As cleanup proceeds in the 101,000-gallon oil spill from a ruptured pipeline near Refugio State Beach in Santa Barbara County, workers in San Luis Obispo County have continued to quietly toil in a two-decade-long effort to clean up millions of gallons of oil that leaked in the Guadalupe oil field.
Like the Santa Barbara spill, this one also reached the ocean, although most of the contamination was onshore, saturating a large area of the Guadalupe-Nipomo Dunes in the southwestern corner of San Luis Obispo County.
Cleanup and restoration work on what was considered one of the nation’s worst oil spills is expected to continue at the Guadalupe dunes for at least another 10 years — serving as a warning that oil spill remediation is a long and complex process.
Two decades into the work, the Guadalupe cleanup continues to present a challenge for regulators and site owner Chevron. They want as much of the toxic oil removed as possible, but massive excavations damage the sensitive ecosystem of the dunes, which are home to several rare and endangered species such as the snowy plover, California red-legged frog and the La Graciosa thistle. “It’s complicated,” said Rich Chandler, an engineering geologist with the Central Coast Regional Water Quality Control Board. “There are always environmental trade-offs in projects like this.”
More than 40 oil plumes
The 2,700-acre oil field was an active oil field from 1946 to 1994. During that time, millions of gallons of an oil called diluent leaked from rusty pipes and settled into the sand dunes.
Diluent is similar to kerosene and was used to thin the heavy crude oil produced in the field. The field was originally owned and operated by Union Oil of California, often called Unocal. In 2005, Chevron bought out Unocal and took over work at the oil field.
The first large excavation was an emergency operation in 1994 along the beach to prevent the toxic pollution from entering the ocean. Sheet walls have also been installed to prevent the oil from moving toward the ocean or the nearby Santa Maria River, said John McKenzie, a senior planner with San Luis Obispo County.
“Diluent is a toxic material to humans, wildlife and plants, and therefore presented a risk to ecological and human health,” he said.
Since then, more than 40 pockets of contamination, called plumes, have been excavated and more than 1 million cubic yards of contaminated soil have been removed. This material is taken to the Santa Maria Landfill, where it is used as cover material.
Envision a football field buried under a mountain of dirt more than 450 feet high — that is what 1 million cubic yards of contaminated soil looks like.
Too damaging to remove
There are also three water treatment units at the site that remove contamination from groundwater, Chandler said. These units use activated carbon to remove the oil and can clean it up to the point where laboratories cannot detect it.
Over the years, workers have also removed about 150 miles of pipeline. Workers are beginning to remove the dozens of oil pads and roads that crisscross the field.
“We expect two to four years of work to remove the pads,” said Carri Douglas, Chevron’s Guadalupe oil field team leader. “Finishing cleanup and restoration is expected to take another five to 10 years.”
In spite of all the work that has been done at the oil field, a large volume of diluent remains in the ground. About half of the known plumes near the surface have been cleaned up, and large plumes of oil remain deep underground where it would be too environmentally damaging to excavate.
“We remove enough contaminated soil to protect human health and wildlife,” Chandler said. “We don’t think there is any need at this point to do any more large excavations.”
Chevron officials won’t say how much the company has spent on the massive cleanup over the years, or how much it expects to spend in the future.
In 1998, Unocal agreed to pay $43.8 million in damages to county and state agencies, which was earmarked for various restoration and water quality projects, future pollution response, penalties and litigation costs.
At that time, Unocal officials said they expected to spend hundreds of millions of dollars on a decadeslong cleanup. As a comparison, a Plains All American spokesman said last week that the company estimates it will spend about $92 million on the Refugio cleanup.
Two weeks ago, the county Board of Supervisors approved the latest contract with an independent company to monitor the Guadalupe Dunes cleanup. The $1.8 million contract with Marine Resource Specialists is being paid by Chevron.
Drought slows restoration
In addition to cleaning up the site, workers are also busy restoring it. More than 20 acres of wetlands have been created and restoration crews are removing invasive veldt grass and replacing it with native plant species.
“Trucks, excavators and veldt grass removers are all busy out there,” McKenzie said. “It’s a large group.”
Veldt grass is a bunchgrass native to South Africa that was introduced to California in the 1940s as a range improvement crop. Since then, it has spread widely along the Central Coast. Veldt grass dominates large areas of dune systems, disrupting ecosystem function and greatly reducing biodiversity.
Unfortunately, California’s extreme four-year drought is slowing restoration work. The dry conditions are causing many of the newly planted shrubs to die.
“Hopefully, the drought will end soon,” Douglas said. “Restoration will take longer if the drought continues.”