Quaddick Reservoir Dam is an earth embankment about 330 ft. long, with a maximum height of about 12 ft. TWo spillways, with a combined width of 78 ft., occupy a portion of this length. A dike is located in a saddle about 2,000 ft. east of the dam. The dam has a wet well intake structure with a 30 in. dia. outlet pipe controlled by a sluice gate. The drainage areas is about 24 sq. mi, and the maximum active storage to the top of the dam is 5,100 acre-ft. The dam and dike are judged to be in generally fair condition. The side walls of the west spillway appear to have been overtopped, resulting in some erosion of the embankment. The backfill along the east spillway has also settled. Most of the riprap protection downstream from both spillway chutes has been washed away. The masonry wall at the downstream end of the outlet pope is in poor condition. Brush and saplings have become established downstream of the west abutment area, in the east spillway discharge channel and on the upstream slope. There are several areas of local erosion on the crest, upstream and downstream slopes, and some rodent burrows on the downstream slope. Seepage was noted below the toe in the right abutment area and through the masonry outlet wall. The test flood would overtop the dam by about 1.3 ft. and the dike by about 2.8 ft. The combined spillways would pass about 30 percent of the test flood without overtopping the dam or dike provided that the stoplogs were not installed on the west spillway crest.

North Grosvenordale Pond Dam is a composite masonry and earth dam consisting of two downstream stepped, ashlar faced masonry overflow sections, a granite block and earth fill right abutment and an earth fill right abutment and and earthfill dike on the left abutment. The entire length of the dam is about 2,400 ft. It is a run-of-the-river dam which once served the industrial needs of the downstream mill. Outflows through the millrace are now used for fire protection of the mill. North Grosvenordale Pond is about 1.5 miles long and has a surface area at spillway level of about 60 acres. The drainage area above the dam is about 99 sq. mi. and the maximum storage to the top of the dam is estimated at about 840 acre-ft. The dam is judged to be in generally fair condition. At the time of the inspections, water was flowing over the right spillway, so that it was not possible to observe the condition of the downstream ashlar face, or to determine whether there is any erosion at the toe of the spillways. The crest of the left spillway is higher than the right spillway. The difference is less than 6 in. The sluiceway through the left spillway is inoperative. Some of the left spillway stones have been dislodged and displaces. Several joints in the training walls are in need of repointing. The bridges over the spillways are in a deteriorating condition. Tree and brush growth is abundant along the left abutment dike. The spillways are not adequate to pass the 1/2 PMP test flood of 25,400 cfs without overtopping the non-overflow sections of the dam. The test flood would overtop the dike by about 2.2 ft. The spillway can pass 4,950 cfs or about 20 percent of the test flood without overtopping the dike.

The dam at Deep River Reservoir is a zoned earth embankment approximately 900 feet long, 62 feet high with an average crest width of 20 feet. It was originally constructed in 1926, 7 and raised in 1971, 2 to its present configuration. It is owned by the City of Norwich, Connecticut and operated by the Department of Public Utilities as the main surface water supply of the City. The dam has an agee overflow spillway at the right abutment. The spillway is a converging chute type with a drop to a stilling basin at the toe of the dam. The outlet works and control tower are centered on the embankment and discharges from the tower's wet well flow through a reinforced 42 inch diameter condiut beneath the dam. An earth embankment dike 240 feet long in an adjacent cove of the reservoir contains an erodable fuse plug emergency spillway. As a result of the visual inspection and the review of available data regarding this facility, the dam is considered to be in GOOD condition. To assure the long-term performance of this structure, several items of concern require attention: modifications need to be made to the existing relief well monitoring system in order to more accurately record the seepage flow, a localized erosion immediately upstream of the left abutment of the dam must be repaired, and vegetable growth in the downstream channel of the emergency spillway should be removed. The maximum outflow capacity of the spillway under a stillwater condition is equal to 18,860 CFS which represents more than 100 percent of the test flood.

Mechanicsville Dam is a composite masonry and earth dam consisting of a stepped stone masonry overflow section surmounted by a concrete superstructure forming 16 spillway bays, an earth dike on the right abutment, and a stone wall and abandoned power house on the left abutment. The entire length of the dam is about 568 ft. It is a run-of-the river dam which once served the power needs of a downstream industrial complex. The only purpose of the dam now is to pond water for a dry hydrant located in Mechanicsville. The reservoir is about 8,000 ft. long and has a surface area at spillway level of about 44 acres. The drainage area above the dam is about 112 sq. mi. and the maximum storage to the top of dam is estimated at about 900 acre-ft. The height of the dam is 21.75 ft. The dam is judged to be in generally fair condition. There is no low level dewatering facility. The piers of the concrete spillway bridge are badly eroded and the right abutment dike is covered with tree and brush growth. There is a gap in the left abutment stone wall about 8 ft. wide. The abandoned power house is in disrepair and the dam shows no sign of having received any maintenance in recent years. There is a low-lying boggy zone about 300 ft. below the dike. The test flood outflow would overtop the left abutment wall by about 5.5 ft. and the right abutment dike by about 2.8 ft. The spillway can pass 10,200 cfs or about 33 percent of the test flood outflow without overtopping the left abutment.