A unique public-private partnership is revitalizing the town of Corinna, Maine. This fast-track project involving a major Superfund site cleanup restored Corinna's downtown hub several years sooner than traditional Superfund cleanups by using an aggressive approach and a unique synergy developed among federal, state, local, and private stakeholders. As a result, this project was awarded an Engineering Excellence Award from the American Council of Engineering Companies (ACEC) and the Maine Chapter of ACEC.
Established in 1816, Corinna is a bucolic New England mill town 20 miles west of Bangor with a population of 2100. The town straddles state Route 7 and serves as a gateway to the Moosehead Lake region and nearby mountains. Corundel Lake, located just north of Corinna, lies along the second largest bird flyway on the East Coast and provides a home to ducks, herons, kingfishers, and Canada geese.
Eastland Woolen Mill operated a textile mill on the east branch of the Sebasticook River in downtown Corinna for more than 90 years, but in 1996 the mill was shuttered when the company filed for bankruptcy. The mill's closing had a major impact on the close-knit community. Stores closed, jobs were lost, and contamination was found on the mill's 25-acre site.
Process wastewater containing chlorobenzene compounds used in mill operation's had been discharged into the underlying soil, groundwater, and river sediments. The site was soon placed on the U.S. Environmental Protection Agency's National Priorities List, designated a Superfund site, and planning for the cleanup began. The mill was located over the river and contained a mill pond impounded by a dam. To effectively clean the site, the downtown's main roadway, a bridge, the river, and a historic building had to be relocated so the contamination could be excavated and treated. This posed a daunting task.
Fast-Tracking the Design
With overall responsibility for the project, the EPA retained the U.S. Army Corps of Engineers (USACE) to manage the entire project. MACTEC Engineering and Consulting, located in Portland, Maine, was contracted by the USACE to provide investigative and design services for the cleanup and restoration. As EPA's partner in the project, the Maine Department of Environmental Protection also dedicated substantial resources to the planning and implementation of the project.
In order to speed the design, primary stakeholders—including the Maine DOT, environmental organizations, and local officials—were encouraged to participate in the conceptual planning stage and attend workshops during the design phase. This hands-on involvement by the stakeholders helped expedite the formal design review and approval process and resulted in a quick consensus for the final design.
The design called for the excavation of contaminated soil and sediments, which included excavating and relocating the river channel and reconstructing the roadway and bridge over the new channel. The dam was permanently removed and the mill pond converted back to a free-flowing river. Contaminated sediment was excavated from the riverbed during low-flow conditions. Pumps and temporary bypass piping were used to divert river flow around the excavation area. Temporary box culverts were installed in the existing river channel to convey flows until the new roadway, bridge, and river channel construction were completed and new riverbanks were stabilized. Once all flows were diverted to the new river channel, the box culverts were abandoned in place and filled with flowable fill.
The river restoration design included creating a new free-running river with a low-flow channel for fish passage, channel blocks, riffles, runs, and pools. River-bank wetlands were allowed to naturally revegetate, avoiding costly landscaping. The river substrate was designed to mimic the substrate in the existing river. To provide a more environmentally friendly bank stabilization, riverbanks in many areas were designed with a geogrid mat instead of standard riprap. This material provided bank stability to withstand flood flows while allowing for growth of riverbank vegetation.
The river restoration methods integrated natural restoration into the design resulting in cost savings—components were selected based on river flow patterns that stabilized after dam removal, minimizing the effort needed to successfully complete the restoration. Reaching consensus on the strategy among all stakeholders saved the project time and money. By returning the mill pond to a free-flowing river and permanently relocating the river, the cost of having to abandon the temporary channel and recreate a permanent channel along the former alignment was avoided.