West Hopkinton Penstock Rehabilitation, West Hopkinton, New Hampshire

The consultant needed to develop a cost-effective design to rehabilitate two penstocks that run partially under NH Route 127. To achieve a design that meets current regulatory standards, the consultant designed a reinforced shotcrete liner that could be constructed inside the existing penstocks without disturbing the traveling public. The project was completed using the trash rack as a single access point. The consultant’s design tied the new 5-in-thick shotcrete liner to the existing circa-1906 wood-stave pipe,1989 steel pipe, and the surrounding soil to provide the structural support needed. A smooth coating on the interior of the liner decreased friction along the penstock, which did not result in a substantial reduction in power production. The design met the client’s goals to rehabilitate the penstocks and maintain the facility’s ability to produce power; it was also completed without disrupting the flow of traffic on NH 127.