Projects

Service: Phase I and II ESA and Subsequent Indoor Air Sampling
Facility Type: Mixed-Used Building with Affordable Housing Management Owner

Description:

For purposes of a building retrofit, ACC performed a Phase I Environmental Site Assessment (ESA) in accordance with ASTM Standard E1527-13 to evaluate for the presence of environmental impacts to the Subject Property.

The owner of the Site requested a Phase I ESA to obtain lending for Site renovations including a soft retrofit of their existing building located in San Francisco. The building was developed as a mixed-use building with ground floor commercial units and residential dwellings on the floors above. During historical research, ACC discovered that a dry cleaning facility previously occupied one of the buildings commercial units. In addition, ACC identified the up gradient large maintenance garage building as a potential off-site environmental concern given documented hazardous materials use and generation for approximately 90 years. Due to the previous dry cleaning operations, and off-site concerns, ACC recommended additional investigation, based on potential for both site to use the solvent tetrachloroethylene (PCE). 

ACC collected three sub-slab soil vapor samples using vapor pin technology and in accordance with Department of Toxic Substance Control (DTSC) guidance: Advisory – Active Soil Gas Investigations (July 2015). Sample concentrations were compared against the Regional Water Quality Control Board (RWQCB) Human Health Risk Levels (HHRLs) for vapor intrusion, and detected elevated concentrations of PCE above residential and commercial thresholds. Based on the detection locations and concentrations, ACC concluded that the source of the PCE contamination is likely attributed to an off-site source, and not from the former dry cleaning tenant. Due to the elevated concentrations of PCE in soil vapor, additional testing was recommended to rule out potential impacts to indoor air. 

ACC subsequently conducted indoor air sampling at the site to determine if there was a human health risk associated with the elevated concentrations of PCE in soil vapor. ACC collected five indoor air samples and one exterior ambient air sample. Indoor air samples in the basement detected concentrations of PCE and trichloroethylene (TCE) above the direct exposure HHRLs for residential properties, but below commercial HHRLs. ACC determined that due to the basement and first floor of the building being occupied by maintenance areas and commercial tenants respectively, the elevated concentrations of PCE and TCE in indoor air did not pose a risk to human health. Based on thorough testing of the site, ACC was able to help the client close the issue, and obtain necessary grants for the building renovations.