Shortly after We Energies reported the incident at its Oak Creek coal-burning power plant near Milwaukee, environmentalists tried to draw a connection with the December 22, 2008, massive slurry spill at the Tennessee Valley Authority’s Kingston coal plant in Roane County, Tenn., after an impoundment failed. That spill has led to a re-evaluation of coal ash by the U.S. Environmental Protection Agency.

Most of the old coal pile that collapsed at Oak Creek did not make it into the lake but, instead, remained on the bank. No one was injured in the incident. A month after the spill, the cleanup was almost complete. Water tests conducted by the Wisconsin Department of Natural Resources showed that Lake Michigan had not been polluted by the spill.