XXX Terming the relocation of the Yosemite Valley railway to avoid Exchequer reservoir "a unique problem," Railway Age, technical publication of Chicago and New York, carries an excellently illustrated article describing the construction in its issue for March 20. The article is as follows:

XXX"The Yosemite Valley railroad, a standard gauge line, extends from Merced, Calif., in the San Joaquin valley to El Portal, on the western boundary of Yosemite National park, a distance of 24 miles, the road lies on the eastern edge of the valley and at the latter point enters the Merced river canyon, along the bottom of which it continues to El Portal, crossing the river twice in its ascent.

XXX"At Exchequer, seven miles above Merced Falls, the Merced irrigation district is building a dam which will raise the water level about 300 feet and form a reservoir extending upstream some 12 miles. In order to place the road above high water, while maintaining the same ruling grade, one per cent compensated, it was necessary to relocate the 17 mile section from Merced Falls to Detwiler. This was accomplished without increasing the total ascent, owing to the fact that there were several stretches of level and descending grade in the old line.

XXX"The new location threw the line into the broken country near the top of the canyon walls, along steep slopes averaging from 25 degrees to 30 degrees and entailed extremely heavy work, even with a maximum 12 degree curve freely used. The material consisted in large part of badly contorted seamy shale, frequently talcose, and necessitating flat slopes in excavation. The close proximity of the new and old lines, the steep slopes and character of the material were causes of serious interruptions to traffic over the operated road while blasting was going on. The grading quantities totaled 1,700,000 cubic yards, averaging 100,000 cubic yards per mile, the work being done by steam shovels, of which 13 were employed on the job at one time.

XXX"The canyon is subject to occasional heavy rain storms and there are numerous side drainages; these conditions required the installation of a large number of culverts, the smaller ones being corrugated pipe, the larger ones concrete arches. There are four tunnels on the line, the shortest being 440 feet in length, the longest 1673 feet, and the total length of all 3613 feet. The excavation of these tunnels was troublesome, and timbering was required for practically their entire lengths. They are to be lined with concrete before the line is operated.

XXX"The most interesting structures on the new road are the steel bridges, of which there are five, aggregating 2965 feet in length. Four of these consist of deck girder approach spans and two 643 feet continuous through trusses each resting on three supports. The piers supporting these trusses vary in height from 83 feet to 229 feet with a full reservoir they will be from 68 feet to 214 feet under water.

XXX"On account of the fluctuation of the water level in the reservoir and the consequent danger of corrosion, the piers are of plain concrete, except in the upper 13 feet above the high water level. The high ones supporting the truss spans are of ordinary dumbbell section with square corners and side buttresses; the batter is variable, decreasing towards the bottom. Special care was taken in deciding on the foundation, diamond drill holes being put down to solid rock and jack hammered holes bored over entire area 10 to 12 feet below them.

XXX"The concrete proportioning, mixing and placing was carefully controlled, the methods used being a combination of those of Abrams, Talbot and Fuller. The sand was inundated, water accurately measured and frequent slump tests made. The results, as regards strength, density and uniformity, have been most satisfactory and have justified the extra time and expense required over the old arbitrary method. The aggregate consisted of sand up to an inch, intermediate up to 1 1/2 inch and coarse up to 2 1/2 inch.

XXX"The relocated line will be completed and ready for operation about May 1, 1926, at an estimated cost of $4,000,000. The work is being carried on by contract under the supervision of Jerome Newman, consulting engineer of the Yosemite Valley railroad, San Francisco, California. We are indebted to W. L. White, general manager of this road, for information contained in this article."

(Accompanying photographs of: Typical Tunnel Construction, New Roadbed Construction and Bridge No. 3)