Whigville Reservoir Dam is an earthen embankment structure with a concrete/boulder core wall. The dam is 460 feet long and has a maximum height of 54 feet. The 40 foot long concrete/boulder spillway is located at the right side of the dam. Slope paving forms the approach to the spillway. The downstream face is mortared stone masonry. Stone masonry training walls form the wasteway section. The outlet works consist of an upper and lower gatehouse each of which connect to submerged concrete intake structures. A 24 inch diameter blow off pipe passes under the wasteway channel to a stone masonry waste pot. The dam is judged to be in generally poor condition. The riprap on the upstream face is in generally good condition. The vertical and horizontal alignment is good. The downstream slope is covered with an extensive growth of trees and brush. Apparent seepage and wet areas were noted near the toe and at both sides of the spillway channel. The concrete parapet walls are in fair condition, with areas of erosion, spalling and deterioration noted. The concrete spillway weir is in poor condition with severely deteriorated concrete. The spillway is not adequate to pass the PMF spillway test flood outflow (7730 CFS) without overtopping the dam. The test flood would overtop the dam by about 4.2 feet. The spillway would pass about 20 percent of the test flood outflow without overtopping the dam.

The Farmington Reservoir Dam is an earth embankment impounding an unnamed tributary to the Pequabuck River and is reported to have been built in 1895. The dam (including spillway) is 760 feet long and eight (8) feet wide at the top. The dam has a maximum impoundment capacity of 64 acre-feet and is about 8 feet in height from the toe of the downstream slope to the top of the dam. The spillway is a 32 foot long, and 2.8 foot high, concrete, ogee shaped weir. There is no information available on outlet pipes. Based upon the visual inspection at the site and past performance, the dam is judged to be in poor condition. There are areas requiring attention, monitoring, and maintenance such as seeps along the toe of the embankment, erosion on the upstream and downstream slopes, location and operation of outlet and inlet structures and valves, and removal of trees. Peak inflow to the impoundment at the test flood is 315 cfs; peak outflow is 250 cfs with the maximum stage in the reservoir at 383.7, or 1.0 foot below the top of the dam. Based on this information the dam is not expected to overtop at the test flood condition. The spillway capacity with the pool at top of dam is estimated to be 525 cfs which is greater than 100% of the routed test flood outflow.

The Goodwin Dam is an earth and rock embankment with an earth core that is 800 feet long and 125 feet high. It has an emergency spillway, channel, gate house and diversion tunnel. The dam and its appurtenant structures are in good condition. The dam will pass the Probable Maximum Flood (recommended Spillway Design Flood) without overtopping the dam. Some recommended measures to be undertaken by the owner, should include the establishment of metering points for seepage measurement and periodic inspections of the dam. It is not urgent to implement these recommendations.

The Nepaug Dam is a semi-arch gravity type dam with a spillway. It is 6500 feet long and 113 feet high. The Phelps Brook Dam is an earth dam with a concrete core wall. It is 1,250 feet and 67 feet respectively. Both of these dams are located at opposite ends of the Nepaug Reservoir. The Phelps Brook Dam has no overflow. The project will pass the Probable Maximum Flood (recommended Spillway Design Flood) without overtopping the dam. The general condition of both dams and appurtenant structures is good. Some recommended measures to be undertaken by the owner include monitoring movements of parapet walls at the upper gate house of the Phelps Brook Dam, monitoring seepage at both dams and vibrations at the Nepaug Dam during periods of heavy flow.