Selma Pressure Treating Site Implements Enhanced Remedy
An enhanced remedy was recently implemented at the Selma Pressure Treating Site south of the city of Fresno, California. This remedy is estimated to save approximately $30 million and to reduce the time estimated to reach cleanup goals by several decades.
The Selma Pressure Treating Site is a former wood treating facility located south of the city of Fresno, California. This site, which was one of the first Superfund sites listed on the National Priorities List, was placed on the NPL in 1983 as a result of environmental contamination resulting from decades of wood treating operations. In 1998, a pump and treat (P&T) system was built to address ground water that was heavily contaminated with hexavalent chromium. While the treatment system was effective at reducing the level of contamination in the ground water, an independent optimization review was performed in 2001 in order to identify opportunities to improve the efficiency of the remedy and reduce operating costs. Shortly thereafter, EPA began a pilot project to supplement the P&T remedy with in situ bioremediation. The in situ remedy involves injecting molasses into the ground water in order to increase the metabolism of naturally occurring microorganisms, which effectively convert the hexavalent chromium to a less toxic form.
The highly successful pilot project led to several phases of injections across the site over the last three years. The in situ approach has rapidly reduced levels of contamination from as high as 80,000 parts per billion (ppb) in ground water to non-detectable levels in a matter of weeks. The enhanced remedy is expected to speed up cleanup by several decades - at a savings of approximately $30 million - compared to relying solely on the initial P&T remedy.
The Selma Pressure Treating site is one of more than 50 Superfund-financed ground water remedies that have received independent optimization reviews. Optimization is intended to facilitate systematic review and modification of existing P&T systems to promote continuous improvement and to enhance overall remedy and cost effectiveness. Additional case studies, project implementation reports, and related guidance are available on the Superfund Remedy Optimization page, or at Clu-In.