Hoover Dam, Lower Portal Access Road, U.S. Highway 93, Boulder City

Source document Quoted word for word from HAER NV-27-S. 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 (start) 1 (middle) 1 (end) Date of Construction: Engineer: Six Companies, Inc. Builder: Six Companies, Inc. U.S. Highway 93 Vicinity of Boulder City Clark County Nevada USGS Hoover Dam, Nevada-Arizona 7.5 Minute Provisional UTM Coordinates: (start) l (middle) (end) Statement of

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

The Lower Portal Tunnel Access Road was an important feature in the construction of Hoover Dam. The road provided access to the bottom of Black Canyon at a point about one mile downstream from the dam construction site. Here a coffer dam was constructed and diversion tunnels were bored northward on the Nevada and Arizona sides of the river. Report Prepared by: Associated Cultural Resource Experts (ACRE) Sangre de Cristo Road, STE 202 Littleton, CO Date: April HOOVER DAM, LOWER PORTAL ACCESS ROAD HAER NO. (Page 2) HISTORIC AMERICAN ENGINEERNG RECORD HOOVER DAM, LOWER PORTAL ACCESS ROAD HAER NO. The Lower Portal Tunnel Access Road was an important feature in the construction of Hoover Dam.

The road provided access to the bottom of Black Canyon at a point about one mile downstream from the dam construction site. Here a coffer dam was constructed and diversion tunnels were bored northward on the Nevada and Arizona sides of the river. Description: The Lower Portal Tunnel Access Road is a paved road leading from U.S. Highway 93 to the Lower Portal Tunnel. The road exits current U.S. 93 to the south and opposite the Bureau of Reclamation warehouse complex, about one mile east of Hoover Dam. Access to the road is controlled by a gate structure including two battered stone columns with extruded mortar joints.

The road courses southward on a sinuous route through a canyon for about feet, and terminates at the Lower Portal Tunnel, a 1,900-foot tunnel leading to the Nevada side of the Hoover Dam power plant. The road is about 20 feet wide and is paved with asphalt. In many areas, the roadway is cut into natural slopes. Access to the road is controlled by a gate structure including two battered stone columns with extruded mortar joints, similar to the rockwork in retaining walls in the U.S. 93 approach to Hoover Dam. Each column has a hooded light at top. Original gate hinges remain on both columns, but the original gates have been replaced with an electric gate that is not attached to the columns.

History: Prior to the beginning of construction of Hoover Dam, the bottom of Black Canyon could only be accessed by floating down the Colorado River. When preliminary construction activities began in Six Companies, Inc. constructed a series of roads to allow travel of men and equipment from the construction base in Boulder City to various locations near the dam site, including a rough road blasted from a sheer mountainside at the upstream mouth of Black Canyon. To allow work to begin downstream from the dam site, Six Companies, Inc. constructed a road down a steep canyon to the bottom of the river gorge. A number of bridges and walkways were built across the river near the end of the road to allow access to the Arizona side of the river.

As the dam was nearing completion, a 1900-foot long tunnel was bored through the Nevada canyon wall to allow vehicular access to the Hoover Dam power plant by means of what then became known as the Lower Portal Tunnel Access Road.

Source document Quoted word for word from HAER NV-27-S. 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 HOOVER DAM, LOWER PORTAL ACCESS ROAD HAER NO.

(Page 3) 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, Henderson-Mead Transmission Line 2

Source document Quoted word for word from HAER NV-27-S. 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 HOOVER DAM, LOWER PORTAL ACCESS ROAD HAER NO. (Page 4) 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.