DeKalb County, Georgia, part of the urban core of metropolitan Atlanta, owns and operates the Seminole Road Landfill which has been accepting municipal solid waste since the 1970s. In accordance with Georgia Environmental Protection Division (EPD) regulations, the County has been conducting groundwater, surface water, and methane monitoring at the landfill.
Monitoring data showed landfill gas to be migrating from an unlined area causing concentrations of some groundwater contaminants to rise above groundwater protection standards despite the presence of an existing gas collection and control system (GCCS) and a gas perimeter collection system (PCS) to manage landfill gases at the site. DeKalb County established two primary objectives to improve their landfill gas management program: (i) achieve continuous compliance with respect to methane migration and groundwater quality; and (ii) use the generated gas as fuel for a 3.2 megawatt (MW) landfill-gas-to-electricity (LFGTE) project that was designated to become the first supplier in a power company's green power portfolio.
Geosyntec's Scope of Services
DeKalb County selected Geosyntec to operate and maintain the GCCS and PCS, perform compliance monitoring for the landfill, and assist the County with environmental permitting, engineering design, and construction aspects of the LFGTE project. Geosyntec's approach began with an analysis of historic and newly-collected GCCS and PCS performance data. Working-hand-in-hand with County staff, Geosyntec prepared a multi-step plan to improve system performance. Geosyntec's performance optimization plan focused on: (i) increasing vacuum throughout the GCCS and PCS; (ii) increasing the frequency of pumping from selected high-liquid-level extraction wells; (iii) extracting gas from a previously inactive horizontal collector; (iv) installing new gas extraction wells; and (v) upgrading an existing condensate sump. Implementation of the performance optimization plan produced the desired system operational and environmental compliance improvements. Perimeter gas monitoring probes, which previously had high methane concentrations, showed declining concentrations after the optimization effort and, within two months, demonstrated that the landfill met its objectives with respect of methane migration. Similarly, monitoring data also showed significant improvement in groundwater quality.
For the LFGTE project, Geosyntec worked closely with the County to secure the required environmental permits and facilitate the design/build procurement process. Geosyntec prepared air permit documents for submittal to Georgia EPD, provided technical support to County staff at public hearings, and prepared responses to comments from Georgia EPD and the public. Working with County legal and purchasing departments, Geosyntec prepared the draft request for proposal (RFP) and contract documents for the LFGTE design/build process. Geosyntec assisted the County in implementing its procurement process by distributing of the RFP to potential bidders, conducting a pre-bid meeting, and preparing and issuing responses to questions received from bidders. During the LFGTE facility construction, Geosyntec provided oversight on behalf of the County to bring the LFGTE project into full operation.
Geosyntec's performance optimization plan resulted in achieving control of landfill gas migration and its operating facility objectives regarding compliance with Georgia EPD regulations. With concurrence from Georgia EPD, methane monitoring frequency has been decreased from monthly to quarterly. Groundwater quality at the site is improving. Geosyntec worked closely with the County to bring the LFGTE facility project online. The Seminole Road Landfill LFGTE project became the first supplier to deliver retail "green power" from any renewable source to power company customers through Georgia's voluntary Green Energy program.