The Concord River is one of the largest tributaries to the Merrimack River and historically contained significant runs of river herring and American shad. Three man-made structures exist on the river and include the Middlesex Dam, the Centennial Island Hydroelectric Project, and the Talbot Mill Dam.

The purpose of the Middlesex Dam Breach Stabilization Project is to maintain and improve upstream fish passage at the breached dam site located on the Concord River in Lowell, Massachusetts. This site now consists of an island, and minor and major channels surrounding what was once the concrete abutments of the dam. In the early 1980s the dam on the major channel was extensively breached. The remains of the dam now include only the concrete abutments. A hydraulic assessment of the site has indicated that during low flow conditions in the spring ( 650 cfs), fish passage would be impeded at this site.

The Natural Resources Conservation Service has conducted a site survey and developed plans showing dimensions and relative positions of the island side abutment and adjacent ledge in the main channel at the Middlesex Dam. Given the results of site surveys and the hydraulic assessment, it is now intended that an eight-foot-wide channel of smooth laminar flow be created along the island side of the main channel. Options to achieve this objective have been reviewed and it is expected that sections of ledge in the river channel, that result in turbulence along the island side bank, will be removed using a combination of mechanical equipment, explosives, and manual labor. The project is now in the permitting stage and it is expected that it will be completed in late summer or early fall during low flow periods.