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Max Schmidt, NRCS Soil Survey Project Manager retired, Grand Junction <br />Office, and Bureau of Reclamation and EPA research on polyacrylamide <br />used to line canals, ditches, and ponds to decrease transit losses. <br />Soils in the area develop redoximorphic features as a result of impeded or excess surface water; <br />this allows water to infiltrate through weathered fractures in the Mancos shale to an impermeable <br />shale layer (Schmidt and BOR 1977 & 1985). Impermeable shale depths vary from the ground <br />surface to depths of ~30 feet (Weston and BOR 1977). Water trapped in this horizon creates an <br />unconfined perched water table and what would appear to be formation of near surface wetland <br />soil inclusions and groundwater pockets (Rayer & Weston). The lack of water in the area <br />precludes natural redoximorphic soil feature development; except where soils are in direct <br />contact with perennial streams (Ken Weston and BOR 1977 & 1985). Studies on canal seepage <br />that were conducted during the Colorado River Basin Salinity Control Project indicate that sub- <br />surface water tables directly relate to water levels present in irrigation canals and ditches (Ken <br />Weston and BOR 1977 & 1985). Local area soil scientists believe that wetlands would not exist <br />in the Grand Valley if it were not for irrigation, except when directly associated with perennial <br />streams and permanent bodies of water (Weston, Rayer, Schmidt). When these scientists were <br />asked if these wetlands would remain if irrigation was removed, they replied with a "No". <br />Significant Nexus <br />Physical <br />These areas with wetland characteristics are adjacent to non jurisdictional irrigation ditches that <br />provide insignificant contributions to the system other than returning irrigation flows. Natural <br />runoff is limited in the arid environment and the lateral irrigation ditches in the area do not <br />convey runoff from anything but small non jurisdiction intermittent washes that only flow in <br />times of severe localized precipitation events (BOR 1977). The functions of regulation of flow <br />and flood attenuation are not applicable to irrigation ditches in the project area. Surface water <br />connections from the Colorado River and into the Mack Lateral irrigation ditch are controlled by <br />head gates during irrigation season. <br />Chemical <br />Natural salinity from salt-shrub desert and selenium transport from Mancos shale is expected <br />when soils maintain extended periods of saturation. Irrigation runoff is assumed to include <br />fertilizers and herbicides (not tested). Irrigation ditches may also provide a filtration and storage <br />capacity for agriculturally related chemicals. Groundwater re-charge and creation of the perched <br />water table can be viewed as a potential negative function as it mobilizes selenium and salinity <br />that will be eventually transported into the Colorado River (TNW). <br />Biological <br />The habitat supports common amphibians and incidental use by terrestrial species that are <br />characteristic of the salt desert shrub community. Active Northern Harrier Hawk nests were <br />found in polygons A and H, and mule deer were frequently observed in these areas as well. <br />WestWater Engineering Page 9 of 75 January 2008 <br />DBMS 430 <br />