ground switch for the transformer bank protective scheme. Some of the details of the 230-kilovolt switchyard are shown on figure 174. Station-service power to the switchyard is carried on an overhead messengersupported circuit from the transformer dock at the powerplant to distribution transformer KW1A located in switchyard bay Y1. Standby station-service power for the powerplant is provided by a 12-kilovolt tie with the Pacific Gas and Electric Co. system. The Pacific Gas and Electric Co. 12-kilovolt circuit also supplies power to the valve structure. The disconnecting facilities, fuses, and metering facilities for the power supplies are furnished and installed by the Pacific Gas and Electric Co. and are located at the Y-point where the circuits to the valve structure and the powerplant separate. See figure 173. 227. Switching Equipment. (a) Station-Service Transformer KW1A.--The station-service transformer in the switchyard is a single-phase, dry-type, self-cooled, outdoor type, supplied by E. V. Lane Corp. and Gunther and Shirley Co., construction contractors under specifications No. DC-5640, on an extra work order. It has the following electrical characteristics: Capacity High voltage (rated) Low voltage (rated) Taps, low-voltage winding 15 kilovolt-amperes 480 volts 120/240 volts 5 and 10 percent below . . None (b) 230-Kilovolt Power Circuit Breaker JY5A.--An oil circuit breaker is installed in bus tie bay Y5 of the switchyard. It was manufactured by the General Electric Co. and has the following electrical characteristics: Each breaker bushing is equipped with one 300-1-ampere single-ratio bushing-type current transformer having an accuracy class of 10 L 2,000. (c) Miscellaneous. --In addition to the above switching equipment there are six disconnecting switches, one air circuit breaker, one current transformer, three lightning arresters, and a distribution cabinet. See figure 173 for a listing of major electrical equipment installed at Clear Creek Powerplant and Switchyard. This list also includes electrical ratings and purchase information. 228. Steel Structures. The transformer takeoff and switchyard steel structures are designed to withstand the loads shown on the design drawings, imposed by tension buses, line conductors, and ground wires; the loads due to wind and structure weight; and loads from the supported electrical equipment. 229. Switchyard Equipment Operation. The 230-kilovolt disconnecting switches at Clear Creek Switchyard are not capable of making or breaking loads, magnetizing current of the transformer banks, or linecharging currents of the magnitudes that exist in this system. They will therefore be closed or opened only with the system deenergized with the exception of switches 685 (WY5A) and 683 (WY5B), which may be opened or closed when breaker 686 (JY5A) is open. The switching diagram is shown on figure 173. Breaker 686 (JY5A) does not have sufficient interrupting capacity to interrupt faults on this system and therefore is used only for switching duties. 11. Power Supply to Appurtenant Structures 230. Clear Creek Tunnel Intake Structure. The electrical system for the intake structure is described in section 194. 231. Clear Creek Penstock Valve Structure. The electrical system for the penstock valve structure is described in section 195. CHAPTER VI. Design--WHISKEYTOWN DAM A. General 232. Location and Purpose. Whiskeytown Dam (fig. 175) is located in Shasta County, Calif., on Clear Creek, approximately 10 miles by highway west of Redding, Calif., as shown on the location map, figure 2. The dam captures and regulates releases of Trinity River water from the Clear Creek Powerplant, and diverts this water, plus the usable flow of Clear Creek (see sec. 1), into the Spring Creek Power Conduit, which in turn conveys the water to the Spring Creek Powerplant. 233. General Description of the Dam and Appurtenances. The principal features involved in the construction of Whiskeytown Dam were earth dam embankments, tunnel spillway (fig. 176), tunnel outlet works, and roads connecting the dam crest and the outlet works control house with the existing Whiskeytown Dam access road, as shown on figure 177. The main dam embankment is approximately 2, 250 feet long at crest elevation 1228.0 and has a height of approximately 272 feet above the bed of Clear Creek. The dam has a maximum base width of about 1, 500 feet and a top width of 30 feet. Additional embankments, one over 1, 050 feet long and 75 feet high and another over 700 feet long and 20 feet high, were required in saddles on the right abutment. (These two saddle dams have an actual combined length of 1, 820 feet.) Appurtenant structures include a glory-hole tunnel-type uncontrolled spillway with a capacity of 28, 780 second-feet at water surface elevation 1220.5, and a tunnel-type outlet works with a capacity of 900 secondfeet at water surface elevation 1110.0, and capable of withdrawing water from two different levels in the reservoir. These are discussed in sections 236 and 237, respectively. 234. Whiskeytown Reservoir. Storage capacity in the reservoir is allocated as follows: At elevation 1210.0 the reservoir has a surface area of about 3, 220 acres and a total capacity of 241,096 acre-feet. B. Feature Description 235. Earth Dam Construction. A double cap and grout curtain was placed in the bottom of the cutoff trench below elevation 1075, with the upstream grout curtain continuous from approximate dam station 11+70 to the left abutment of the dam. Grouting was also performed in rock surrounding the spillway and outlet works shafts and tunnels. The zone 1 portion of the dam embankment consists of selected weathered rock (clay, silt, sand, and gravel sizes) compacted by tamping rollers to 6-inch layers. The zone 2 portions of the dam embankment consist of selected weathered rock (silt, sand, and gravel sizes, and rock fragments to 8-inch maximum size) compacted by tamping rollers to 12-inch layers. The zone 3 portions of the dam embankment consist of selected rock fines compacted by crawler-type tractor to 12-inch layers. The zone 4 portion of the dam embankment consists of rockfill placed in 3-foot layers. The upstream slope of the dam embankments above elevation 1095 is protected by a 3-foot layer of riprap on 18 inches of bedding, and the downstream slope is protected by a 2-foot-thick rock blanket. (a) Test Apparatus Installation. --In view of the design of the embankment and the foundation conditions of Whiskeytown Dam, the only instrumentation included in the construction specifications was for embankment settlement points. During operation of the structure, settlement points will provide performance data on cumulative settlement and horizontal deflection of the surface of the dam with respect to the crest centerline. The approximate location of points and details of installations are shown on figure 177. 236. Spillway. Details of the spillway are shown on figures 178 and 179. The spillway consists of a glory-hole-type inlet structure (fig. 180), a tunnel with a reducing elbow, and a flip-bucket structure. The inlet structure has a 92-foot-diameter ungated crest at elevation 1210.00, which is the top of Whiskeytown Reservoir conservation storage. Air is supplied through an air inlet pipe to the throat control section, at elevation 1093.46. The air inlet pipe is encased in concrete below the crest and extends above the crest through a pier located at the downstream end of the structure. A bellmouth transition extends from the circular spillway crest, elevation 1210.00, to elevation 1127.00, reducing from an inside diameter of 88 feet at the crest to an inside diameter of 24 feet 6 inches at the lower elevation. A reducing elbow comprises a transition from the 24-foot 6-inch diameter throat of the inlet structure to the 21-foot-diameter portion of |