Healthy ecosystem: Turning an ash pond to a wetland

Rendering of converted wetland

Dow and The Nature Conservancy (TNC) developed a nature valuation methodology to support Dow’s Valuing Nature Goal. A Dow-TNC team used this methodology to determine both the business value and environmental benefits that an ecological restoration would bring to a former ash pond site.


A 23-acre ash pond site adjacent to Dow’s Michigan Operations plant along the Tittabawassee River was set for closure. The site was a cooling pond that was built in the late 1940s to cool water from an on-site coal-fired power plant. The site was surrounded by an earthen berm constructed of sand and silt, with approximately 90,000 cubic yards of ash in place. Dow’s remedial objective for the ash pond site was to address soil and groundwater contamination on the property associated with past operations. The project had a defined closure strategy, which involved putting a traditional cap in place and long-term maintenance, including groundwater treatment and monitoring. The ash pond property is adjacent to the Poseyville Riverside project, a 14.5-acre abandoned concrete facility that is owned by the City of Midland.


The goal was to close the ash pond in a way that best reduced operational and maintenance costs and liability, while meeting state agency requirements and enhancing ecosystem services.


After an extensive study, Dow chose an ecological restoration that included excavating the ash and associated soil for secure disposal in an approved landfill and restoring the historic wetland, forest and prairie on the property. As part of an overall, cohesive restoration plan, Dow also studied the benefits of ecologically restoring the adjacent property owned by the City of Midland. Ultimately, the Dow Riverside Wetlands will establish a 23-acre conservation wetland that adds recreational amenities to the City of Midland, while improving nearly a mile of riverfront across from the downtown area. The restoration of the former ash pond site to a wetland improves important ecological functions in the area while enhancing natural habitat through the reintroduction of more than 25,000 plants, including 60 species of trees, shrubs, grasses and other native plants. The natural diversity of the project area supports biodiversity, improves water and air quality, and creates an important connection to a vast network of parks, open spaces and trails in the Midland area.


It is estimated the project will result in $2 million (net present value over 10 years) versus a standard brownfield restoration, mainly due to reduced costs and liability.Read more about the project’s evaluation here.