Hoover Dam, Arizona-Nevada Switchyard, U.S. Highway 93, Boulder City

Source document Quoted word for word from HAER NV-27-F. Not written, edited or summarised by this site.

U.S. Highway 93 Vicinity of Boulder City Clark County Nevada USGS Hoover Dam, Nevada-Arizona 7.5 Minute Provisional UTM Coordinates: 1 Date of Construction: Engineer: Bureau of Reclamation Builder: Bureau of Reclamation U.S. Highway 93 Vicinity of Boulder City Clark County Nevada USGS Hoover Dam, Nevada-Arizona 7.5 Minute Provisional UTM Coordinates: Statement of

Source document Quoted word for word from HAER NV-27-F. Not written, edited or summarised by this site.

The Arizona-Nevada Switchyard is one of six switchyards built between and to provide terminals for major transmission lines carrying electricity to markets in California, Nevada, and Arizona. All of these facilities were built by the Bureau of Reclamation as elements of the Boulder Canyon Project, and Reclamation documents referred to the entire complex of switchyards as "Boulder Switchyard." The Arizona- Nevada Switchyard is therefore a contributing element of the switchyard complex that was a major feature of the Hoover Dam development and contributed to the historical significance of the complex.

Report Prepared by: Associated Cultural Resource Experts (ACRE) Sangre de Cristo Road, STE 202 Littleton, CO Date: April HISTORIC AMERICAN ENGINEERNG RECORD HOOVER DAM, ARIZONA-NEVADA SWITCHYARD HAER NO. (Page 2) The Arizona-Nevada Switchyard is one of six switchyards built between and to provide terminals for major transmission lines carrying electricity to markets in California, Nevada, and Arizona.

All of these facilities were built by the Bureau of Reclamation as elements of the Boulder Canyon Project, and Reclamation documents referred to the entire complex of switchyards as "Boulder Switchyard." The Arizona-Nevada Switchyard is therefore a contributing element of the switchyard complex that was a major feature of the Hoover Dam development and contributed to the historical significance of the complex. Description: The Arizona-Nevada Switchyard is the southwestern-most of six electric power switchyards on the Nevada side of Hoover Dam. The fenced perimeter of the switchyard is x and the site for the facility was excavated into a northwest-facing slope.

The switchyard exists at two levels: a lower concrete service building 21' x that houses oil storage for circuit breakers and control equipment, and an upper graveled deck that contains bus structures, oil circuit breakers, disconnect switches, capacitors, and oil tanks on concrete foundations. The switchyard receives power from two transmission lines that cross the river from the Arizona powerhouse and a tie circuit to the Metropolitan Water District Switchyard. A single transmission line exits to the west of the Arizona-Nevada Switchyard. History: The Arizona-Nevada Switchyard was the last of six major federal switchyards to be constructed at Hoover Dam.

Installation of generating units A-3 and A-4 required the construction of a new switchyard to accommodate an incoming circuit from unit A-4 (Circuit No. an incoming circuit from unit A-3 (Circuit No. the outgoing Basic South (now Hoover-Boulder City Tap or Hoover-Mead) transmission line, and a tie line between the new switchyard and the existing Metropolitan Water District Switchyard to allow interchange and switching between circuits. The Arizona-Nevada Switchyard was constructed between and principally to provide power to users in Arizona and Nevada, and hence its name.

Principal items installed in the yard were four 1000-ampere, 3-phase oil circuit breakers; eight sets of motor-operated disconnecting switches for isolating oil circuit breakers; three single-pole, outdoor-type lightning arresters; about 100 tons of galvanized structural steel for supporting insulators, buses, and disconnecting switches; two 10,000-gallon oil storage tanks; a sewage disposal system; a 6- inch cast-iron water line for fire protection; and a 919'-long duct bank to an intersection with the control cable tunnel near the Metropolitan Water District Switchyard. The x switchyard was built into a northwest-facing slope on the south side of the highway, to the west of the Southern California Edison Switchyard and southwest of the Metropolitan Water District Switchyard.

The switchyard was built at two levels: a lower concrete service building for oil storage for circuit breakers and control equipment, and an upper graveled deck for installation of bus structures, oil circuit breakers, disconnect switches, capacitors, and oil tanks on concrete foundations. Excavation of rock for the switchyard proper began in late HOOVER DAM, ARIZONA-NEVADA SWITCHYARD HAER NO.

(Page 3) and was completed in February excavation for the access road and the service building began in March Concrete placement for the service building and footings began in May and was completed in June The steel bus structure was completed in September and installation of oil circuit breakers and disconnecting switches were completed in early In addition to oil storage and filtration, the 21' x service building contained carrier-current and telephone equipment, alternating-current distribution board DHA and direct-current distribution board BHA, service-station transformers, busses, fuses, and incidental equipment. A 60-cell, 125-volt battery and two battery chargers were also installed in the service building.

A 7- foot chain-link fence was built around the switchyard, and a similar fence and gate were installed to separate a part of the interior of the service building. Construction of the switchyard and the connecting transformer circuits was completed by the Howard P. Foley Company of Salt Lake City on May 14, Unit A-4 was released for commercial operation on April 30, and unit A-3 was released for commercial operation on September 18, The Arizona-Nevada Switchyard did not undergo extensive alterations in size or principal surface equipment until when a number of changes were made to the switchyard in preparation for transfer of operations to Mead Substation. One additional steel structure was constructed in the switchyard.

