Location
Grand Rapids, Michigan
Start Date
15-5-2024 1:00 PM
End Date
15-5-2024 1:30 PM
Description
Power utilities are increasingly challenged by regulatory agencies to implement remediation strategies that are able to anticipate long-term changes to groundwater quality in response to closure activities. However, unanticipated changes to site geochemistry during closure can have unforeseen impacts leading to groundwater impairments caused by leaching of coal combustion residual (CCR) constituents. In some cases, the cessation of recharge flux may even further inhibit the natural rehabilitation of a site by further shifting it from the pre-existing conditions. Here we present an evaluation of multiple closure scenarios where 3-D reactive geochemical modeling was used to evaluate constituent flux and concentration downgradient of the unit undergoing closure. Modeling identified that there was no measurable difference in time to achieve compliance at downgradient monitoring wells when comparing 90% to 100% ash removal. Additionally, modeling identified the current regulator-approved closure approach of 90% closure-by-removal with the addition of a cap on the CCR unit results in an equal if not better reduction in flux and improvement in groundwater quality than 100% closure-by-removal. Thus, the current regulator-approved strategy is the most appropriate for achieving groundwater compliance.
Document Type
Presentation
Effectiveness of Various CCR Unit Closure Strategies
Grand Rapids, Michigan
Power utilities are increasingly challenged by regulatory agencies to implement remediation strategies that are able to anticipate long-term changes to groundwater quality in response to closure activities. However, unanticipated changes to site geochemistry during closure can have unforeseen impacts leading to groundwater impairments caused by leaching of coal combustion residual (CCR) constituents. In some cases, the cessation of recharge flux may even further inhibit the natural rehabilitation of a site by further shifting it from the pre-existing conditions. Here we present an evaluation of multiple closure scenarios where 3-D reactive geochemical modeling was used to evaluate constituent flux and concentration downgradient of the unit undergoing closure. Modeling identified that there was no measurable difference in time to achieve compliance at downgradient monitoring wells when comparing 90% to 100% ash removal. Additionally, modeling identified the current regulator-approved closure approach of 90% closure-by-removal with the addition of a cap on the CCR unit results in an equal if not better reduction in flux and improvement in groundwater quality than 100% closure-by-removal. Thus, the current regulator-approved strategy is the most appropriate for achieving groundwater compliance.
