Subsurface Investigation and Limited Removal Action

Subsurface Investigation and Limited Removal Action

This customer owns a property in the town of Truro that had an oil smell. They thought it was coming from residue sprayed into the air by a furnace that had a combustion problem. The furnace and oil tank were both removed and the property converted to propane so there was no longer a source of oil. They called us to see if CommTank could clean-up the oil smell. Jeff May, an ASHI certified home inspector and indoor air quality specialist, referred this customer to CommTank. CommTank proposed doing a site investigation and providing a written report of our findings.

Vapor Intrusion Testing

A CommTank environmental technician preformed a subsurface vapor investigation that included 6 vapor points and 3 soil borings under the concrete floor. The soil did not smell of contamination but the concrete did. It turns out that polyethylene sheeting was placed under the floor when it was poured to prevent radon gases from coming in to the home. It is a common practice that contractors use when building a new home. A CommTank engineer determined that the oil line had a small leak while the tank and burner were connected and that the oil was trapped between the concrete and poly sheeting. The customer smelled oil vapor because it was wicked up into the concrete during hot days and circulated throughout the home.

Omniguard differential pressure recorder set up in basement

Subsurface Investigation

CommTank then proposed doing a Limited Subsurface Investigation (LSSI). Three soil borings were advanced in the basement and two soil borings were advanced at the exterior foundation. The highest measured concentration of total volatile organic vapors (TVOVs) showed that the oil traveled across the concrete floor and flowed through punctures in the polyethylene sheeting.

Basement excavation to remove residual oil contamination

Excavation Activities Related under Massachusetts Law

Under Mass law a Limited Removal Action (LRA) is used to remove petroleum-contaminated soil (PCS) resulting from a leaking 275-gallon No. 2 fuel oil aboveground storage tank (AST). The LRA for this site consisted of excavation, transportation and disposal of petroleum contaminated soil and petroleum stained concrete in the vicinity of the leaking fuel lines. All the contaminated soil was loaded on to a CommTank truck for transportation to a licensed soil treatment facility. This work also included the installation of shoring, bracing and supports required during excavation. Negative air machines were utilized to minimize vapors emanating to the rest of the house.

At the project completion CommTank had excavated 20 tons of petroleum-contaminated soil and brought the excavation to the surrounding grade using clean fill obtained from an off-site source. The concrete floor was then restored to the match the existing floor. After completion of the basement restoration, a Limited Removal Action Outcome Report was prepared detailing the clean-up method used in order to achieve site closure.

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