NEWARK, CA — Evergreen Oil has spent months trying to improve its relationship with unhappy neighbors after years of foul odors and a large fire last year that drew citations from regulatory agencies.

Those efforts may have been undercut by recent accidents, including an oil leak last month, a small fire in March, and a large explosion and fire 17 months ago that left a plant employee with a broken arm.

But the recycling company has some changes in store.

Evergreen Oil, founded in 1984, has several operations at 6880 Smith Ave., near Cherry Street. It treats up to 55 million gallons of wastewater each year; treats, stores and disposes of hazardous waste; and re-refines waste oil — making it the only facility of its kind in Northern California.

All of that soon may change, city officials said.

"The owners are looking to sell the company and the plant," said Terrence Grindall, Newark's community development director.

Whoever buys the company could shutter the facility, or it could continue the same operations employed by Evergreen, Grindall said.

"Whatever happens, we'll continue to work with them to address any problems," he said.

Evergreen Oil officials reached by phone last week declined to comment on the company's sale.

Meanwhile, another major change looms — plant manager Bob Gwaltney has taken a new job, with Friday his last day with Evergreen. He will be replaced by George Lamont, the company's executive vice president, who will manage the Newark facility until a permanent candidate is hired.

One of Lamont's biggest challenges will be to limit the plant's odors, a chronic problem that has angered neighboring residents. Lamont said the plant's odor compliance now is under control because employees have made it a priority.

"It's been a very dramatic turnaround, and we're happy to see that the issue is behind us," he said.

But some neighbors living in a large housing tract on the eastern side of Cherry Street disagree. The plant's odors "continue to happen occasionally," said Newark resident Lori Lowe, who lives less than a mile from the plant.

Lamont said the number of complaints is far lower now than a few years ago. "If we don't receive the complaint, we don't know about it," he said. "That's the only thing we can go by."

Evergreen came under greater scrutiny after March 29, 2011, when malfunctioning waste oil equipment started a two-alarm fire that caused a hydrochloric tank to rupture.

Evergreen temporarily halted its re-refinery operations by closing two waste oil stations — called "Train 1" and "Train 2." After repairs, Train 2 eventually reopened. Train 1, an older station that sustained most of the damage in the fire, remains closed, but Evergreen hopes to reopen it soon, Lamont said.

The accident prompted Cal-OSHA to issue four citations and fine the company nearly $22,000 for workplace infractions.

In the past 18 months, the Bay Area Air Quality Management District has issued two notices of violation to Evergreen, agency spokesman Ralph Borrmann said. Last year, the Department of Toxic Substances Control said inspectors in November 2010 discovered three infractions, including mixing used oil with other hazardous waste, agency spokeswoman Randi Jorgensen said.

The plant's recent infractions have prompted Consumer Watchdog, a consumers' rights organization, to call for Evergreen to permanently to close its Newark plant and for regulatory agencies to come down harder on the company.

Since the explosion and fire nearly 17 months ago, Evergreen has taken steps to improve its workplace safety, Lamont said. In addition, the company has sought community feedback by holding a public meeting, forming a community advisory panel that includes residents, and providing a phone hot line for neighbors to call.

Still, problems persist.

In March, a small fire started in a 55-gallon drum mislabeled by a company that delivered it to the facility, said Patricia Ortiz, a spokeswoman for the Department of Industrial Relations. In July, the plant was evacuated when a pipe containing oil was broken, causing a leak.

Also, while some neighbors say they appreciate Evergreen's new spirit of community outreach, others say it has room for improvement.

After the oil leak last month, for example, neighbors feared the worst when the Alameda County fire hazardous materials team arrived and TV news helicopters hovered above, Lowe said. She said the company employee who answered the community hot line seemed reluctant to provide information and revealed a leak had occurred only after she repeatedly asked him questions about it. She said she would have appreciated it if the company had sent a note to residents explaining exactly what happened.

"But they didn't," she said. "I was really kind of disappointed in that."

Contact Chris De Benedetti at 510-353-7011. Follow him at Twitter.com/cdebenedetti