Owner/Client
Talen Energy
Location
Washingtonville, PA
CEC Services
- Geotechnical Engineering
- Site Grading / Earthwork Analysis
- Hydrogeologic Site Investigations
- Environmental Monitoring / Compliance Support
- Coal Combustion Product Management
- Site Characterization
- Hydrogeology & Groundwater Modeling
- USEPA CCR Rule Compliance
Owner Objective
Talen Energy Corporation (formed by a merger of PPL Energy Supply, LLC and RJS Generation Holdings, LLC) owns and operates a steam electric station in central Pennsylvania. The surrounding area includes rural farmland and one small community of homes with domestic water wells. Talen Energy was under a Consent Order and Agreement from the PADEP to investigate and close a coal combustion residuals (CCR) impoundment associated with the power generating plant.
CEC Approach
CEC performed a Basin-Wide Hydrogeologic Assessment, building on previous investigations. The impoundment is elevated above the original grade resulting in groundwater flow directions out and away from the impoundment. Groundwater flow from the impoundment is restricted by a slurry wall. Our assessment included well installation within and outside of the basin, groundwater sampling, a digital groundwater model and a human health risk assessment. We prepared a Basin Wide Hydrogeologic and Risk Assessment Report. CEC also prepared cap system alternatives for use in closing the basin. Based on a feasibility study, we also prepared a residual waste permit modification to increase the CCR final grades to promote surface water run-off and reduce the potential for long-term ponding on the cap system. The permit modification included an alternate final cover system.
The Basin Wide Hydrogeologic Report was accepted by the PADEP with little comment. PADEP approved the permit modification allowing continued use of the basin for CCR disposal and also approved the alternate final cover system resulting in a significant cost savings to the owner. CEC prepared an Abatement/Closure Options Analysis Report as the final obligation of the Consent Order. The Abatement/Closure Options Analysis utilized the groundwater model to evaluate closure scenarios submitted in the permit modification as well as an alternate capping option. The groundwater flow model was used to predict changes to groundwater elevations within the impoundment and the resulting groundwater flow from the impoundment in response to closure. Results lead to Talen proposing to close the basin using the geosynthetic cap in accordance with the permit modification.
CEC also performed engineering and environmental compliance support at the basin for the USEPA CCR Rule. Engineering support included preparation of a Factor of Safety Analysis, Structural Stability Analysis, an Inflow Flood Design Control Plan, a Closure Plan, and a Post-Closure Plan. CEC also used our knowledge of the site hydrogeology to design and install a Groundwater Monitoring System in accordance with Section 257.91 of the CCR Rule. CEC is providing groundwater monitoring support for the basin under the CCR Rule including the preparation of plans and procedures to ensure that the groundwater monitoring meets the requirements of Section 257.93 of the CCR Rule for baseline sampling, as well as development of a statistical analysis plan to evaluate the baseline data. CEC will also initiate and conduct the CCR Rule Detection Monitoring Program for the basin in accordance with Rule Section 257.94 after the baseline sampling is completed.
