Ash Pond Closure in Place Using In-Situ Soil Stabilization

Jeffery Miller, Haley & Aldrich, Inc.
Marc Okin, NiSource, Inc
Jeff Loewe, NiSource, Inc
William Haswell, Haley & Aldrich, Inc.

Description

In-Situ Soil Stabilization (ISS) was selected for the closure of a four-acre inactive ash pond in the Midwest. ISS was identified as a preferred means of closure due to site-specific technical challenges that complicated a removal approach and impacted cost. As part of design and permitting, a robust bench program was completed to evaluate application of ISS; results of the first phase of the bench program focusing on strength & permeability were presented at WOCA 2022. In the subsequent two years the project team completed the second phase of bench testing, a multi-tiered leachability evaluation, as well as design, additional pre-construction bench testing, and ISS implementation. The multi-tiered leachability evaluation, which is the primary focus of this presentation, was developed to assess the post-ISS flux of metals to groundwater, and address Agency requests to demonstrate that ISS will result in reduced concentrations of metals in Site groundwater. This assessment included additional strength and permeability testing, modified non-destructive SPLP testing (1312), Leachability Assessment Environmental Framework (LEAF) analytical (1315), and groundwater modeling based on Site hydrogeologic conditions and LEAF results. Results of the combined bench program further supported ISS application as a viable closure technology resulting in long-term reductions of metals leaching. As the project moved from the bench and design phase and into construction, challenges arose that were addressed by the team; these challenges included geotechnical stability/ instrumentation, impacts of surrounding fill on ISS performance, non‑homogeneous ash, and non-technical challenges including reagent price fluctuation and construction cost inflation. The work completed by NIPSCO and Haley & Aldrich to vet the use of ISS for a closure application has helped close a gap in industry (CCR and ISS) data / literature and afforded the team flexibility in terms of what approaches are available for the closure of legacy units and CCRMU’s.

 
May 15th, 2:00 PM May 15th, 2:30 PM

Ash Pond Closure in Place Using In-Situ Soil Stabilization

Grand Rapids, Michigan

In-Situ Soil Stabilization (ISS) was selected for the closure of a four-acre inactive ash pond in the Midwest. ISS was identified as a preferred means of closure due to site-specific technical challenges that complicated a removal approach and impacted cost. As part of design and permitting, a robust bench program was completed to evaluate application of ISS; results of the first phase of the bench program focusing on strength & permeability were presented at WOCA 2022. In the subsequent two years the project team completed the second phase of bench testing, a multi-tiered leachability evaluation, as well as design, additional pre-construction bench testing, and ISS implementation. The multi-tiered leachability evaluation, which is the primary focus of this presentation, was developed to assess the post-ISS flux of metals to groundwater, and address Agency requests to demonstrate that ISS will result in reduced concentrations of metals in Site groundwater. This assessment included additional strength and permeability testing, modified non-destructive SPLP testing (1312), Leachability Assessment Environmental Framework (LEAF) analytical (1315), and groundwater modeling based on Site hydrogeologic conditions and LEAF results. Results of the combined bench program further supported ISS application as a viable closure technology resulting in long-term reductions of metals leaching. As the project moved from the bench and design phase and into construction, challenges arose that were addressed by the team; these challenges included geotechnical stability/ instrumentation, impacts of surrounding fill on ISS performance, non‑homogeneous ash, and non-technical challenges including reagent price fluctuation and construction cost inflation. The work completed by NIPSCO and Haley & Aldrich to vet the use of ISS for a closure application has helped close a gap in industry (CCR and ISS) data / literature and afforded the team flexibility in terms of what approaches are available for the closure of legacy units and CCRMU’s.