SITE REMEDIATION AND
EMERGENCY RESPONSE NEWSLETTER

June 2009
No. 129

EPA Announces $37 Million Plan to Clean Up DDT-Contaminated Sediments in Ocean Floor off Palos Verdes Peninsula, CA

EPA has issued a plan to begin cleanup of sediments contaminated with 100 tons of DDT and 10 tons of PCBs lying on the ocean floor close to the Palos Verdes Peninsula in California.  The Montrose Chemical Co., once the world’s largest producer of DDT, is responsible for the chemical contamination of a 17-square-mile area of the ocean. While DDT production was banned in the U.S. in 1972, Montrose continued producing it for export until the mid-1980s. The cleanup proposed by EPA will cost nearly $37 million.

While the capping of contaminated sediments in New York and Boston harbors has been successful, the Palos Verdes site is vast in comparison. It is much deeper at 120 feet below ocean surface and is subject to stronger currents. In addition, it slopes down into an undersea canyon. In the best scenario, less than one-fourth of the contaminated area is susceptible to treatment.

For the past 10 years, EPA has been studying the contamination.  A pilot project it conducted in 2000 tested capping with clean silt three areas of contaminated sediment, each covering 45 acres. The results were mixed.  The impact from the barge dump disturbed settled sediments.  (See SR&ER No. 25 of September 2000.)

EPA will conduct several more studies before beginning cleanup.  Most importantly, it has to refine the method of dumping clean silt to form the cap.  The cleanup proposal is an interim plan that may be changed or expanded over time, according to EPA.

The new preferred alternative would more gently distribute an 18-inch cap of clean sand and silt over 320 acres of ocean floor, approximately 200 feet below the surface.  At a cost of $36.6 million, the preferred alternative  plan would cover nearly 37 tons of DDT in the most heavily contaminated area of the Palos Verdes Shelf and meet the EPA goal of improved surface water quality by 2023.

An alternative solution, costing $64 million, would have capped twice as much territory and improved surface water quality by 2019.

EPA will not make a decision on the more costly cap until it has more data.  It has detected a trend showing that DDT is breaking down much faster than expected through the process of dechlorination.  With more research, EPA hopes to be able to accelerate dechlorination.

The agency describes the capping as a “risk-reduction project, not a risk-elimination project.”  Dredging the contaminated sediment was deemed too costly and more harmful to the environment than leaving the DDT in place.

The period for public comment on the EPA proposal ends July 15.

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