A specialty chemical company manufactured a variety of pesticides, herbicides, saccharin, dyes, and detergents for over 15 years, and collected the wastewater and sludges in on-site lagoons. State regulators discovered groundwater and creek ecosystem contamination involving 27 different organic compounds including benzene and toluene. The 85-acre site was named to the NPL list in 1989. In order to protect the adjacent Big Black Creek and the 1,800 people living within a 1.25 mile radius of the site from contaminated groundwater, the U.S. EPA installed extraction wells to capture, contain, and treat contaminated groundwater. The original Record of Decision (ROD) called for a groundwater treatment plant and on-site incineration of 800,000 cubic yards of soils and sludges. The incineration component of the remedy was later replaced with a less-costly, but still expensive on-site landfill to contain lagoon sludges and site debris.
Geosyntec's Scope of Services
Geosyntec was retained by the PRP group as part of a team to develop a more cost-effective closure remedy for the site which resulted in replacing the expensive landfill with a barrier wall, a soil cover for the lagoon area with phytoenhancement, shallow groundwater treatment using constructed wetlands, and groundwater monitoring. Geosyntec designed the 2000-ft long, 80-to-115 ft. deep "U" shaped soil bentonite slurry wall to contain shallow groundwater and redirect flows to the constructed treatment wetlands within and a diffuser wetlands outside the wall. Our engineers prepared plans, specifications, and construction-related bid documents, and provided Engineer-of-Record and onsite CQA services during construction of the barrier wall (Phase 1 of the project).
For the lagoon area cover design and construction, Geosyntec performed data collection activities including an inventory and quantification of the site debris to be placed under the lagoon cover. Geosyntec also made determinations of sludge strength parameters to support the debris and cover system. The final cover contours simulate the surrounding rolling Michigan topography. Geosyntec provided design criteria requirements, drawings, specifications, calculations, and portions of the construction cost estimate for the lagoon area final cover work (Phase 2).
After more than 15 years of site investigations and technology assessments, the current design/construction team has moved this project forward with a remedy that takes advantage of passive constructed wetland treatment technologies and is fully protective of sensitive adjacent environments. The slurry wall was completed in 2006, and phase 2 initiated. The site is slated for redevelopment as industrial land uses.