HOOVER DAM, LOS ANGELES BUREAU OF POWER & LIGHT HAER...

HOOVER DAM, LOS ANGELES BUREAU OF POWER & LIGHT LINES 1-3 (Boulder Dam) (Boulder Canyon Dam) U.S. Highway 93 Boulder City vicinity Clark County Nevada

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WRITTEN HISTORICAL AND DESCRIPTIVE DATA

HISTORIC AMERICAN ENGINEERING RECORD PACIFIC GREAT BASIN SUPPORT OFFICE

National Park Service U.S. Department of the Interior

1111 Jackson Street Oakland, CA 94607

HAER NV-27-M NV-27-M

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HISTORIC AMERICAN ENGINEERNG RECORD HOOVER DAM, LOS ANGELES BUREAU OF POWER & LIGHT LINES 1-3

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Date of Construction:

Engineer:

Builder:

Present Owner:

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HAER NO. NV-27-M

U.S. Highway 93 Vicinity of Boulder City Clark County Nevada

USGS Hoover Dam, Nevada-Arizona 7.5 Minute Provisional 1997 USGS Boulder Beach, Nevada 7.5 Minute 1970 USGS Boulder City, Nevada 7.5 Minute 1983 UTM Coordinates: Los Angeles BPL Line 1: 1 l .0703450.3988227 (start)

1 l.0698483.3983680 (end segment) Los Angeles BPL Line 2: 1 l.0703436.3988189 (start)

1 l.0698560.3983636 (end segment) Los Angeles BPL Line 3: 1 l.0703411.3988104 (start)

1933-1939

Los Angeles Bureau of Power and Light


City of Los Angeles

Not Applicable

Transmission lines

1 l.0698553.3983607 (end segment)

The Los Angeles Bureau of Power and Light transmission lines included pioneering technology in high-voltage transmission. The lines were crucial elements of the Hoover Dam electrical complex, particularly in the role played by Hoover Dam power in World War II industries and post-war development in southern California. At the time of construction, these lines transmitted electricity at a higher voltage than any other longdistance transmission line in the world.

Associated Cultural Resource Experts (ACRE) 8341 Sangre de Cristo Road, STE 202 Littleton, CO 80127

April 2004

Location:

Statement of Significance:

Description:

History:

HISTORIC AMERICAN ENGINEERNG RECORD

HOOVER DAM, LOS ANGELES BUREAU OF POWER & LIGHT LINES 1-3 HAER NO. NV-27-M

(Page 2) U.S. Highway 93 Vicinity of Boulder City Clark County Nevada

USGS Hoover Dam, Nevada-Arizona 7.5 Minute Provisional 1997 USGS Boulder Beach, Nevada 7.5 Minute 1970 USGS Boulder City, Nevada 7.5 Minute 1983 UTM Coordinates: Los Angeles BPL Line 1: l 1.0703450.3988227 (start)

11.0698483 .3983680 ( end documented segment) Los Angeles BPL Line 2: 1 l .0703436.3988189 (start)

1 l.0698560.3983636 (end documented segment) Los Angeles BPL Line 3: 1 l.0703411.3988104 (start)

1 l.0698553.3983607 (end documented segment)

The Los Angeles Bureau of Power and Light transmission lines included pioneering technology in high-voltage transmission. The lines were crucial elements of the Hoover Dam electrical complex, particularly in the role played by Hoover Dam power in World War II industries and post-war development in southern California. At the time of construction, these lines transmitted electricity at a higher voltage than any other long-distance transmission line in the world.

Three identical, high-voltage transmission lines were built by the Los Angeles Bureau of Power and Light (LABPL) from a switchyard at Hoover Dam to Los Angeles, California. The singlecircuit steel towers of these lines are narrow-waist type with the base rotated 45 degrees to the direction of the line. Tower bases are 32' square, and the towers are 109' 2" inches from base to the overhead ground wires at the towers' highest points. From 65'-long cross-members, three conductors are suspended under insulator strings composed of 24 1 O" porcelain insulators. The LABPL lines included 2,422 single-circuit towers, with an average span of 984' between towers; the western end of the line was built with 257 double-circuit towers.

The documented segments of these transmission lines originate at the LABPL Switchyard, on the Nevada rim of Black Canyon above Hoover Dam, in Section 29, T.22S-R.65E. The documented segments of 1 and 3 extend southwestward to the point where the transmission lines cross the south section line of Section 25, T.22S-R.64E. Line 2 was documented to a point southwest of Boulder City Substation. All towers in these segments are standard suspension, single-circuit design.

