Warren Hills Dam Decommissioning

Princeton Hydro was contracted by the Warren Hills School Regional School District (WHRSD) to provide a completed dam inspection, dam breach scenario, hydrologic and hydraulic (H&S) modeling, inundation analysis, and hazard classification for the Warren Hills Dam. Located on a tributary of Pohatcong Creek in Washington Township, Warren County, the earthen dam was constructed circa the 1930s and was reconstructed in the 1990s involving spillway repairs.

Upon the completion of Princeton Hydro’s careful evaluation of alternative assessments contained in the inspection report, the Warren Hill School District made the decision to seek dam removal. The unsatisfactory condition rating contained in the inspection report, as well as the need for WHRSD to us an adjacent structure for academic activities in Fall 2020, contributed to the decision.

Princeton Hydro was then contracted to facilitate the dam decommissioning and throughout the project development, performed the site survey for the identification of hazardous materials; wetland delineation; site investigation; and sediment sampling, analysis, and probing. Princeton Hydro preformed a stream assessment of the channels upstream of the impoundment, and the downstream mill race. Sediment probes were completed throughout the impoundment to determine the depth of unconsolidated material (sediment) and provide a general understanding of the substrate encountered at refusal depth. The proposed channel within the impoundment reflected existing upstream reaches, the anticipated natural channel type, and the assumed pre-dam channel: a boulder dominated cascade, approximately 12 feet wide, up to two-foot max depth, and 10% slope, with occasional/irregular boulder steps. As part of the engineering design, Princeton Hydro also conducted planning, permitting, and construction management and oversight.

The completed design involved sediment excavation and onsite storage, as well as stable channel creation. Through an accelerated schedule Princeton Hydro worked to complete the permitting and dam removal before the start of the 2019 school year.