Soil Vapor Assessment at Former Fuel Site
Carpinteria, CA
Background
McAlister GeoScience conducted a Phase II Environme
ntal Site Assessment (ESA) involving soil vapor sampling at a vacant commercial property in Southern California. The assessment was completed following a prior Phase I ESA that identified a Recognized Environmental Condition (REC) associated with the historical operation of a gasoline service station on-site.
The former service station, originally developed in the late 1950s, included an underground storage tank (UST). However, no documentation was available confirming whether the UST had been removed or whether subsurface impacts had been evaluated. Given the potential for petroleum-related vapor impacts beneath the existing building, a focused soil vapor investigation was recommended.
Environmental Assessment
To evaluate potential vapor intrusion risk, McAlister GeoScience advanced three borings in the area of the former UST and collected soil vapor samples at approximately three feet below ground surface. The borings were allowed to equilibrate prior to sampling in accordance with California Department of Toxic Substances Control (DTSC) guidance.
Samples were collected using Summa canisters and analyzed for volatile organic compounds (VOCs) by EPA Method TO-15. The analytical suite focused on petroleum-related compounds, including benzene, toluene, ethylbenzene, and xylenes (BTEX), as well as other potential vapor-phase constituents.
Key Findings
• VOCs, including BTEX compounds, were detected in soil vapor across the site
• Benzene was detected above commercial/industrial screening levels in one sample location
• All other detected compounds were below their respective Environmental Screening Levels (ESLs)
• Calculated cancer risk and hazard index values were within acceptable regulatory thresholds
• Site conditions were classified as Low Priority based on risk evaluation
While benzene exceeded screening levels in a single location, risk modeling using site-appropriate attenuation factors demonstrated that overall vapor intrusion risk remains within acceptable ranges for commercial use.
Outcome
From a commercial real estate and lender perspective, this is exactly the kind of result that keeps deals moving.
Despite a historical use that often raises red flags—former gasoline service station with undocumented UST removal—the targeted Phase II investigation provided the data needed to confidently assess risk. The presence of petroleum-related vapors was identified, but concentrations were shown to be below levels of concern for human health under current and reasonably anticipated commercial use scenarios.
The conclusion was clear: no additional investigation or remediation is warranted at this time.
That means no unexpected cleanup costs, no regulatory delays, and no barriers to redevelopment or transaction closing.
Why It Matters
Sites with historical fuel use don’t automatically translate to deal killers—but they do require the right level of investigation.
This project is a good example of how a focused, data-driven Phase II ESA can:
- Resolve uncertainty tied to historical RECs
- Quantify actual risk (not just potential risk)
- Support lender and investor confidence
- Keep transactions on schedule
Need help navigating a flagged property?
McAlister GeoScience specializes in fast, defensible environmental due diligence that supports real estate decisions, not slows them down. Need a quote for your next project? Reach out here!