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<br />t'J <br />.- <br />. <br /> <br />-' <br />o <br />,~-:-:) <br />~ <br /> <br />CHAPTER II <br /> <br />DESCRIPTION OF ALTERNATIVES <br /> <br />Geoloav <br /> <br />Stubb Ditch.--The alignment of the Stubb Ditch crosses four major geologic <br />units in the east end of the Grand Valley. The upper reach near palisade <br />crosses a deep slope wash deposit comprised of sand, gravel, cobbles and <br />large boulders derived from the nearby Bookcliffs. Near Mount Garfield, <br />the alignment crosses several alluvial fans that contain clay, sand, <br />gravel, and boulders also derived from the Bookcliffs. Between Mount <br />Garfield and Clifton, a broad deep deposit of alluvium consisting primarily <br />of clay, sand and some gravel is crossed. In the Clifton area, outcrops of <br />Mancos Shale and shale derived soils are encountered. <br /> <br />All excavation required along the Stubb Ditch during construction would be <br />done with common excavation methods. Blasting would not be required unless <br />large boulders are encountered in the slope wash deposits in the upper <br />reach of the canal. Other problems may include high ground-water tables <br />and soft saturated soils. These problems would be most likely to occur in <br />the reaches crossing the alluvial fans and fine-grained alluvium along the <br />middle reaches. In the areas of Mancos Shale outcrops, the potential of <br />expansive clays is present. <br /> <br />Price Ditch.--The alignment of the Price Ditch crosses only two major <br />geologic units. The uppermost reach in the Palisade area traverses deep <br />slope wash deposits formed at the base of the nearby Bookcliffs. Sand, <br />gravel, cobbles, and large boulders comprise this unit. The materials are <br />quite permeable and drain well, thus a high water table and soft saturated <br />soils are not expected to be a problem. The remainder of the Price Ditch, <br />however, crosses a broad deposit of primarily fine-grained alluvium <br />consisting of sandy clay and clayey sand with some gravel. The alluvial <br />deposit is thick, and drains poorly, thus high water tables and soft, <br />saturated soils are common at very shallow depths. <br /> <br />Mancos Shale would not be encountered during construction of this canal. <br />All excavation would be by common excavation methods. The only blasting <br />that may be necessary would be isolated to the upper reach where large <br />boulders may be encountered in the slope wash deposits. <br /> <br />Construction Materials <br /> <br />The same construction material borrow sites as described in the FEIS would <br />be used to construct the Price and Stubb Ditches. The FEIS identified 13 <br />sites north of the Government Highline Canal which are mostly on Federal <br />land administered by the Bureau of Land Management. One site south of the <br />Government Highline Canal is also on Federal land. The 672 acres of <br />construction material sites identified in the FEIS would not be expanded <br />for the improvement of these two ditches. Use of the sites outlined in the <br />FEIS included necessary steps to reclaim the land after completion of <br />construction. The timing of use of these sites is scheduled to occur at <br />the same time as FEIS construction activities on the East End Government <br />Highline Canal. <br /> <br />Construction Methods <br /> <br />It is anticipated that construction methods would be traditional, however, <br />they would be constrained in many areas because existing improvements or <br /> <br />9 <br />