DTSC gives update on cleanup near Topock

The California Department of Toxic Substances Control gave interested Parker area residents an update on cleanup activities at the Pacific Gas and Electric Co. Topock Compressor Station July 28.

The PG&E station compresses natural gas so it can be transported through pipelines to customers in northern and central California. The station began operation in 1951 and is located 12 miles southeast of the City of Needles, Calif., and about a half-mile from the Colorado River.

From 1951 to 1985, hexavalent chromium was used at the station as an anti-corrosion agent in its cooling towers. From 1951 to 1968, cooling tower wastewater was discharged into percolation beds in a dry wash area located next to the station.

In 1964, PG&E began to treat the wastewater to remove hexavalent chromium. In the early '70s, the company installed an underground injection well to receive treated wastewater and a series of lined evaporation ponds.

In 1985, the company stopped using the chromium-based additive as an anti-corrosive agent and switched to a phosphate-based solution.

In 1996, the company and the DTSC entered into a voluntary agreement to investigate the nature and extent of and to clean up any contamination resulting from the station operations. In 1997, the groundwater and Colorado River water monitoring began.

Chromium is a natural metal found in rocks, soil and the tissue of animals and plants. Hexavalent chromium is the toxic variety and is considered a human carcinogen

On March 8, 2004, PG&E began extracting chromium-contaminated groundwater near the station to prevent it from reaching the Colorado River. Contamination has not been detected in the Colorado River and there is no threat to the public.

Years of environmental investigations and groundwater monitoring indicate that the affected groundwater, known as the plume, extends northeast from the station under Bureau of Land Management lands. The plume is approximately 2,400 feet long, 1,300 feet wide and lies approximately 80 to 175 feet below the ground surface.

Five slant wells were installed in 2007 extend underneath the Colorado River and allow for groundwater sampling.

Currently, 35 wells monitor the plume, including 12 wells in the floodplain area next to the river. Seven of the wells were installed in 2003 to better monitor the edge of the plume closest to the river. Nine of the floodplain wells have never detected hexavalent chromium.

Of the three wells that detected hexavalent chromium, the one closest to the river has exceeded the California drinking water standard of 50 parts per billion two times, with the concentration as high as 111 ppb. The affected floodplain wells, plus a few others, are currently sampled on a weekly basis.

The presentation by DTSC was at the Parker Senior-Community Senior. The information was extensive and participants could walk through exhibits and queries could be answered.

The DTSC gives the public a chance to have input into the cleanup process and also to keep area residents updated on the cleanup process. The department hopes to have the final Environmental Impact Report completed by November 2010. As for a final cleanup of the plume, it is hard to determine at this point in time.

The project reports, fact sheets at be found at:

www.dtsc-topock.com.

Information for Parker residents is available at the Parker Public Library and the Colorado River Indian Tribes Library.

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