Uranium levels high in creek near Rifle water plant site
Citizen Telegram Editor
The proposed site of Rifle’s new $25 million water treatment plant is also where scientists studying a uranium-contaminated plume of groundwater at the nearby East Rifle mill tailings site have found the highest levels of uranium close to a nearby seasonal creek that drains near the site.
Geological scientist Kenneth Hurst Williams with the Lawrence Berkeley National Laboratory in Berkeley, Calif., told City Council of the findings during a Monday, June 16, workshop meeting. Williams and other scientists have been researching the East Rifle tailings site since 2007, under a contract with the U.S. Department of Energy, which removed tons of mill tailings from the East and West Rifle sites for storage in a cell north of Rifle in the 1990s.
Williams said samples taken from a creek and two wells just east of the proposed water plant site – which is just northeast of the East Rifle tailings site off U.S. Highway 6 – between March 2012 and May 2013 found readings as high as 100 parts per billion of uranium at a site near the creek. The federal Safe Drinking Water Act has a 30 parts per billion standard to be considered safe to drink, he noted.
“It looks like it’s natural and not related to the mining that went on in the area,” Williams said.
While the high readings do not mean the site cannot be used for the new water plant, since no groundwater will be used, it caught some council members by surprise.
The city has been reviewing the plan for the new water plant, after two bids for the project came in $8 million to $11 million higher than the city engineer’s estimate and the funds available to build the plant.
City Council was scheduled to consider the next step for the water plant during their special meeting after the workshop, but City Manager Matt Sturgeon said staff was still refining the plans and the item was delayed until their next meeting.
Earlier this month, Sturgeon approved a $75,000 contract with Kumar & Associates of Denver to do some geotechnical testing of soils at a 65-acre site adjacent to the original proposed location of the plant, which was given to the city decades ago by the Union Carbide Corp. The company milled vanadium and uranium at the East Rifle site and the larger West Rifle site, where the city wastewater treatment plant is located, as far back as the 1940s.
The city received two bids last month for the water plant project: Alder Construction, located in Salt Lake City, Utah, submitted a base bid of $33.1 million and PCL Construction, located in Phoenix, Ariz., with an office in Glenwood Springs, submitted a base bid of approximately $36.5 million.
The city received a $25 million loan from a revolving loan program, administered by the Colorado Water Resources and Power Development Authority, to build the plant. Two years ago, Rifle voters approved a 3/4 cent sales tax increase to help repay the loan. Sturgeon noted the delays have not affected the funding for the project. He said the sales tax cannot be used on other city needs.
The project was originally designed to include improvements to the city’s raw water pump station, a new 24-inch raw water pipeline to the new 40,000-square-foot plant, a radio tower at the Graham Mesa plant for remote data transmission of information about the city’s water system to the pump station and then by cable to the new plant, and connections to water transmission and main lines.
City officials have said the existing Graham Mesa water plant is aging, undersized to serve projected population growth and unable to meet possible tougher federal water quality standards in the future. Construction work was expected to last up to two years.
Plume moving slower than expected
Williams also told City Council that the main goal of the study – to see if the East Rifle contaminated groundwater will be naturally flushed into the Colorado River, where it will be diluted to safe levels – has found much slower migration than expected has occurred. Samples taken over the years continue to show groundwater contamination at similar levels.
In an interview on Tuesday, June 17, Williams explained a combination of microbial activity that converts uranium to an insoluble form and absorption by other microbes might be preventing the uranium from being flushed into the river.
A lack of expected flushing action has also been reported at other mill tailings sites in the Colorado River basin, Williams said.
“So we want to try and figure out why is this hanging around so much,” Williams said. “Getting a better understanding of this process can help us develop better estimates on how long it will take to naturally remediate these sites.”
The East Rifle site will continue to be tested and researched by Williams and other scientists for the next several years.
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