Project Name: Former Rainbow Cleaners, Northview Shopping Center, Westminster, Colorado
Date Project Began: September 2005
Date Project Completed: Ongoing
Project Description: Casey Resources, Inc. (CRI) completed environmental investigations at a former dry cleaner operation and identified significant tetrachloroethene (PCE) impact in bedrock and groundwater. The information was summarized in an Integrated Corrective Action Plan (ICAP) which was submitted to and approved by the Colorado Department of Public Health and Environment (CDPHE) under the Resource Conservation and Recovery Act (RCRA). The ICAP remediation was implemented with the removal of indoor soils to approximately five feet below the floor surface and installation of a passive vapor venting system. As part of the indoor remediation, CRI was requested to provide environmental monitoring during building sanitary sewer pipeline replacement and to conduct 8-hour indoor air monitoring to assess air quality in building areas adjacent the sewer line repairs. CDPHE correspondence and negotiations were an integral part of the monitoring of the sewer pipeline repair project. Following the completion of the indoor remediation, CRI presented to CDPHE that outdoor remediation should not be conducted due to the extremely hard and impermeable bedrock conditions and the fact that the PCE plume did not appear to be migrating. CDPHE, however, indicated that some sort of remediation of the source area would be required. In response to this requirement, CRI prepared an amendment to the ICAP which stated that outdoor excavation would be replaced with in-situ chemical oxidation at known source locations. CRI noted to CDPHE that the geologic conditions at the site would likely inhibit effective in-situ treatment. In May 2007, in-situ remediation was completed by injecting oxidation reagents into the subsurface in previously identified contaminant source areas at the former Rainbow Cleaners. Post remediation groundwater sampling indicated significant reduction in PCE concentrations; however, by the fourth quarter the contaminant concentrations had rebounded in the source areas. In response to the concentration rebound, CRI converted the passive vapor venting system within the former cleaner unit to an active venting system and installed a smaller vapor venting system in the adjacent commercial space. CDPHE has indicated that an Environmental Covenant will be required after completion of two years of annual monitoring of downgradient compliance wells.
Type of Contamination: PCE contaminated soil and groundwater.