Following removal of a heating oil underground storage tank, diesel-range petroleum hydrocarbons remained present in inaccessible soils directly beneath this residence. The contaminated soils presented a risk of petroleum vapor intrusion (PVI) into the home, which included a basement bedroom.

TechSolve conducted Tier I and Tier II PVI investigations, which included sub-slab vapor sampling and indoor air monitoring. These investigations indicated that, while concentrations of some contaminants exceeded screening levels in the subsurface, indoor air was not being unacceptably impacted. Five rounds of indoor air monitoring were conducted over several years to confirm these findings. The results of the investigation reassured the homeowners and met requirements of the Washington State Pollution Liability Agency so that no further action was required.

Key Project Elements:

• Assessment of Vapor Intrusion
• Multi-Year Monitoring
• No Further Action Required