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CHAPTER III ALTERNATIVES The alluvium along the canals and laterals varies widely from lean clay to silts to silty gravels of varying origins; however, the materials are predominantly rock-f ree, fine-grained soils. Problems to be considered during design of the canals and laterals include the potential of the soils and shale to expand; high ground water tables in some areas; soft, saturated soils; frost susceptible soils; and soils with a high salt content. Construction Materials Although specific amounts of earth materials have not been quanti- fied, substantial volumes would be required for lining the canals and for installing pipe laterals, including fine-grained soils to reshape the waterway sections before placing membrane lining or pipe. Material would also be needed as covering for membrane lining; embankment for detention ditches, dikes, and dams; surfacing for roads; and aggregate for concrete production. Field reconnaissance of construction material sites was conducted to locate the large volumes of fine-grained soils needed during construc- tion. The exploration was essentially limited to the area north of the Government Highline Canal because the lands south of the canal are either irrigated croplands, homesites, or are otherwise intensively developed. Fourteen sites containing large volumes of fine-grained soils, classified as sandy silts, silty sands, and lean clays, have been identified that could furnish suitable refill materials. Thirteen of the sites are north of the Government Highline Canal and are mostly on Federal land admin- istered by the Bureau of Land Management. One site south of the canal is also on Federal land withdrawn by Reclamation. The Features Map on page 19 shows the location of these construction material sites. Sand and gravel for concrete production, membrane covering, and road surfacing would be derived from previously developed sources along the Colorado and Gunnison Rivers as shown on the Features Map. Cur- rently, three commercial operations produce ready-mix concrete, and these and other operations also produce sand and gravel suitable for membrane covering and road material. The acreage needed for the construction material sites, shown on the Features Map, is estimated at 672 acres of federally owned and 114 acres of privately owned land which would be obtained by temporary rights-of-way and/or agreements. The Federal Land Policy and Management Act of 1976 requires that all lands withdrawn from the public domain be reviewed and justified to determine if they are being used for project purposes. The review is scheduled for 1986, and all involved entities will be able to make recommendations to justify the retention of any lands. (Reclamation's intent would be to keep those areas needed to operate and maintain the Grand Valley Unit.) Construction material sites would probably be relinquished with the retention of special use permits. In addition, these construction material sites could probably provide a source of embankment material for the detention ditch and dike 30