2004-09-14_GENERAL DOCUMENTS - M1977208

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n Wildlife Resources Assessment Cemex "C" Pit and CKD Disposal Site Page 3 3.3 Environmental Setting The site is located within the geologic structural depression known as the Denver Basin, and the erosional feature known as the Colorado Piedmont (Chronic and Williams 2002). Surface geology on the site is comprised primarily of the Niobrara Formation and lower Cretaceous bedrock including the Carlisle shale, Greenhorn limestone and Graneros shale (Colton 1978). The St. Vrain floodplain to the north of the plant is comprised of Piney Creek alluvium. Much of the southern portion of the site is comprised of Slocum alluvium, Pleistocene aged deposits that cover the Cretaceous sediments. Elevations of the analysis area range from a low of about 5,175 feet along the southern half of the east boundary near "A" Pit (Figures 2 and 3) to a high of approximately 5,410 feet at the southwest corner. Topography is generally flat or gentle slopes, and slopes downhill from west to east. Soils are primarily Niwot soil, Loveland soil, Manvel loam, and Laporte very fine sandy loam (USDA Natural Resources Conservation Service, 1975). With irrigation, soils typically range from class I-III, and without irrigation are most often class VI. These soil types are typically used for irrigated and nonirrigated crops, pasture, and rangeland. Mining has altered much of the soil distribution in the southern portion of the site. Approximately one-third mile of St. Vrain Creek is found along the north boundary (Figures 2 and 3). St. Vrain Creek is the principal drainage in northern Boulder County. Man made water features include the Boulder Feeder Canal (Photo Points 6 and 11), passing through the plant site from the northwest to the south-central boundary. The Swede Ditch is located on the east side of the Boulder Feeder Canal, and generally runs parallel to the canal (Figures 2 and 3). Vegetation cover in the analysis area is largely a result of historic agricultural practices and more recent mining activities. The riparian corridor along St. Vrain Creek has the only remaining natural vegetation community and native habitats on the entire plant site. Primary vegetation communities and cover types are as follows: Riparian: native riparian vegetation is located along St. Vrain Creek on the north boundary of the cement plant site. Artificial riparian vegetation is found along irrigation ditches, particularly the Swede Ditch in the western and southern portions of the analysis area (Photo Point 5). Other scattered stands are found around pond margins and swales to the north and east of the cement plant. "A" Pit has both mature riparian vegetation and an abundance of early succession riparian vegetation (Photo Points 3 and 4). ' Tame Pasture: the majority of the analysis area that is not included in the Lyons Quarry is grassland planted into European pasture grasses, primarily smooth brome (Bromus inermis). Both native and non-native herbaceous vegetation is found in these pastures. The largest areas are directly north, east and west of the cement plant. Another ' significant area begins just to the south of "C" Pit and continues south to Hygiene Road (Figure 3 and Photo Point 6). Reclamation Sites: most reclamation sites in the Lyons Quarry (refer to Figure 3 and Photo Points 2-5 and 11) have been planted with Russian wild rye (Elymus junceus), intermediate wheatgrass (Thinopyrum intermedium), crested wheatgrass (Agropyron cristatum) and smooth brome (Bromus inermis). This seed mix was used per the reclamation plan in the original 1977 CMLRB permit. One area near the southwestern corner of the Lyons Quarry also has plantings of native shrubs, including chokecherry (Prunus virginiana) and wild plum (Prunus americana).