PROJ00020

• Contract/PO #: C153567
• Contractor Name: Grand Junction, City of
• Contract Type: Loan
• Water District: 72
• County: Mesa
• Bill Number: SB 89-85
• Loan Projects - Doc Type: Feasibility Study

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Sub-alternative B-1: Unlined Open Channel

The unlined channel approach would involve the construction of basin-to-basin
diversion canals in reaches A and D. Some channel upgrading in reaches Band E
would also be required to confine a 30 cfs flow where channel definition is
presently minimal. Other minimal improvements that must be made include
membrane lining and slope protection through the slide area. Otherwise, this
approach woul d util ize exi s ti ng dra i nageways without further improvements or
bank stabilization. The drawback to this approach is that is relies entirely
on nature to protect against erosion. Many years of exposing and positioning
rocks in the stream bed would be required to form a natural rip-rap barrier, in
conjunction with the development of stream bank vegetation. Meanwhile, 0 & M
costs would be extensive. The clear advantage to this alternative is a low
initial capital cost.

Sub-alternative B-2: Rock-lined Open Channel

This sub-alternative is similar to B-1 except that the entire water course
would be shaped and appropriately lined with rap-rap to protect against
erosion. Rip-rap linings are categorized as shown in Figure 3-4 as having a 9"
maximum stone size for flat slopes and a 24" maximum stone size for steep
slopes, thus, the 9" section would apply to reaches A, D and F, while the 24"
section appl ies to reaches B, C and E. Because of the extreme length of the
conveyance system, full length erosion protection is very costly.

3-7