No ID_Partial Approval SAR 9-27-2018_20200526

ROY COOPER
Governor
MICHAEL S. REGAN
Secretory
S. DANIEL SMITH
Director
NORTH CAROLINA
Environmental Quality
May 26, 2020
Chrissy Piechoski
Remediation Project Manager
Ashland LLC
500 Hercules Road, Wilmington, DE 19808
[phone] (direct)
[phone] (cell)
[e-mail]
Ref: Partial Approval Site Assessment Report - September 27, 2018
Meeting May 28, 2019 regarding IMAC values and SAR preparation
Former Cape Industries Waste Injection Facility (Hercules Site)
Wilmington, New Hanover County, North Carolina
Dear Ms. Piechoski,
The Division of Water Resources (DWR) acknowledges the receipt of two documents related to the
Former Cape Industries Waste Injection site (Hercules) site assessment: (1) Site Assessment Report
(SAR) dated September 27th 2018, prepared by Groundwater and Environmental Services, Inc. for
Ashland Incorporated and (2) Notes for the meeting conducted on May 28, 2019 and received on
August 1, 2019.
DWR believes that the current SAR provides an adequate evaluation of the site conditions and
appropriate conceptual understanding of the Contaminants of Potential Concerns (COPCs) and their
pathways at the site. However, there are some aspects of the SAR that will need to be revisited and
resubmitted as part of the Corrective Action Plan. An approved site assessment addressing items 1-
5 in 15A NCAC 02L .106(g) is required before the implementation of a corrective action plan.
Therefore, the DWR partially approves the SAR and authorizes the preparation of the Corrective
Action Plan (CAP) according to the requirements in 15A NCAC 02L .106(h). The following comments
will need to be appropriately addressed in the CAP.
D QNorth Carolina Department of Environmental Quality I Division of Water Resources
Wilmington Regional Office 1 127 Cardinal Drive Extension I Wilmington, North Carolina 28405
ENCRTH CAROINh
Department 0 Dvtranmentxi 910.796.7215

Chrissy Piechosky
Former Cape Industries Waste Injection Facility (Hercules Site)- SAR Comments
2/6
1. Recommended Interim Maximum Allowable Concentration (IMAC) for p-Toluic acid is 35
ug/1 (or ppb) and for Acetic acid is 5000 ug/l: NCDEQ continues to support the use of the
IMAC for both COPCs based on the language established in the 15A NCAC 02L rules and the
statements of the NCDEQ toxicologist during the May 28, 2019 meeting between NCDEQ,
Hercules LLC, GES, and Integral Consulting. No additional toxicity information or guidance
values for p-toluic acid have been identified since the May 2019 meeting. DWR recommends
not to use the statement indicating that "IMAC values are not enforceable standards". IMAC
values are enforceable since they are established when a standard is not available [i.e., p-
Toluic/acetic acid concentrations not listed in 15A NCAC 02L .0202 (h)]. Otherwise, the
enforceable value would be the practical quantitation limits for those compounds [Ref: 15A
NCAC 02L .0202 (c)].
2. Groundwater Uses: Discuss the main source of groundwater in the area and the uses of the
Black Creek aquifer, Cape Fear aquifer, and Surficial aquifer for the region.
3. Groundwater Sampling Results: GW sampling results from June 2018 show exceedances in
IMAC for p-toluic acid in 700ft. aquifer in OB-3 for both p-Toluic acid (41,OOOug/L) and Acetic
acid (660,000 ug/L). In the 1,000 ft. wells OB-4 (31,000 ug/L), OB-12 (58ug/L), 013-
14(12,000ug/L) and OB-15(6,700ug/L) (ref page 20). (ref page 20). These wells are located
on the northern portion and center of the site (ref Fig 23A). Please provide laboratory results
for the well OB-13 which is in the 300ft. aquifer. It seems that results of this sampling were
not provided in the report. Was this well sampled in 2018? If not, please explain. For the
preparation of the CAP, provide complete sampling records for the 2020 sampling event.
4. Concentration Trend Graphs (Period 2000-2017):
DWR recommends to continue sampling at the current frequency, based on the following
observations:
a. Acetic Acid: (1) 300-ft. - The graph shows OB-13 and OB-17 concentrations below
IMAC. However, the graph also shows an OB-17 concentration increase from 2013 to
2017 and no data point for OB-13 after 2013; (2) 700- ft. - Concentrations in OB-3
have been consistently above IMAC with a decreasing concentration trend from 2007-
2013 that reverted in 2013, when concentrations started increasing again; (3) 1000-
ft. - Concentrations in OB-4 have been consistently above IMAC but decreasing since
2000. For all three zones, sampling needs to continue to better visualize
concentration trends. Please include 2020 sampling records for the preparation of
the CAP.
b. p-Toluic Acid: (1) 300-ft. - Please verify nomenclature; the graph depicts in red non -
detect values that are higher than some of the values that are detected. As previously
mentioned, OB-13 seems to have not been sampled in 2018; (2) 700- ft. - OB-3
concentrations have been consistently above the IMAC value (39,300 ug/L in 2001
and 41,000 ug/L in 2018). A decrease in concentrations is not appreciable. The
overall concentration trend has remained stable from 2000 to 2017; (3) 1000-ft.-
Concentrations above the IMAC are apparent in OB-4, OB-14, and OB-15, while in 013-
12 concentrations have been close to the IMAC. For all three zones, sampling needs

