Snooks Pond Dam Repair and Rehabilitation

JMT, as Spectra Environmental, provided engineering services for the rehabilitation of the Snooks Pond Dam, which abuts a private residence, and related environmental services. Spectra performed the hydrologic analysis for the drainage basin and the hydraulic design of the new discharge control features and completed an environmental assessment and permit applications. The team conducted a hazard classification analysis, a geotechnical study, and stability and seepage analysis.

Spectra initially designed a replacement of the dam before the client chose to rehabilitate the existing dam. The dam rehabilitation consisted of installing a full-height concrete skin on the upstream face of the dam to correct seepage problems, and the addition of service and auxiliary spillways to meet current regulatory standards. A box drop inlet was designed to serve as the service spillway, and an earthen diversion channel served as the auxiliary spillway to convey low frequency storms. An existing sluiceway was retained to maintain a nominal overflow to a mill pond below the dam. A concrete liner was installed in the sluice where it passes through the dam to reduce seepage into the dam structure.

The water level behind the dam following construction remains the same as the pre-repair water level, controlled as before by the sluice invert. The crest of the dam was raised to accommodate a 100-year storm without overtopping.

In addition to the proposed dam repairs, maintenance excavation of the eastern portion of the pond was conducted to return the pond to its original depths.