4501_Henderson_MSWLF_GWCAMNARequestResponse_DIN28478_20170919

September 19, 2017

Sent Via Email – [e-mail]

Mr. Marcus Jones
Henderson County
Director of Engineering
802 Stoney Mountain Road
Hendersonville, NC 28791

Re: Request for Monitored Natural Attenuation Parameter Modification
Closed Unlined Henderson County MSW Landfill
Henderson County
Solid Waste Permit Number 4501
DIN 28478

Dear Mr. Jones:

The NC Solid Waste Section (Section) has completed a review of the Request for Monitored Natural
Attenuation Parameter Modification dated July 26, 2016 (DIN 28477) and submitted on behalf of
Henderson County by Golder Associates NC, Inc. for the closed unlined Henderson County MSW Landfill,
Solid Waste Permit Number 4501.

The Section approved the County’s selected remedy for this landfill on March 11, 2015 that included the
implementation of In-Situ Enhanced Bioremediation (EB) and Monitored Natural Attenuation (MNA) (DINs
23909 and 23950). In addition, the County’s Corrective Action Plan dated June 2015 was approved on July
13, 2015 (DINs 24715 and 24716).

The two year MNA baseline sampling concluded in March 2017, and the County is requesting a
modification to MNA sampling at the landfill. The current full list of MNA parameters consists of the
following: alkalinity, carbon dioxide, chloride, biological oxygen demand (BOD), chemical oxygen demand
(COD), ethane, ethene, methane, hydrogen, ferrous iron, nitrate, nitrite, sulfate, sulfide, total organic
carbon (TOC), and volatile fatty acids (VFAs). The County would like to reduce the number of MNA
parameters to monitor semiannually to the following: alkalinity, carbon dioxide, chloride, ethane, ethene,
methane, hydrogen, ferrous iron, nitrate, and sulfate. Also, the County is requesting to stop monitoring
the following MNA parameters BOD, COD, nitrite, sulfide, TOC, and VFAs semiannually, and instead the
County is proposing to monitor the full list of parameters for the last two semi-annual events of the first
5-year evaluation period (second semi-annual water quality monitoring event of 2019 and first semi-
annual water quality monitoring event of 2020) for the Corrective Action Evaluation Report (CAER). The
modified MNA list would then be used for all semiannual events starting with the second 2020 event to

the final year (last two semiannual events) of the next 5-year evaluation period, when the full list would
again be monitored.

Based upon the technical evaluation, the proposed request to monitor for the specific MNA parameters,
BOD, COD, nitrite, sulfide, TOC, and VFAs, every five years is not approved at this time because these MNA
parameters provide important insight into the overall long term natural attenuation at the landfill. The
MNA parameters assist to determine site variability and rates of change in geochemistry, flow, and
contaminant concentrations.

However, the Section will approve an alternate frequency for the MNA parameters BOD, COD, nitrite,
sulfide, TOC, and VFAs. Sample these specific MNA parameters semiannually every three years. Therefore,
the next sampling events for these specific MNA parameters will be twice in 2020. In addition, continue
to sample the MNA parameters alkalinity, carbon dioxide, chloride, ethane, ethene, methane, hydrogen,
ferrous iron, nitrate, and sulfate on a semiannual basis.

If you have any questions or concerns regarding this letter, please feel free to contact me by email at
[e-mail] or by phone at 828.296.4706. Thank you for your continued
cooperation with this matter.

Sincerely,
Jaclynne Drummond
Compliance Hydrogeologist
Solid Waste Section, Division of Waste Management
NCDEQ

cc sent via email: Greg Wiggins, Henderson County
Jason Watkins, Field Operations Branch Head
Deb Aja, Western District Supervisor
Elizabeth Werner, Permitting Hydrogeologist
Lee Hill, Environmental Senior Specialist
Larry Frost, Permitting Engineer
Dusty Reedy, Golder Associates