DEQ-CFW_00042133

AWAWANPOdft
NCDENR
North Carolina Department of Environment and Natural R your
2xtc3r R Matt"oyvs, Di cttlr Division of Waste Management
August 16, 2006
CERTIFIED MAIL
RETURN RECEIPTREQUESTED
ED
Mr, Michael E. Johnson
Environmental Manager
DuPont Fluoroproducts:- Fayetteville Works
22828 NC highway 87 W
Fayetteville, NC 28306-7332
. E ; ,r. ovemo
tiiiE 't G. 19ogs Jr, Secie!a y
33
Re: NOTI for Phase II RCRA Facility InyestiRation Report
DuPont Fluoroproducts - Fayetteville Works
EPA ID # NCD 047 368 642
Dear Mr. Johnson:
The North Carolina Hazardous Waste Section (HWS) has reviewed Phase II RCRA Facility
Investigation Report. As a result of the review process, the HWS has concluded the Phase II RFI report
does not constitute an acceptable report. Comments intended to offer guidance and aid with revisions to
the report are enclosed,
The HWS has not completed its reviewed of Appendix A, which deals exclusively with APFO.
DuPont -Fayetteville can expect to receive comments on Appendix A in a few days,
DuPont -Fayetteville should submit responses to the Hazardous Waste Section's comments and/or
revisions to the Phase II report within ninety (90) days of the receipt of this letter. If your office has
questions concerning this correspondence, please call me at [phone],
Sincerely,
Larry Stanley, Hydrogeologist
NC Hazardous Waste Section
Enclosure
cc: Jon Johnston, EPA Region 4 rc: Bud McCarty
Bobby Nelms Bob Glaser
Jamie VanBuskirk (DuPont-CRG) Karim Pathan
Larry Stanley 1WLarry Stanleyt'Q 6
1646 Mail Service Genter, Raleiah, North Carolina 27699-1646
Phone [phone] FAX [phone] ,4 Internet htt :3i'v..,astoriotnc.org.
.C,(1W'.rQ4r!IJr'i';'!
C: \inehlgsldupont-fay-pliase]]RF 1-report-hr. doe
DEQ-CFW 00042133

DuPont Fluroproducts - Fayetteville Worl
Fayetteville, North Carolina
EPA ID # NCD 047 368 642
NC Hazardous Waste Section's Comments on
Phase 11 RCRA Facilltv Investigation ort
(Does Not Include Comments on Appendix A)
Section 3.1
Phase 11 Goals and Objectives
1) DuPont -Fayetteville should correct the numbers assigned to each objective. The numbers are
currently listed as 7 through 12.
Section 3.2.1
Objective 4
2) The text in this section of the report states that groundwater flow in the area of the wastewater
treatment plant is toward the southeast. However, Figure 4;land other passages In the text of the
report indicate that groundwater flows to the southwest. DuPont -Fayetteville should correct the
text in Section 3.2.1.
Section 3.4.1
Decontamination Procedures
3) The fourth bullet in Section 3.4.1 contains the phrase "and Decontamination Procedures."
DuPont -Fayetteville should explain the meaning of this phrase. If the phase is a misprint, it
should, as appropriate, be either corrected or removed from the text.
Section 3.4.2 In -situ Groundwater Installation and Sampling
Section 3.4.3 Piezometer Installation
Section 3.4.4 Monitoring Well, Installation
4) Subsurface lithology was reported for all groundwater monitoring wells installed during Phase
11 of the RFI. DuPont -Fayetteville should describe the method(s) used to collect the subsurface
samples (i.e., split spoon sampler, drill cuttings). The sampling method should also be indicated
on the boring logs contained in Appendix B.
DEQ-CFW-00042134

Section 4.2.1
Summary of QC Findings
5) According to laboratory reports, the analytical results for several semi -volatile organic
compounds in groundwater were not reported because of low recoveries. Some of the
compounds are Appendix IX constituents.
DuPont -Fayetteville should discuss these constituents in more detail. The discussions
should include possible constituent concentrations in groundwater, uses of these compounds at
the facility, areas of the facility where these compounds are used, and possible releases of these
compounds to the environment.
Section 4.3.1
Groundwater Analylical Screenin Pro rocess
b) The north Carolina 2L groundwater rules state that "substances which are not naturally
occurring and for which no standard is specified shall not be permitted in detectable
concentrations in Class GA or Class GSA groundwaters" (I5A NCAC 2L .0202 (c)). The HWS
has adopted. the 2L groundwater standards through policy and guidance. (Sce Guidelines for
Establishing Remediation Goals at RCRA Hazardous Waste Sites (Revised May 2005). This
guidance document can be viewed at the HWS's Internet site.)
When a 2L groundwater standard or IMAC for a constituent are not available, the NC
Hazardous Waste Section has used the EPA Region IX PRG tap water standards for preliminary
screening purposes. (Region IX PRG tap water standards were, for example, used in
environmental indicator evaluations.) However, if a 2L groundwater standard is not available
and an IMAC cannot be developed, the groundwater standard for a non -naturally occurring
constituent becomes, by default, the constituent's analytical detection limit. The 2L groundwater
rules are enforced by the NC Division of Water Quality.
Section 4.4
SWMU and AOC Analytical Results
7) Chlorodibromomethane, which is listed in Table 5 (Groundwater Analytical Detections), has
an Interim Maximum Allowable Concentration (IMAC) of 0.41 ug/L. (A synonym for
chlorodibromomethane is dibromochloromethane.) IACs are enforceable under the NC 2L
groundwater rules. The HWS recommends that DuPont -Fayetteville use IMAC's in the
groundwater screening process.
N
DEQ-CFW 00042135

