment. The length and depth of the trench were established to minimize the
potential for off-site migration of the contaminants present in the groundwater.
The treatment compound contains an oil/water separator for the removal of residual free-
product, an air diffuser, two (2) backwash units, and four (4) 200 lb carbon polishing
units. Additionally, an air compressor provides compressed air for system operation.
Water collecting in the system sump is transferred to the treatment compound by an ARO
Model 365 dual diaphragm pump with 1-inch inlet/outlet. Water and product interface
generated by the pumping process are transmitted via 1-inch chemical resistant rubber
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piping into the system compound, at which point the pumped discharge is fed into a
coalescing oil/water separator.
The oil water separator is of stainless-steel construction, and has an approximate capacity
of 140-gallons. The unit contains two 45-mil slant rib coalescers, and an adjustable PVC
skimmer. Design flow rate for the oil/water separator is 25 gpm. Any product generated
during the separation process is piped to a 55-gallon recovery drum, equipped with a level
sensor and a high level shut-off switch. The shut-off is designed such that a high product
reading within the recovery drum will shut down the recovery sump, thereby restricting
the ability of the system to overfill the drum. Groundwater generated during the
separation process is fed via gravity into a surge tank, where the water is stored prior to
transfer into the Low Profile Vacuum Induced Aerator.
Transfer pumps utilized throughout the system are Vertiflo Series 1300, Model 1312 (or
equivalent) horizontal motor mounted end suction pumps, capable of up to 50 gpm flow
rates.
As sensors in the surge tank elevate to the point at which transfer of water begins, the
transfer pump actuates and pumps the stored water from the holding tank into the aeration
system. The two stage Low Profile Vacuum Induced Aerator for use on the Site is of 304
stainless-steel construction, with a maximum design flow rate of 34 gpm. Air for the
process is supplied by a Rotron HPC High Pressure Blower. The unit has an effective air
to water flow ratio of 211:1, and an approximate retention time of fourteen minutes.
Calculated removal efficiency of the unit is greater than 98% for BTEX, and greater than
94% for MTBE. The total fluid capacity of the unit is approximately 307-gallons, and the
aeration chamber capacity is approximately 210-gallons. From this process, the aerated
water is then passed through two backwash filters, rigged in parallel, and either into a
second sump (and then on through particulate filters) or straight into four 200-lb. high
pressure Granulated Activated Carbon (GAC) Units.
The GAC Units are rigged in two sets of series paralleled, and are placed in line to
complete the treatment process prior to discharge. The GAC Filtasorb 300 units are of
reinforced fiberglass construction, and have a design flow rate of 40 gpm. Maximum
pressure for these units is 150 psi.
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Raleigh, North Carolina 27603
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The groundwater remediation system described above was installed on the Site and
became operational during December 1995. This system was built as specified in the
“Corrective Action Plan for Petroleum Contaminated Soils and Groundwater”, released
by ECE on October 12, 1994. An Authorization to Construct and a NPDES Permit were
issued by the then NCDENR-DEM and received by A.G. Lee Oil Company on May 30,
1995. A permit renewal application for the system was submitted to the NCDENR on
October 23, 1997. The NCDENR issued a Certificate of Coverage under the General
Permit (NCG510000) on April 21, 1998.
1.4.1.2 System Operation
The groundwater remediation system associated with the Leeway Service Center has run
inconsistently from December 1995 through September 2001. Groundwater Quality
Monitoring Compliance Report Forms are completed on a monthly basis, which detail the
monitoring of system effluent on a monthly basis. Groundwater recovered by the
treatment system has not yielded substantial free product, but a petroleum sheen has been
visible on the influent entering the oil/water separator. At the present time, the
remediation system is not in operation.
1.4.1.3 System Effluent Sampling
Sampling of the remediation system effluent stream and continuous measurement of
discharge volumes (in gallons) are requirements of the NPDES Permit obtained for the
Site. These data are necessary to ensure compliance with contaminant and flow
limitations imposed on the remediation system.
Sampling of the effluent stream is accomplished through the collection of treated water at
a sampling point located on the discharge side of the GAC units contained in the system.
Effluent samples collected from the system were analyzed by EPA Method 8260 (plus
MTBE) and 9071 (oil and grease). Additional analyses are performed for total suspended
solids (TSS), and manganese, ferrous iron and lead by EPA Method 200.7. All of these
analyses are requirements of the NPDES Permit for the Site.
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The most recent sampling (July 06, 2001) of the effluent stream at the Site indicated the
presence of low levels of compounds by EPA Method 8260. Detected in this sample
were methylene chloride, chloroform and MTBE at levels of 0.6, 2.0 and 70 ug/l,
respectively. Analysis for ferrous iron and manganese revealed these compounds at
levels of 3,590 and 480 ug/l, respectively. Analysis for total lead did not reveal the
presence of the compound at levels above the method detection limit. Analysis for oil
and grease and total suspended solids did not show the presence of targeted analytes at
levels above the method detection limit. Data for this sample indicate minor contaminant
breakthrough.
