Looking Beyond the Initial Environmental Concern
Environmental due diligence does not always lead where you expect it to.
McAlister GeoScience recently completed a Phase II Environmental Site Assessment (ESA) at an industrial property in South El Monte, California. A previous Phase I ESA had identified a Recognized Environmental Condition (REC) related to a potential former underground storage tank (UST), prompting additional investigation.
Historical building permits showed an application for a 550-gallon UST and fuel pump dating back to 1971. However, records documenting the removal or abandonment of the tank were unavailable, and its location and current status were unknown. For a commercial or industrial property an undocumented UST can raise questions about potential petroleum impacts, environmental liability, and what additional investigation may be needed before a transaction or redevelopment can move forward.
Putting the UST Concern to the Test
McAlister GeoScience conducted soil and soil vapor sampling to evaluate whether the reported former UST had impacted the property. Petroleum hydrocarbons in the gasoline, diesel, and motor oil ranges were not detected above laboratory reporting limits. Metals were below applicable commercial/industrial screening levels or naturally occurring background concentrations, and VOCs were generally not detected at levels of concern.
In short, the investigation did not identify evidence that the suspected former UST had caused significant petroleum impacts to the soil, but the soil vapor results were not as promising.
An Unexpected Finding in Soil Vapor
Tetrachloroethylene (PCE) was detected in all soil vapor samples at concentrations above applicable commercial/industrial screening levels. Other detected compounds were below their respective screening levels.
PCE is a chlorinated solvent commonly associated with uses such as dry cleaning, degreasing, and other industrial activities. Importantly, the investigation did not find the petroleum impacts that would typically support the former UST as the source of the soil vapor issue. Based on the sampling results, the PCE impacts may instead be associated with an off-site source.
McAlister GeoScience recommended additional soil and soil vapor sampling to better define the extent of the impacted area and evaluate whether the source of the PCE is located off-site.
Why This Matters for Commercial Real Estate
This project is a good example of why Phase II investigations are about more than simply confirming a concern identified during the Phase I. The original question centered on an undocumented UST. The investigation provided useful evidence that petroleum impacts were not present in the areas tested, while also identifying a separate soil vapor condition requiring further evaluation.
For buyers, sellers, lenders, and property owners, that distinction can be critical. Understanding what is actually impacting a property, and whether the source may originate on-site or off-site, helps the project team make more informed decisions about additional due diligence, risk, and the path forward. The key is defining the issue clearly enough to understand what comes next.
McAlister GeoScience provides Phase I and Phase II Environmental Site Assessments and environmental investigation services for commercial and industrial properties throughout California, Washington, and more. If an environmental concern comes up during due diligence, our team can help determine the next step and keep the process moving.