Retrofit work on Laramie River Station ponds continues on schedule

Laramie River Station's bottom ash pond 1 with its new liner installed. In the background of the photo, you can see bottom ash pond 2.

 Crews completed work to retrofit the liner on the Laramie River Station bottom ash surface pond 1 in early January. The work is being completed to comply with the Environmental Protection Agency’s (EPA) Coal Combustion Residuals (CCR) Rule. The three coal-fired units at Laramie River Station located near Wheatland, Wyoming, are subject to the rule.

The EPA’s CCR Rule, which took effect in October 2015, establishes standards for the disposal of solid waste in landfills and surface impoundments. Basin Electric is reconstructing two bottom ash ponds (BAP1 and BAP2), as well as an emergency holding pond. The east emergency holding pond work was completed in September 2020.

Bobby Nasset, Basin Electric supervisor of civil engineering, said the project started last year with treating existing wastewater with a mobile water treatment plant to remove 65 million gallons from the ash ponds to the raw water pond, which is used for plant operations. Then, more than 200,000 cubic yards of waste and contaminated subsoil were removed before installation of the new, two-part liner.

“The new liner system includes two layers: geosynthetic clay liner (GCL) went down first, and then HDPE, or high-density polyethylene,” Nasset said. “There was a lot of coordination moving hundreds of millions of gallons of wastewater. The solid waste has been tricky to work with because it doesn’t dehydrate well and we had to use sumps and trenches to collect and pump water out. We had a lot of help from the plant staff at Laramie River Station, especially considering that we were doing this during a time of year when pipes can freeze up.  The staff at the plant has come up with a lot of solutions for changing conditions.”

Nasset said the goal was to finish this work as soon as possible because Apr. 11 is the last day water can be sent to non-retrofitted ponds from the plant. “We are essentially playing musical chairs with the water, draining it from the pond we are working on, into another compliant pond, and then back into the pond we have retrofitted,” Nasset said. “Right now, we are filling bottom ash pond 1 so it can be used for operations.  Then we can start dewatering bottom ash pond 2. We will work on removing solid waste from pond 2 this spring followed by liner installation in the summer.”

Kevin Solie, Basin Electric senior environmental compliance administrator, said pond 1 was found to have a minor seepage leak. Basin Electric worked with an engineering firm to develop a plan for remediation on that pond. The method chosen involves the use of proven, reliable groundwater pumping technology and is expected to restore the underlying aquifer faster than other alternatives.  “We’re moving quickly. The reconstruction of the pond removes the source of groundwater impacts and the installation of groundwater extraction wells should be finished by late summer,” Solie said. “It’s important to note that the leak did not extend beyond the plant site, and did not impact anyone’s water, wells, or residents downstream.”

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