Removal of vegetation also looked at as possible contributing factor
OAK CREEK, WI — “Water takes the easy way, the path of least resistance, as it flows over the surface or underground.
Water was doing just that when it became a player in Monday’s dramatic bluff collapse at We Energies’ Oak Creek Power Plant on the Lake Michigan shoreline, a geologist said.
The easiest path available to water seeping out of the bottom of a hilltop unlined storm water retention basin at the property was the adjacent coal-ash filled ravine, said Doug Cherkauer, emeritus geosciences professor at the University of Wisconsin-Milwaukee. Ash is less compact and less stable than the clay rich glacial soils in the rest of the hill or the bottom of the ravine, he said.
Monday’s dramatic bluff collapse at the property likely will be linked to water gradually saturating ash at the bottom of the old ravine, essentially lubricating the area between the ash and the clay-rich till at the bottom of the ravine, Cherkauer said Wednesday.
Saturated ash would have started oozing out of the bottom of the old ravine causing the top of the bluff to collapse and fall down the hill, Cherkauer said.
Mud and ash cascaded more than 300 feet down the slope to the lake, destroying a temporary storage building and carrying a trailer, storage units, a pickup truck and construction equipment in its wake. No worker was injured.
Building the storm water pond so close to the old ravine and without a lining were a pair of bad decisions, Cherkauer said.”
— Thomas Content and Don Behm, Milwaukee Journal Sentinel