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HomeMy WebLinkAboutNCG120038_Tier III_20230313 DocuSign Envelope ID:64EBBAC9-65C2-4AEB-B7B2-24355BD59497 SMITH GARDNER aD°RE'S EL �Fg 14 N.Boy:an Avenue,RaieiO NC 27603 919.628.0577 tvvww.smithgardnerirc.com ENGINEERS N C Department of March 10, 2023 Linvironmental Quality Received Ms. Lily Kay MAR 13 2023 Environmental Program Consultant NCDEMLR - Winston-Salem Regional Office Winston-� lem 450 West Hanes Mill Road, Suite 300 Ticnal Office Winston-Salem, NC 27105 RE: Phase 2 Pond 3, Pond 4,and Pond 5 Tier 3 Corrective Action Plan Davidson County Landfill Certificate of Coverage#NCG120038 General Permit#N CG120000 Dear Ms. Kay: The following is a corrective action plan prepared by Smith Gardner, Inc. (S+G) on behalf of Davidson County (County) to address the Tier 3 exceedances at the Phase 2 Pond 3 (Basin 3, Phase 2 Pond 4 (Basin 4), and Phase 2 Pond 5 (Basin 51 Stormwater Discharge Outfalls (OutfaI.0 at the County's landfill facility (Landfill). An overview of historic sample results at each Outfall within the current permit period is attached. The Landfill is permitted to discharge stormwater under General Permit No. NCG120000 and Certificate of Coverage No. NCG120038 (Permit) issued July 1, 2021. A summary of exceedances and corrective actions (both completed and proposed) are included below. Background Following sampling results from the April 2022 monitoring, an initial Tier 3 Corrective Action Plan was submitted to NCDEQ to address Tier 3 exceedances for TSS at Basin 31. Following review of the initial plan with NCDEQ, the County was notified that the previously approved alternate source demonstration for fecal coliform approved by NCDEQ in 2013 was no longer effective following reissuance of the Permit. The Tier 2 Corrective action plan was subsequently revised to address future corrective actions for fecal coliform at the Landfill. A meeting to discuss the revised Tier 3 Corrective action plan was held between S+G and NCDEQ on June 2, 2022. Following the results of this discussion, it was determined that monitoring requirements are limited to areas of the landfill which are subject to "industrial activities". As a result, a permit modification request was submitted to NCDEQ on September 13, 20221. Review and approval of both the Tier 3 Corrective Action Plan following the April 2022 monitoring period and the permit modification request are currently pending. The permit modification request was retransmitted to your attention December 12, 2022 at which time review and approval was pending a site inspection. This current Tier 3 plan serves to consolidate these multiple requests, document the history and site conditions of each outfall at the Landfill, and to propose a framework for future corrective actions and monitoring requirements. "Phase 2 Pond 3 Tier 3 Corrective Action Plan" prepared by Smith Gardner, Inc. dated May 27, 2022. z "Proposed Revisions to NPDES Monitoring Plan" prepared by Smith Gardner, Inc. dated September 13, 2022. DocuSign Envelope ID:64EBBAC9-65C2-4AEB-B7B2-24355BD59497 Ms. Lily Kay March 10, 2023 Page 2 of 4 Site Description The Site is located off of Old Hwy 29 in Thomasville, North Carolina and operates under NC Solid Waste Permit 29-06. The Site includes a closed, lined Phase 1 municipal solid waste (MSW) landfill, an active, lined Phase 2 MSW landfill, a closed construction and demolition (C&D) debris landfill, and one closed, unlined MSW landfill unit (Holly Grove Landfill). Currently, the Site is required to monitor all stormwater discharge outfalls (SDOs) associated with the Active Phase 2 landfill unit as summarized in Table 1. Table 1. Davidson County SDO Inventory and Drainage Area Descriptions Outfall ID Drainage Area Description PH-2 SB-1 Phase 2 MSW Landfill, no active filling operations, landfill areas (or PH-2 Pond 1) stabilized with good vegetation PH-2 SB-2 Phase 2 MSW Landfill, active filling operations, daily and intermediate (or PH-2 Pond 2) soil cover PH-2 SB-3 Phase 2 MSW Landfill, no active filling operations, landfill areas (or PH-2 Pond 3) stabilized with good vegetation PH-2 SB-4 Phase 2 MSW Landfill and soil borrow area, no active filling operations, (or PH-2 Pond 4) landfill areas stabilized with good vegetation, borrow area with unearthed materials ands arse vegetation PH-2 SB-5 Soil Borrow Area 5, no active filling operations, unearthed materials (or PH-2 Pond 5) ands arse vegetation PH-2 SB-6 Soil Borrow Area 6, no active filling operations, unearthed materials (or PH-2 Pond 61 ands arse vegetation These locations are shown on the attached Figure 1. Potential Pollutant Exposure Areas Potential pollutant areas at the Site include: (1) the active landfill, (2) the active borrow areas, (3) vehicular traffic, and (4) the leachate storage area. The active landfill is the primary potential pollutant area as defined by the general permit. Additionally, the active borrow areas provide a potential pollutant source through the excavation and transport of unearthed materials. The leachate storage tank area functions to store leachate prior to transportation to the local Publicly Owned Treatment Works (POTW). This storage area includes a glass-fused- to-steel bolted tank inside a secondary containment tank (also glass-fused-to-steel). Lastly, vehicle traffic associated with waste