Chrissy Piechosky
Former Cape Industries Waste Injection Facility (Hercules Site)- SAR Comments
3/6
to continue to better visualize concentration trends. Please include 2020 sampling
records for the preparation of the CAP.
S. Groundwater Modeling: A more detailed description of the modeling work is necessary since
model results will be the basis for the design of the proposed corrective action. DWR
recommends to use the Groundwater Modeling Policy Groundwater (NCDENR Division of
Water Quality - Aquifer Protection Section, May 31 2007) that can be found in our website:
https://files.nc.gov/ncdeg/Water%20Quality/Aquifer/o20Protection/APS%20Policies/Groundwa
terModelingPolicy-20070531.pdf. DWR requires detailed discussions and tabulated lists of the
parameters that were used in the models, as requested below:
a. Provide specific details of the model that was used to produce the Figures 31 & 32. It
is hard to evaluate the model without knowing the parameters that were used.
b. Provide a hydraulic model figure depicting all surface water bodies and boundary
conditions used in all the aquifers. Also, if there are water withdrawal wells present
at or near the site, discuss if anthropogenic recharge and withdrawals were
considered.
c. It is mentioned on page 31 that the MODFLOW hydraulic model was calibrated to
observed head values. Please provide a figure showing the observed and predicted
heads in all monitoring wells in the model domain and an analysis of standard
deviation. Can the calibration be done with historical head values measured at the
site and can the model simulate a good representation of observed head values?
d. MT3D Fate and Transport Model: Provide a more thorough development of the
reactive transport model. For instance, the specifics of boundary conditions
(simulated grid homogeneity, anisotropy), though based on the site description (and
USGS paper), adequate study has been done on the regional and site geology. Provide
a sensitivity analysis to identify which parameters (i.e., effective porosity, aquifer
dispersivity, retardation factors, degradation rates, etc.) affect the predicted values
the most and a range of appropriate site -specific values for these parameters and
their effects on the model results.
e. Discuss the specifics of the reactions and reaction rates of the COPC within the
modeling section. There is discussion of the rate limiting conditions of degradation
pathways, in Section 4.2.7.1 and 4.7.2.2, however Section 8.3 -Fate and Transport
Model —does not address the details of the evolution of aquifers as the plume
migrates subsurface and away from the injection zone.
f. Provide a table specifying the modeled reactions and their degradation rates (and
limiting/inhibiting factors). Also, cite the analyte-specific model parameters (which
are currently all cited as "literature research").

Chrissy Piechosky
Former Cape Industries Waste Injection Facility (Hercules Site)- SAR Comments
4/6
g. Provide a more comprehensive discussion of the simulated degradation pathways
given that the degradation mechanisms and pathways are complex and
spatiotemp orally heterogeneous. Discussion of that nature could address the
simulation of transition zones present in the aquifers and any foreseeable limitations
in attenuation pathways.
h. Provide a more comprehensive discussion of the development of the p-toluic
attenuation rate based on Mann -Kendall analysis in Section 8.1. Based on the
information in Appendix J (Mann -Kendall Analysis), the attenuation trend in the 700-
ft aquifer is based on a single sampling point and may not represent the bulk nature
of the aquifer. Additionally, there is concern that the overall p-toluic acid reaction is
non -linear, involving rate limiting steps and reaction stages in both aquifers. Using
Mann -Kendall analysis to develop a "bulk attenuation rate" may not be an accurate
reflection of the processes.
i. Include and discuss the other COPC in the modeling investigation. Include additional
figures delineating the model prediction of plume migration. Horizontal and vertical
vantages would be helpful. Provide simulated time series of figures representing
pressure (or proxied by pH) and remaining COPCs.
j. It seems that the p-toluic acid concentration was not modeled for the 700ft. zone.
Please provide modeling results for p-toluic acid in this zone.
k. For p-toluic acid, the concentrations modeled were 35,000 and 56,000 ug/l. Please
model a larger range of concentrations in p-toluic acid simulations.
1. The Regional Hydrogeology, Section 3.3, page 14 mentions that at depth 1000 ft. is
the Upper Cape Fear aquifer and that "no estimates of the hydraulic conductivity or
transmissivity were found for the Upper Cape fear because the aquifer is not used for
water supply". What values were used in the model?
m. Also, Regional Hydrogeology, Section 3.3, page 14 mentions easterly groundwater
flow in the Upper Cape Fear Aquifer discharges off shore into the Atlantic Ocean, and
Figures 9 & 12 confirm the movement of groundwater towards the east. Is this flow
factor considered in the MT3D model?
n. Are there preferential pathways present at the site which are identified, and have they
been taken into account for the MT3D model? Please discuss.
o. Above all, for all COPCs, model results must fully assess the horizontal and vertical
extent of the contamination approaching their respective 2L standards or IMAC.
Please discuss and map the results to satisfy the requirements in 15A NCAC 02L .0106
(g) (4)
6. Follow up items listed in the meeting notes received in August 2019:
a. Hercules requests that NCDEQ submit the October 2018 White Paper on p-toluic
acid toxicity to the EPA for review and comment:
b. The NCDEQ will follow up with the EPA for an opinion on the IMAC for p-toluic acid:

