National Program For Inspection Of Non Federal Dams Uncanoonuc Lake Dam Number 2 Nh 00021 Nhwrb No 9304 Merrimack River Basin Goffstown New Hampshire Phase I Inspection Report

The dam is an earthen embankment structure with a central concrete core wall about 147 ft. in overall length and 9 ft. high from the crest of the dam to downstream toe. The dam is considered to be in fair condition. It is classified as small in size and significant in its hazard classification. (Author).

The dam is a 188 ft. long, 16 ft. high earth embankment dam. The condition is fair. The visual inspection did not disclose any immediate safety problems. The dam's spillway will not pass the test flood, therefore it is recommended that the owner engage a qualified engineer to evaluate further the potential for overtopping the inadequacy of the spillway. (Author).

St. Pauls School Dam is a concrete overflow section approximately 15 ft. high from the bottom of the upstream channel to the top of the training walls and approximately 100 ft. long between the training walls. The upstream face of the concrete section is vertical and measures approximately 9 ft. from its crest to a concrete apron on the channel bottom. The dam is in fair condition at the present ime, with a few major concerns which must be corrected. The size is intermediate with a significant hazard potential. The dam could be damaged by the discharge over the abutments. It is not anticipated that lives would be lost. Keywords include: Visual inspection, Dam safety, Merrimack River Basin, Concord New Hampshire, and Turkey River.

Todd Lake Dam is a concrete capped, gravity rock wall and earth fill structure with a maximum height above the downstream channel of 16.5 feet. The 57 foot long concrete cap serves as a spillway and includes two 12 foot long depressed sections which permit the installation of 12 inch high flashboards. The dam's size is intermediate with a significant hazard potential. The dam is in fair condition. Deficiencies in the areas of spillway capacity and possible structural stability require additional engineering investigations. Only a few relatively minor operation and maintenance improvements are necessary. Keywords include: Visual inspection, Dam safety, Merrimack River Basin, Bradford New Hampshire, and Ring Brook.

Lake Franklin Pierce Dam consists of a central concrete gravity ogee spillway with earth dike embankments. Total length is 1,870 ft. and maximum height is 43 ft. The dam is assessed to be in fair condition. No serious problems were detected, although some suspicious seepage was noted which should be monitored closely. Overtopping potential is considered high. Keywords include: Visual inspection, Dam safety.

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 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 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).

Mountain Pond Dam is located on the north end of Mountain Pond in Sanbornton, N.H., in mountainous terrain two miles south of the village of New Hampton. The dam is an earth embankment, 97 feet long and 14 feet high with a gated 8-inch outlet. The impoundment stores the water supply for the Town of New Hampton and is also the fire protection reserve. It is small in size with a low hazard potential. The test flood is in the range of a 50 to 100 year frequency. The condition of the dam is considered to be fair, requiring that modifications be made by the owner within 1-2 years after receipt of this inspection report. Keywords include: Inspection, Dam safety, Merrimack River Basin, Sanbornton, New Hampshire, and Tributary of Pemigewasset River.

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.