Projects : Conversion of Spillway Tunnel to Hydropower

Development of hydropower at the Flannagan Dam in Haysi, VA required that the existing open spillway tunnel be pressurized to a head of more than 200 feet. D’Appolonia, a Dynamic Power Technologies Group company, was retained to determine the condition of the rock and concrete liner in the 16-foot-diameter tunnel. A testing program was developed to evaluate the potential effect of high pressure on the tunnel liner and surrounding rock. Testing consisted of: (1) drilling core borings into the invert, crown and sides of the tunnel at three locations, (2) hydraulic pressure and Goodman jack testing, (3) a crack survey, and (4) laboratory testing of rock and concrete samples to determine strength and deformation characteristics. Drilling and other work in the tunnel were performed while low levels of water were released through the tunnel.