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Section 3 <br />Field Data Collection Procedures <br />3.1.1 Initial Site Coring and Evaluation <br />At each site, a preliminary boring will be sampled to determine initial site conditions <br />and depth of streambed sediments. This core will be visually evaluated for the <br />presence of different soil features that indicate the contact between streambed <br />sediment and the underlying aquifer, such as changes in color, grain size, texture, and <br />organic matter content. The depth of any contact below the streambed will be used to <br />determine the sample depths of the remaining cores and subsequent hydraulic <br />evaluations. <br />3.1.2 Channel Cross-Section Profiling <br />streambed geometry will also be defined for the streambed transects using the stream <br />channel cross-sections. The stream channel cross-sections will be surveyed to a <br />temporary benchmark. A survey reading will be taken at each change in slope along <br />the streambed or every 10 feet if there is no significant change across the streambed. <br />The temporary benchmark placed during the stream conductance fieldwork will be <br />surveyed by a licensed Colorado surveyor using precision differential GPS methods. <br />All relative elevations will be updated to elevation above mean sea level after receipt <br />of survey results. It is anticipated that the surveying will occur within 2 weeks of the <br />end of field activities described under Task 34.1 to minimize the chances of the <br />temporary benchmark being disturbed. <br />3.1.3 Grain Size Analysis <br />Up to a total of six streambed sediment samples will be collected for grain size <br />distribution analysis from up to three core holes at each transect location. It is <br />expected that two samples will be collected from each core hole, however this maybe <br />adjusted in the field according to the sediment thickness at each location or other <br />factors influencing the availability of core material for geotechnical grain-size <br />analysis. At the five stream gage locations, up to two additional core holes will be <br />sampled upstream and/or downstream of the transect, with up to an additional 4 <br />sediment samples collected from these cores for grain size distribution to help define <br />local spatial variability. A total of up to 200 core samples are anticipated to be <br />collected for geotechnical grain size testing, with up to six samples at each of up to 30 <br />transects, with up to an additional four samples each of the five stream gage locations. <br />Anticipated locations for core sample collection at each transect will include one from <br />a shallow zone in the river, one from an intermediate depth, and one from the deeper <br />portion of the river, as field conditions allow. Core samples will be collected with a <br />device capable of sampling soft saturated sediments, such as a Kajak-Brinkhurst core <br />sampler or other comparable equipment, using methods presented in ASTM D-4823- <br />95 Standard Guide for Core Sampling Submerged Unconsolidated Sediment. The <br />cores will represent across-section of streambed sediment layers. <br />The materials retrieved from the sediment core holes will be described by the field <br />geologist in a bound field notebook, and representative core intervals for geotechnical <br />`~ ~ <br />3-2 <br />FINAL SPDSS T33 WORK PLAN &3-OS.DOC <br />