DEQ-CFW_00034317

6324 Fainiew Road
Charlotte, NC 28210
Tel. [phone]
Fax [phone]
DuPont Engineering
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'IV OR 2005
Receiv v December 16, 2005
Hazardous Waste
Mr. Larry Stanley
61 Section
Division of Waste Management
NC Department of Environment
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ez 1,
And Natural Resources
1646 Mail Service Center
Raleigh, NC 27699-1646
Re: Revised RCRA Phase 11 Investigation Work Plan Update
DuPont Fayetteville Works
EPA ID No. NCD 047 368 642
Dear Mr. Stanley:
DuPont has received your comments, dated December 14, 2005, on the RCRA Phase 11
Investigation Work Plan Update. As a result, please find enclosed a revised work plan. The
revisions reflect our proposed responses as discussed with you via telephone on December 14,
2005. For ease of review, a comment -by -comment response is also enclosed with this letter.
If you have any questions or comments, please do not hesitate to contact me at [phone].
Thank you for your prompt attention to this matter.
Si ely,
eexSi
.
Jamie Van Buskirk
CRG Project Director
Enclosures
Cc: Michael Johnson
Fayetteville Works Environmental Manager
File
DEQ-CFW-00034317

RCRA Phase II Investigation Work Plan Update
Objective 2
Characterize Surface W
1) Just as a reminder, the two surface water sampling points (Locations F and G) and the two in -
situ groundwater sample locations (Locations H and 1) are reversed when the text is
compared to Figure I -Locations Map.
DuPont Response —
Figure I has been revised to correct this error.
2) The HWS will direct EPA-SESD to collect a sediment sample at the surface water location
currently designated as Location H on Figure 1. The sample will be analyzed for APFO. T
sample will be collected during the sampling event scheduled for late January. I
DuPont Response —
DuPont recognizes the desire to conduct sediment sampling in the subject drainage
ditch although the comment does not contain a stated objective that will be met by doing so.
Nonetheless DuPont will collect a sediment sample at this location and accommodate
whatever split sampling desire the HSW has. It is requested that additional consideration be
given to developing a stated objectivefor this sampling effort to aid in determining the
appropriate analysis result evaluation process. In addition, the sampling protocols and
procedures should also befurther evaluated by DuPont and HSW.
Note: As discussed above this location has now been correctly identified as "Location F"
Figure I of the revised work plan. I
Objective 3
Characterize Groundwater Qualily North and Northwest of the APFO Facility
3) A wind rose diagram included with DuPont-Fayetteville's Part B permit application shows a
strong northeast -southwest orientation. At the APFO facility, southwest winds should blow
toward monitoring well SMW-03. Attempts to sample this well were unsuccessful because
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OEQ-CFVV_00034318

the well was dry. The HWS recommends that DuPont collect a groundwater sample at this
well location and analyze it for APFO.
DuPont Response —
DuPont has and will continue to try and collect a groundwater samplefrom this
location. If this location remains dry then it may be necessary to place another monitoring
point at this location screened at a lower depth to pull the desired sample. This decision will
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will be conducted during the Phase III RFI event.
4) At the location of the APFO unit, northeast winds would blow toward the facility's Butacite
unit. The HWS recommends that DuPont collect a groundwater sample in the vicinity of the
Butacite unit. The sample should be analyzed for APFO.
DuPont Response -
Sample location SMW-01 was originally and intentionally located to correspond with
this seasonal wind direction. It has consistently been non-detectfor APFO. DuPont
&s*e Iy-mwkv
closer to the APFO Manufacturingficility in this direction. SMW-01 has apparently been
deemed to be toofar away by HWS. No information exists that would indicate that the
Butacite@ manufacturing area is a more appropriate location to collect APFO groundwater
data. DuPontfeels that the current location of SMW-01 is appropriately located to monitor
potential groundwater impactsfrom potential airborne deposition in this direction, especially
as it would relate to the potentialfor off -site migration.
However, in order to try and address the HWS desire, DuPont will collect a shallow
groundwater APFO samplefrom the Butaciteg area during subsequent, Phase III RFI
sampling activities. This part of thefacility will be the subject of an investigation related to
the discovery on a new RCRA Corrective Action AOC (reference correspondencefrom Mike
Johnson dated 12108105). It is assumed that shallow groundwater monitoring will be
d�*Vakw�'
list at an appropriate and agreed upon location(s).
5) As relayed to Jamie VanBuskirk during our telephone conversation of December 9, Ms.
Yvonne Martin, who is with Region 4's Water Programs Enforcement Branch (ATEB),
contacted the HWS concerning C-8 in the groundwater at the DuPont -Fayetteville facility.
Ms. Martin indicated that EPA -HQ and the WPEB are asking DuPont to monitor the
groundwater at public water systems located near the Fayetteville facility. EPA is developing
a list of PWSs that are close to the facility, but the list has not been finalized.
DuPont Response —
Based on our telephone conversation on 12114105, a response to this comment is not
warranted at this time.
10-7 fff MI
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DEQ-CFW-00034319

