Kehm Run Dam Removal Design

Princeton Hydro was contracted by American Rivers to design, apply for permits, and provide construction administration services for the removal of the Kehm Run Dam, an earthen embankment, 270-feet long by 22 feet high, with a cast-in-place ogee spillway, about six (6) feet in height. The former impoundment was five (5) acres in size and contained an estimated 40,000 cubic yards of accumulated sediment. Princeton Hydro conducted a bathymetric survey, developed engineering plans, performed hydrologic and hydraulic analysis, applied to PADEP Dam Safety for a Restoration Waiver, and also to the York County Soil Conservation District plan approval. As part of the regulatory activities, Princeton Hydro subcontracted for a bog turtle (Glyptemys muhlenbergii) Phase I assessment, PA Historic and Museum Commission (PHMC) notices, and filed for a PA Fish and Boat Commission (PFBC) water lowering authorization. The dam was breached in 2019, and the project was completed the following year, with follow up site visits in 2021.

The project was challenging due to the quantity of sediment encountered and its fine-grained nature as a colloidal (very small clay particles), with a relatively small stream immediately downstream. As a result of PADEP Dam Safety inspecting the site, expressing their concerns about the quantity of sediment, Princeton Hydro prepared a revised breach design that provided containment of the sediment, while deregulating the dam. As a result, the former lakebed created an opportunity for its use to as a nature-based BMP to address nutrient loading to the Susquehanna River and Chesapeake Bay. The Susquehanna River Basin Commission saw this opportunity and funded a next phase to further enhance the wetlands created to improve sediment capture from the watershed.

This was a challenging project and has been documented by American Rivers in their blog as “Taking the Lemons and Making some Dam Lemonade”. As a project that provided significant lessons in adaptive management and making the most out of a challenging project.