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.

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.

Whitney Dam consists of a 1,400 foot long earth embankment and a 120 foot wide grassed emergency spillway. The outlet consists of a concrete riser with 7.5 foot long weirs on each side and a 30-inch reinforced concrete outlet pipe discharging into Patten Brook at the toe of dam. Maximum height of dam is 52 feet with a maximum storage capacity of 1,960 acre-feet. Based on the visual inspection, Whitney dam appears to be in good condition. Only one small cedar tree is growing on the embankment and there is evidence of recreational vehicles climbing the embankment in three locations. The rodent screen on one foundation drain outlet is partially missing and the slide gate stem at the principal spillway outlet is bent and appears to be inoperative. Calculations by the Soil Conservation Service show a peak inflow of 6,500 cfs. and a peak outflow of 1,930 cfs. with a maximum water surface elevation 2.0 feet below the crest of dam, which was used as the test flood.

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.

The dam consists of a concrete principal spillway, embankments to the right and left of this spillway and an emergency spillway near the right end of the dam. The principal spillway is a concrete chute with weir-boards at the upstream end and the emergency spillway is an unlined channel cut into the right end of the embankment. A swale, which will overflow to the toe of the dam at approximately the same elevation as the auxiliary spillway, exists at the left end of the dam. There is no low-level outlet at the dam. Based upon the visual inspection at the site and past performance, the dam appears to be in fair condition with items which require repair, maintenance and monitoring. These include spalling of the concrete walls at the principal spillway, seepage through the embankments, trees and brush on the embankments and in the emergency spillway, erosion of the upstream slopes, extending the embankment to fill the swale at left end of the dam, and debris and overhanging brush in the spillway discharge channels. The total spillway capacity at the same pool level is 820 cfs, which is greater than 100% of the routed test flood outflow.