6) DuPont -Fayetteville should discuss the "direct push drop -down screen sampling technique" in
more detail. The HWS is notfamiliar with this method of developing a vertical geochernical
profile.
DuPont Response —
A more detailed description of this sampling approach at Locations H and I is
contained in Section 4. 0 of the revised work plan. This discussion has been updated to
reflect work andfindings that have already been accomplished. You are also encouraged to
contact Mr. Bryan Heath of our office at [phone] if more information is needed.
Objective 5
ConducrIWA Dat
7) The concentrations of some of the MNA parameters listed in Attachment A of the work plan
(i.e., alkalinity, chloride concentration, and carbon dioxide concentration) should be compared
to background concentrations. DuPont -Fayetteville should indicate which monitoring wells
are considered background wells for MNA purposes.
DuPont Response —
As described in Section 4.0 of the revised workplan, NAF-01 has been added to the list
of locations to be sampled aspart of the MNA program development. NAF-01 is located in
an appropriate, upgradient location and will serve as a background monitoring point.
8) The concentration of iron in the form of Fe+2 gives more information about the potential for
anaerobic biodegradation of chlorinated organic compounds than does the concentration of
total iron. The HWS recommends that DuPont -Fayetteville have MNA groundwater samples
analyzed for
DuPont Response -
Becauseferric (oxidized or Fe3+) iron is insoluble at neutralpH it is likely that a total
iron measurement in non -turbid groundwater is representative of concentrations of soluble
reduced (ferrous or Fe2+) iron in -situ as is anticipated with groundwater at the site.
Obtaining a direct measurement of reduced iron from groundwater samples is difficult
because the exposure of the sample to oxygen will result in the oxidation of reduced iron to
produced oxidized iron and in this way compromise the measurement. We propose to
interpret total iron measurements in groundwater as a measurement of reduced soluble
iron in situ. This interpretation will be reviewedfor consistency with other geochemical
evidence collectedfrom the wells (e.g. redox, dO2, suy'ate, nitrate, sulfide and contaminant
behavior) to ensure that it is a reasonable assumption. However, should the groundwater in
a well be turbid or if thepH is low this interpretation will be revisited and if necessary a
direct method of measuring reduced iron will he identified and applied in thefield andlor
laboratory.
[Wecember 16, 2005
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DEQ-CFW-00034320

Considering the schedule shown in Section 6.0 of the work plan, DuPont -Fayetteville
should discuss the comments contained in this letter with the HWS as soon as possible. Please
don't hesitate to contact me at [phone].
DuPont Response —
It does not appear that resolution of any of the issues will negatively impact the
existing schedule. We are currently in thefteld installing the two in -situ groundwater
samplingpoints (Locations H and I) and will soon be installing the monitoring wells along the
river (Locations A, B, C, D, and E). Barring any issues related to inclement weather, this
work should befinished in time to conduct sampling activities as presently schedule to start in
the last week of January 2006.
It is important to also note that an additional modification to the workplan has been made
since submittal. Figure 2 of the revised workplan has been modified to reflect the addition of
another surface water samplingpoint (Location K). This point is located where 1-95 crosses
the Caper Fear River. The identifying nomenclature of the other samplingpoints on Figure 2
have also been modified slightly to reflect the inclusion of this new point.
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