The original Hoover Dam power contracts required the City of Los Angeles to transmit power for itself, the Metropolitan Water District, municipalities, the Southern Sierras Power Company, and other utilities, but those other entities could opt for transmission by means other than the City's system. The Los Angeles Bureau of Power and Light (LABPL, also referred to as the L.A. Department of Water and Power) would obtain power from the first four generating units to come online at Hoover Dam (N-1 through N-4). After extensive research, LABPL determined that transmitting power at 287,500 volts over two circuits would be economical; after line losses, the transmission lines would deliver 275,000 volts at Los Angeles. Right-of-way and other considerations determined that the company would build two single circuits that would extend about 225 miles southwestward from a switchyard at Hoover Dam and then a double-circuit line for the final 41 miles. Long-distance transmission at this high voltage had not been attempted at that time, and the LABPL lines would necessarily include several important design innovations.

Sources:

HOOVER DAM, LOS ANGELES BUREAU OF POWER & LIGHT LINES 1-3 HAER NO. NV-27-M (Page 3)

Large-diameter conductor was desirable to limit corona losses in the transmission lines. Traditional, solid-copper conductors at this diameter would be unacceptably expensive, both in the cost of the conductor and in the increased bulk and cost of the supporting towers. A tubul<1r copper conductor 1.4" in diameter was adopted that successfully addressed these issues; this type of conductor had been developed in Germany and had not been previously used in the United States. Lightning protection for the lines also required innovation: two overhead ground wires and copper rods buried under the circuits and attached to each tower.

Tower design was critical: the structures had to be of sufficient height and strength to maintain economical and safe conductor spans between towers, but the structures had to be economical to build and maintain. The single-circuit steel towers were narrow-waist type with the base rotated 45 degrees to the direction of the line. Tower bases were 32' square, and the towers were 109' 2" from base to the overhead ground wires at the towers' highest points. From 65'-long crossmembers, three conductors were suspended under insulator strings composed of 24 1 O" porcelain insulators. The insulation for the conductors was not determined by the safety margins for current transmission, but by a need to protect the conductors from frequent lightning strikes.

LABPL began construction of its transmission system in June 1933 with the assistance of a $22.8 million loan from the Reconstruction Finance Corporation. Three nearly identical transmission lines were planned (called Boulder 1, 2, and 3). Boulder 1 and 2 were completed as a pair during the summer of 1936. The two lines were built parallel to each other from Hoover Dam to Upland California, and the lines in this distance were connected with an underground counterpoise system consisting of two copper wires for each tower, placed 135' apart where they cross-connected. These two wires crossed diagonally to intersect each tower, resulting in a corridor 400' wide.

Commercial power production at Hoover Dam power plant began on October 26, 1936, when generating unit N-2 was brought on-line to energize the LABPL Boulder 1 and Boulder 2 lines. The load over these lines served Los Angeles, Pasadena, Glendale, and Burbank, California, and the 287.5-kv load was a world record for long-distance transmission at that time. Generating units N-1, N-3, and N-4 were in regular operation by early 1937, feeding electricity through the LA Switchyard to the Boulder 1 and Boulder 2 transmission lines.

LABPL Boulder 3 transmission line was constructed in 1939 and 1940 with towers, conduit, and other equipment virtually identical to Boulder 1 and 2 lines, but the Boulder 3 line was not built with a sunken counterpoise system. Boulder 3 was built parallel to Boulder 1 and 2 in the vicinity of Hoover Dam, but the new line's route diverged considerably from the other two lines in some areas of western Nevada and California. Boulder 3 was connected to an extension built in the LA Switchyard to handle both the outgoing line and incoming transformer circuit No. 3 from the A-1 generating unit. The transmission line and switchyard were completed in the early months of 1940, and the transmission line was placed in service on April 21, 1940.

The three Los Angeles transmission lines proved to be extremely durable and reliable, and these lines played a crucial role in delivering power to the Los Angeles area during and after World War II. Beginning in 1970, portions of these lines in western Nevada and California were converted to 500-kv transmission and interconnected as part of the western grid system. All three of these lines continued to transmit power from Hoover Dam at 287.5-kv until the mid-1990s, when the lines were converted to more conventional 230-kv transmission. Minor changes have occurred to the towers of these lines, including installation of bird guards, new conductors, and replacement of some insulators.

