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f=~ _ • Page 1 t'' David J. Cooper, Ph.D. July 16, 2001 Cynthia Parker Sage Hill Farms 8234 WCR 28 Platteville, CO 80651 Dear Cynthia: Dsvid J. Coops 2650 Lafayette Drive Boulder, CO 80305 July 16, 2001 Phone 303 4996441 Fax 303 4996441 e-mail: dcooper~rmi.rret REGs ~~~D Jl1L 13 2001 pirision of Minerals and Geo(6g(/ Subject Potential Impacts of Nuc Property Sand and Gravel Mine Wetland ecosystems develop and persist in sites where saturated and anaerobic soils occur for extensive periods of time during the growing season on most or all years. Some wetlands have saturated soils at all times of the year, while others are saturated for shorter periods of time. Wetlands also vary in whether the ever have standing water, and for those that do, how deep the water ponds. Wetland plant species are adapted for life in saturated and anaerobic soils. However, different wetland plant species occupy different hydrologic niches. For example, hard-stem bulrush (Schoenop/ectus /acustris} can tolerate perennially saturated soils, and deep standing water, while arctic sedge (Juncus arcticus) grows in seasonally saturated soils and is intolerant of deep standing water. Thus, along a complex hydrogeologic gradient, such as is found where a depression intersects a seasonally variable water table, a wide range of plant species are found, producing diverse and highly productive communities. A large wetland with a complex hydrogeologic gradient and a wide range of plant species occurs in the northeastern portion of your Sage Hill Farm. This wetland occupies a depression that intersections the South Platte River / St. Vrain River shallow unconfined alluvial aquifer. The static water table of this aquifer is above the soil surface in the czntral portion of the wetland for parts of the year, and this produces saturated soils over the entire wetland area. The wetland center is dominated bythree-square bulrush (Schoenop/ectus pungens), with patches of hard-stem bulrush and cattails (Typha angustifolia and T. lafifolia). These plants are all adapted to live in seasonally or permanently saturated soils, and at least seasonal inundation. On the basin margin are communities dominated by species that tolerate seasonally or permanently saturated soils, but only very shallow standing water, e.g. spikerush (Eleocharis pa/ustris), Nebraska sedge (Carex nebraskensis), hairy sedge (Carex lanuginosa) and others. On the driest margins of the wetland are species that tolerate both seasonally saturated soils and high soil salt concentrations, inGuding foxtail barley (Critesion jubatum) and other species.