As of September 03, 2001, a total of 2,096,560-gallons of groundwater had been treated
and discharged by the system. The system was shut down on September 03, 2001 with
the consent of the NCDENR-RRO due to the fact that the bulk of the groundwater
contaminant plume has now migrated across US Highway 70 and beyond the “radius of
influence” of the groundwater recovery trench.
1.4.1.4 Monthly Operation Maintenance Costs
Operation of the cleanup system including scheduled maintenance time, parts and
electricity was averaging approximately $1,300/month. Effluent sampling and analysis
for NPDES discharge requirements was averaging $400/month and semiannual
groundwater sampling, analysis and reporting costs are approximately $7,000/event with
two sampling events per year currently being completed. Recently, sampling was cut
back to an annual basis. Therefore, the sum annual total for these costs is on the order of
$27,400/year.
1.4.1.5 Future Remediation Activities
While groundwater has not been restored to the 2L Standards, ECE believes that
consideration should be given to leaving the cleanup system off for a more extended
period of time due to the fact that the bulk of the remaining groundwater contamination is
now located beyond the “radius of influence” that the current system can be expected to
provide. ECE believes that the “rate of return” for the costs to operate the existing
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cleanup system in an area that is now in the “tail” of the groundwater plume is
questionable. However, if the contaminant levels rebound in the current systems recovery
area in the future then the existing system can be re-started at a later date.
ECE on behalf of A.G. Lee Oil Company prepared and submitted to the NCDENR
Raleigh Regional Office a September 22, 1999 report entitled; “System Enhancement
Recommendations Report Leeway Service Center Site”. This report proposed Dual
Phase Extraction (DPE) in order to address the bulk of the contaminant plume that is now
well past U.S. Highway 70. DPE incorporates the use of a vacuum pump for recovery of
groundwater and soil vapors, while dissolved-phase contaminants in the process would be
treated and discharged by conventional methods (i.e., air stripper and activated carbon).
A “conceptual” design was completed using the existing plume delineation and the
assumption that full access is given to the Peele property across U.S. Highway 70. The
DPE system would be positioned near the warehouse and use 24 recovery wells
(assuming a 20-foot radius of influence) in three major areas of concern. Actual location
and number of recovery wells required for this approach is subject to change.
NPDES Information
An Authorization to Construct and a NPDES Permit were issued by the then NCDENR-
DEM and received by A.G. Lee Oil Company on May 30, 1995. A permit renewal
application for the system was submitted to the NCDENR on October 23, 1997. The
NCDENR issued a Certificate of Coverage under the General Permit (NCG510000) on
April 21, 1998.
1.5 Groundwater Conditions
1.5.1 Proximity to Potential Receptors
Up to ten homes located off Pecan Lane and as close as 800-feet north of the Site are
supplied water by either private water supply wells or the available Town of Clayton
water supply. However, an updated well survey completed during May of 2010 revealed
that the homes closest to the Site have now either hooked onto the available Town of
Clayton water supply or onto a water supply well located further from the Site. This
updated well survey revealed that the nearest in-use water supply well is now located
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1,050 feet northeast of the Site and source area while the next closest in-use water supply
well is located 1,190 feet northeast of the Site. Alternate water supplies are readily
available from the Town of Clayton should these homes require a change in their water
supply.
Section A, Figure 1A is an updated receptor map identifying the two in-use wells located
closest to the Site and contaminant source area. The solid circle on this figure represents
a 1,000 foot radius of the Site source area while the dashed circle indicated a 1000 foot
radius of the leading edge of the contaminant plume which is located off-Site and north of
US 70. These two supply wells identified as SW-1 and SW-2 were last sampled on May
23, 2011 as part of a groundwater monitoring event.
The densely wooded area located to the west of the Site (in the vicinity of wells MW-17,
18, 27, 29, 31, 32, 33, 34 and 35) continues to be at risk as the plume has impacted the
groundwater in the area. ECE contacted the U.S. Corps of Engineers regarding the
potential for the area to be classified as a protected wetland, but the Corps of Engineers
has been non-responsive in making a determination. Ms. Karen Harmon, with the
NCDENR-DWM, Raleigh Regional Office indicated to ECE that regardless of a
determination by the Corps of Engineers, she considered the area to be a wetland and
therefore it is also considered to be an impacted receptor. Since then Johnston County in
which the Site is located has now come under the direction of the Fayetteville Regional
Office (FRO) of the NCDENR. A recent discussion with Mr. Bob Heath of the FRO
indicated that he would most likely consider this a wetland or a surface water body, but a
determination will need to be made as to whether this is an impacted receptor.
