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c.: <= ~. 'P'. " C BUREAU OF RECLAMATION REPORT The impervious layers lie nearly parallel to the surface. Thus the deep percolating water from irrigation is expected to travel through the coarse sands and gravels over the impervious strata and appear in the natural drains and the artificial drains that would be installed as a part of proj- ect development. Soils in the area have developed from.alluvial material under the influence of a cool, semiarid climate. On the higher terraces the soils are only slightly calcareous. Land Classification A detailed land classification survey of the project area was made in 1948 and 1949. Land class information, including boundaries and classi- fication symbols, was plotted on topographic maps at a scale of 400 feet to the inch and from the se maps acreages were computed. Soil borings were made throughout the project area to obtain soil samples for testing in the field laboratory. A minimum of one hole to each 40 acres was dug to a depth of 5 feet. To secure deeper soil profiles, holes 12 feet deep were dug with a power auger on representative areas. These deep profiles were examined to determine the character of the substrata, depth to impervious material, and probable subsurface dra~nage. Subsurface data were also obtained from river banks and exposed cuts. Soil samples were analyzed for salts, pH value, lime content, and, on questionable drainage areas, for permeability. Specifications used in establishing land classes were formulated by the Bureau of Reclamation on the basis of chemical and physical properties of the soils and topographic and drainage features. Five land classes were established as follows: Class l--Land highly suitable for irrigation farming; capable of producing any crop climatically adapted to area. Class 2--Land moderately suitable for irrigation farming but less desirable than Class 1 land because of soil, topographic, or drainage deficiencies; capable of producing any crop climatically adapted to area. Class J--Land of restricted suitability for irrigation farming because of pronounced deficiencies in soil, topographic, or drainage factor s; sui table for hay and grain crops and rotational pasture with more costly farm practices than are required on Class 1 and 2 land; particularly adaptable to pasture. Class 4--Land with at least one excessive deficiency that prevents production of rotational crops; suitable for pasture or meadow land. Class 6--Land considered permanently nonarable. 6