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Alluvial Ya((n~ Floor lrtvetri,galiort • Powell (1952) drilled seven holes across the Purgatoire River alluvium immediately above the confluence of the Purgatoire River with Lorencito Canyon at the river crossing. Powell (1952) also drilled nine holes across the Purgatoire River alluvium west of Cordova, 1.0 mile east of the confluence of the South Fork of the Purgatoire and the Purgatoire. Hydrologic baseline characterization was initiated in January 1996 with the establishment of four surface water stations along Lorencito Canyon and two stations along Cow Canyon and one station each near the mouths of Alamosa, Chimney, Puertecito, and Jeff Canyons. Sampling of two surface water stations along the Purgatoire was initiated in June 1996. Field parameters (flow, pH, EC, temperature and D.O.) have been acquired monthly. Full suite water quality characterization occurred quarterly when water was flowing (see Surface Water Technical Report). MontFtly mapping of perennial reaches throughout the permit azea have supplemented the baseline data collection. The soil investigations were performed July 16 through 18, 1996. Five pits were dug in Lorencito Canyon, three in Cow Canyon, one in Jeff Canyon, and two in Chimney Canyon. Soil horizons were delineated, textures were characterized, and rooting density was noted. Data were acquired from the unpublished Las Animas County Soil Survey on potential rooting depth, available water capacity, land use and production. • Vegetation data was acquired June 17 through 26, 1996. Two grassland reference areas were established in Lorencito Canyon, and production statistics were derived from clippings of 20 transects. Annual and perennial grass and forb production were separated from one another. Production samples were clipped, placed in weight-tared bags, air-dried, and weighed to obtain results, which are summarized in the Vegetation Technical Report. SECTION 3 -RESULTS AND DISCUSSION Geology The site is underlain by rocks of the Upper Cretaceous and Paleocene Raton and Poison Canyon formations. The Raton formation is a sedimentary sequence of sandstones, shales, siltstones, and coal units. The Raton formation developed on a gently sloping alluvial plain cut by a meandering fluvial system with extensive back swamps where deep deposits of peat formed. This environment created the thick coal beds of the Raton Formation, which is mined in this area. These coal beds are sometimes split by siltstone and sandstone bank deposits. The Poison Canyon formation is derived from a regressive marine environment and consists of fan deposits. The Poison Canyon is acliff-former and is composed of sandstones, conglomerates, and thin yellow shale beds. In places, faults and flexures occur through the various strata of the area. Following deposition of the basin sediments, an orogeny with intense folding and subsequent thrust faulting occurred . west of the site. Shears developed in an east-west pattern, and normal tension faults have developed in a complementary set of fractures trending N10°W and N80°E. Site visits and review Avt.4751December 13, 1996 2