Fuel Oil Impact Beneath Building
​Remediation Using Chemical Injections
Bedford, MA

Horizontal Drilling Beneath Building

Injection of Activated Sodium Persulfate

Background:
​A release of heating oil was discovered in 1987 near the loading dock at the rear of a 49,000 square foot commercial building. Initial response actions conducted by others included soil excavation and a limited in-situ oxidation program in 2003 and 2004. These response actions resulted in a condition of no substantial hazard and a temporary solution under the Massachusetts Contingency Plan. A permanent solution was considered infeasible because a significant portion of the released fuel oil was inaccessible beneath the one story, slab-on-grade building.

The passing of the building's owner required the sale of real estate holdings and distribution of the proceeds in accordance with her will. A buyer could not be found for the property because of the potential environmental liability associated with the oil contamination which was in the Zone 2 of a municipal drinking water production well. ES&M was contracted to complete a remedy that would reduce the potential environmental liability such that a buyer could be found.

Project Description:
ES&M completed investigations which included field pilot tests to evaluate chemical oxidation, air sparging, and soil vapor extraction remedial approaches. ES&M identified and evaluated remedial action alternatives and prepared a technical specification which described an aggressive in-situ chemical oxidation (ISCO) program designed to reduce concentrations of petroleum in soil and groundwater. 

Our plan included the installation of ten horizontal injection wells that placed nearly one-half mile of screen in the target treatment zone. Five injection events were completed to inject a total of 150,000 pounds of sodium hydroxide activated sodium persulfate over a three-year period. During the course of these injections, oil that was periodically observed as a thin film in some wells disappeared, as did the oil sheen observed in water samples collected from other source area wells. Significant decreases of both volatile petroleum hydrocarbon and extractable petroleum hydrocarbon concentrations were measured in water samples collected from many key wells. 

After the fifth injection event, the injection program was temporarily halted to allow sulfate concentration in groundwater to dissipate and to allow site conditions to stabilize such that a clear measure of cleanup progress could be made. Based on the impressive improvement in site conditions, the property was sold. The new owner elected to assume responsibility for all additional response actions and MassDEP reporting.
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