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I I I I I I I I I I I I I I I I I I I OJ3186 management of the area that would enhance public safety and address land management concerns such as the refuse and sewage dumping problems. 3. EXISTING ENVIRONMENT AND FORESEEABLE EFFECTS 3.1 PHYSICAL RESOURCES 3.1.1 Physiography, Geology and Soils The John Martin Dam and Reservoir Project, located in the Arkansas River Valley of southeastern Colorado, lies within the High Plains section of the Great Plains Physiographic Province (Fenneman 1931). The region is characterized by flat to gently rolling uplands with a few shallow tributary valleys. There is relatively little topographic relief, and elevations in the area vary from about 3,750 feet in the river's flood plain below the dam to about 4,200 feet on hill tops several miles to the north. The basic geologic formations exposed along the Arkansas River Valley in the vicinity of John Martin Dam are Cretaceous sedimentary rock deposits that very slowly dip to the north- northeast. Most of the dam site is within the Lower Cretaceous Dakota sandstone formation that is inter-bedded with various shales. Graneros shale, an Upper Cretaceous sandy shale member of the Benton formation, also underlies part ofthe north wing dam. Soils in the Arkansas River Valley near John Martin Dam have been categorized as the Las-Apishapa-Bankard and the Las-Glendive Associations for Bent County (Preator et a/. 1971; Pannell et a/. 1966). These soils occupy the low-lying flood plain, bottom lands, and nearby terraces along the river. Some of the soils are clayey and poorly drained while others are loamy to sandy and are well to excessively drained and highly erodible. The no-action alternative would have no effect on physiography, geology or on soils at the John Martin Project. Proposed construction of campgrounds at the Overlook Recreation Area and proposed changes in access road alignments and construction of day-use parking lots in the Sandstone and Overlook Recreation Areas that would occur with the CSP proposal and the South Beach alternative may affect soils due to increased surface water runoff; however, these recreation areas are situated on rocky Pleistocene gravel terraces and soil erosion from surface water runoff would be insignificant. 3.1.2 Climate The climate of the Arkansas River valley is semi-arid continental. Colorado's eastern plains are characterized by hot and sunny summers, mild, dry, and sunny winters, and wide daily and annual temperature ranges. The area experiences considerable wind especially in the spring, humidity is generally low, and precipitation is low and variable. Evapotranspiration is usually very high in the summer. Average annual precipitation is 12 inches with most of the yearly 19