Pacific Southwest, Region 9
Serving: Arizona, California, Hawaii, Nevada, Pacific Islands, Tribal Nations
Molasses Injections at Selma Superfund Site Result in Multiple Environmental and Economic Benefits
Located near the town of Selma, the Selma Superfund Site is a former wood-treating facility located approximately 15 miles south of the city of Fresno, California. The site is situated in a transition zone between agricultural, residential, and industrial areas and encompasses nearly 18 acres of land.
Contaminated with heavy metals, including hexavalent chromium and arsenic, the ground water was formerly treated solely with a pump and treat (P&T) system. In order to improve the efficiency of the remedy and reduce operating costs, EPA began a pilot project to supplement the P&T remedy with in-situ remediation. The in-situ remediation involved injections of Molasses into the contaminated plumes in order to increase the metabolism of naturally occurring micro-organisms, which effectively convert the hexavalent chromium into a less toxic form.
The remedy rapidly reduced chromium concentrations in the groundwater from 80,000 ppb to un-detectable levels within a 3-week time frame and has led to several phases of injection across the site over the last three years. Compared to a mere initial P&T system, the in-situ remedy is expected to reduce cleanup goals in a much shorter time-span, from 75 years to 5 years, and save approximately over $30 million in cleanup costs. Additionally, the remediation will reduce chemical-use by 1/3 of original estimations and decrease off-site disposal transportation by 1/2 of initial projections. Moreover, electricity consumption on-site will decrease by 215,000 kilowatt-hours per year and result in significant emission reductions, including approximately 368,000 lbs. of CO2 emissions each year for the next 75 years.