Platte River Power Authority to update monitoring wells

The Environmental Protection Agency’s coal-combustion residuals rule went into effect on Oct. 19, requiring the Platte River Power Authority to update its groundwater monitoring wells at the Rawhide Energy Station north of Wellington.

According to Ben Brents, a representative from the Denver branch of the EPA, the implementation of energy station’s groundwater monitoring and corrective action plans should be completed by October 2017, 30 months after the publication of the rule in April 2015.

“A summary of the requirements to be completed includes: install the groundwater monitoring system; develop the groundwater sampling and analysis program; initiate the detection monitoring program; and begin evaluating the groundwater monitoring data for statistical increases of background levels,” Brents said.

The Federal Register defines coal-combustion residuals, or CCRs, as a byproduct of the combustion of coal in order to generate steam for heat and electricity. There are two main types of CCRs: fly ash and bottom ash. Both pose risks to human health and the environment when they are not disposed of properly. The new EPA rule mandates that CCRs be dealt with in three ways: beneficial use, such as repurposing the waste; on-site disposal; or off-site disposal.

Courtney Stewart, an environmental engineer at the PRPA, said bottom ash is mixed with water and pumped through pipe into two transfer ponds. The transfer ponds are constructed below the existing grade to safely contain the aqueous solution. The transfer ponds are also lined with 18 inches of clay in order to contain the waste and prevent contamination.

When one transfer pond fills, the water is allowed to evaporate and the remaining bottom ash is dried and trucked to a monofill, which is a landfill only for the ash. Chris Wood, the PRPA environmental servicers manager, said there is another naturally occurring clay liner at the monofill.

“The monofill is located on an engineered clay liner and an impervious, naturally occurring shale layer which is 1,000 feet thick and very unlikely to be contaminated,” Wood said.

In this monofill, the CCRs are compacted and contoured to match the natural topography of the area. Once the monofill is filled, the native soil and seeds are brought in to diminish the monofill’s environmental impact.

“The ash is contoured, covered by 2-feet of topsoil, and seeded for stabilizing vegetation,” Wood said “This process is very effective in terms of containing the ash and preventing any type of offsite contamination.”

Additionally, Wood said, the PRPA diverts storm water to avoid the infiltration of the monofill by groundwater. According to Wood, this keeps any contaminants from reaching the water table.

Colorado Department of Public Health and Environment spokesman Warren Smith said when Rawhide’s monofill was last inspected in 2012, which it passed.

“CCR monofills are usually inspected on a one- to five-year cycle, depending upon the facility’s compliance history,” he said.

According to Stewart, Rawhide produces about 70,000 tons of CCRs per year, of which roughly 9,500 tons is fly ash put to beneficial use. The rest is disposed of in the monofill. Wood said the PRPA follows standard best practices when disposing of CCRs and drilling monitoring wells. Wood said the PRPA still monitors the groundwater, both upstream and downstream from the monofill to ensure there is no contamination.

The new EPA rule requires an update to the monitoring wells, but only requires the power company to drill two wells at Rawhide. Brents said the number of wells Rawhide was required to drill was based on a site-specific combination of hydrogeologic and groundwater sampling standards. PRPA has eight monitoring wells, which it has monitored for 20 years, and is in the planning phase of drilling 10 more, Wood said.

According to Wood, the PRPA also uses standard best practice when sampling wells and testing the samples. A third-party collects the samples and conducts the tests in order to ensure no conflicts of interest.

“The sampling procedure includes bailing the well and allowing ground water to recharge,” Wood said.

Stewart added: “No analysis is done on site, all of [the tests are done] at independent labs.”

According to Smith, it is the PRPA’s responsibility to have the samples taken and report the results. There are strict criminal penalties for false reporting, which is a strong incentive for the accurate reporting of results, he said.

“In addition, we receive the facility’s groundwater monitoring report every year,” Smith said. “The state always has the option of taking independent groundwater samples if there are concerns about the data being reported by the facility.”

One of the last provisions of the EPA rule is to take corrective action if groundwater contamination is detected.

Wood said in the event of contamination, the PRPA would immediately notify the authorities and regulators, and any affected landowners. He added, “No drinking water wells are associated with the aquifer located below the monofill.”

“There has never been a release of ash from Rawhide’s monofill or bottom ash transfer ponds,” the PRPA’s official website says. “There has been no evidence that anything contained in the ash has leached into ground or surface water.”

Smith confirmed the PRPA’s claim and said that Rawhide has not come under any scrutiny from the health department regarding its monofill.

Editor’s note: This story was updated Feb. 4, 2016 to reflect correct amounts of fly ash used for beneficial purposes and to better described what is sluiced to engineered retention ponds.

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