Sigma helps treat Alterra Coffee parking lot site


Concentrations of tetrachloroethylene (PCE), trichloro- ethylene (TCE), and their degradation products were observed at characteristically hazardous concentrations in soil samples collected at a vacant lot that formerly housed a commercial cleaning / laundry facility. Development plans for the vacant lot, located adjacent to residential properties, called for a parking lot to serve new business development. Groundwater beneath the site was also impacted with chlorinated volatile organic compounds (CVOCs). Based on initial site investigation activities completed by other consultants, The Sigma Group completed additional site investigation activities including vapor intrusion assessments to evaluate potential remedial options.

Based on additional investigation data, a detail remedial action plan was prepared and presented to the Wisconsin Department of Natural Resources (WDNR) for review and approval. The remedial action plan consisting of in situ soil treatment via chemical oxidation with potassium permanganate to reduce the residual CVOC mass within the area of highest contamination, excavation and off-site disposal of soil exhibiting lower contaminant concentrations, placement of clean cover material over the treated area, and installation of a passive soil vapor venting system and vapor migration cut-off trench to prevent the accumulation and migration of volatile vapors from the residual soil and groundwater contamination.

Following receipt of WDNR approval, Sigma implemented the RAP during 2004-2005. The site is currently an asphalt paved parking lot with native vegetation landscaping. Post-remediation and natural attenuation groundwater quality monitoring is on-going across the site.