Section 4.4.2
8) Soil samples were collected at SWMU 9 A, B, & C as part of confin-natory sampling
activities. The samples were analyzed • volatile organic compounds, methanol, glycols,
fluoride, chloride, • petroleum hydrocarbons (TPH), chromium, nickel, iron, and lead. TPH
was detected in two samples, SWMU 9AB-01 and SWMU 9AB-02, at concentrations of 42 an4
65 ppm, respectively.
In addition, TPH was detected in monitoring well MW-1 2S at a concentration of 680 ppb,
Interpretations of groundwater flow presented in the Phase 11 RFI report indicate that this well
may be downgradient of the northern limit of SWMU 9A.
DuPont -Fayetteville should integrate these occurrences of TPH into the conceptual site
model, Additional characterization of TPH contamination in soil and groundwater may be
Section 5.1.2 — Chemical Sgqjag
Initial MNA Evaluation
9) DuPont -Fayetteville should present the constituent concentrations and parameter values that
were collected to assess whether natural attenuation processes are operating. Displaying this data
in a table format would be acceptable. A more detailed presentation will assist the HWS with
understanding site conditions and should constitute the basis for future discussions concerning
remedial options.
Section 5.3.4-Incomplete Exposure Pathways
Groundwater
10) DuPont -Fayetteville operates a drinking water well that serves the facility's recreation center.
The facility should include this well in an evaluation of the potential for a complete
groundwater -to -human exposure pathway. In addition, DuPont -Fayetteville should make the
necessary changes to the text of the report.
Section 5.3.4 - Incomplete Exposure Pathways
Indoor Air
11) DuPont -Fayetteville states that the EPA Draft Guidance for Evaluating the Vapor Intrusion to
Indoor Air Pathway from Groundwater and Soils (Subsurface Vapor Intrusion Guidance), 2002
was used to evaluate the vapor intrusion from groundwater to indoor air pathway. However,
DuPont -Fayetteville used the OSHA PELs and ACGIH TLVs to calculate indoor air target
DEQ-CFW-00042136

concentrations and then compared the concentrations in groundwater to these concentrations.
This is not the recommended approach in the EPA draft guidance. The EPA draft
guidance recommends doing a tiered screening, where if volatile organic chemicals have been
detected within 100 feet of occupied buildings, the next step is to compare the concentrations of
chemicals of concern in groundwater and/or soil gas to target concentrations. Comparing the data
in Table 5 with target groundwater concentrations calculated based on an attenuation factor of
0.00 1 and assuming that partitioning across the water table obeys Henry's Law (Table 2c in
EPA's draft guidance), the following chemicals exceed the target concentrations:
Bromoform (MW- 116/15/05; NAF-08B 6/21/05)
Methylene chloride (NAF-01 6/15/05; NAF-03 6/17/05, 10/18/05; PZ-06 6/16/05,
10/14/05)
Dichlorodifluoromethane (NAF-05A 10/13/05, NAF-08B 6/21/05)
Tetrachloroethylene (NAF-05A 10/13/05, NAF-08B 6/21/05)
Trichloro ethylene (NAF-08B 6/21/05)
The HWS recommends that DuPont -Fayetteville take soil -gas samples to see if these
chemicals continue to be above screening levels. If these samples show concentration-,; below the
target concentrations (Table 2c in EPA's draft guidance), then the HWS agrees with the
conclusion in the report, i.e., that vapor intrusion of VOCs from groundwater to indoor air is not
expected to be a potential concern at this time. If the soil -gas samples show concentrations
above the screening levels, then a site -specific assessment may be needed. (Comment #11 was
contributed by Susan Goldhaber,)
Section 6,2
Recommendations and Path Forward
12) On several occasions, DuPont and the HWS have discussed an overall strategy for
completing the RF1 at DuPont -Fayetteville. Prioritizing all SWMUs and AOCs and performing
an environmental indicator evaluation have been part of this strategy. The HWS suggests that
Phase III of the RFI would be the appropriate time to address these objectives.
4
DEQ-CFW-00042137