The relocation of the road, carrying it along precipitous bluffs and through mountains of stone, has been a tremendous problem and by far the biggest part of the construction program. Because of the inaccessibility of the project, the public in general is unacquainted with the problems and magnitude of the work - considered by engineers as serious a piece of construction as any ever attempted on a transcontinental railway.

Various locations were surveyed and several eminent engineers were employed by the District in selecting the final location on which the new road is now being built and in estimating the total cost. The requirements of the Yosemite Valley Railroad Company that the new line be approximately the same length as the old resulted in the decision to bridge the reservoir at Pleasant Valley.

Bids on the relocation of the railroad were opened by the District September 4, 1923, but the work was not let until nearly a year later. In the meantime a new bond issue had been voted and the work re-advertised. On August 12, 1924, F. Rolandi signed a contract with the District for reconstruction of seventeen miles of the Yosemite Valley Railroad not including the five bridges. On December 9, 1924, the American Bridge Company signed a contract with the District for the designing, furnishing and erecting the steel work of five railroad bridges.

Their bid was an alternative proposal calling for continuous truss type riveted design for the big bridge across the reservoir at Pleasant Valley and this alternative proposal was conditional on the District completing the upper five miles of the new railroad to allow the bridge company to move its equipment and bridge steel over the new railroad to the bridge sites and to erect the steel work directly from cars rather than transferring it up the slope from the present Yosemite Valley Railroad. On November 21, 1924, Davis, Heller & Pearce signed the contract with the District for construction of the concrete piers and abutments for the five railroad bridges.

The seventeen-mile relocation of the Yosemite Valley Railroad will necessitate the excavation of 1,500,000 cubic yards of rock and earth, the construction of four concrete lined tunnels having a total length of 3,615 feet, besides the minor items of arches, culverts, retaining walls, tracklaying, ballasting, etc., and the construction of five railroad bridges requires 81,000 cubic yards of excavation and placing 45,600 cubic yards of concrete. The steelwork totals 7,207,000 pounds. Bridge No. 3, which carries the railroad across the reservoir, is 1600 feet long and the base of rail is 236 feet above low water. Seventy per cent of the total steel goes into this one bridge.

The work on the railroad has progressed according to schedule in respect to yardage moved and work done, but the quantities of excavation both in the railroad work and the foundations for bridge piers and abutments have greatly exceeded the original estimates due to the unstable character of the rock encountered. This same unstable condition of the rock in the tunnels made necessary to timber practically the entire length and the timbered section required considerably more concrete than the untimbered section.

A force of 497 men working on the railroad excavation and tunnels. The equipment being used for this work consists of 14 steam shovels, 3 gas shovels and 3 air shovels, 65 horses and mules, 24 dump trucks, 86 dump cars, 12 dinkeys, 7 compressors, 38 jackhammers, 16 leyners, 2 concrete mixers, etc. Forty men are working on the surfacing and track laying and 129 men are working on the railroad bridges, making a total force of 666 men.

The walls of the Merced River canyon at the site of the Dam are extremely narrow. Here the main line of the Yosemite Valley Railroad clings to the granite cliffs over 100 feet above the river, and traffic over its line must be maintained without interruption. This condition made the problem of providing adequate space for the erection of mixing plants, shops and gravel bins for storage of thousands of tons of material required in the construction of the dam a most serious one. As only one day's supply of aggregate could be stored, a plant that would meet this situation had to be built.

M. H. Slocum, superintendent, upon whom full responsibility of the entire construction rests, with characteristic dispatch designed and built necessary structure, which clings to the walls of the canyon along the railroad tracks far above the river. At Hopeton, sixteen miles below the Dam, he constructed a gravel plant. The plant has not only supplied material for the Dam but an 120,000 tons of aggregate for construction of bridges, tunnels and ballast on the relocated line of the Yosemite Valley Railroad, the present tracks which will be some 220 feet under water upon the completion of the Dam.

The wonderful organization of the work shows itself in the fact that twenty-two trains daily are operated over the Yosemite Valley Railroad. All the gravel, cement, lumber, and metal work has to be hauled over this line.