2019.05.03_CCO.p12_LetterPFASMassLoadingModelPlan

May 3, 2019

Sheila Holman Assistant Secretary for the Environment
N.C. Department of Environmental Quality 1601 Mail Service Center
Raleigh, N.C. 27699-1601
[e-mail]

Re: Chemours’ Proposed Scope of Work for Cape Fear River PFAS Mass Loading Model Pursuant to Consent Order Paragraph 12

We have reviewed Chemours’ proposed work plan for the Cape Fear River PFAS Mass
Loading Model pursuant to paragraph 12 of the consent order and provide the following
comments on behalf of Cape Fear River Watch.
• With regards to Section 4.4.2, page 14, more information is needed about the long-term
wells, or LTWs, being used to analyze groundwater discharge from the Black Creek
Aquifer to the Cape Fear River. In particular, Chemours should provide all the borehole
logs and monitoring well construction details to verify Geosyntec’s findings.
• Accurately analyzing PFAS mass loading into the Cape Fear River requires at least one
wet weather sampling event taken during wet months, or during a period with higher
precipitation.
• In Section 4.3 page 13, Chemours should be evaluating aerial deposition from the facility
to the Cape Fear River, as well as to its tributaries—Georgia Branch and Willis Creek. It
is not currently clear from the plan that the company is doing so.

• With regard to Sections 4.3 (page 13) and 4.6 (page 15), it is not clear that the extent of
aerial deposition from the facility has been fully evaluated, which is important to
understanding these pathways. Geosyntec appears to be evaluating off-site groundwater
using only residential well sampling. However, it is possible that the residential well sampling program assesses an area smaller than the aerial deposition from the facility, in which case the PFAS mass loading of aerial deposition off-site and to the Cape Fear
River and its tributaries will not be fully evaluated.

• It is not clear that this plan assesses surface water contamination from runoff that comes
in contact with on- and off-site contaminated soil. This is a source of PFAS loading into
the Cape Fear River and its tributaries, and should be assessed.

Thank you for your consideration of these comments.

Sincerely,
Jean Zhuang

Cc (via email): Dana Sargent, CFRW Kemp Burdette, CFRW
Bill Lane, DEQ
Francisco Benzoni, NCDOJ
Michael Abraczinskas, DAQ Michael Scott, DWM Linda Culpepper, DWR
David Shelton, Chemours
Brian Long, Chemours
John Savarese, Wachtell, Lipton Joel Gross, Arnold & Porter