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HomeMy WebLinkAbout7601_RandolphCountyMSWLF_MNAMonReqResp_DIN28561_20171018 October 18, 2017 Sent Via Email – Paxton.Arthurs@randolphcountync.gov Mr. Paxton Arthurs, P.E. Randolph County Public Works Director 725 McDowell Road Asheboro, NC 27205 Re: Monitored Natural Attenuation Parameter Modification Request Closed Randolph County Landfill Solid Waste Permit Number 7601-MSWLF-1983 DIN 28561 Dear Mr. Arthurs: The Solid Waste Section (Section) has completed a review of the Request for Monitored Natural Attenuation Parameter Modification (DIN 28540) submitted on behalf of Randolph County by Golder Associates (Golder) for the Closed Randolph County Landfill, Solid Waste Permit Number 7601. The facility is currently undergoing monitored natural attenuation (MNA) as a remedial strategy to reduce groundwater contaminant concentrations. Golder has completed the four MNA baseline monitoring events and requested to modify the MNA parameter list and schedule. The current full list of MNA parameters includes: 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 modified MNA parameter list would include: carbon dioxide, chloride, ethane, ethene, methane, hydrogen, ferrous iron, nitrate, and sulfate. Golder also requested to monitor the abbreviated list semiannually and the full MNA parameter list during the last two semiannual monitoring events of each five-year evaluation period. Sulfide, VFAs, TOC, and alkalinity were proposed to be removed from the MNA semiannual monitoring list because their concentrations have been reported at levels below the Environmental Protection Agency’s (EPA) natural attenuation screening levels. Golder also requested to remove BOD and COD from the full list of MNA parameters since those parameters are not used in the EPA screening protocol. In addition, Golder requested to perform the MNA screening models on an annual basis instead of after each semiannual monitoring event. The Section approves the request to reduce the MNA parameter list to include: carbon dioxide, chloride, ethane, ethene, methane, hydrogen, ferrous iron, nitrate, and sulfate during routine semiannual monitoring. Randolph County may also perform the EPA screening models on an annual basis. The Section does not approve removing BOD and COD from the full list of MNA parameters. Although BOD and COD are not included in the EPA screening protocol, BOD values could quantify the amount of oxygen used by microorganisms to oxidize organic compounds and the conversion of organic material, measured as COD, to methane could also provide further evidence of reductive dechlorination. The Section will allow an alternate frequency of full-scale MNA monitoring to the final semiannual events of every third year instead of every fifth year to better detect potential changes to environmental conditions and contaminant plume characteristics. If you have any questions or concerns regarding this letter, please feel free to contact me by email at ervin.lane@ncdenr.gov or by phone at 919.707.8288. Thank you for your continued cooperation with this matter. Sincerely, Ervin Lane Compliance Hydrogeologist Solid Waste Section, Division of Waste Management NCDEQ cc sent via email: Jason Watkins, Field Operations Branch Head Deb Aja, Western District Supervisor John Patrone, Environmental Senior Specialist Perry Sugg, P.G., Permitting Hydrogeologist Ming Chao, P.E., Permitting Engineer Dusty Reedy, P.G., Golder Associates NC, Inc.