Means Brook Reservoir Dam and Gatehouse Rehabilitation, Shelton, CT — Aquarion Water Company of Connecticut
The Means Brook Reservoir Dam is a concrete gravity dam that was constructed on rock in 1916 in Shelton, Connecticut. The aging dam required repairs in to improve reliability and safety, modernization and rehabilitation of the gate chambers, and replacement of the deteriorated upstream and downstream faces of the dam and the crest, which were severely spalled and delaminated. Hydraulic, hydrologic, and structural studies had indicated that the dam would be overtopped by about 3.9 feet by the Probable Maximum Flood, and that the dam did not have sufficient stability factors of safety for this extreme loading condition. The dam reportedly overtopped by about four inches during the 1955 flood. In 1977, modifications were made to the dam including extension of the spillway to its current length of 100 feet, and construction of a 2.1-foot high concrete parapet wall along the upstream crest of the dam.
Tata & Howard provided design and construction administration for the rehabilitation of the dam that included the following:
- Concrete repairs to the crest and both faces of the dam:
- Deteriorated and delaminated shotcrete and concrete removed to sound concrete;
- Anchor dowels and reinforcing installed, and new concrete surfaces poured;
- Upstream face was resurfaced to a depth of about six feet below spillway, and the downstream face to two feet below grade;
- New concrete surface designed with a nominal thickness of 12 inches on the downstream face and six inches on the upstream face.
- Installation of rock anchors post-tensioned in holes drilled through the dam into the rock foundation to improve stability and provide adequate factors of safety for overtopping by the Probable Maximum Flood.
- Removal and replacement of one section of the spillway training wall, and removal and resurfacing of concrete on remaining walls.
- Repairs and improvements to the gatehouse and chambers:
- Reshingling of gatehouse roof;
- New steel plate exterior door for additional security;
- Blocking up the existing windows;
- Replacement of antiquated electrical system;
- Replacement of both of the inoperable sluice gates and their appurtenances in the upstream gate chamber;
- Replacement of the former vertical brass ladders in the intake gate chambers with new fiberglass ladders, including a base for fall protection and retrieval system;
- Replacement of wooden stairs in the lower gatehouse with new aluminum ships ladder;
- Replacement of the pneumatically operated butterfly valve on the 30-inch service main in the basement of the lower gatehouse with an electrically operated butterfly valve that can be remotely controlled;
- Installation of an extension stem and electric operator;
- Replacement of the 8-inch chamber drain and 10-inch auxiliary outlet gate valves;
- Replacement of wooden hatches over floor openings within the gatehouse with aluminum grating with cover plates;
- Installation of chain link fence along portions of the spillway training wall for safety; and at both ends of the dam for security;
- Installation of galvanized steel pipe railings along the upstream and downstream crest of the dam for safety; steel pipe rails were chosen for the dam crest instead of chain link fence because the dam crest is subject to overtopping.
The project received a 2017 Excellence in Engineering Merit Award from the American Council of Engineering Companies, Connecticut. Read more here.