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<br />0: 1881 <br /> <br />PROJEm' LANDS <br /> <br />In 1959, the Bureau of Reclamation completed the classification of <br />60,400 acres of 1/ nd in the Trinidad area. These lands are situated in <br />three pnysiographic positions: the river bottomlands, the river terrace <br />lands, and the uplands such a s the Model area and parts of the Baca and <br />John r s Flood areas. The bottomland soils have developed from alluvium <br />deposi ted by the river or by side streams. The soils consist of mixtures <br />of materials, they are deep but are not well adapted to irrigation because <br />of fine textures and poor development of soil structure. The topsoil <br />is predominantly heavy clay loam, and the subsoil is generally clay or <br />1e avy clay loam. The substrata material is clay with some clay loam. <br />These soils are generally inadequately aerated, therefore, crop yields <br />are low and subsurface drainage is poor except in some areas that have <br />coarse textured substrata. The soils of the terrace lands were also <br />developed from alluvial materials brought in by side streams or by the <br />river. <br /> <br />Generally the top soils are clay loam and quite uniform in texture. <br />The subsoils are also uniform and consist of loam or silt loam with sandy <br />loam in some places. The substrata of these terrace soils will average <br />about 10 feet in thickness and consist of clay loam and very sandy loam. <br />These substrata are SUfficiently permeable to provide adequate subsUrface <br />drainage. In the upland areas the soils of the Model area have devleoped <br />from the Granerous Shale which underlies the area. The soils are <br />mOderately well suited for irrigation and both topsoils and subsoils <br />range from clay loams to clay. Beneath the soil profile is a relatively <br />thick layer of sandy weathered shale Which provides adequate subsurface <br />drainage. Other upland areas confined largely to the Baca and ;r oim 's <br />Flood areas have soils which developed from the Pierre Shale. The topsoils <br />and subsoils here are similar in texture to those of the MOdel, but lack the <br />sandy substratum below the subsoil. Because of this restricted subsurface <br />drainage, they are ill-adapted to irrigation. No saline or alkaline soils <br />are expected to develop from future irrigation with the project on about <br />70 percent of the irrigable lands. They have remained free from accumulations <br />of salt and alkali under irrigation in the past and in the future the <br />application of greater water supplies will provide greater leaching. <br />Because drainage is adequate, these soils are expected to remain free from <br />harmful accumulations of salts. About 30 percent of the irrigable area has <br />mOderately saline conditions in the subsoils. These conditions are associated <br />with restricted subsurface drainage conditions. AJ.though maximum yeilds <br />cannot be obtained on these lands, their limited productivity is not expected <br />to drop. In some places, however, saline and alkaline conditions were <br />such that land was classed as non=irrigable. Tbese areas are primarily <br />in the southeastern part of the Model tract and in isolated areas in other <br />parts of the service area. Inadequate drainage is responsible for this <br />condition. <br /> <br />8 <br />