Chrissy Piechosky
Former Cape Industries Waste Injection Facility (Hercules Site)- SAR Comments
5/6
NCDEQ staff submitted a request that EPA review the Hercules white paper
on May 7, 2019. EPA has not responded to our request to date. If Hercules
would like to request a review of the white paper, the contact at EPA is:
Teresa Shannon
STSC/ERASC Administrator and Project Lead
National Center for Environmental Assessment (NCEA)
U.S. Environmental Protection Agency
26 W. Martin Luther King Drive (MS A-110)
Cincinnati, Ohio 45268
[phone] voice; [phone] fax
[e-mail]
c. The NCDEQ will review the SAR and provide feedback to Hercules:
The DWR partially approves the SAR and authorizes the preparation of the
Corrective Action Plan (CAP) according to the requirements in 15A NCAC
02L .106(h) given the comments in this letter are appropriately addressed in
the CAP.
d. The NCDEQ will provide a response to the October 2018 White Paper on p-toluic
acid toxicity
NCDEQ continues to support the use of the IMAC for p-toluic acid based on
the language established in the 15A NCAC 02L rules and the statements of
the NCDEQ toxicologist during the May 28, 2019 meeting between NCDEQ,
Hercules LLC, GES, and Integral Consulting. No additional toxicity
information or guidance values for p-toluic acid have been identified since
the May 2019 meeting.
e. The NCDEQ will provide a response on whether a risk -based approach showing
acceptable risk would still require long-term monitoring until the IMACs and other
statutory endpoints were achieved.
Reducing or stopping monitoring under any clean up approach (including
risk -based remediation) is site -specific, and within the site, it would be well -
specific. In general, if the responsible party wants to pursue no further
action based on a risk -based remedy for groundwater then the RP must
demonstrate that all potential receptors are protected when groundwater is
still showing contamination. Discontinue monitoring can be problematic if
in the future, the RP ask DWR to make a decision and data are not available
to substantiate a response since monitoring stopped prematurely and
inappropriately.
f. The NCDEQ will provide information regarding whether a remedial option exists that
will not require long-term monitoring.
At this point, long-term monitoring is required. Currently, sampling is
performed every two years, this sampling frequency could be re-evaluated
in the future to determine if its reduction is feasible.
g. The NCDEQ and Hercules will share additional research information regarding p-
toluic acid as it becomes available.

Chrissy Piechosky
Former Cape Industries Waste Injection Facility (Hercules Site)- SAR Comments
6/6
Please find enclosed two documents: (1) NC Interim Maximum Allowable
Concentration (IMAC) calculations spreadsheet; (2) Groundwater Standard
Summary Document by the Division of Water Resources. At this point, we
do not have additional information to share.
7. Continue sampling at the current sampling points and frequency. Please refer to items 3, 4,
and 6(e) above.
Please submit the Corrective Action Plan within 90 days. If you would like to discuss the
remedial options before submittal, please contact me at [e-mail]
and we can set up a meeting as needed.
Sincerely,
DocuSigned by:
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E3ABA14AC7DC434...
Morella Sanchez King, PhD, PE
Regional Supervisor
Water Quality Regional Operations Section
Wilmington Regional Office: 127 Cardinal Drive Extension;
Wilmington, NC 28405
Cc Groundwater & Environmental Services, Inc. (Att. Joseph Keller/Katherine Hall)
3701 Saunders Av.1 I Richmond, VA 23277
Central Office File- Attention: Rick Bolich, WQROS
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