Hoover Dam, Los Angeles Switch Yard, U.S. Highway 93, Boulder City

Source document Quoted word for word from HAER NV-27-A. 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: l Date of Construction: Engineer: U.S. Bureau of Reclamation Builder: U.S. 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: l Statement of

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

The Los Angeles Switchyard was the first and largest of the six major federal switchyards at Hoover Dam. When the first stage of the switchyard began operations in it provided electricity at the highest voltages ever transmitted over long distances. Nearly all major equipment in the switchyard was designed and built especially for this facility. This switchyard played a key role in providing Hoover Dam electricity to war industries in southern California during World War II, and it continued to be important in the post- war industrial and residential boom of that area. Report Prepared by: Associated Cultural Resource Experts (ACRE) Sangre de Cristo Road, STE 202 Littleton, CO Date: April HOOVER DAM, LOS ANGELES SWITCHYARDS HAER NO.

NV-27-A (Page 2) The Los Angeles Switchyard was the first and largest of the six major federal switchyards at Hoover Dam. When the first stage of the switchyard began operations in it provided electricity at the highest voltages ever transmitted over long distances. Nearly all major equipment in the switchyard was designed and built especially for this facility. This switchyard played a key role in providing Hoover Dam electricity to war industries in southern California during World War II, and it continued to be important in the post-war industrial and residential boom of that area. Description: The Los Angeles Switchyard is long and wide in overall dimensions.

A concrete oil house x is at the south end of the switchyard and at a lower level than the main switchyard deck, so that the roof of the oil house forms the southern part of the switchyard equipment area. The oil house was used for storage and purification of oil used in the massive oil circuit breakers in the yard. The oil house includes an oil pump, a massive oil storage tank, a carbon dioxide frre control system, and an office/workroom. The main area of the switchyard includes a massive bus system, oil circuit breakers, disconnect switches, lightning arresters, and other equipment. The switchyard is enclosed by a reinforced concrete retaining wall on the west, a curb wall on the north, and a woven-wire fence around the entire switchyard perimeter.

History: In and Bureau of Reclamation contractors constructed the first stage of the City of Los Angeles Switchyard, which also was known as the Boulder Switchyard and the Los Angeles Bureau of Light and Power (LABLP) Switchyard. The initial stage of construction provided connection between the first two Hoover Dam generating units to be completed and the first two transmission lines built from Los Angeles. A second phase of construction occurred in to connect the third transmission line to Los Angeles. In the years of operation, this switchyard also provided power to and transmission lines running to Boulder City, Las Vegas, and Pioche, Nevada. When constructed, this switchyard was perhaps the largest such facility in the world, at least in terms of the capacity of installed equipment.

Transmission at voltages as high as had not been done previously, and nearly all equipment for the switchyard was designed specifically for this facility. The unique equipment was described in a Reclamation publication: New oil circuit breakers were designed by General Electric engineers to meet the ultra-high-speed switching requirements of the system. These breakers are of the impulse type and will interrupt amp. At in less than three cycles or seconds. They have eight breaks in series housed in the horizontal insulating tube. As the breaker opens, impelled by a strong spring, oil under pressure is forced across each break to extinguish the arc formed there. Each three-phase group of single-phase units occupies an area 22 x 54 ft. and stands 27 ft. high.

Only gallons ofoil, approximately 10 HOOVER DAM, LOS ANGELES SWITCHYARDS HAER NO. NV-27-A (Page 3) percent of that required by a conventional breaker of this size, is required for a three-phase unit. Of this amount only 210 gallons are exposed to the arc. This feature preserves insulating qualities of the oil, limits the weight of the switch, and simplifies oil handling in isolated locations such as those of the these desert switching stations. Lightning Arrestors for the switchyard and switching stations present an unusual appearance. The central column is the Thyrite arrestor itself being supported by the three strings of insulators around the outside. The bottom of the assembly is secured to the base through a spring tension to keep it from swaying.

