On 6/30/97, at about 3:50 P.M., an unexpected plant shutdown due possibly to a lightning strike resulted in the collapse and failure of the No. 3 feeder penstock just upstream of the powerhouse. The main penstock and No. 3 feeder penstock buckled, and the No. 3 penstock ruptured. Damage to penstocks, minor damage to powerhouse. Uncontrolled flow for over two hours resulted in substantial scouring and redeposition up to 1/2 mile in the downstream river. From 5/20/98 DIDR: On June 30, 1997 the number three steel penstock ruptured about 5 feet upstream of the project powerhouse. The resultant discharge of water scoured the earthfill around the powerhouse and several hundred feet of the main supply line of the penstock collapsed following closure of the intake gates and the resultant rapid dewatering of the line. Removal of debris in the tailrace began on July 1, 1997 following coordination with the FERC and the appropriate state agencies. A sand trap was constructed about 1/2 mile downstream of the powerhouse. The stream bed is being flushed of the additional sediment and the banks and stream bed reformed under the direction of a fluvial geomorphologist. The license applicant began submitting plans and specifications for ensuring stability of the middle and upper thrust blocks and replacement of the steel pipeline on September 11, 1997. Much of this work was being done at this time by the license applicant himself and the contractor.
