1 - Alaska Energy Data Inventory

3.01 GENERAL.This section describes the hydraulic design of the power tunnel, surge tankand penstock for Alternate Plan I of the Crater Lake phase of theSnettisham power facilities. (Alternate Plan II is essentially the samehydraul ically as Alternate Plan I. Reference to Alternate Plan I in thissection applies as well to Alternate Plan II.) The surge tank designrequires consideration of the plant operating conditions, expected turbinecharacteristics and the total head losses in the conduit system from thereservoir to the powerhouse.The power conduit will be connected to a turbine-generator unit which is tobe installed in the existing powerhouse built for the Long Lake phase ofthe Snett i sham project. Des i gn memorandum 23 shows detail s of the CraterLake phase that are not included in this section. Only the generalhydraul ic aspects of the alternative power conduit al inement and conduitsizes are discussed in this section; alternative specific features such asgate structures, trashracks and rock traps could be incorporated into boththe· recommended plan and the alternative plans, and are therefore notspecifically considered in this section.3.02 DESCRIPTION OF POWER CONDUITS.A. Alinement.The Alternate Plan I power conduit plans and profiles are shown onPlates 23, 25 and 26. The invert of the power tunnel entrance isapproximately 783 ft and the invert of the rock trap is set at 775 ft. Theminimum power pool elevation is set at 825 to assure adequate clearanceover the top of the trashrack and lake tap opening.Although a wet or drylake tap scheme could be utilized in the alternate plan, minimumelevation is set at 825 ft based on a dry lake tap.poolThe lower terminus ofthe power tunnel was determined after considering site topography,hydraulic transients in the surge tank and water hammer (maximum andminimum) between the surge tank and the unit. The invert of the powertunne 1 at the surge tank is at e 1 evat i on 745. The gate chamber wi 11 belocated at sta 14+00 approximately 650 ft from the power tunnel entrance.83-2