Loughberry Lake Dam

Beneath the bustling Route 50 access corridor, Loughberry Lake Dam impounds Saratoga Springs’ principal water supply source. Schnabel provided engineering services to bring the dam into compliance with New York State Department of Environmental Conservation (NYS DEC) dam safety regulations and New York Codes, Rules, and Regulations (NYCRR) Part 673 Dam Regulations.

The dam’s facilities comprise a 40-foot-high earthen embankment, concrete spillway, 48-inch CMP auxiliary spillway, gated low-level outlet through the principal spillway, and an outlet-works tower with water supply gates. We initially performed hazard class and engineering assessments and developed both an Emergency Action Plan (EAP) and an Inspection and Maintenance Plan. The hazard class assessment utilized results from detailed 2-D hydraulic modeling and inundation mapping of dam breach flows to assess potential downstream hazard drivers in comparison with NYS DEC Publication DOW TOGS 3.15 – Guidance for Dam Hazard Classification.

The comprehensive engineering assessment (EA) was performed consistent with NYS DEC Publication DOW TOGS 3.1.4 – Guidance for Dam Engineering Assessment Reports. The EA required a dam safety inspection; engineering evaluations for the watershed hydrology, spillway hydraulics, and embankment stability; and conceptual remedial measures to address identified deficiencies. The new EAP was produced using inundation mapping developed from 2-D hydraulic modeling, and it included updated notification flowcharts, preparations, and responsibilities. The inspection and maintenance plan was developed to assist Department of Public Works staff with maintaining dam safety through the identification and documentation of ongoing activities. We also recommended improvements for upstream slope stability and spillway capacity.

Following an extensive geotechnical exploration program of both upstream (underwater) and downstream embankments, Schnabel is now completing the design of the comprehensive rehabilitation of the dam.  The rehabilitation including refurbished principal and auxiliary spillway conduits, a new principal spillway and water supply connection, a new energy dissipation structure for transitioning principal and auxiliary spillway discharges to the downstream channel, and rock-filled stabilization of the underwater upstream embankment slope.