This documentation of features of Hoover Dam and associated structures was accomplished by Associated Cultural Resource Experts (ACRE). ACRE completed documentation of21 features in

Project Information:


October 2002. Documentation on four linear features was extended and an additional 3 features were newly documented in February 2004. 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 (NV-27) and 25 short forms for individual structures: Hoover Dam, Los Angeles Switchyard (NV-27-A); Hoover Dam, Southern Sierras/CEP/Southern California Edison 138-kV Switchyard (NV-27-B); Hoover Dam, Metropolitan Water District Switchyard (NV-27-C); Hoover Dam, State of Nevada Switchyard (NV-27-D); Hoover Dam, Southern California Edison 230-kV Switchyard (NV-27-E); Hoover Dam, Arizona-Nevada Switchyard (NV-27-F); Hoover Dam, Static Towers and Lines (NV-27-G); Hoover Dam, Los Angeles Relay Control Building (NV-27-H); Hoover Dam, Switchyard Fire House (NV-27-I); Hoover Dam, Promontory Water Tank (NV-27-J); Hoover Dam, Control Cable Hoist House (NV-27-K); Hoover Dam, Transformer Circuits 1-15 (NV-27-L); Hoover Dam, Los Angeles BPL Lines 1-3 (NV-27-M); Hoover Dam, Southern California Edison North and South Lines (NV-27-N); Hoover Dam, Hoover-Basic Magnesium North and South Lines (NV-27-0); Hoover Dam, Metropolitan Water District Line 1 (NV-27-P); Hoover Dam, United States Construction Railroad (NV-27-Q); Hoover Dam, U.S. Highway 93 Nevada Segment (NV-27-R); Hoover Dam, Lower Portal Access Road (NV-27-S); Hoover Dam, Kingman Switchyard (NV-27-T); Hoover Dam, U.S. Highway 93 Arizona Segment (NV-27-U); Hoover Dam, Explosives Magazines (NV-27-V); Hoover Dam, Nevada Downstream Waste Tailings (NV-27-W); and Hoover Dam, Nevada Spoils Tunnel (NV-27-X); and Hoover Dam, Henderson-Mead Transmission Line 2 (NV-27-Y).

This documentation was prepared for three federal agencies: U.S. Department of Transportation, Federal Highway Administration (FHW A), 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. FHW A plans to construct a bridge over the Black Canyon of the Colorado River about 1,500' 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 FHW A.

Historian:


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.

Kurt P. Schweigert, Associated Cultural Resource Experts, 2004.

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HISTORIC AMERICAN ENGINEERNG RECORD ADDENDUM TO


Page 8

U.S. Highway 93 Vicinity of Boulder City Clark County Nevada

USGS Hoover Dam, Nevada-Arizona 7.5 Minute Provisional 1997 USGS Boulder Beach, Nevada 7.5 Minute 1970 USGS Boulder City, Nevada 7.5 Minute 1983 UTM Coordinates (NAD 27);

1933-1939

Los Angeles BPL Line 1: 1 l .0703450.3988227 (start) 1 l .0698420.3977800 ( end segment)

Los Angeles BPL Line 2: 11.0703436.3988189 {start) 1 l.0693470.3977759 (end segment)

Los Angeles BPL Line 3: 11.0703411.3988104 (start) 11.0693544.3977711 (end segment)



City of Los Angeles

Present Occupant: Not Applicable

Present Use:

Significance:

Report Prepared by:

Date:

Transmission lines

The Los Angeles Bureau of Power and Light transmission lines included pioneering technology in high-voltage transmission. The lines were crucial elements of the Hoover Dam electrical complex, particularly in the role played by Hoover Dam power in World War II industries and post-war development in southern California. At the time of construction, these lines transmitted electricity at a higher voltage than any other longdistance transmission line in the world.

Associated Cultural Resource Experts (ACRE) 8341 Sangre de Cristo Road, STE 202 Littleton, CO 80127

January 2005

Location:

Statement of Significance:

History:

Sources:

HISTORIC AMERICAN ENGINEERNG RECORD ADDENDUM TO


Page 9 U.S. Highway 93 Vicinity of Boulder City Clark County Nevada

USGS Hoover Dam, Nevada-Arizona 7.5 Minute Provisional 1997 USGS Boulder Beach, Nevada 7.5 Minute 1970 USGS Boulder City, Nevada 7.5 Minute 1983 UTM Coordinates (NAD 27): Los Angeles BPL Line 1: l l .0703450.3988227 (start)

l l.0698420.3977800 (end segment) Los Angeles BPL Line 2: l l .0703436.3988189 (start)

ll.0693470.3977759 (end segment) Los Angeles BPL Line 3: l l.0703411.3988104 (start)

1 l.0693544.397771 l (end segment)

The Los Angeles Bureau of Power and Light transmission lines included pioneering technology in high-voltage transmission. The lines were crucial elements of the Hoover Dam electrical complex, particularly in the role played by Hoover Dam power in World War II industries and post-war development in southern California. At the time of construction, these lines transmitted electricity at a higher voltage than any other long-distance transmission line in the world.

