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Hexavalent chromium cleanup planned

April 28, 2018

NEEDLES — An informal open-house presentation about remediation of a chromium six plume at the Pacific Gas and Electric Topock Compressor Station was held at the Needles Regional Senior Center on April 17.

From 1951 to 1985, PG&E used hexavalent chromium as a corrosion inhibitor for the facility’s gas compression cooling tower. From 1951 to 1964, the hexavalent chromium was dumped into dry washes and treated wastewater was discharged into ponds for storage and evaporation. Eventually, hexavalent chromium seeped into the groundwater and created a plume under PG&E’s compressor station.

PG&E self-reported contamination of the ground water in 1996 and testing located an underground plume from 28 to 35 feet below ground and covering about 150 acres. Operations at the station also resulted in contamination of soils located both inside and outside the station’s fence line.

“In order to clean up the plume PG&E is going to be injecting molasses, ethanol and other chemicals to change the chemistry of the plume. When the water pushes the plume through the wells it will change Chromium 6 into Chromium 3 which is non-toxic,” said Mike Anderson, Department of the Interior consultant. “So then they’ll pump the clean water out and put it back uphill to flush all the contamination through the wells.”

According to a PG&E graph of the project timeline, the remedy wells are scheduled to start in September of 2018 with completion in April of 2020; the remedy pipelines are scheduled to start construction in December of 2018 and are scheduled to finish construction in August of 2020.

“There’s a level of chromate that you find anywhere and that is 32 micrograms per liter. That is the target. You can’t get it below that level because that’s the naturally occurring chromium,” said Anderson. “As of right now the micrograms per litter are in the thousands in some places, so there’s a real problem.

“It’s going to be a long process. They have models that every time they keep flushing water through it, predict how much longer you have to keep doing that until it’s clean,” said Anderson. “The models that they’ve run say it could take up to 20 or 30 years before it gets where it needs to be.”