For a PDF version of this Case Study with photos - click HERESeneca Companies was initially hired by a convenience store company to conduct both a Phase I and Phase II Environmental Site Assessment (ESA) of the Subject Property. In the end, the convenience store company chose not to purchase the property. The company who now owns the Subject Property serves as a transfer facility for donated goods. The Phase I ESA of the Property identified the following Recognized Environmental Conditions:
A Phase II was then conducted to assess the site for the presence of volatile organic compounds (VOCs), through soil and soil vapor sampling. The initial site visit resulted in field observed clean soil but the investigation was unable to reach groundwater. Soil samples were non-detectable VOCs. The soil vapor results contained concentrations of VOCs which exceed the indoor air target levels for a commercial property.A subsequent geotechnical investigation reached groundwater and that sample contained tetrachloroethane (or PERC, a chemical commonly used in dry cleaning operations). This finding prompted the indoor air assessment. The State of Colorado does not have subsurface soil vapor screening levels, Seneca recommended an indoor air assessment be conducted to assess whether VOCs were present in the building. The building on the Subject Property has a basement area on the north end which adjoins the dry cleaner property and is approximately five to six (5-6) feet below grade.The basement area is strictly used for storage; rarely are there any personnel spending significant time down there.The Owner then asked for an indoor air assessment to be completed. Seneca conducted a survey to identify potential pathways for vapor to migrate into the building and/or accumulate in the building like floor drains, cracks in the foundation, elevator shafts and crawl spaces.Summa canisters are stainless steel vessels used to collect air samples. The Summa canisters were placed in four (4) strategic locations based on the survey findings. The canisters were then placed in the pre-determined locations at approximately four (4) to five (5) feet off the ground and activated to pull a gradual sample over an eight (8) hour period. The area was sealed off, doors were locked and signs were placed on the doors in order to keep all personnel out of the area during the eight (8) hour period. Upon completion of the test, the canisters were then collected, deactivated and submitted to a certified laboratory for analysis for VOCs by an Environmental Protection Agency (EPA) approved method known as Selected Ion Method (SIM).Results from all four (4) samples resulted in detections of the same two (2) VOC’s benzene and PERC, at relatively similar concentrations. Benzene was the only detection slightly exceeding the Colorado Department of Public Health and Environment (CDPHE) regulatory limit was in sample AS-3.Based on the air sample results and the limited use of the basement area for workers during a work day, Seneca did not believe it was necessary to install vapor mitigation system(s) in the basement. If the area use changes and workers occupy the storage room on the northern half of the basement, for eight (8) hour days, then a vapor mitigation system may be warranted. The primarily occupied area of the upstairs was not of concern at this time. It is believed that the VOCs may originate from the up gradient dry cleaner property. The Owner was advised to request a “Contaminated Aquifer” letter from CDPHE, which would state contaminants are migrating onto the property from some other source. This letter will release the Owner from any potential liability issues in the future. At the request of the Owner, Seneca submitted a package to CDPHE and will be looking into the matter. An unknown sump, or well-type structure, is located behind the neighboring dry cleaner, next to a shed which stores hazardous chemicals (assumed to be PERC). It is unknown if this is, or ever has been, used to dispose of dry cleaning solvent waste. If it has stored the solvent waste, this structure could be a source of the contaminants.