Electrostatic stresses are distributed over the entire length of the arrestor by the circular shield arrangement around the top . . . . the Bowie disconnecting switches and the Westinghouse high- speed de-ion oil circuit breakers which are installed in the switchyard. The breakers are designed to interrupt 2,500,000-kva. in less than three cycles the disconnecting switch contact showing the protective hood over the moveable blade contact which protects against freezing and corrosion as well as decreasing the liability of corona formation.

Excavations for the switchyard were begun on May 25, and pouring of concrete footings in the switchyard began in July By the end of that year nearly all excavation and footing placement had been completed, and the oil house at the south end of the switchyard was complete except for installation of a roof slab. On July 27, forces of the Los Angeles Bureau of Power and Light began constructing the massive steel bus structures in the switchyards, and installation of electrical equipment followed.

The first two circuits within the switchyard were completed in early October and Hoover Dam power was first transmitted to Los Angeles through this switchyard on October 9, Power plant Unit N-2 was placed in regular operation on October 22, providing power through the LA Switchyard to Los Angeles and other surrounding cities. Regular operation of Units N-1 and N-4 followed later that year, providing power to the LA Switchyard and a second transmission line to Los Angeles. The initial switchyard consisted of four bays that accommodated two power lines to Los Angeles. Each line from the powerhouse handled the output of one transformer bank, and each transformer bank handled the output of two generators operating in parallel.

To handle the output of generating Units A-1, A-2 and temporarily handle the output ofN-5, an extension to the southern end of the existing LA Switchyard bays was necessary. To integrate the bus system, a ring bus was constructed with a tie bus over the top of the existing buses. To avoid outages on the two existing lines to Los Angeles, the new metal work and bus installation were accomplished while the substation remained energized. Construction of the switchyard extension began in May and all of the steel structures for the switchyard extension and Circuit No. 3 were completed by the end of that year. Bus work included changing the former direct bus connections for individual lines to a ring bus that connected all three lines.

Installation of oil circuit breakers in the switchyard was completed on December 4, Detail work in the switchyard was completed in early and the third transmission line was placed in service on April 21, HOOVER DAM, LOS ANGELES SWITCHYARDS HAER NO. NV-27-A (Page 4) Impulse oil circuit breakers for the two new bays of the LA Switchyard were built by General Electric. The type triple-pole, single-throw, high-speed, outdoor breakers were rated volts, amperes at 60 cycles, and interrupting capacity of 3,500,000-kva. These circuit breakers were an innovation from the conventional tank-type breakers. Each breaker consisted of a horizontal unit supported on vertical columns, which were supported by a fabricated steel framework. The operating mechanism was supported under the framework.

The horizontal unit contained the breaker mechanism and interrupting element. The end columns supported the horizontal unit and housed the cascade current transformers. All portions of the breaker were protected from weather by porcelain shells. Structural steel for the extension and all footings were constructed during the closing months of The overhead bus system, two oil circuit breakers, and disconnecting switches were installed in January The new equipment was initially used to connect generating units A-1 and A-2 to the original system for the two existing transmission lines. When the third transmission line was completed on April 21, the equipment in the switchyard extension was used to power the new line.

Few changes have occurred within the LA Switchyard since the period of original construction, The most important change has been the replacement of the huge Westinghouse oil circuit breakers with smaller General Electric breakers. Original bus works, lightening arresters, disconnect switches and other equipment are intact or only slightly altered. Most of the functions of the LA Switchyard became obsolete or redundant when Mead Substation was completed in the The original circuits were converted to transmission, and by the circuits simply passed through the switchyard en route to Mead Substation.

Source document Quoted word for word from HAER NV-27-A. 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 of21 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 (NV-27-I); 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, LOS ANGELES SWITCHYARDS HAER NO. NV-27-A (Page 5) Henderson-Mead Transmission Line 2

Source document Quoted word for word from HAER NV-27-A. 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.