Work at this former natural gas compressor station was performed under an AOC between the client and USEPA Region III and an Administrative Order between the client and the state of Kentucky. This facility is located in Floyd County, Kentucky in a rural area with dispersed residences. During multiple site investigations, various petroleum hydrocarbons, including dissolved phase volatile organic compounds (VOCs), were detected in the groundwater. Light phase non-aqueous liquids (LNAPL) thicknesses were detected on the groundwater surface in select areas.
Over the past several years, an extensive network of recovery wells and monitoring wells had been installed at the facility. In the mid-1990s, AGES installed and has maintained a groundwater pump-and-treat system, which has prevented the discharge of groundwater and LNAPL to a nearby creek. AGES staff have completed system outfall sampling, quarterly monitoring well sampling and LNAPL thickness monitoring. To determine if the pump-and-treat program could be terminated, a risk assessment was performed to develop risk-based action levels for groundwater that are protective of surface water in the creek. Based on the evaluation, no further action was required to address dissolved constituents in groundwater at the site. However, further action was required to prevent LNAPL at the site from adversely impacting the creek before the current pump-and-treat system could be terminated.
Response Action Work Plan
Prior to termination of the existing pump-and-treat system, AGES developed a response action work plan that proposed a modified system to remove LNAPL from groundwater to the extent necessary to eliminate it as a potential source of adverse impact to the creek. The work plan included a modified groundwater monitoring program and confirmation sampling to ensure that constituent concentrations remain less than action levels after the pump-and-treat system was shut-down. Following submittal of the work plan to the KYDEP, AGES and client representatives met with the KYDEP to negotiate LNAPL monitoring and sampling frequencies included in the work plan. Endpoints for the response action were also negotiated.
Implementation of the Selected Remedial Technologies
Upon USEPA and KYDEP approval, a total of six (6) LNAPL recovery wells were installed in the area where LNAPL has consistently been detected. Hydrophobic skimmers were then installed in each of the recovery wells to pump LNAPL to the surface via built-in pneumatic bladder pumps. A dedicated air supply hose and a dedicated product discharge hose were installed from an on-site remediation building to each recovery well via underground PVC conduit. All recovered product flowed into a single hose then to a 55-gallon product collection drum.
After start-up of the LNAPL collection system, AGES submitted a work plan to the KYDEP to terminate the existing pump-and-treat system and to reduce the level of site monitoring. Negotiations with the KYDEP are currently in progress. Groundwater monitoring and LNAPL thickness monitoring are on-going at the site.
1.) By developing risk-based action levels, AGES was able to demonstrate that a streamlined LNAPL collection system could be used at the site.
2.) AGES negotiated extensively with KYDEP regarding the configuration of the streamlined LNAPL collection system and requirements for groundwater monitoring. As a result, the client had substantially reduced costs in remedial and monitoring requirements.