disposal, operations, and maintenance are transient across the Site. Current Site Activities As can be seen on Figure 1, the Phase 2 MSW landfill unit is peaked in the center between drainage Areas 1 and 2 and between Areas 3 and 4. This peak was designed to allow the County to fill the northern-most areas of the footprint first, followed by operations in the southern portion of the Site (future Areas 4 and 51. Currently, Areas 1, 2, and 3 have been filled to an interim grade, covered with soil and stabilized with grass. We do not anticipate activity on the DocuSign Envelope ID:64EBBAC9-65C2-4AEB-B7B2-24355BD59497 Ms. Lily Kay March 10, 2023 Page 3 of 4 northern facing slopes of these areas for approximately 5 years while Areas 4 and 5 are constructed and filled. Basin 3 Following the results of the February 2023 monitoring period, Basin 3 is currently in Tier 3 status for TSS and Fecal Coliform. Following corrective actions, sampling results for both parameters have declined, including a compliant reading for TSS in February 2023. Additionally, fecal coliform has decreased to near compliant status (1,060 cfu/100 mL) in February 2023, indicating improvements as a result of these corrective actions. As a result, additional corrective actions for Basin 3 are proposed to be postponed pending review of the permit modification request submitted September 13, 2022. Basin 4 Basin 4 is currently in Tier 3 status for TSS and Fecal Coliform. Past corrective actions to address both parameter exceedances include additions of rip rap to the skimmer pad to elevate of the basin skimmer outlet, additions of #57 stone to the upstream face of the riser outlet protection, and additions of silt fencing upstream of the riser structure. Following these corrective actions, improvements to both TSS and fecal coliform has been observed showing decreases of 83% and 98% between discharge events, respectively. Due to these improvements noted at for each parameter, S+G proposes no additional corrective actions at this time in lieu of additional monitoring to continue to observed these changes in discharge concentrations. Basin 5 The primary land cover discharging in the Basin 5 is comprised of soil borrow for landfill activities. Due to this fact, areas of disturbed land are common as earthen materials are excavated for landfill activities. In an effort to limit elevated discharge concentrations of TSS, The County will work to limit the extent of the disturbed area as much as practicable. Continued efforts to reestablish vegetation in undisturbed areas or previously disturbed areas will continue and assessed for effectiveness through monthly monitoring of the outfall discharge. Fecal Coliform Alternate Source Demonstration Sources of Fecal Coliform As documented in the past, the likely source of fecal coliform contamination at the Landfill is local wildlife. An alternate source demonstration of fecal coliform source loading within the Basins was prepared by S+G and approved by NCDEQ in 2013. Historic results indicate consistent fecal exceedances at the closed Phase 1 MSW landfill (since final closure in 2010) the closed C&D landfill, and the active Phase 2 MSW landfill. Based upon the wildlife present at the site and the presence of fecal coliform exceedances at the closed landfill units we believe the fecal coliform results are indicative of animal use of the sedimentation basins and are not due to the landfill or related activities at the site. Evidence of wildlife populations at the site available in the attached photolog. DocuSign Envelope ID:64EBBAC9-65C2-4AEB-B7B2-24355BD59497 Ms. Lily Kay March 10, 2023 Page 4 of 4 S+G has prepared a revised sampling plan to assess the natural background condition in the surrounding watershed of the Landfill. Three (3) sampling locations are proposed at surface water locations surrounding the site, including both upstream and downstream sampling locations relative to the Landfill. Future monitoring of these sampling locations will provide information on the level of fecal coliform in the adjacent watershed areas and contextualize the results seen so far in the Outfalls. The proposed sampling locations can be seen on the Figure 1. If you have any questions, or require further information, please contact us at (9191 828-0577 or by email. Sincerely, SMITH GARDNER,INC. EDocuSigned by: DocuSigned by: - �bvxs E 5B6B3 4J96Ao74D7 Matthew M. Jones, E.I. Pieter K. Scheer, P.E. Staff Engineer, ext. 153 Senior Engineer, ext.123 mac(asmithgardnerinc.com pieterfasmithgardnerinc.com Figures: Figure 1 - Proposed Fecal Coliform Sampling Locations Attachments: Phase 2 Pond 3 Historic Stormwater Data Phase 2 Pond 4 Historic Stormwater Data Phase 2 Pond 5 Historic Stormwater Data Photographic Log cc: Steven Sink, Davidson County Joan A. 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Phase 1 Pond 4 F- F -r r �p 07:07AM 1211812012J 0079 SEDPOND DocuSign Envelope ID:64EBBAC9-65C2-4AEB-B7B2-24355BD59497 PHOTOGRAPHIC LOG Client: Davidson County landfill Project: Sedimentation Basin Animal Activity Evaluation Project No. Davdco-13-2 Photo No. Date: 3 1/11/2013 Direction Photo Taken: P 7.9 t, Northeast Description: . Phase 2 Pond 3 ,} s r '� r; e. din �:~�. .•0. :� is�^'. # ttati' 'v �•.. ' irr Photo No. Date: 4 1/11/2013 Direction Photo Taken: N/A , Description: s . Phase 2 Pond 3 t s e 3 -