PROJ00455

• Contract/PO #: C153583
• Contractor Name: Ute Water Conservancy District
• Water District: 0
• Bill Number: XB 99-999
• Loan Projects - Doc Type: Feasibility Study

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overall tunnel length and its elevation. This alignment suffers from a number of limitation and flaws,

including:

. There is no proper location for construction of the west portal due to the steep
topography of the general area along the alignment;

. The construction of a tunnel could de-stabilize the canyon wall along 1-70 due to
proximity of the tunnel;

. The construction of the access construction/maintenance road to the west portal will
be extremely difficult and costly due to steep topography; and

. The construction and maintenance operations will have an negative impact on
highway operation and the safety of motorists due to the close proximity of the
tunnel construction to 1-70.

Due to these design, permitting, construction, and maintenance problems this alternative was not
investigated any further.

Three typical tunnel cross-sections were evaluated. These cross sections are shown on Figure 5-4.
All the typical sections involve constructing a tunnel section approximately eight feet high by seven
feet wide. Typical cross-section 5A as shown on Figure 5-4 would involve placing approximately six
inches of bedding material along one wall of a 42-inch in diameter steel pipe on the tunnel cross-
section. The steel pipe would be left exposed in the tunnel and would require some type of coating
such as paint to prevent corrosion. This cross-section would require construction of portal doors
to minimize air flow along the pipe during the winter months. Typical section 5B has bedding
placed in the bottom of the tunnel section and a six foot inside diameter reinforced concrete pipe
placed on top of this bedding with loose sand placed between the pipe and the excavation. Typical
section 5C would be similar to the existing Plateau Tunnel. This section includes a 42-in. -diameter,
steel pipe placed on bedding and backfiIled to a depth of approximately one foot over the top of
the pipe. A crawl space approximately three feet high would exist above the pipe and backfill in
the tunnel section.

Tunnel lining considerations for the proposed excavation are considered to be minimal and similar
to those in the initial Plateau Tunnel construction. It is believed that some minor amount of
temporary support will be required at several spots along the tunnel alignment but most of the
excavation can be unsupported. It is anticipated that no permanent lining will be required.

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