Unocal excavation at Avila Beach removes 95% of hydrocarbons
Santa Maria, March 21, 1996 -- Unocal today said the emergency excavation at Avila Beach earlier this year removed approximately 95 percent of the petroleum contamination in the excavation area and eliminated the threat to public health.
"This emergency excavation project was extremely successful," said Bill Sharrer, Unocal's manager for environmental affairs. "We accomplished the clean up safely and quickly, and removed the threat to public health posed by the contamination."
Sharrer pointed out that some residual contamination was left at deeper depths that cannot be removed by excavation. "The layer of residual contamination is at least nine feet below the surface and does not pose a threat to public health," Sharrer said.
The emergency excavation project became necessary after routine monitoring showed that as a result of past winter storms, petroleum hydrocarbons under the sand were at a depth of two and one-half feet. The hydrocarbons beneath this area of the beach consisted of a combination of crude oil and diesel fuel.
The excavation project removed approximately 7,500 cubic yards of contaminated sand and replaced it with clean purchased sand during the three-month project that was completed in January.
Under the authority and oversight of the regulatory agencies, Unocal added nutrients and oxygenated additives to enhance biodegradation of the remaining petroleum contamination. Pilot studies on soils collected from the site have proven extremely successful, with high rates of biodegradation of the petroleum contaminants. Unocal and the regulatory agencies will continue to monitor the bioremediation efforts at the excavation site.
Test results of the remaining contamination in the subsurface soil showed petroleum levels ranging from non-detect (ND) to a single sample with a concentration of 11,500 parts per million (ppm). The contamination averages 2,300 ppm in the 3-foot residual contamination layer based on the sampling.
Updated: March 1996