Unocal Corp. has pledged an open ended budget to clean up a massive underground spill of a kerosine/diesel mix diluent in California's Guadalupe oil field that went unreported for years.
In making the pledge, Unocal Vice Pres. John Imle Jr. offered a public apology on behalf of the company. Imle promised an open ended budget to clean up at least 113 acres underlying the 2,300 acre field in San Luis Obispo County. Unocal has spent more than $2 million for Guadalupe remediation since 1990. It has operated the field for more than 40 years, using the diluent to thin Guadalupe heavy crude for pipeline shipment.
The company is negotiating with private landowners with interests in the field for a permanent shut-in while it steps up remediation efforts likely to last beyond 2000. That scraps Unocal's earlier plan to sell its leases in the field.
Meantime, the San Luis Obispo County district attorney is seeking criminal charges against Unocal for allegedly polluting groundwater and failing to report leaks that occurred as long ago as 1985, among other alleged violations. Civil actions by the state attorney general also are expected.
Environmental groups in California are calling for a boycott of Unocal products, comparing the severity of environmental damage from the Guadalupe underground spill with the Mar. 24, 1989, Exxon Valdez tanker spill off Alaska.
SCOPE OF THE SPILL
San Luis Obispo County officials estimate the spill at 120,000 bbl of diluent.
Unocal hired separate consultants to estimate the figure by a Mar. 11 hearing at the state regional water quality control board.
Imle said the company used about 23 million bbl of diluent during more than 40 years of operations and may have allowed 1% of that total or less to leak. Currently, the company is using hot water in lieu of the kerosene/diesel mix to dilute Guadalupe heavy crude.
The hardest problem Unocal faces is cleaning up diluent at the field's edge along the California coast, said Marjorie Hatter, a Unocal environmental specialist who was appointed Guadalupe response manager and reports directly to Imle.
In 1990, the company built a 1,000 ft underground bentonite barrier that so far has failed to keep some of the diluent from seeping into the ocean.
In addition, Unocal drilled 18 extraction wells that have recovered 16,000 bbl of diluent along the coastal fringe of the field.
Inland, another eight well pumping system is ready to test extraction techniques and separate water from diluent.
Research shows 28 sites over 113 acres are polluted, most likely from pipeline and storage tank leaks. Most of the worst contamination was found in a 60 acre site underlying diluent storage tanks.
Guadalupe had been producing 1,200 b/d in 1990, but all wells were shut in after the spill was reported. Only a few were activated later. Today's production is 240 b/d.
ADVANCED TECHNIQUES
Unocal is resorting to novel methods to assess extent of the spill and clean it up.
During the past 6 months, the company has conducted a major research project to determine the extent of diluent contamination. It entails use of vapor probes that detect carbon dioxide emitted from bacteria that break down the diluent.
"It's a very fast way to cover a lot of territory," Hatter said, compared with traditional methods of soil borings and exploratory wells. That cut the screening time from the expected 2 years to only 6 months and dramatically reduced the number of wells needed, she said.
The expected number of exploratory wells needed to find the underground contamination accordingly has fallen to 33 instead of perhaps 10 times that number.
An overall cleanup plan, under study by state agencies, may include bioremediation and air sparging in addition to extraction. Bioremediation in this case involves pumping air into the ground to activate bacteria. Air sparging involves releasing greater volumes of hot air to vaporize hydrocarbons.
OTHER ENVIRONMENTAL WOES
The Guadalupe spill is the latest in a string of environmental problems in San Luis Obispo County that Unocal is grappling with.
The company also is cleaning up an unrelated but comparable long term underground spill of gasoline, diesel, and crude oil beneath the main street of Avila Beach, a town just north of Guadalupe field. Originally detected in 1988, that spill is being cleaned up with 26 vapor recovery wells, an effort expected to last another 6 years.
In addition, Unocal had a 150 bbl oil spill into the ocean near Avila Beach, and the company frequently fields complaints from residents about odors from its Nipomo Mesa refinery.
"We know we have to regain trust," a Unocal official said. "And the community should know that this has top level, board of directors' attention."
Copyright 1994 Oil & Gas Journal. All Rights Reserved.
