Vapor intrusion (the movement of constituents into the indoors from subsurface contamination) is one of the PA Department of Environmental Protection’s (DEP) site characterization requirements under the Act 2 and Storage Tank Programs. At the Woodland Retirement Center, Herbert, Rowland & Grubic, Inc. (HRG) assessed and mitigated the vapor intrusion pathway, which provided the client with Act 2 liability protection following an accidental heating oil release.
A heating oil odor in one area of the facility provided the first indication of the release. Emergency response actions controlled the discharge of oil to a stormwater drain. Temporary radon fans were used to ventilate subsurface soil. Air sampling demonstrated the fans’ effectiveness in meeting indoor air quality standards.
HRG determined the release occurred beneath a concrete floor slab. Oil contaminated soil was excavated to the extent feasible without compromising foundation integrity. Three shallow wells were installed to remove heating oil in perched groundwater. Post excavation GeoProbe™ soil samples showed that residual soil impacts were limited to the soil and gravel beneath the concrete slab floor where the release occurred.
PADEP approved an Act 2 Cleanup Plan which addressed any impacts to groundwater and indoor air from the residual soil contamination. The final remedy demonstrated attainment of the Act 2 Statewide Health Standard for groundwater and the Site Specific Standard for residual soil impacts beneath the floor.
The soil remedy was facilitated by a deed restriction consistent with the Uniform Environmental Covenant Act (UECA). The deed covenant utilizes the concrete floor slab as a cap to prevent direct contact with residual soil impacts and continued use of the sub slab ventilation fans.
HRG developed a post-remedial care plan that upgraded the temporary ventilation fans to ensure reliable long-term operation as well as a post remedial care plan with periodic air quality monitoring to demonstrate their continued effectiveness. That monitoring demonstrated that the fans were no longer required to meet indoor air quality standards. An amended deed covenant which eliminated the obligation to run the sub slab fan system was approved by PADEP.
