Coal Ash Pond Dewatering – Muskegon MI

The BC Cobb Plant served West Michigan from 1948 to 2018, providing power from its location on the shores of Muskegon Lake. After nearly 70 years of operation, the plant was decommissioned in 2018, leaving the site dormant.

In the summer of 2020, Diversified Dewatering was contracted to dewater the former coal ash ponds at the site. This challenging project was constrained by limited access, as the area was surrounded by dike walls on three sides. With access roads barely wide enough for standard trucks, all equipment and materials had to be transported using off-road tracked vehicles.

The project began with DeWind One-Pass Trenching, the parent company of Diversified Dewatering, installing a bentonite slurry wall along the north and west sides of the ash ponds. Once the slurry wall was in place, Diversified Dewatering commenced dewatering operations.

The site was reshaped by the prime contractor, and the ponds were drained to the water table elevation of approximately 580 feet (Lake Michigan’s level), with a final excavation depth of 567 to 565 feet—12 to 15 feet below Muskegon Lake’s surface. Diversified installed 12 deep well casings at strategic locations around the site to lower the groundwater table, allowing for safe coal ash removal. These wells were connected to a common HDPE discharge line leading to an on-site groundwater treatment system.

Additionally, wellpoint systems were installed along the east dike wall embankment and the south side of the site to enhance dewatering efforts. Once dewatering was complete, the entire site was stripped to the virgin sand beneath, and all coal ash material was transported off-site to a certified landfill.

The project, which spanned just over a year, was completed safely, on time, and in collaboration with the prime contractor and other subcontractors.

Project Highlights

– Integrated Solutions: Combined slurry wall installation and standard dewatering techniques ensured project success.

– Efficient Operations: Electric-powered dewatering pumps and treatment controls minimized downtime.

– Large-Scale Excavation: Successfully dewatered and maintained 33 acres of mass excavation.

– Overcoming Access Challenges: Leveraged track-mounted drill rigs and jetting equipment to navigate limited site access.