Project Name: Jackman Penstock Replacement
Summary: Novel piping material provided cost and technical advantages
Client: Public Service of New Hampshire
Project Location: Hillsborough, NH
Project Size: 2,400 feet
• Hydro Facility Assessment
• Hydro Feasibility and Planning
• Penstock Inspection and Design
Project Timeframe: 2005 - 2006
Relationship with Client: Since 1980’s
Public Service of New Hampshire’s (PSNH) 3 MW Jackman Station hydroelectric facility had 5,000 feet of wood stave penstock made up of 1970’s, 1954, and original 1926 vintage wood stave sections. Because the downstream sections of the wood penstock were leaking badly and were structurally deteriorating resulting in a significant rupture in 2003 that impacted abutting properties, PSNH decided to replace the lower 2,400 feet.
Kleinschmidt conducted a feasibility study for replacing the penstock by evaluating five pipe materials: wood stave, concrete, HDPE plastic, steel, and fiber reinforced polymer (FRP). The corrosion resistance and relative stiffness of FRP pipe meant it could be supported on the existing grade and half buried, rather than placed on saddles or completely covered in a buried trench. This design flexibility, combined with a longer projected service life, and lower relative material prices lead to a competitive total construction cost for the FRP alternative. After PSNH selected FRP as the pipe material, Kleinschmidt provided a final design package and assisted with contractor bidding, obtaining permits, and construction services for replacing the downstream 2,400 ft section of the wood stave pipe.
The pipe was half buried in the shallow trench of the existing penstock, requiring minimal excavation costs and environmental disturbance. PSNH realized significant construction cost savings as partially backfill the penstock was seven times less expensive per foot than to support it above ground without any reduction in service life.