Remediation work ramps up at Questa Mine
Environmental remediation efforts are ramping up at the site of the Chevron Questa Mine, which closed permanently in 2014 after nearly 100 years of underground and surface molybdenum mining.
Chevron purchased the Questa Mine in 2005 when it acquired the Uncocal Corporation, a centuryold oil company with oil fields in Asia that were highly attractive to Chevron. In 2011, the Questa molybdenum mine and tailings site, which represented Chevron’s only hard rock mining property, were added to the National Priorities List and declared a federal Superfund site required to be cleaned up.
During a mine tour last Friday (April 8), company officials told the Taos News that the mine cleanup and restoration activity is likely to extend into the 2050s, with underground water pumping and treatment operations anticipated to continue “in perpetuity.” Contaminated water is pumped to the treatment facility from underground collection points across the mine site, and seepage of contaminated water from springs along the edge of the mine near the Red River is controlled by a series of French drains.
Rachel Conn, deputy director of Amigos Bravos, said the water protection group “continues to have concerns about Spring 13, which is discharging contaminated water to the Red River at higher than anticipated volumes.”
“We hope that Chevron can quickly address this issue,” she continued, adding that “we are happy that the U.S. Environmental Protection Agency has denied Chevron’s request to phase out Clean Water Act permit coverage at the mine site. Clean Water Act permit coverage is essential to both protect water quality and provide regular public participation avenues. Amigos Bravos advocated for several years in opposition to Chevron’s request and we are pleased with EPA’s decision.”
A wastewater treatment plant at the mine is enclosed “in the largest building in Taos County,” said Tommy Lyles, manager of risk mitigation communications with Chevron. “It treats between 800 and 950 gallons per minute,” and discharges about a million gallons of treated water every day.
Cindy Gulde, regulatory affairs advisor with Chevron, said prior issues with excessive aluminum contamination in the Red River had been resolved. “People used to see, like, a white foam collect on the bank in some places” during low flows, she said. The company has completed several major remediation projects already, including the restoration of Eagle Rock Lake, a former gravel pit that had become heavily polluted over the years.
Meetings with representatives from the EPA, state Environment Department and New Mexico Energy, Minerals and Natural Resources Department occur on a monthly basis at the remediation project’s offices, which are perched atop the former mine site at an elevation well over 8,000 feet.
“It can get down to about 25 degrees below zero up here — not counting the wind chill,” said Jim Merrigan, project manager with
Granite Construction. Despite the springtime winds and cold temperatures, Merrigan loves his work.
“I think we’ve moved over 1.2 million cubic yards of dirt since October, 2021,” when operations kicked into high gear, Merrigan said with pride.
Merrigan oversees one of the main projects underway at the moment. Using a fleet of 45-ton, six-wheel-drive articulated haul trucks, along with large bulldozers and other earth moving equipment, his workers are leveling, installing drainage, and preparing to eventually cover the Capulin waste rock pile. It’s one of nine towering rock piles with steep sides that contain roughly 300 million tons of waste material that was removed from underground tunnels and a staggeringly deep open pit over the mine’s history.
“We’re rebuilding the rockpiles into a stable configuration,” summarized Chevron Field Engineer Don Bush, looking down the side of the rockpile, where perilouslooking
main access roads are named “Stairway to Heaven” and “Highway to Hell.” He said that piezometers and slope indicators will be installed — and monitored for the foreseeable future — in each rock pile. To avoid erosion and encourage revegetation, the rock piles are required to be leveled to a slope between 2::1 and 3::1, meaning they’re no steeper
than a three-foot rise for every foot of distance.
Because the waste rock material is acidic and causes precipitation runoff to turn acidic, the final phase of the rock pile reclamation will involve laying down a threefoot “evapotranspiration” cover of approved material that is sourced and from a single neighboring rock pile and which will be run through a screening plant that also tests for contamination levels.
Each rock pile project will require an estimated five-to-seven years of work to complete, according to company officials.
“The cover will be made up of material less than eight inches in size that is non-acid generating and meets the molybdenum [content] standard of 600 parts per million,” Gulde said, though no timeline was given for when groundcover would be laid down.
A pilot project on the Goathill waste rock pile using three different methods for laying down cover material has begun to yield results. Although the only vegetation that’s visible to the naked eye on the most successful experimental ground cover plot is chamisa, Chevron believes it is close to determining the optimum method of installing the cover to avoid erosion. The pilot project was intended to wind up in 2024 but has been extended until 2027, Gulde said.
A similar pilot project relating to ground cover revegetation is underway at the mine tailings site — located miles from the mine on the other side of the Village of Questa — has yielded some sparse plant growth. Company officials could not identify what specific types of vegetation had proven most successful on the test plot, which is intended to support Chevron’s plan to remediate the tailings site using two feet of cover rather than the three feet of material called for in the project’s guiding documents.
The seed is “a mix of native forbs, grasses and shrubs,” Christian Isely, Chevron’s public affairs advisor, said in a follow up email. Gulde said the company expects to ramp up its remediation work at the tailings site next year.
While around 300 mine workers were estimated to have been laid off as a result of the mine’s closure, almost two-thirds that number of people are currently working on cleanup and restoration projects.
“There are currently 173 people actively employed on-site on a daily basis,” said Isely, who lives in Questa, which has struggled to reinvent its post-mine economy despite a helping hand from Chevron.
“Of those, 79 workers are long
term local residents, representing 46 percent of our on-site workforce,” Isely said. “These numbers include Chevron [employees], along with our business partners Granite Construction, Arcadis, Entact, WSP-Golder, and Securitas.” He said there are job opportunities with all five contracted companies, and emphasized the stable nature of the employment.
“We’re sequencing the different projects to retain the workforce benefit,” Isely said, explaining that workers won’t see gaps in employment during the next several phases of remediation work. “When we’re finished with Goathill, we’ll go to the tailings site; then it’s back to the next rockpile.”
Conn lauded Chevron’s efforts on behalf of the workforce.
“We are glad that Chevron is taking into account workers by scheduling restoration and remediation such that there will be no gaps in employment,” she said. “Amigos Bravos has long advocated for robust restoration requirements as being important for both jobs and the environment.”