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National Program for Inspection of Non-Federal Dams. Maltby Lake Dam Number 1 (CT 00111), Connecticut Coastal Basin, West Haven, Connecticut. Phase I Inspection Report.

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This 26 foot high water supply facility dam consists of two main sections. The upstream section is an earthfill dam built in 1862. The downstream part, built in 1900, is a stone masonry gravity section. The area between the two sections was filled in 1900 with a well-compacted clayey soil adjacent to the older upstream fill material. The spillway is a 21.5 foot long broad-crested stone masonry weir discharging to a concrete and stone channel which leads to a concrete arch culvert under Connecticut Route 34 immediately downstream of the dam. The outlets consist of a 16 inch supply main and a 10 inch low level outlet, both of which are gated on the downstream side of the dam, the 16 inch pipe at a gatehouse at the toe of the dam, and the 10 inch by a gate in a manhole at the toe of the dam. In addition there is a 20 inch pipe through the dam which carriers water from the upper Maltby Lake No. 2 to the downstream gatehouse. From the gatehouse, a water line runs to the filtration plant on the opposite side southeast of Route 34. Based upon the visual inspection at the site and past performance, the dam appears to be in good condition. No evidence of instability was observed in the downstream masonry section, the upstream earthfill section, or any appurtenances. The test flood is equivalent to one-half the Probable Maximum Flood PMF. Peak inflow to the reservoir is 1450 cfs peak outflow is 1220 cfs with the dam overtopped 0.6 feet. Based upon our hydraulic computations, the spillway capacity is 520 cfs without the swale overflow, which is equivalent to 43 of the routed test flood outflow.

Subject Categories:

  • Hydrology, Limnology and Potamology
  • Civil Engineering

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