Evaluating Monitored Natural Attenuation​ Paired with Source Control​ .pdf

Kelly Ferri, SynTerra Corporation
Craig Eady, SynTerra Corporation
Kathy Webb, SynTerra Corporation

Description

Effective Remedial Measure: Evaluating Monitored Natural Attenuation Paired with Source Control Authors Mrs. Kelly Ferri - United States - SynTerra Corporation Mr. Craig Eady - United States - SynTerra Corporation Mrs. Kathy Webb - United States - SynTerra Corporation Abstract Monitored natural attenuation (MNA) coupled with source control is a viable component of remedial technologies evaluated under an assessment of corrective measures for coal combustion product (CCP) units with Appendix IV constituent concentrations greater than groundwater protection standards (GWPSs) downgradient of the waste boundary. To demonstrate the effectiveness of source control and MNA, groundwater data and geochemical conditions from four CCP units closed by decanting, dewatering, and excavation were evaluated under pre-excavated and post-excavated conditions. Each constituent exhibits a unique geochemical behavior related to the Site-specific constituent partition coefficient, response to changing geochemical parameters, and sorption capacity of the soil and/or rock matrix. Non-reactive constituents migrate in groundwater as soluble species and are reduced in concentration with distance primarily by physical processes such as dispersion, dilution, and diffusion. Variably reactive constituents exhibit mobility depending on groundwater geochemical conditions and availability of sorption sites. Reactive constituents tend to remain in mineral phase assemblages that are stable under variable conditions, demonstrating sorption as an effective attenuation mechanism. Redox parameters are useful in understanding the changing geochemical conditions pertaining to oxidizing or reducing environments for chemical dissolution or sorption through co‐precipitation and adsorption of constituents with precipitation of iron/manganese and aluminum oxides. Data from post‐excavation case studies demonstrate the effectiveness of natural attenuation to reduce constituent concentrations, in a reasonable period of time after source control is complete. Decreasing concentration trends may not be apparent during the early stages of source control. However, these case studies demonstrate how MNA can be effective where post-source-control data are not yet available. Data evaluation after source control can be used to evaluate whether additional remedial measures, paired with MNA, are needed. Conducting MNA evaluations after excavation reduces the areas and constituents targeted for other remedial techniques, if needed.

 
May 15th, 10:30 AM May 15th, 11:00 AM

Evaluating Monitored Natural Attenuation​ Paired with Source Control​ .pdf

Grand Rapids, Michigan

Effective Remedial Measure: Evaluating Monitored Natural Attenuation Paired with Source Control Authors Mrs. Kelly Ferri - United States - SynTerra Corporation Mr. Craig Eady - United States - SynTerra Corporation Mrs. Kathy Webb - United States - SynTerra Corporation Abstract Monitored natural attenuation (MNA) coupled with source control is a viable component of remedial technologies evaluated under an assessment of corrective measures for coal combustion product (CCP) units with Appendix IV constituent concentrations greater than groundwater protection standards (GWPSs) downgradient of the waste boundary. To demonstrate the effectiveness of source control and MNA, groundwater data and geochemical conditions from four CCP units closed by decanting, dewatering, and excavation were evaluated under pre-excavated and post-excavated conditions. Each constituent exhibits a unique geochemical behavior related to the Site-specific constituent partition coefficient, response to changing geochemical parameters, and sorption capacity of the soil and/or rock matrix. Non-reactive constituents migrate in groundwater as soluble species and are reduced in concentration with distance primarily by physical processes such as dispersion, dilution, and diffusion. Variably reactive constituents exhibit mobility depending on groundwater geochemical conditions and availability of sorption sites. Reactive constituents tend to remain in mineral phase assemblages that are stable under variable conditions, demonstrating sorption as an effective attenuation mechanism. Redox parameters are useful in understanding the changing geochemical conditions pertaining to oxidizing or reducing environments for chemical dissolution or sorption through co‐precipitation and adsorption of constituents with precipitation of iron/manganese and aluminum oxides. Data from post‐excavation case studies demonstrate the effectiveness of natural attenuation to reduce constituent concentrations, in a reasonable period of time after source control is complete. Decreasing concentration trends may not be apparent during the early stages of source control. However, these case studies demonstrate how MNA can be effective where post-source-control data are not yet available. Data evaluation after source control can be used to evaluate whether additional remedial measures, paired with MNA, are needed. Conducting MNA evaluations after excavation reduces the areas and constituents targeted for other remedial techniques, if needed.