EFS was contracted by a client to provide soil mixing services for a site in Wisconsin. Prior remediation efforts consisting of a groundwater pump and treat system operated at the site until 2004. An amendment to the Record of Decision (ROD) modified the treatment strategy to excavation or in-situ treatment of hot spot areas in order to meet the remedial action objectives for the site in a shorter time period. In–situ treatment was selected as the remedy and focused on five specific “hot spot” source areas containing elevated concentrations of trichloroethylene (TCE) in soil and groundwater.
Initial site activities included the establishment of staging and laydown areas and installation of erosion control measures. Following set-up, EFS excavated and stockpiled 215 cubic yards of clean topsoil and 1,160 cubic yards of overburden soils to access the treatment intervals. Soil mixing was performed to promote in-situ chemical reduction through biotic and abiotic degradation mechanisms with the addition of Daramend®, a proprietary product that consists of a soluble substrate and zero-valent iron (ZVI). Daramend® was delivered in bulk and blended on-site and delivered to the targeted treatment intervals using an excavator mounted dual axis mixing tool to depths of up to 18 feet below grade. Post-mixing verification sampling confirmed the achievement of design mix ratios in each of the treatment cells. Geotextile fabric was installed and each treatment cell was backfilled to grade with the overburden soils and topsoil. Following topsoil placement, each area was reseeded to promote site restoration.
Project highlights included:
- In-situ treatment of 2,250 cubic yards of TCE impacted soils.
- Soil mixing to depths from 9- 18 feet below grade with a dual-axis blender.
- Successful addition of 120,000 pounds of Daramend®.
- Verification of 2% design mix throughout the treatment areas.
- Project effort completed within the project schedule and within budget.