transmission lines are terminated on peaks on the 138- and 69-kilovolt structures, respectively. Overhead ground wires also run from the 138- and 230-kilovolt structures to the structures around transformer bank KY2A and from the 138- and 69-kilovolt structures to the structures around transformer bank KY1A. The 24.9-kilovolt structure is equipped with 6-foot steel masts, and the 12.5-kilovolt structure is equipped with 5-foot steel masts. The steel structures are connected to the switchyard grounding system which is tied to the powerplant grounding mat. Lightning arresters are provided on all terminals of power transformers KY1A, KY2A, and KX2A. One set of lightning arresters is mounted on the 138-kilovolt main bus structure for the protection of potential transformers VY9A. Another set of lightning arresters is mounted on the 69-kilovolt main bus structure for the protection of potential transformers VX1A. One set of lightning arresters is mounted on the outgoing line of each of the two 24.9kilovolt bays to protect equipment in those bays. One set of lightning arresters is mounted at each end of the 12.5-kilovolt overhead transmission line to protect the three-phase auxiliary station-service power from the powerplant. Also, a set of lightning arresters is mounted for each of the three power transformers all located on the powerplant deck. 134. Grounding System. Most of the protective grounding system in the switchyard consists of 3/4-inch by 20-foot ground rods grouted in rock; however, the ground rods along the south fence are 3/4 inch by 10 feet which are driven in soft earth. All ground rods were placed at intervals of 20 feet or less inside the fence and around transformers or lightning arrester banks and connected together by a network of No. 4/0 A.W.G. stranded copper cable. Fenceposts are connected to the ground mat at approximately 40-foot intervals. All steel structures, circuit breaker tanks, power transformers, oil tanks, lightning arresters, and other metallic items are connected to the ground mat by lateral cables and risers. The switchyard ground mat is connected to the powerplant ground mat by four 500, 000-circular-mil stranded copper cables which extend in the control cable tunnel. CHAPTER X. Design -- VISITORS' CENTER AND SERVICE FACILITIES 135. General. An attractive visitors' center building (fig. 170), with restroom and comfort facilities, has been provided at the right abutment of Flaming Gorge Dam. A parking area of adequate capacity has also been provided at this abutment. The visitors' center building is reached by an access road about 8 miles long from a junction on Utah State Highway No. 44 (see fig. 3). From the visitors' center the access road crosses the dam to the left abutment, then continues about 2 miles east to the community of Dutch John. A turnoff near the left abutment leads to the powerplant at the bottom of the canyon. A turnoff at the right abutment parking area towards the southwest leads to the switchyard, located on a bench approximately 50 feet lower than the parking area. The visitors' center building is at the same elevation as the crest of the dam. It is of steel frame construction utilizing glass areas and natural stone walls. Interior finishes are of natural birch and ceramic tile along with acoustical ceilings. This building provides a focal point for visitor activity and convenience. 136. Service Yard Area. The service yard area, located in front of the service bay of the powerplant, is the main access and storage area for the powerplant. It was made large enough so that heavy equipment trailers could be turned around. Also, the ringfollower gate house and hollow-jet gate platform are so situated that mobile servicing equipment can be moved into position. The parking area is contained by a concrete gravity wall having a 0.7 to 1 slope on the fill side and a vertical face on the exposed side to elevation 5582. Below this elevation the wall has a 0.5 to 1 slope. The top of the parking area is at about elevation 5620.5. An 8-inch sewer-pipe drain embedded in gravel at elevation 5604 with outlets through the wall at 20-foot centers provides drainage through the fill. Figure 171 shows details of the service yard. The following loading assumptions and conditions were used in the design of the retaining wall: Loading assumptions: (1) Water level in saturated backfill to elevation 5608. (2) Earthquake of 0.1g horizontal in any direction and 0.05g vertical. For both conditions (1) and (2), shear friction factor should be larger than 4.0. (3) Saturated fill to elevation 5620.0; 60-ton trailer hauling unit; Tailwater elevation 5601.6. |