SALT LAKE CITY — Bureau of Land Management officials say it will be a year, maybe two, before they are prepared to give a complete "all-clear" to the site of an oil well leak that ultimately reached the Green River.

Though the site about 12 miles southeast of the city of Green River has been visually "scrubbed" clean of any noticeable hydrocarbon or salt products, BLM spokeswoman Lisa Bryant said, mineral specialists will continue to visit the site for monitoring, as they did Wednesday.

"The BLM will continue to monitor for additional cleanup," Bryant said. "Everyone has agreed that it is good, but we want to make sure there is something that we didn't see, something that doesn't naturally attenuate or bubble up."

A final visual inspection in mid-June by the BLM, Environmental Protection Agency and the state Division of Oil, Gas and Mining gave a preliminary all-clear, but the concern is there may be some small, hidden patches of contaminated soil, roots or rock that could be exposed over time, she said.

"Anything (the contractors) could see has been removed," Bryant said.

The rocky, sparsely vegetated wash lies below what is called the Salt Wash Oil Field south of I-70 that contains federal land occupied by two oil wells operated by SW Energy.

A 1969-era oil well experienced an equipment failure below surface on May 21, resulting in the release of produced water mixed with some oil and mineral compounds such as salt.

Bryant said no one knows for sure how much of the fluid ultimately escaped before the well was "shut-in," but containment measures to prevent the fluid from reaching the Green River — 5 miles downstream — were breached in a torrential rainstorm two days later.

Environmental advocacy organizations such as the Utah Rivers Council and the Sierra Club raised objections about the contamination of the river and failure of the containment system.

A team from the Utah Division of Water Quality, the EPA, BLM and the state oil and gas division conducted an inspection via a river trip, and Bryant said another trip will likely take place later this summer to assess any evidence of residual contamination.

She added the first trip did not reveal any contamination, other than at the mouth of the drainage.

John Whitehead, assistant director of the Utah Division of Water Quality, said scientists tested the river at the confluence of the wash, as well as locations above and below the confluence. The river is the key tributary of the Colorado River, which is the drinking water supply for 40 million people.

"We sampled the river on the day of this big rainstorm," Whitehead said. "We scrambled … to go down there. We tried to sample at the confluence, but our results were non-detect."

The division issued a notice of violation to the operator and is waiting for the company's response.

Bryant said the well operator will bring in special equipment to pull the well's "plumbing" to the surface as part of the investigation to determine what went wrong.

Email: amyjoi@deseretnews.com, Twitter: amyjoi16