MARQUETTE — Another step in the long and complex process of decommissioning the Presque Isle Power Plant in Marquette is in the works, as the last coal combustion residual landfill at the power plant is being covered and shut down.

This work is being done in conjunction with the closure of the coal-fueled plant, which was retired on March 31 by We Energies, a WEC Energy Group subsidiary.

“With the retirement of PIPP, We Energies has no further need of landfill capacity and closure of Landfill #3 has been initiated,” Alison Trouy, spokesperson for WEC Energy Group, said in an email.

The company operated three landfills occupying around 200 acres adjacent to the power plant for nearly 25 years.

The first two landfills closed in 1994 and 2006, respectively. The two closed landfills currently have “long-term maintenance and monitoring being conducted under post-closure plans approved by the Michigan Department of Environment, Great Lakes, and Energy,” EGLE officials said in a press release.

While the three landfills initially occupied around 200 acres, less than 8 acres of landfill area remain active. Construction of the final cover began in June and it’s anticipated that the final cover will be placed over the area by October, Trouy said.

At this time, the “final cover over the ash landfill, including a flexible membrane cover liner to prevent infiltration, is nearly completed,” EGLE Materials Management Division District Supervisor Philip Roycraft said in an email.

Furthermore, “the EGLE Materials Management Division will be overseeing the closure under the Michigan solid waste law and new amendments for coal combustion residuals passed by the Michigan Legislature in 2018,” EGLE officials said in a press release. “Once closed, the 30-year post-closure period required by Michigan law will commence for all three landfills, with continued maintenance and monitoring.”

The site is currently permitted under the National Pollution Elimination System for discharge-treated coal combustion residual landfill leachate, as well as cooling water and stormwater, according to EGLE officials.

In the past, the site discharged up to 140 million gallons per day of cooling water, but this discharge will stop with the closure of the plant, a press release about the closure states.

Stormwater generated on site that comes in contact with regulated materials will still be addressed by the site’s NPDES permit, while leachate will be treated at the Marquette Area Wastewater Treatment Plant, EGLE officials said.

“Landfill leachate (water in contact with ash) is being pumped and hauled for treatment at this time, but volumes have been decreasing since installation of the cover,” Roycraft said.

Closing the Presque Isle Power Plant is part of a a larger plan by WEC Energy Group to move from coal to natural gas, wind and solar energy sources. On the same day the coal-fueled power plant was closed, Upper Michigan Energy Resources Corp., another subsidiary of WEC Energy Group, began commercial operation of the A.J. Mihm Generating Station in Baraga Township and the F.D. Kuester Generating Station in Negaunee Township, Trouy said.

“The shift away from coal power should significantly cut Michigan’s emissions of carbon dioxide, the most prevalent greenhouse gas associated with global warming,” Trouy said. “The shift from coal to natural gas should also result in significant reductions in the emissions of mercury, acid gases, and many toxic metals. These environmental benefits should also come at a lower cost. A study by the Institute for Energy Research, published in 2016, documented that natural gas power is now 16% less expensive than coal power.”

The closure is a complex and ongoing process, UMERC Director Richard Rayborn told the Marquette City Commission in May, with the company tentatively planning demolition to begin in 2021.

At this time, the city of Marquette and We Energies are still in discussions about what the remainder of the power plant property will be used for after the plant is decommissioned, officials said.

“We are still discussing the future of the power plant property with the city of Marquette,” Trouy said. “Our focus for now is the continued, multi-year decommissioning process.”

Cecilia Brown can be reached at 906-228-2500, ext. 248. Her email address is cbrown@miningjournal.net.