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Home My WebLink About9606_WayneCountyMSWLF__GWAssessmentResponse_DIN27649_20170418 April 18, 2017 Sent Via Email – Tim.Rogers@waynegov.com Mr. Tim Rogers Wayne County 460B South Landfill Road Dudley, NC 28333 Re: Groundwater Quality Assessment Near MW-13 Wayne County Subtitle D Lined MSW Landfill Wayne County Solid Waste Permit Number 9606-MSWLF DIN 27649 Dear Mr. Rogers: The NC Solid Waste Section has completed a review of Groundwater Quality Assessment Near MW- 13 dated March 10, 2017 (DIN 27648) and submitted on behalf of Wayne County by Municipal Engineering Services Co., P.A. for the Wayne County Subtitle D Lined MSW Landfill, NC Solid Waste Permit Number 9606-MSWLF. The document was submitted in response to a confirmed Benzene groundwater exceedance at groundwater monitoring well MW-13 since 2015. Wayne County initiated Assessment Monitoring when the NC Solid Waste Section required the County to conduct Appendix II monitoring at groundwater monitoring wells MW-1 through MW-16R in accordance with 15A NCAC 13B .1634 in August of 2016 (DIN 27582). Also, during this monitoring event, dissolved methane and chloride were collected to determine if landfill gas and/or liquid leachate may be the source of the groundwater exceedance. Based upon the initial Appendix II Assessment Monitoring event conducted in August 2016, Benzene exceeded the regulatory groundwater standard at groundwater monitoring well MW-13 and Mercury exceeded its regulatory groundwater standard at groundwater monitoring well MW-4. Other volatile organic compounds, semi-volatile organic compounds, pesticides, herbicides, and inorganics have been detected at quantifiable and estimated concentrations at the groundwater monitoring wells, but below the regulatory groundwater standards. In addition, Toluene was detected at surface water sampling locations SW-1 and SW-6. In response to the Benzene exceedance detected at groundwater monitoring well MW-13, additional assessment activities were initiated. A temporary groundwater monitoring well, TMW-13A, was installed downgradient of groundwater monitoring well MW-13 at the facility compliance boundary. Also, P1-7, an existing observation well from Hydrogeologic Design Study for Phase 1 was utilized, and HAB-1, a boring located between the landfill and upgradient of groundwater monitoring MW-13 was used and converted to a landfill gas monitoring well, MP-102. Groundwater samples were collected in January 2017 from TMW-13A, P1-7, and MP-102, and analyzed for Appendix I volatile organic compounds. The analytical results indicated no groundwater exceedances of the Appendix I volatile organic compounds. In addition, methane gas has been detected within the headspace of groundwater monitoring wells MW-13 and MW-16R. Landfill gas monitoring well MP-101 was installed, and a methane gas cut-off trench was installed outside and near the liner limit. Landfill gas monitoring at MP-101 and MP-102 after the installation of the methane gas cut-off trench indicated no detections of methane gas. The report further stated that the caps on the well casings affixed to groundwater monitoring well MW- 13 will not be left tightly sealed to allow accumulated landfill gas to vent and reduce intrawell partitioning. Based upon these assessment activities, the County states that the landfill will remain in the Assessment Monitoring Program and is requesting that since levels of Benzene have decreased to allowable levels and corrective actions have been implemented that no further action be required at this time. If concentrations of contaminant(s) are detected within groundwater monitoring well MW- 13 above the regulatory standards in a future compliance event, an Assessment Monitoring Work Plan will be developed. As a result, Wayne County must take all necessary steps to ensure the protection of public health and the environment and is required to remain in the Assessment Monitoring Program in accordance with 15A NCAC 13B .1634. Also, be sure all groundwater and landfill gas monitoring well caps are secured to ensure a tight seal, and future Assessment Monitoring activities will be determined based upon the analytical results of the February 2017 Appendix I plus Appendix II detections event and the August 2017 full Appendix II event. A part of the Assessment Monitoring Program includes two different semiannual monitoring events. The first event is sampling of groundwater monitoring wells for the full suite of Appendix II constituents. The second monitoring event is a continuation of Detection Monitoring and involves sampling of all groundwater monitoring wells for Appendix I constituents and any Appendix II constituents that have been detected during any Appendix II monitoring event. Appendix II constituent detections consist of quantifiable concentrations and estimated (J) values. To report a constituent as detected is a more accurate representation of groundwater quality since there is a high probability that it is present within the groundwater. Also, after each Appendix II monitoring event in which one or more new Appendix II constituents are detected, the County is required to collect four consecutive semiannual samples from all the groundwater monitoring wells at the landfill to establish background concentrations for the newly detected constituents. If you have any questions or concerns regarding this letter, please feel free to contact me by phone at 828.296.4706 or by email at jaclynne.drummond@ncdenr.gov. 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: Jason Watkins, Field Operations Branch Head Drew Hammonds, Eastern District Supervisor Wes Hare, Environmental Senior Specialist Ed Mussler, Permitting Branch Head Ming Chao, Permitting Engineer Christine Ritter, Permitting Hydrogeologist Jonathan Pfohl, MESCO