EPA Method 6200b (Supply Well Analytical Results) – June 19, 2012
Analytical data for samples obtained from the two drinking water wells located adjacent
to the Site (SW-1 & SW-2) will be included in a report under a separate cover.
1.5.3 Groundwater Flow
Groundwater flow through the Site was determined to trend to the north across Highway
70, with a continuing trend to the west-northwest through the low lying wetlands area.
This direction of groundwater flow is consistent with gradient flow as determined though
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past measuring events conducted at the Site. The gradient as measured during May 2012
is depicted on Figure 3.
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2.0 CONCLUSIONS AND RECOMMENDATIONS
Based on analytical data for the May 2012 groundwater sampling event numerous
compounds were present in samples collected from several monitoring wells at levels in
excess of their maximum allowable concentration(s) defined by the 2L Standards. Data
for this sampling event continue to indicate the presence of high levels of dissolved phase
petroleum contaminants centered in the vicinity of MW-4 at the Site itself, as well as the
area surrounding MW-14, MW-27 and MW-33 located on NCDOT right of way and the
former Peele property across US Highway 70, respectively.
However, new data obtained from monitoring well MW-39 suggests that there may be
some minor plume migration in the direction of the private supply wells located along
Pecan Lane, to the north-northwest of the Site. This statement is based on the laboratory
reports for this May 2012 and the previous March 2011, March 2010 and April 2009
monitoring events which indicate that targeted petroleum contaminants in the samples
collected from this well were found at concentrations in excess of their 2L standards.
If the NCDENR concurs, then one (1) additional monitoring well (proposed MW-40 on
Figure 2) could be installed northwest of MW-36 and MW-39 in order to delineate the
edge of the plume to the 2L standards in the direction of the nearest potable supply wells.
The cost for completing and sampling this additional well could be off-set by not
sampling MW-8 or MW-32 during future events. MW-8 and MW-13 have been outside
the limits of the contaminant plume for some time, and are not currently needed to
delineate the current groundwater plume, while MW-40 could prove useful in delineating
the edge of the plume in the direction of these potable supply wells. MW-40 could be
installed at the same time of the next monitoring event that should take place in March of
2013.
Finally, because monitoring wells MW-17, MW-18 and MW-29 could not be located
replacement wells MW-37 and MW-38 were installed as shown on Figure 2 during early
2009. The core of the plume is migrating through this low lying wet area and these wells
help to better characterize the extent of groundwater contamination northwest of the Site.
Groundwater hydraulic gradient movement appears to remain consistent with past
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gauging events at the Site, and continues to flow to the west, with a trend to the
northwest.
While groundwater has not been restored to the 2L Standards and there are no longer any
supply wells within a 1,000 foot radius of the source area, ECE believes that the existing
cleanup system should remain off due to the fact that the bulk of the remaining
groundwater contamination is now located beyond the radius of influence that the current
system can be expected to provide. ECE believes that the “rate of return” for the costs to
operate the existing cleanup system in an area that is now in the “tail” of the plume is
questionable. However, if the contaminant levels rebound in the current system recovery
area during the future then the existing system can be re-started.
ECE on behalf of A.G. Lee Oil Company has prepared and submitted to the NCDENR
Raleigh Regional Office a September 22, 1999 report entitled “System Enhancement
Recommendations Report Leeway Service Center Site”. This report proposed Dual
Phase Extraction or DPE (a.k.a. Bio-slurping) in order to address the bulk of the
contaminant plume that is now well past U.S. Highway 70. DPE incorporates the use of a
vacuum pump for recovery of groundwater and soil vapors, while dissolved-phase
contaminants in the process would be treated and discharged by conventional methods
(i.e., air stripper and activated carbon). ECE believes that if the NCDENR will still
require active remediation in the future then consideration may be given to building this
system and not restarting the old one.
However, at this time, ECE recommends that annual groundwater monitoring should
continue. Three factors contributing to this recommendation include the following: 1)
while there are no longer any potable supply wells located within a 1,000 foot radius of
the source area the lateral edge of the contaminant plume as found in monitoring wells
MW-36 and MW-39 is located within 600 feet of the nearest in-use supply well; 2) the
low lying area to which the core of the groundwater contamination plume is migrating has
been considered a wetland and impacted receptor in the past.
East Coast Environmental, P.A. appreciates the opportunity to be of assistance with this
project. ECE recommends that a copy of this document be submitted to the North
Carolina Department of Environment and Natural Resources, Division of Water Quality,
Fayetteville Regional Office to the attention of Mr. Bob Heath.
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Section A
Figures
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Section B
Tables
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Section C
Analytical Data
May 9, 2012 Groundwater Sampling Event
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