Laserfiche WebLink
were often found in this vegetation type. The dominant grasses included Poa pratensis <br /> (Kentucky bluegrass) and Agropyron smithii (western wheat-Wass). Cirsium canadensis <br /> (Canada thistle), Carduus nutans (musk thistle), Melilotus oficinale (yellow <br /> sweetclover), and Tarauacum otTicinale (dandelion) were the most frequently observed <br /> forb species. <br /> The native vegetation of areas in Section 28 has been largely replaced by annual <br /> agricultural crops, including corn, sugar beets, and forage. Remaining native <br /> vegetation is restricted to small patches adjacent to irrigation ditches, and is comprised <br /> largely of Populus deltoides individuals and Salix exigua clumps. <br /> Hydrology <br /> As evidenced by the significantly different vegetation communities, the hydrologic <br /> regime of the area of interest is largely determined by topography and elevation. <br /> Upland areas above the relict oxbows and topographic lows are dry, with no evidence <br /> of ponding or water retention. Within the microtopographic lows, there is standing <br /> water or evidence of standing water during the growing season. Below the farm pond, <br /> it appears that the embankment and/or bottom of the pond is porous, as the soils are <br /> saturated immediately below the embankment. The farm pond was holding water <br /> during the course of the field investigation. The Last Chance Ditch was flowing during <br /> the field investigation, as was St. Vrain Creek. <br /> The surface hydrology of the areas developed for agriculture in Section 28 has been <br /> altered. Based on the surrounding topography, it appears that historically, surface <br /> water drainages were present which drained the quaternary and tertiary alluvial terraces <br /> and traversed the lower alluvial terraces on their course to St. Vrain Creek. Evidence <br /> of these historical surface drainages can be observed in Sections 4, 5, 6, 32, and 33. <br /> These drainages may have been intercepted (as evidenced by the Lupton Bottom Ditch <br /> immediately below the tertiary alluvial terrace in Sections 5, 32, and 33), or modified <br /> and channelized (Last Chance Ditch and the ditch in Section 28). <br /> Soils <br /> Soils within the area of interest are representative of their genesis and topographic <br /> position. The Natural Resource Conservation Service (USDA, 1980) identifies five <br /> soil map units within the property. The primary alluvial terrace contains Bankard <br /> sandy loam soils. This soil is comprised of deep, somewhat excessively drained soils <br /> from recent alluvial sources. Bankard soils are not listed as hydric in the national list <br /> l . of hydric soils (USACE, 1987). Soils of the secondary alluvial terrace and a portion of <br /> the tertiary terrace are considered aquolls and aquepts, formed from alluvial sources <br /> along bottomlands and floodplains. Aquoll and aquept soils are identified as hydric by <br /> definition (USACE, 1987). On the tertiary alluvial terrace, Altvan loam, flooded <br /> aquolls and aqucpts, and Nunn clay loams are mapped. Altvan and Nunn series soils <br /> arc deep, well-drained soils formed in alluvial and/or colian deposits. <br /> -3- <br />