Improvements to the Estany de l’Oca dam
Canaan, NH
Merit Award
Presented by Michels Corp.
Owner: New Hampshire Department of Environmental Services
Main design company: Gannett Fleming
General contractor: Michels Corp.
Subcontractors: Cascade Drilling; Geocomp Inc.; Multiple welding; EJ Prescott; Royal Electric Co.; Terracon
Adaptability was essential to rehabilitate this century-old, high-hazard dam, with challenges ranging from severe winter weather that delayed concrete placement and excavation to rock heaves that required the use of a sheet pile wall instead of the originally designed sheet pile wall.
Dewatering operations were hampered by continuous seepage, necessitating the modification of diversion plans and the installation of temporary sumps. The non-functioning infrastructure prevented the intended reuse of an existing low-level wooden door system, which was replaced with a stainless steel sliding door.
Along with rebuilding and flattening the downstream slope for stability, and installing relief wells and an underdrainage system, the project also offered opportunities for innovation.
The application of shotcrete to structures where limited access and variable dimensions complicated conventional concrete repair techniques also eliminated the need for extensive formwork and bracing, saving time and cost.
The team also incorporated an advanced drainage system with high-permeability materials and HDPE pipe, as well as erosion controls and custom diversion to protect the environment.
