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bare rocky areas construction scars would be covered with top- soil (where availablel or finely divided job excavated material, fertilized and seeded with native grasses. Seedling trees would be planted in areas which were originally forested. To inhibit erosion and to add organic matter to the soil, chipped tree slash and underbrush would be stockpiled and spread over the restored areas, In bare rocky areas, the construction site would be re- stored as nearly as possible to its original condition. B. TUNNEL CONSTRUCTION 1. Methods o ~ (.."l U\ I I 6. Waste Disposal Tunneling is a major item in every plan investigated. Tunnels in the igneous and metamorphic rock of the Sawatch Range (gener- ally between Homestake Valley and Cross Creek Valley) would probably be blast excavated. Use of tunnel boring machines would be permitted at the contractor's option, but machine tunneling in these types of rock has generally not compared favorably with blast excavation in either construction time or costs.' The Red Cliff and Turkey Creek Tunnels under Plans F and F-' would penetrate sedimentary formations, and use of boring machines could possibly be more appropriate for these tunnels. I Disposal of wastes produced during construction operations would be in conformity with regulations established by the U, S. Forest Service. The following minimum standards are anticipated: I I I . Portable toilets would be provided at all construction sites. Wastes would be coilected daily and deposited in an accept- able disposal facility at approved disposal points. All tunneling from Homestake Valley to Cross Creek Valley would be accomplished from portals in Homestake Valley. The Red Cliff Tunnel under Plans F and F-' would be driven from its western portal. The Turkey Creek Tunnel under Plans F and F-' would probably be driven from both portals. A mobilization and operations area would be required at or near each working portal. Such areas would require 3 to 5 acres of space and would be provided with temporary structures and facilities for administrative, operational and maintenance activities, together with necessary uti lity systems. I . Control of dust due to construction operations would be provided by surfacing access roads, mobilization and oper- ations areas, and other areas subject to traffic with select tunnel muck or other suitable granular material. Supple- mental control measures such as sprink ling and chemical palliatives would also be employed when necessary. Equipment used in the actual tunneling processes would be elec- tric or pneumatic powered. Tunnels would generally be driven on an ascending grade, except where driven from both portals, with water seepage into the bore drained by gravity to the working portal. All tunnels would be lined with concrete to minimize maintenance and to provide improved hydraulic performance. I I I . Solid wastes would be collected periodically and stored for recycling or buried in approved landfill sites. After construc- tion is completed, landfill sites would be restored as described under Section III.A-5 above. . Pollution of streams with turbid runoff from construction areas would be prohibited. Construction of temporary sedi- mentation basins to intercept runoff from construction areas, tunnel drainage, and other turbid water would be required. I f necessary to provide satisfactory sedimentation of suspended matter, chemical treatment would be required. I I I * Engineering Geologic Investigations for the Homeslake Extension Pro- ject, Woodward-Clevenger & Associates, February, 1973. I 24