A suspected CCR impoundment release resulted in increasing concentration trends of select CCR-related constituents (e.g., calcium, sulfate, chloride, arsenic, mercury) in multiple downgradient monitoring wells.
High resolution site characterization (HRSC) of groundwater downgradient of the CCR impoundment was performed using multiple tools to evaluate CCR groundwater impacts and serve as the basis for selecting and designing a groundwater remedy. HRSC at this CCR facility included: 1) surface geophysical surveys using electrical resistivity imaging (ERI) around CCR impoundments to evaluate zones of elevated specific conductivity as an indicator of CCR groundwater impacts; and 2) direct push technology (DPT) investigations for collection of relative hydraulic conductivity, real-time vertical profiles of electrical conductivity (EC), and depth-discreet groundwater samples. The DPT investigation evaluated preferential contaminant flow paths and confirmed CCR groundwater impacts with depth during a single mobilization. Cross-sections were used to display the ERI, EC, and DPT data with existing lithologic and groundwater monitoring well data to inform the development of a conceptual site model (CSM). Once the CSM was developed, a groundwater extraction system was designed, constructed, and brought online under an aggressive schedule to address identified CCR impacts. The remedial system included the installation of nine extraction wells with a total flow rate up to 250 gallons per minute (gpm). Extracted groundwater is treated by a groundwater treatment system before disposal. Due to the concentrations of groundwater constituents, corrosion/scaling issues were predicted by geochemical modeling and subsequently observed during system operation. The potential for scaling was addressed through system design and as part of routine system operation/maintenance. Since system startup, routine groundwater monitoring indicates substantial declines in groundwater concentrations.
- Geosyntec Authors: Lane Dorman
- All Authors: Lane Dorman, Geosyntec; Lauren Petty, Southern Company Services
- Title: The Utility Solid Waste Activities Group (USWAG) Coal Combustion Residual (CCR) Workshop's Session 1
- Event or Publication: Event
- Practice Areas: Groundwater Assessment and Remediation
- Citation: Allison Kreinberg (Ohio) presented "Approval of an Alternate Source Demonstration Under Oklahoma's State CCR Program" and Lane Dorman, P.G. (Florida) Presented "Case Study: High Resolution Site Characterization (HRSC) to Inform CCR Groundwater Remedial Design and Implementation" at the Utility Solid Waste Activities Group (USWAG) Coal Combustion Residual (CCR) Workshop's Session 1 on June 18, 2020.
- Date: June 18, 2020
- Publication Type: Platform Presentation