EFFICIENCY OF SOIL VAPOR EXTRACTION AS A GROUNDWATER REMEDIAITON TOOL FOR OIL REFINERIES IN THE CENTRAL VALLEY OF CALIFORNIA

Many of the old petroleum oil refineries in the Central Valley of California caused soil contamination and groundwater degradation problems with petroleum hydrocarbons generated over the years from their aboveground storage tanks (ASTs) and underground crude oil delivery pipelines operations. Most refineries in the area adopted soil vapor extraction (SVE) technique as their main soil and groundwater remediation tool probably due to the SVE’s reputation as an already accepted, recognized, and cost-effective technology. Our review of the historical site characterization and remediation reports indicate that SVE technique was highly effective in remediating groundwater impacted with chlorinated hydrocarbons (such as TCE and PCE) in some industrial sites of this region such as former Dow Chemical Company in Fresno of Fresno County and former Sprague Electric Company in Visalia of Tulare County. However, SVE was much less effective in other sites such as Bakersfield Refinery in Bakersfield of Kern County for the petroleum hydrocarbon cleanup. At the refinery, SVE operation started in 1992 and the SVE system is still being operated in conjunction with other remediation technique (air sparge) to clean up the benzene and total petroleum hydrocarbon groundwater plumes. The effectiveness of SVE needs to be quantified for different scenarios.

The objective of this research is to utilize available data collected from the three sites mentioned above to evaluate the effectiveness of the SVE as a sustainable soil (and subsequently groundwater) remediaiton tool, and to verify its application range from the hydrogeological point of view. The evaluation will also include the type of contaminants and their values of vapor pressure, water solubility, and Henry’s Law constant. The challenges of this research lie on the complex composition of petroleum and petroleum products and also on the contaminants occasionally being added to the site soils through the leaks and spills occurring by the on-going refinery operations.