In Situ Oxidation of PAH Contaminants Associated With Former Manufactured Gas Plants

Seldom are engineering controls to mitigate impacts from MGP cleanups more stringent to protect objects rather than human health. This paper describes the design challenges encountered to protect collections and artifacts inside a historic museum in Santa Barbara, California while implementing the in situ ozone treatment of manufactured gas plant (MGP) residuals. The approved remedial action plan provides for in situ ozone sparging to treat saturated zone soil and groundwater impacted by polycyclic aromatic hydrocarbons and volatile organic compounds (VOCs). Conventional air sparge and soil vapor extraction compliment the chemical oxidation treatment strategy. The goal of the in situ ozone treatment is to restore groundwater to drinking water standards within a two year timeframe.

The museum buildings are constructed of adobe bricks (one structure dating back to 1817) and contain collections such as; textiles, paintings, fine art, leather goods and books. One major risk factor that could affect museum collections is fugitive ozone and other VOCs generated during the in situ remediation. Some of the challenges in designing the treatment system involved installing the gas distribution hardware below ground so as not to interfere with functions held on the museum grounds, and concealing all of the gas generation equipment within an architecturally compatible and acoustically rated compound.

The engineering controls to mitigate impacts from chemical agents generated during remediation activities include: 1) sealing the museum doors, windows and roof joints, 2) installing an air intake handling system capable of maintaining a positive air pressure inside the building, 3) installing a “high efficiency” air filtration system in conjunction with the air handlers, 4) designing the soil vapor extraction system to working in conjunction with in-situ ozone sparging, and 5) installing a state–of–the–art, integrated monitoring system to detect ozone intrusion into the museum, interruption in the HVAC system and power failures, all of which will automatically shut down the generation of ozone.

In summary, this paper will present by a case study explaining how the use of an innovative chemical oxidation technology allowed for the in situ remediation of groundwater at a culturally sensitive site.