National Program For Inspection Of Non Federal Dams Massabesic Lake Dam Nh 00103 Merrimack River Basin Manchester New Hampshire Phase I Inspection Report

The dam is a large concrete and stone masonry dam with earth embankments. The overall length is about 500 ft. with a maximum height of 27 ft. The dam is assessed to be in poor condition. Problems include structural cracking of an unknown origin, embankment seepage, and low spillway capacity. A test flood of 23,700 cfs inflow into the reservoir would overtop the dam by about 3.2 ft. (Author).

The dam is an earth embankment structure. The dam is 286 ft. long and 22 ft. high. The condition of the dam is fair in spite of a continued history of seepage through the dam that has not been eliminated by refacing the upstream side of the dam. The estimated PMF would overtop the dam by 6.6 ft. (Author).

The dam is a 404 ft. long, earth-filled rock crib which incorporates a 58 ft. long spillway and a 42 inch diameter steel pipe outlet controlled by a stoplog weir. It is intermediate in size with a significant hazard potential. The dam is in poor condition at the present time. The dam requires considerable maintenance. (Author).

The concrete dam is about 180 ft. long and is constructed on a circular arc. It is small in size with a low hazard potential classification. The dam is in fair condition. At the present time, there is no way to draw down the level of the reservoir. A program of annual technical inspections of the dam should be undertaken.

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 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).

The dam is a 450 ft. long, 35 ft. high earthfill dam with cemented rubble stone masonry core walls. The dam is intermediate in size with a significant hazard potential. The test flood is taken as 1/2 of the PMF. Generally the dam is in fair condition. (Author).

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 a cut stone masonry dam with a central timber section. The dam is 131 ft. long and 14.7 ft. high. The spillway of the dam is considered to be inadequate in that it can only pass 26% of the spillway test flood without overtopping the dam. There are remedial actions which should be implemented by the owner within one year of the receipts of this report.