Coal ash deposits played big role in Oak Creek bluff collapse

OAK CREEK -- State regulators investigating a bluff collapse at an Oak Creek power plant in October 2011 say one of the biggest factors that led to the collapse appears to be coal ash that was deposited in the ravine in the 1950s and 60s.

The state DNR says the depth of the ash deposit was up to 35 feet at some locations within the former ravine. While coal ash is used as structural fill on construction projects, it can be equivalent to natural soils under the proper conditions -- meaning it can erode.

Officials say the utility may have violated regulations when it built a pond in and above a coal-ash landfill on its Oak Creek site.

The collapse swept mud and ash into Lake Michigan. No one was hurt.