Cleaning Up Chromium

From 1956 to 1985, the United Chrome Products plant in Corvallis, Oregon, took a steady toll on the environment. Leaky plating tanks and the discharge of rinse water into a disposal pit caused soil and ground-water contamination underlying the facility. Adjacent to the plating tanks, contamination was greater than 60,000 mg chromium/kg soil and ground-water contamination exceeded 19,000 mg/l chromium. In nearby drainage ditches, surface-water contamination exceeded 200 mg/l chromium. Superfund remediation, which began in 1988, continues today, and data indicates that the cleanup has been a success. Monthly ground-water extraction has climbed steadily since August 1988, when 15,523 gal. were extracted, to the 502,000 gal. that were removed in December 1991. Meanwhile, the concentration of the chromium in the ground water has been progressively declining from an average of 1,923 mg/l to 65 mg/l. Using an infiltration-extraction, pump and treatment system, engineers have demonstrated that with a little flexibility, conventional remediation techniques for soil and ground water can overcome complex geotechnical conditions. More significantly, the project has implications that extend beyond the Corvallis site. Chromium cleanups pose problems, not because of the size of the individual remediations, but because of the large number of contaminated sites throughout the country. Drawing from the results at Corvallis, EPA is using this project as a model of what can be done to clean up similarly polluted sites.