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• c. Soil Type Influences on Wastewater Treatment <br />Deep sandy soils which have sandy subsoils and allow rapid percolation of water are generally <br />well adapted to the support of a septic tank filter-field for the adequate treatment of effluent <br />from individual sewage systems. As the topsoil and/or subsoil becomes more shallow and less <br />sandy (more clayey), more restrictions in soil permeability and filter-field adequacy are <br />encountered. In areas where percolation is slow or moderately restricted, it is necessary to <br />construct more generous septic tank filter-fields in order to treat sewage wastes adequately <br />and maintain sanitary conditions. Very heavy (clayey) soils which exhibit over restrictions in <br />water percolation are not suited to septic tank systems, and sanitary conditions usually cannot <br />be maintained even with the use of oversized filter-fields coupled with prudent usage during <br />times when precipitation and soil moisture content is abnormally high. Where there are thin <br />porous soils in conjunction with fractured bedrock or shallow bedrock, pollution problems <br />may occur from septic tank systems, due to excessive leaching into groundwaters. <br />Sewage treatment lagoons, on the other hand, are best adapted to areas which have heavy <br />soils. The construction of aerobic lagoons in sandy areas sometimes presents performance <br />problems because the lagoons do not seal in sandy soils and water retention for adequate <br />periods is difficult to maintain. <br />d. Soils of the Project Area <br />• The Keenesburg area soils are made of sandy loam soils. The soil series, the Valent and the <br />Osgood, makeup most of the area on the proposed mine site west of Ennis Draw. The <br />Osgood is a deeply developed soil with a slight amount of clay in the subsoil. The Valent has <br />shallower soil development as evidenced by lighter co{ors in the subsoil with no increase in <br />clay depth. Both are extremely sandy. <br />Appendix L-I, Soil and Vegetation Inventory. Revegetation Research. Keenesburg Area, <br />By D. N. Heyder, Dale Romine, R. D. Heil and W. A. Berg, <br />November 1978, provides detailed information on the soil resources of the permit area. <br />• <br />75 <br />