The sinkhole that killed a Chevron Corp. employee on an oil field west of Taft Tuesday appeared just months after the company performed underground construction work at the site to address concerns raised by state regulators.

Chevron said the work, done in March at the request of the state Division of Oil, Gas and Geothermal Resources, involved burying two perforated pipelines to contain oil field fluids that were seeping to the surface during steam injection, a common process used to enhance oil production.

A DOGGR spokesman wrote in an email Thursday that the agency did request that something be done about the seeping and that Chevron provided "courtesy updates" on its work, but that the division did not issue a permit or consult on the construction.

"There was nothing formal," spokesman Don Drysdale wrote in an email. "DOGGR told Chevron that the surface expressions (seeping) were unacceptable and Chevron said they would handle it."

Meanwhile, the county coroner's office confirmed Thursday that the worker, 54-year-old Bakersfield resident Robert David Taylor, died due to accidental immersion in a sink hole filled with oil field byproducts. A news release from the office did not state what specifically killed him.

A former co-worker of Taylor, mechanical engineer Eric Berger, recalled him being "a wonderful guy."

"He was a humble man, hard working, easy to work with, always charming," Berger said. "Just he was a great guy. Anybody who ever worked with him felt a loss."

Chevron has expressed its condolences; DOGGR did so publicly Thursday.

"Our most sincere condolences go to Mr. Taylor's loved ones and coworkers. Those who work in oil fields, whether regulator or operator, are acutely aware that they can be dangerous places," Drysdale's email said.

Cal-OSHA has confirmed that it is investigating the incident. An agency spokeswoman could not be reached for comment Wednesday or Thursday.

Although ground subsidence is not uncommon in oil fields, Chevron and DOGGR said they had never seen or heard of a sinkhole like the one Taylor fell into while walking with three other employees at about 10:45 a.m. Tuesday.

"We don't know what caused this," Chevron spokeswoman Carla Musser said Thursday.

Musser said DOGGR has required similar construction work of other companies operating in the same part of the prodigious Midway Sunset oil field. She added that the pipelines Chevron buried at the site are intended to collect fluid, not the steam that is injected underground at high pressure to produce oil.

Several oil companies operating in Midway Sunset did not return calls requesting comment Wednesday and Thursday. A spokeswoman for Aera Energy LLC noted in an email that the company is not currently injecting steam in the area.

A former DOGGR regulator alleged Thursday that the construction work required by the agency may have contributed to the sinkhole's formation.

Mike Stettner, who regulated underground injection work at DOGGR for about two decades, said the seepage at Midway Sunset before Chevron's recent construction presented no environmental threat but that the agency considered it unsightly.

When Chevron put in pipes to drain the seeping fluids, Stettner theorized, steam worked its way up through the soil -- but it didn't reach the surface. He said this may have saturated and weakened the ground in a way that would not have been visible on the surface.

Employees would have had "no suspicion whatsoever that there was this bubble of steam underneath them, so when one of them stepped on it -- stepped in that area -- it just gave way," Stettner said, adding that he was unaware of what specific construction work Chevron recently did at Midway Sunset.

Cal State Bakersfield geologist Jan Gillespie said subsidence has long occurred as a result of steam injection operations in Kern County, though it generally happens very gradually.

Gillespie, who said she is familiar with steam injection operations in Midway Sunset, suggested that the steam may have shattered the brittle, diatomaceous soil under the Chevron lease, causing the ground to collapse.

"That may be why it fell so abruptly," she said.

DOGGR expressed optimism that Taylor's death will be followed by improved safety in local oil fields.

"Our hope is that improved oilfield safety awareness and practices are the ultimate outcome of this most unfortunate incident," Drysdale's email stated.