Three identical, high-voltage transmission lines were built by the Los Angeles Bureau of Power and Light (LABPL) from a switchyard at Hoover Dam to Los Angeles, California. The singlecircuit steel towers of these lines are narrow-waist type with the base rotated 45 degrees to the direction of the line. Tower bases are 32' square, and the towers are 109' 2" inches from base to the overhead ground wires at the towers' highest points. From 65'-long cross-members, three conductors are suspended under insulator strings composed of 24 1 O" porcelain insulators. The LABPL lines included 2,422 single-circuit towers, with an average span of 984' between towers; the western end of the lines in California were built with 257 double-circuit towers.

The documented segments of these transmission lines originate at the LABPL Switchyard, on the Nevada rim of Black Canyon above Hoover Dam, in Section 29, T.22S-R.65E. LAABPL Lines 1 and 3 were previously documented from the LABPL Switchyard southwestward to a point where the transmission lines cross the south section line of Section 25, T.22S-R.64E. LABPL Line 2 was previously documented from the LABPL Switchyard southwestward to a point in the SE\/.i of Section 2, T. 23S-R.64E. This Amendment extends documentation of all three transmission lines to the southwestward, to the locations where the LABPL lines are intercepted in the SW\/.i of Section 29, T.23S-R.64E by intertie transmission lines to Mead Substation. All towers in the documented segments are standard suspension, single-circuit design. All towers throughout the documented segments are identical in design aild materials, except for standard leg extensions on some towers to accommodate topographic features.

The history of the LABPL Lines 1, 2, and 3 was submitted previously in HAER No. NV-27-M.

Documentation of features of Hoover Dam and associated structures (HAER No. NV-27) was accomplished by Associated Cultural Resource Experts (ACRE). ACRE completed documentation of 21 features in October 2002. Documentation of four linear features was extended and an additional 3 features were newly documented in February 2004. Both phases of documentation were conducted as part of the historical/engineering recordation of Hoover Dam-

Project Information:

Historian:

ADDENDUM TO HOOVER DAM, LOS ANGELES BUREAU OF POWER & LIGHT LINES 1-3

HAER NO. NV-27-M (Page 10)

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 (NV-27) and 25 short forms for individual structures: Hoover Dam, Los Angeles Switchyard (NV-27-A); Hoover Dam, Southern Sierras/CEP/Southern California Edison 138-kV Switchyard (NV-27-B); Hoover Dam, Metropolitan Water District Switchyard (NV-27-C); Hoover Dam, State of Nevada Switchyard (NV-27-D); Hoover Dam, Southern California Edison 230-kV Switchyard (NV-27-E); Hoover Dam, Arizona-Nevada Switchyard (NV-27-F); Hoover Dam, Static Towers and Lines (NV-27-G); Hoover Dam, Los Angeles Relay Control Building (NV-27-H); Hoover Dam, Switchyard Fire House (NV-27-1); Hoover Dam, Promontory Water Tank (NV-27-J); Hoover Dam, Control Cable Hoist House (NV-27-K); Hoover Dam, Transformer Circuits 1-15 (NV-27-L); Hoover Dam, Los Angeles BPL Lines 1-3 (NV-27-M); Hoover Dam, Southern California Edison North and South Lines (NV-27-N); Hoover Dam, Hoover-Basic Magnesium North and South Lines (NV-27-0); Hoover Dam, Metropolitan Water District Line 1 (NV-27-P); Hoover Dam, United States Construction Railroad (NV-27-Q); Hoover Dam, U.S. Highway 93 Nevada Segment (NV-27-R); Hoover Dam, Lower Portal Access Road (NV-27-S); Hoover Dam, Kingman Switchyard (NV-27-T); Hoover Dam, U.S. Highway 93 Arizona Segment (NV-27-U); Hoover Dam, Explosives Magazines (NV-27-V); Hoover Dam, Nevada Downstream Waste Tailings (NV-27-W); and Hoover Dam, Nevada Spoils Tunnel (NV-27-X); and Hoover Dam, Henderson-Mead Transmission Line 2 (NV-27-Y).

This Addendum to HAER No. NV-27-M was prepared for the U.S. Department of Energy, Western Area Power Administration (Western), Desert Southwest Customer Support Region, Phoenix, AZ. Previous documentation of HAER No. NV-27-M recorded electrical features associated with Hoover Dam before planned alteration of some structures to allow doublecircuiting necessary to accommodate construction . of a bridge and highway realignment near Hoover Dam, This Addendum extends documentation of the three transmission lines to partially fulfill responsibilities of Western under Section 110 of the National Historic Preservation Act ( as amended).

Project Manager, historian, and photographer for this Addendum was Kurt P. Schweigert of Associated Cultural Resource Experts. Research and documentation for this Addendum consisted of field inventory and large-format photography only; additional historical research was not conducted.

Kurt P. Schweigert, Associated Cultural Resource Experts, 2005.

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