1 - Alaska Energy Data Inventory

that occurs in a reservoir). An excavation at the downstream end of therock trap will prov i de approx imate ly 96 yd 3 of storage vo 1 ume for anymaterials that might reach that far. The trap will be cleaned whenever thepower conduit is drained for normal inspection and maintenance. HEDB hasindicated that the turbine can pass a 2 inch diameter stone once during itslife and can pass a 1/4 inch diameter particle on a more regular basis. Toassure a long turbine life the rock trap is designed so that a 1/16 inchdiameter particles entering the trap from the power tunnel will settle tothe floor of the trap well before reaching the lower trashrack (seereference 2, 3, and 4).F. Trashrack Design. For hydraulic design purposes, the same spacingas that used for the Long Lake trashracks was assumed for Crater Lake. Forthe primary trashrack the bar spacing is assumed at 2-1/2 inches center tocenter and 2 inches between bars. For the secondary trashrack justupstream from the penstock the spacing is assumed at 1-7/8 inches center tocenter and 1-3/4 inches between bars.(1) Primary Trashrack - The primary trashrack will be 19-ft squarewith maximum velocities of 2.1 ft/s through the net area. The primarytrashrack design is discussed in greater detai 1 in subsection 1.05 - "LakeTap" of this appendix.(2) Secondary Trashrack - Prior to the initial period of plantoperation a full circular trashrack 11 ft in diameter will be installedupstream from the penstock (see plate 21). The trashrack will providepositive protection for the turbine during the initial stages ofoperation. Inspection of the new tunnel after some period of partial andfull power operation will allow us to make a decision about whether or notany portion of the secondary trashrack can be dispensed with (the Long Laketunnel operates with a partial trashrack at this location).Bl-8