Maximizing Budget by Sliplining

Manchester, NH Maximizes Budget by Sliplining 600’ Penstock

The 60” diameter 600’ riveted steel penstock managed by Manchester Water Works (MWW) is badly dilapidated and showing indications of leakage. Constructed in 1912, the penstock diverts water from Lake Massabesic to a 375 kilowatt hydroelectric generator. The generator produces income for the City offsetting the energy costs at the water treatment plant.

Wright-Pierce was retained to evaluate whether the existing penstock should be reused, or replaced and whether structural enhancements were necessary. A complete physical inspection was completed on the inside of the pipe and portions of the outside of the pipe. Using both electronic thickness measurements and visual inspections it was determined the pipe either had to be totally replaced or the existing pipe would require a “structural” liner. It appeared the most cost-effective, efficient, and reliable solution was to slipline the existing 60” pipe with a 54” high-density polyethylene (HDPE) pipe. The project was bid with two alternates: complete replacement, or lining the existing penstock. Based on the bid results, MWW decided on using the sliplining method. The construction of the sliplining operation will begin in early 2010.

Sliplining is a proven trenchless pipe rehabilitation technology that offers many advantages compared with traditional open-cut and cover methods. Across the US, cities are opting for the sliplining because of its lower cost, ease of construction, less disruption to the public and least disturbance to the environment.

Wright-pierce is working throughout New England on various trenchless projects.