The bluff failure and landslide at the Oak Creek power plant sent less coal ash and dirt into Lake Michigan than was first projected, but what did end up in the lake cannot be recovered.

That's the assessment of the state Department of Natural Resources, the U.S. Coast Guard and We Energies.

An investigation is continuing into the cause of a bluff failure that sent coal ash from an old disposal area near the Oak Creek power plant into Lake Michigan on Oct. 31. Eric Nitschke, Southeast region director for the state Department of Natural Resources, said Monday his agency's investigation into the collapse's cause is expected to be completed in February.

Recovery of vehicles and equipment from the lake wrapped up in December, but officials have concluded there is no way to recover the ash and soil mix that went into the lake.

"Once coal ash enters the water, there are no effective containment strategies for this type of release beyond preventing additional ash on shore from mobilizing into the water," concludes a report by the National Oceanic and Atmospheric Administration, in conjunction with the Coast Guard.

The ash that traveled into the lake would be so dispersed that it would not have any significant environmental impact, the report found.