No one was inside a trailer nor three box-like storage units that were sucked up in a mudslide as a large section of bluff collapsed Monday next to the We Energies Oak Creek Power Plant. Credit: Mark Hoffman

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Oak Creek - A large section of bluff collapsed Monday next to the We Energies Oak Creek Power Plant, sending dirt, coal ash and mud cascading into the shoreline next to Lake Michigan and dumping a pickup truck, dredging equipment, soil and other debris into the lake.

There were no injuries, and the incident did not affect power output from the plant.

When the section of bluff collapsed and slid from a terraced area at the top of a hill down to the lake, Oak Creek Acting Fire Chief Tom Rosandich said, it left behind a debris field that stretched 120 yards long and 50 to 80 yards wide at the bottom.

Aerial images show a trailer and storage units holding construction equipment tumbled like Tonka toy trucks and were swept along with the falling bluff in a river of dirt that ended in the water.

"This is definitely a freak accident," U.S. Coast Guard Lt. j.g. Brian Dykenssaid.

As a company hired by We Energies began cleanup in Lake Michigan, the utility confirmed that coal ash was part of the debris.

"Based on our land use records it is probable that some of the material that washed into the lake is coal ash," We Energies spokesman Barry McNulty said. "We believe that was something that was used to fill the ravine area in that site during the 1950s. That's a practice that was discontinued several decades ago."

The Environmental Protection Agency is in the process of developing stricter regulations of coal ash following a 2008 Tennessee coal ash pond washout that created a devastating environmental disaster.

No one was inside a trailer nor three box-like storage units that were sucked up in the mudslide, which also pushed a pickup truck into Lake Michigan and destroyed a temporary tool storage shed, We Energies spokesman Brian Manthey said. Some of the equipment was being used to dredge a storm water retention pond close to the lake.

Noting that about 100 construction workers were in the area at the time of the incident just after 11 a.m. Monday, Manthey said "we're very fortunate that there were no injuries reported." The construction workers are not We Energies employees.

Rosandich said contractors were taking an inventory of what exactly was lost in the mud slide.

Fuel sheen on lake

A fuel sheen covered the surface of Lake Michigan next to the plant Monday afternoon. Clean Harbors, the company hired by We Energies, will deploy 1,500 feet of linear boom on the water to contain the debris and fuel. McNulty said the weather forecast for Tuesday is favorable for cleanup of the lake.

The bluff failure was near a new air quality control system under construction. Following the collapse, authorities were testing the soil for stability as well as testing soil around the air quality control building under construction. Manthey said there was no danger of a further collapse.

Just what caused part of the hill to collapse was unknown. The National Weather Service office in Sullivan reported only 0.23 inch of rain fell at Milwaukee's airport Sunday and the only precipitation prior to that was a trace that fell on Oct. 27, meteorologist Ed Townsend said

University of Wisconsin-Milwaukee geology professor Tom Hooyer said that based on aerial images of the site, seepage from a high water table is more likely the cause of the failure than erosion from the lake especially considering Lake Michigan is about 200 feet below the bluff site that failed.

Hooyer questioned whether the retention pond near the site of the collapse had a lining. If not, it's possible seepage from that pond could have loosened the nearby soil, he said.

Manthey said a storm water retention pond uphill from the mud slide is not lined.

Power continued generating at both the original and new coal plants. Because the pollution control equipment was not yet hooked up to the plant, the incident didn't affect operations at either plant, Manthey said.

Oak Creek's water utility was also not affected because the community's water intake pipe is two miles north of the power plant and one mile out into Lake Michigan, Oak Creek utilities engineer Mike Sullivan said. Oak Creek supplies water to residents of its city as well as Franklin and the northern half of Caledonia.

Oak Creek water utility officials were worried that the water pipes it uses to supply water to the We Energies plant might have been severed in the bluff collapse but Sullivan said that did not happen.

Debris flows south

Maureen Wolff lives in Caledonia about a mile from the power plant and can see the plant's smoke stacks from her home. She walked to the lakefront shortly after the incident and was dismayed to see lots of debris and wood floating south toward Racine. Because of the dark color of the debris, Wolff wondered if coal ash ended up in the lake.

"All this is going along the coast line and they're telling people all it is is just a few trailers and possibly some tools. No one is saying what exactly is in it," said Wolff, a Caledonia resident for more than 50 years.

Later Monday afternoon, We Energies confirmed that coal ash was likely in the debris.

A local environmental group leader said coal ash was disposed in multiple locations over the years, when environmental rules were much more lenient.

"We definitely want the environmental agencies and We Energies to study how much of that coal ash, if any, went into Lake Michigan because it does pose such a threat to human health and the environment," said Cheryl Nenn, Riverkeeper with the group Milwaukee Riverkeeper.

Wisconsin has more stringent coal-ash disposal rules than many states, Nenn said, but there are still concerns given the historic practices of ash disposal before the 1970s brought new environmental regulations like the Clean Air Act and the Clean Water Act.

"The (Tennessee) disaster in 2008 highlighted the need to have consistent regulations nationwide and more regulation as to where these things are stored, how they're monitored, and how closely they're put next to drinking water sources," Nenn said, noting Lake Michigan's role as a source for drinking water for more than 40 million people.

The air quality control system project under construction at Oak Creek is the second most expensive construction project ever undertaken by We Energies, with a price tag of $900 million. Construction began in 2008.

The project is adding scrubbers and other pollution control equipment to reduce the emissions of sulfur dioxide and nitrogen oxide.

The air controls will serve the original Oak Creek coal plant, which has four boilers that opened from 1959 to 1967. The original coal plant is just south of the new two-plant coal operation that opened earlier this year, at a cost of more than $2.3 billion.

During an investor conference call last week, company Chairman and Chief Executive Gale Klappa said the project was about 90% complete and was on time and on budget, with the new controls expected to undergo testing before completion in 2012.

In a report filed last week with the state Public Service Commission, We Energies said the air emissions control construction project had gone 2.4 million hours without a lost-time injury.

In 2008, We Energies hired the Washington Division of San Francisco-based URS Corp. to perform the engineering, management, engineering, procurement, construction and commissioning for the project. Known as Washington Group until it was sold to URS, the contractor did a similar pollution-control project on the We Energies coal-fired power plant in Pleasant Prairie several years ago.

URS Washington also built the new natural gas-fired power plant in Port Washington for We Energies, and a coal-fired power plant near Wausau for Wisconsin Public Service Corp.

Journal Sentinel reporters Thomas Content and Sharif Durhams contributed to this report.