Columbia Dam Removal & River Restoration, Knowlton, NJ

Ecosystem Restoration & Mitigation
Dam Removal & River Restoration

August, 2019


Project elements

Removed 18’ high, 330’ long dam impounding 1.5 mile-long lake, and additional remnant dam.

Bank stabilization and riparian corridor planting

Scour protection for Interstate Route 80 bridge and 2 additional county and local bridges

Resting pools and weirs installed for fish passage in high velocity area under Route 80 bridge.


The project required extensive coordination between The Nature Conservancy and a project team which included engineering firm Princeton Hydro and SumCo Eco-Contracting.

Project Synopsis

The Columbia Lake Dam was located on the Paulins Kill River just a quarter mile from its confluence with the Delaware River. Since 1909, the dam impounded a 43 ac lake for ice cutting and to power homes from Knowlton NJ all the way to Philadelphia (almost 90 miles). Removal started in June 2018 during a challenging year of very high water flows. After notching and lowering the lake, the dam was removed and SumCo restored the newly exposed riparian corridor on a NJ Wildlife Management Area, opening up a 10-mile river stretch. Migratory fish returned to this watershed after over 100 years.


The Columbia Lake Dam was ranked by conservation groups in the top 5% of dams with the highest negative impacts on the East Coast. This dam removal restored connection to the third largest New Jersey tributary to the Delaware, improving water quality in a river that supplies drinking water for 17 million people in four states. After being cut off for a century, migratory fish including American Shad and American Eel returned to 10 miles of the watershed, in a restored natural flow regime now able to transport sediment to starved areas of the Delaware. Recreationists hungry for fishing, kayaking, and canoeing will also benefit from the newly opened river access. Local businesses are getting a boost from the ecotourism, and critical transportation infrastructure resilience has been improved by this project. The Columbia Lake Dam removal has become a model for the collaboration and partnership efforts needed to remove dams and restore rivers.

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