Potential and current transformers, control equipment, control cabinets, and associated equipment and wiring were installed or changed in the service building (Boyce Bureau of Reclamation The Arizona-Nevada Switchyard remained in use at the time of documentation in providing current to the Hoover-Boulder City Tap transmission line, also known as the Hoover-Mead transmission line.

Source document Quoted word for word from HAER NV-27-F. Not written, edited or summarised by this site.

This documentation of features of Hoover Dam and associated structures was accomplished by Associated Cultural Resource Experts (ACRE). ACRE completed documentation of2I features in October Documentation on four linear features was extended and an additional 3 features were newly documented in February Both phases of documentation were conducted as part of the historical/engineering recordation of Hoover Dam-prepared for the Department of Energy, Western Area Power Administration; Bureau of Reclamation; and Federal Highway Administration-that includes a narrative for the Addendum to Hoover Dam and individual documentation of 25 features located at the Hoover Dam facility, photo documentation, and documentation of existing historic photographs and site plans.

The recordation conforms to the standards of the Historic American Engineering Record, U.S. Department of the Interior.

Other reports in the HAER collection completed for these projects are a narrative for the Addendum to Hoover Dam and 24 short forms for individual structures: Hoover Dam, Los Angeles Switchyard (NV-27-A); Hoover Dam, Southern Sierras/CEP/Southern California Edison Switchyard Hoover Dam, Metropolitan Water District Switchyard Hoover Dam, State of Nevada Switchyard Hoover Dam, Southern California Edison Switchyard (NV-27-E); Hoover Dam, Arizona-Nevada Switchyard Hoover Dam, Static Towers and Lines Hoover Dam, Los Angeles Relay Control Building Hoover Dam, Switchyard Fire House Hoover Dam, Promontory Water Tank Hoover Dam, Control Cable Hoist House Hoover Dam, Transformer Circuits Hoover Dam, Los Angeles BPL Lines 1-3 Hoover Dam, Southern California Edison North and South Lines Hoover Dam, Hoover-Basic Magnesium North and South Lines Hoover Dam, Metropolitan Water District Line 1 Hoover Dam, United States Construction Railroad Hoover Dam, U.S.

Highway 93 Nevada Segment Hoover Dam, Lower Portal Access Road Hoover Dam, Kingman Switchyard Hoover Dam, U.S. Highway 93 Arizona Segment (NV-27-U); Hoover Dam, Explosives Magazines Hoover Dam, Nevada Downstream Waste Tailings and Hoover Dam, Nevada Spoils Tunnel Hoover Dam, HOOVER DAM, ARIZONA-NEVADA SWITCHYARD HAER NO. (Page 4) Henderson-Mead Transmission Line 2

Source document Quoted word for word from HAER NV-27-F. Not written, edited or summarised by this site.

This documentation was prepared for three federal agencies: U.S. Department of Transportation, Federal Highway Administration (FHWA), Central Federal Lands Highway Division, Lakewood, CO; U.S. Department of Energy, Western Area Power Administration (Western), Desert Southwest Customer Support Region, Phoenix, AZ; and U.S. Department of Interior, Bureau of Reclamation (Reclamation), Lower Colorado Region, Boulder City, NV. This documentation records certain transportation and electrical features associated with Hoover Dam before planned removal or alteration of some structures. FHWA plans to construct a bridge over the Black Canyon of the Colorado River about downstream from Hoover Dam. The Hoover Dam Bypass Project would include realignment of U.S.

Highway 93 on the Nevada and Arizona sides of Black Canyon. The project would include demolition, relocation, or substantial visual impact to a segment of U.S. Highway 93 on the Nevada approach to Hoover Dam, a segment of a former alignment of U.S. Highway 93 in Arizona, electrical transformer circuits in Arizona and Nevada, two electrical switchyards, a segment of the grade of the U.S. Construction Railroad, a stone gate structure for a dam construction and operations road, and six historic transmission lines. This documentation also records certain structures not directly affected by FHWA's Hoover Dam Bypass Project. Electrical transmission facilities at Hoover Dam are administered by Western, but these facilities are within a federal reservation administered by Reclamation.

Documentation of electrical structures is intended to partially fulfill responsibilities of Western and Reclamation under Section 110 of the National Historic Preservation Act (As amended). Some electrical structures addressed by Western and Reclamation would be directly affected by FHWA's Hoover Dam Bypass Project, and all structures addressed by Western and Reclamation are functionally related and geographically near structures addressed by FHWA. Project Manager and historian for the recordation was Kurt P. Schweigert of Associated Cultural Resource Experts. The photographers were Deborah Dobson-Brown and Douglas M. Edwards of Associated Cultural Resource Experts.

This documentation was prepared on the basis of research conducted at Reclamation archives in Denver, CO, and Boulder City, NV; Western archives and files in Denver and Phoenix, AZ; the National Archives and Records Administration in Denver; libraries of the University of Nevada-Las Vegas; and the Western History Collection of the Denver Public Library. This documentation includes information contained in survey reports for the Hoover Dam Bypass Project Environmental Impact Statement, an evaluation of the Western switchyards at Hoover Dam, an evaluation of the Hoover Dam construction railroads, a National Register nomination for Hoover Dam, and other documents.