National Program for Inspection of Non-Federal Dams. Mianus Filter Plant Dam (CT 00040), Southwestern Coastal Basin, Greenwich, Connecticut. Phase I Inspection Report.
CORPS OF ENGINEERS WALTHAM MA NEW ENGLAND DIV
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The dam at the Mianus Filter Plant is a stone masonry dam built in the 1870s and is a source of water supply for the surrounding area. The water treatment facility was renovated in 1954. The dam is approximately 130 feet long, 31 feet high and has a top width of 7 feet. The outlet works for the dam consist of a 65 foot long spillway, a 30 inch supply main to the water treatment facility, a low level blowoff, and two 4 foot wide by 5 foot high flood control gates. Based on the visual inspection, the review of the 1954 renovation plans and past operational performance, the dam is judged to be in FAIR condition. However, there is a concern about the seepage zone at the downstream face of the dam, which requires further study. The dam is classified as SMALL in size and a HIGH hazard potential structure in accordance with recommended guidelines established by the Corps of Engineers. The test flood for this dam is 12 the Probable Maximum Flood PMF. The test flood has an outflow discharge equal to 14100 cfs and will overtop the dam in a stillwater condition. The maximum outflow capacity of the spillway under stillwater condition is 680 cfs which represents approximately 5 percent of the test flood. It is recommended that the owner take the following actions Monitor the seepage on the downstream face, remove the trees from the upstream channel bed and develop and implement a formal emergency warning system.
- Hydrology, Limnology and Potamology
- Civil Engineering