National Program For Inspection Of Non Federal Dams Greggs Falls Dam Nh 00093 Merrimack River Basin Goffstown New Hampshire Phase I Inspection Report

The earth embankment and concrete gravity dam is considered to be in good condition. It is believed to be safe under normal operating conditions. Based on size and hazard classifications in accordance with Corps guidelines, the test flood is the Probable Maximum Flood. In addition to the long term recommendations, there are several remedial measures which should be implemented immediately. (Author).

The dam is a gravity structure constructed of split masonry. It is about 80 ft. long and 17 ft. high. The dam is small in size with a significant hazard potential. The dam is in poor condition at the present time. There are remedial measures and studies which should be implemented by the owner as soon as possible. (Author).

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 a run of the river type dam. It is 633 ft. long with a maximum height of 35.9 ft. The visual inspection of the dam revealed that the dam is in generally fair condition. Noted were some minor cracking and spalling of concrete on the abutments and the poor condition of the gates and mechanical operators. It is intermediate in size with a significant hazard potential. Keywords include: DAMS, INSPECTION, DAM SAFETY, Merrimack River Basin, Concord, New Hampshire, and Merrimack 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 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 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 stone masonry gravity dam with a total length of about 325 ft. It is small in size with a low hazard potential. The dam is in fair condition at the present time. In light of the dam's fair condition, technical inspections should be made every year. (Author).

The Gregg Lake Dam is a dry-laid stone masonry and concrete structure with earthfill embankments. The dam is approximately 9 ft. high, and about 210 ft. long including earth embankments. The dam has three stop log controlled spillways totaling approximately 21 ft. in length, a low level gated outlet, and a sluice gate outlet. Based on the visual inspection, the Gregg Lake Dam is assessed to be in fair condition. The size is intermediate with a significant hazard potential. Major concerns include apparent movement of the stone masonry and potential overtopping and erosion of low areas in the earth embankments. Keywords include: Inspection; Dam safety; Contoocook River Basin; Antrim, New Hampshire; and Gregg Lake Outlet.

Lake Wampanoag Dam is approximately 660 feet long including the spillway and has a maximum height of approximately 22 feet. It consists of an earth embankment with riprap at the upstream face and a loamed and seeded crest and downstream face. Based on the size classification (intermediate) and hazard potential classification (high), the spillway test flood is the PMF.