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r- - r r I ,. , .' ,.. _ l .L \1 ... ..i. CONSTRLlCTION UTILITIES 143 their benefit and at their expense. Similarly contractors at their own cost connected their camps and work with the District high- ways. These stub roads were graded and many were either oil sur- faced or treated with calcium chloride, but were built to last the period of construction only, Prior to beginning work on, and during the erection of, the 230-kv transmission line from Boulder dam to the District pumping plants, 250 miles of additional roads were graded to serve this work and for subsequent use in patrolling the lines. Since these roads were solely for this portion of the project, their cost was charged to this feature and they are described in the chapter on the transmission lines. A paved branch road to be built by District forces from U. S. Highway 60 to the Hayfield pumping plant was authorized April 9, 1937. This road, approximately 3.5 miles in length, was graded in August 1937; the oil mix was prepared and spread in September; and the work completed in November of the same year. In addition to the desel.t roads constructed in conjunction with the main aqueduct work, the District has built roads in the Cajalco area to replace county roads closed by the construction and opera- tion of the reservoir. This work is described in the section of the report pertaining to Cajalco reservoir. Constt'uct-ion and 11I-aIntennHce The District trunk and branch roads were designed and built with a uniforlll 20-foot width of oil cake pavement of a minimum thickness of 3 inches when compressed and having a 3'12-inch crown. On both sides of the paving, shoulders extend 2 to 6 feet on the same or a slightly increased slope to the ditches, providing a roadway with a minimum width of 24 feet. Upon completion of grading, including cuts and fills, the subgrade was prepared by sprinkling and rolling the native material, or, where the material was blow sand or otherwise unsuitable, by spreading and similarly treating selected materials from borrow pits. Upon this subgrade surfacing materials, native or imported or a mixture of the two, as conditions required, were distributed iu windrows and thor- oughly mixed with road oil by blading back and forth or by a tractor-propelled mixing machine. The road mix was then spread in layers and compacted by rollers and under traffic, accompanied by dragging and other treatment necessary to produce a smooth. true, and satisfactory wearing surface.