National Program For Inspection Of Non Federal Dams High Service Distribution Reservoir Nh 00296 Nhwrb 15011 Merrimack River Basin Manchester New Hampshire Phase I Inspection Report

The dam is a concrete lined earth and rock fill embankment that is used as a water supply. The dam has a maximum height of 35 ft. It is small in size with a high hazard potential. In the event of a failure, several downhill residences would be threatened. The reservoir is in good condition. No displacement settlement, or other signs of major distress were observed at the reservoir. (Author).

Baker Floodwater Reservoir Site 11A is a 640 foot long 24 foot high earthen structure. There is one fill zone in the dam which includes a cutoff wall. Top width of the dam is 12 feet. The upstream and downstream embankments are on a 3 horizontal to 1 vertical slope. Appurtenant structures consist of a principal spillway, plunge pool stilling basin and emergency spillway. The visual inspection revealed that the dam is in good condition. The inspections also revealed random surface cracks and scaling of the concrete on the riser structure. It is small in size with a high hazard potential classification. Keywords include: Inspection, Dam safety, Merrimack River Basin, Wentworth, New Hampshire, and Tributary to Baker River.

The Souhegan River Watershed Dam No. 26 is located on Blood Brook, a tributary of the Souhegan River, approximately 2 miles upstream of West Wilton, New Hampshire. The dam is an earth embankment 692 feet long and 79 feet high with a drop inlet service spillway structure and a 30 inch outlet conduit. An emergency spillway 320 feet wide is cut into the left abutment.

The dam is a 691 ft. long 24 ft. high earthen structure. The dam is judged to be in good condition. There were a few items noted during the inspection which require attention. It is small in size with a significant hazard potential. There are no other recommendations resulting from the inspection. (Author).

The dam is a 805 ft. long, 68 ft. high earthen embankment structure with three different fill zones. The visual inspection indicated that the dam is in good condition. The inspection revealed minor deterioration of concrete on the riser structure and at the end of the 4 ft. diameter outlet pipe. It is intermediate in size with a high hazard potential. There are no recommendations for the dam based on the inspection report. (Author).

The dam is a 807 ft. long 48 ft. high earthen structure. The dike is an earthen structure about 600 ft. long and 11.5 ft. high. The inspection revealed both the dam and dike to be in good condition. There were no recommendations for the dam after this inspection. The dam is intermediate in size with a significant hazard potential. (Author).

Chase Pond Dam is a rock filled log crib with timber planking overflow structure between stone and concrete embankments. The overall length of the dam is 103 ft. The timber overflow section is approximately 12 ft. high by 50.5 ft. long and 10 ft. wide at the crest. The embankments, which are approximately 5.4 feet higher than the crest of the timber overflow section, are composed of masonry and concrete on the upstream and training wall faces. As a result of the visual inspection of this facility, the dam is considered to be in poor condition. The dam is small in size with a significant hazard classification. The dam at the outlet from Tannery Pond could be overtopped or breached. Keywords include: Inspection, Dam safety, Merrimack River Basin, Wilmot, New Hampshire, and Chase Pond.

Kelleys Falls Dam is a run of the river type dam, with an overall length of 503 feet. Visual inspection of the dam indicated that the dam is in poor condition. The inspection revealed a number of leaks through the mass concrete spillway section, considerable loss of concrete from the spillway section, seepage around the concrete wall on the right side of the dam, and general deterioration of concrete on the abutments and hydro-building. Based on the intermediate size of the dam and the significant hazard classification and in accordance with Corps of Engineers guidelines, the test flood is one half the Probable Maximum Flood (PMF) or 55,900 cfs. The one half PMF outflow overtops the dam by 6.8 feet. With the water level at the top of the dam, the spillway will pass 38 percent of the test flood outflow. It is recommended that the owner engage a qualified engineer to make thorough investigation of the condition of the foundation of the spillway section of the dam, investigate the structural stability of the spillway section and ways to increase the spillway capacity. Also, the owner should remove the flashboards on the dam immediately. Additional keywords: Merrimack River Basin, Manchester, and New Hampshire.

The dam is an earthen embankment about 420 ft. long with a maximum height of about 25 ft. The dam impounds water from the Brook and the spillway discharges to Harris Pond immediately below the dam. The dam is considered to be in fair condition. It is intermediate in size with a significant hazard potential. (Author).

The dam is intermediate in size with a low hazard potential. The hydraulic analyses indicated that the spillway test flood in Highland Lake is 11800 cfs, of which the North Outlet would experience 3950 cfs. It is recommended that the refined hydrological analyses elsewhere recommended for Highland Lake's South Outlet be undertaken. (Author).