Constructed in 1914 along the Housatonic River, Falls Village Hydroelectric Generating Plant recently rehabilitated Penstock #1 with a custom-designed structural shotcrete liner. Repairing the steel-riveted pipe with spray-applied QUIKRETE^® Shotcrete MS over metal reinforcement proved a durable, cost efficient system that meets the operational capacity and strengthen requirements. Completed by Knowles Industrial Service Corporation (KISC) on behalf of FirstLight Power Resources, the project won the American Shotcrete Association Most Outstanding Repair & Rehabilitation Award.

Selected instead of hand-applied fiberglass mats and structural epoxy liners, the reinforced shotcrete design is a self-sustaining system that will withstand static and hammer pressure generated by water traveling through the penstock to the turbines during plant operation. In addition, the reinforced shotcrete liner did not significantly increase the pipe’s thickness, so the plant will continue to produce nine megawatts of electricity. Finally, a bulkhead gate was installed upstream forcing water flow through Penstock #2 and Penstock #3 at the plant to maintain power output while providing increased jobsite safety.

The full nine-foot diameter, 360-foot long penstock was buried in the river bank, so two large holes were created as access points rather than excavating the entire area. After cleaning the interior pipe with a 5,000 PSI industrial pressure washer, 2,100 feet of 1 ½” reinforced bar mat was welded onto the surface as a continuous slab along with 6.5 miles of longitudinal-spaced #4 rebar and radial hoop shaped #5 rebar. KISC then spray-applied 150 cubic yards of QUIKRETE Shotcrete MS delivered in 3,000-pound bulk bags through a silo system. The four-inch-thick shotcrete lining was finished smooth to eliminate any friction that could slow water flow and decrease plant power generation. The reconstruction was completed by abrasive brush blasting the 10,200 square-foot penstock liner and applying two 30 millimeter coats of high-build epoxy to increase service life and further support unobstructed water flow.

QUIKRETE^® Shotcrete MS – Fiber Reinforced is a single component Micro Silica enhanced repair material that achieves more than 9,000 PSI at 28 days, and features very low rebound and permeability characteristics.