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according to tlne field work plan (CDM 2005). The total number of cores advanced at <br />each location and samples from each location subnnitted for geoteclunical analysis are <br />provided in Table 1. <br />Samples of streambed sediment were collected at up to five corehole locations at each <br />of the 30 field test sites, depending on site conditions and whether the site was one of <br />the stream gage locations at which additional cores were to be sampled. The samples <br />were collected to characterize tlne sediment grain-size distribution at each location. <br />These data were collected in order to determine a correlation between grails-size and <br />K. This correlation will be used to assist in develop>ing input for the conductance term <br />in the Streannflow-Routing Package for the MODFLOW groundwater flow model <br />being developed under Task 48. <br />At 25 field test sites, a total of up to six streambed sediment samples were collected <br />for grain-size distribution analysis from up to three corehole oriented on a transect <br />across the charunel. h1 addition, at the five test sites corresponding to stream gage <br />locations (Henderson, Kersey, Weldona, Balzac and Julesburg), up to ten samples <br />were collected from up to five corelnoles, located upstream and/or downstream of the <br />site survey transect. The additional samples at these five locations were obta>lned to <br />help define local spatial variability in sediment grains-size. Due to conditions <br />encountered in the field, not all samples were collected. The total number of cores <br />and core samples collected at each site are shown in Table 1. <br />At each corehole boning, all intervals with distinct lithologic characteristics were <br />logged in the field, and two samples were generally collected from each corehole. Tlne <br />mmlber of corehole locations at a given field test site was adjusted in the field <br />according to the width of the streambed or other factors influenc>ing the availability of <br />core material for geoteclnnical grain-size analysis. Locations for core sample collection <br />at each transect included one from a location with shallow water depth, one from an <br />intermediate water depth, and one from the deeper portion of the river, as field <br />conditions allowed. <br />Core samples were collected with a WaterMark® Universal Core Head Kit Sediment <br />Sampler equipped with an approximately 4 ft long polycarbonate core barrel. To <br />collect a sediment core, tlne clear, nominal 3-inch diameter polycarbonate barrel was <br />driven into the streambed sediment and the sample was retained iln the core barrel by <br />suction using aone-way check valve in the top of the core barrel. The clear core barrel <br />allows the composition of fine sediment onside to be observed. Tlne sampler was <br />manually driven using a "T" handle and alunninum extension rods as needed. <br />At location SG02, located on the South Platte River below Chatfield Reservoir, and <br />locations SC-11, SG12 and SG13, located on the Cache la Poudre River, the river <br />bottom was armored with cobbles that made it impractical to use the sediment <br />sampler for sample collection. At these locations, a post hole digger and/ or shovel <br />was used to collect sediment samples from the river bottom. In order to obtain <br />samples of the finer material controlling groundwater flow through fine streambed <br />sediment, samples at these locations were sieved on-site through a 1-inch mesh to <br />Fnlal T~zsl: 3~TM 06-28-07.doc 5 <br />