Vapor Intrusion Risk in Downtown Commercial Area

Background

Chlorinated volatile organic compound (CVOC) impacted soil and a CVOC groundwater plume emanated from the former Clothing Care Center site in the City of Ionia, Michigan. The former dry cleaner building was demolished and now is a city green space, but many of the adjacent buildings to the south and west/southwest are operating business with residential tenant spaces on the top floors and a newly constructed church. The CVOC’s trichloroethylene (TCE), tetrachloroethylene (PCE) and cis-1,2-Dichloroethylene (cis-1,2-DCE) were observed in soil and groundwater concentrations exceeding residential criteria and posed a vapor intrusion (VI) risk to surrounding businesses and residences.

The Project

AKT Peerless was contracted to conduct remedial investigation activities to identify whether or not a widespread VI risk was present in the downtown commercial area. If VI concerns were identified, vapor mitigation systems were designed and installed.

Our Role

AKT Peerless conducted remedial investigation activities to better define the horizontal and vertical extent of the known soil gas and groundwater contamination in the area around the former dry cleaner. Sub-slab soil gas sampling was conducted at select businesses to determine the potential risk from harmful vapors entering the structures. The results of the investigation would assist in designing and implementing remedial options, which would include vapor mitigation systems.

Soil gas results indicated a potential risk from harmful vapors entering three locations. AKT Peerless designed and installed two active sub-slab depressurization systems and sealed sumps in these businesses. An additional vapor mitigation system is being designed for the third property after monitoring determined seasonal variability in sub-slab soil gas concentrations. AKT Peerless also conducted performance monitoring of the systems to demonstrate effectiveness of the remedies, reported monitoring results to the Michigan Department of Environmental Quality (MDEQ) and provided operations and maintenance documentation to the MDEQ and affected business owners.

Results

  • Completed Remedial Investigation in the commercial area on behalf of the State of Michigan
  • Identified three structures where a VI concern was present
  • Installed two (2) active sub-slab depressurization vapor mitigation systems (VMS)
  • In the process of designing and installing a third VMS.
  • Conducted performance monitoring to verify system effectiveness
  • Developed operation and maintenance plans for the systems
  • Verified the indoor air quality in the commercial areas (after the installation of the vapor mitigation systems).
  • Determined that vapor mitigation systems were effective in meeting performance objectives that allow for the continued safe occupancy of the buildings.