Interior Alaska’s main electric utility is looking to snuff out lingering groundwater contamination caused by its now-defunct coal ash ponds in Healy.
Environmental Specialist III Toni Geroy said Wednesday that Golden Valley Electric Association (GVEA) has made significant progress on getting the problem under control since identifying it in 2018, but that there’s still another step to go.
The issue gained attention after the Environmental Protection Agency (EPA) set the first federal limits on the amount of toxic metals power plants can discharge in wastewater in 2015.
GVEA ended up recording six toxins in excess of the EPA standards at multiple monitoring sites, which prompted plans to stop use of the unlined ash ponds in a bid to stymie the release of heavy metals into the surrounding soil.
By 2022, Golden Valley had finished cleaning out and backfilling the ponds, according to the new Corrective Measures Assessment, presented Wednesday. Citing the monitoring data since then, Geroy said the approach has proved pretty successful.
“When Golden Valley stopped sending ash to the ponds, predictably, groundwater responded pretty fast,” she said.
Research has linked exposure to toxins commonly in coal ash to cancer, nervous-system disorders and other complications. In one extreme example, a 2008 spill in Tennessee is estimated to have killed more than 50 people who helped clean it up, and sickened many more.
The Interior Alaska utility had been using the ponds since the early 1990s to process ash produced by Healy Unit No. 1 – the older of its two coal power plants. With the ponds now reclaimed, the coal ash has been diverted to an internal processing system in Healy Unit No. 2 for the last few years, Geroy said.
That remedy could create separate hurdles for Golden Valley in the future. The utility had formerly intended to retire the Healy Unit No. 2, which has been less reliable than its older counterpart. But last year, the GVEA board of directors opted to extend the plant's life due to the natural gas crunch in the Cook Inlet.
Geroy said GVEA staff will have to figure out what to do with the ash if Healy Unit No. 2 does eventually get retired, but that they’ll cross that bridge if and when they get there.
“Those two plants are united in many ways that would need to be untangled if we retired either of them,” she said. “So we would have a lot of work to do.”
In the meantime, shutting up shop at the coal ash ponds appears to have worked – for the most part – for getting a handle on the rogue toxic metals. According to the Golden Valley data, contaminants have dropped to federally acceptable quantities at almost every monitoring well.
But the utility is still seeing antimony, arsenic and fluoride numbers come in too high at one site, which Geroy says corresponds to about a fifth of an acre. And Golden Valley needs to enact additional corrective measures to bring those levels down.
To do that, the new assessment presented Wednesday proposes and analyzes three treatments against a series of criteria, including things like expected performance, reliability, ease of implementation and safety impacts, among others.
The report ultimately favors the corrective measure that relies on so-called “geochemical manipulation.” That method involves injecting a mixture into the ground that’s designed to react with and immobilize the unwanted heavy metals released by the unlined ash ponds.
GVEA could finalize their selection in as little as 30 days.