After a study done for the Environmental Protection Agency declared a Columbia lake a “high” rating for hazard potential, the city’s Water & Light Department is beginning top study just how the lake was built.
“Part of the problem here is that we don’t have a lot of documentation of when that lake was built,” Water & Light spokeswoman Connie Kacprowicz said.
CDM Smith performed a study for the EPA in August 2012 on More’s Lake, a body of water north of the city’s Municipal Power Plant. The city uses the lake to store coal ash slurry, a mixture of water and coal powder once the coal is burned for electricity. The report says heavy rains could cause the lake, and the coal ash slurry, to flow over the lake’s dam and into an unnamed tributary of Bear Creek. The “high” rating for hazard potential comes from “urban and commercial development downstream of the impoundment.” The Bear Creek runs east to west just north of Interstate 70 in Columbia, meeting with the Perche Creek.
However, the report also says the lake showed no signs of ever flooding, either over the sides or through the dam.
“We’ve been using it since the 1950s, and we’ve never had any events where it’s overflowed, and obviously we’ve had some heavy rains during that period,” Kacprowicz said. “But it’s just one of those things where they just want us to be safe.”
The report cites a lack of documentation on the lake’s construction in the late 1800s as a main reason for the high hazard rating. Those documents contain engineering and historical records necessary to perform the analysis.
“Supporting documentation was not sufficient with regard to acomplete analysis of impoundment safety,” the report said.
Kacprowciz said there’s nearly no hope in finding those original records. In place, a local engineering firm conducted tests on the soil both in and around the lake and dam to determine if the lake is properly holding the coal ash.
The EPA began reviewing lakes used by coal-burning plants after the Kingston Fossil Plant near Knoxville, Tenn. spilled more than a billion gallons of coal ash slurry into nearby rivers in 2008.
Columbia Water & Light has used More’s Lake for coal ash storage since the 1950s. The wet mixture settles to the bottom of the lake, and crews dredge it out to dry. The dried ash is used as cinders street departments can use on icy roads for traction.
The plant produces around six percent of the city’s electricity, burning coal and wood. Kacprowicz said the plant dumped 5-10 thousand tons of coal ash slurry into More’s Lake last year.
CDM Smith’s report also recommended the city develop a formal plan to maintain the lake and dam.
“We’ve always had a maintenance plan for that, kind of an informal plan, and the EPA is suggesting that we hire a consultant to go through and formalize all those operations and maintenance plans, just to make sure it’s secure,” Kacprowicz said.
The U.S. Army Corps of Engineers conducted a study on the dam in More’s Lake in 1980. That report also cited the lack of engineering records on the lake itself, and also called the lake a “high” risk for hazard.