WSP04498

• File Number: 8276.120
• Description: Grand Valley Unit-Colorado River Basin Salinity Control Project
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 6/1/1983
• Title: Supplement To Definite Plan Report: Stage Two Development Grand Valley Unit
• Water Supply Pro - Doc Type: Definite Plan Report

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CHAPTER V

STAGE TWO PLAN OF DEVELOPMENT

For Stage Two, the Fish and wildlife Service is considering alter-

natives to the acquisition and development of lands.

Ideas inc lude

development of wildlife ponds on the desert side of the Government

Highline Canal, development of cross-drainage features for wildlife

habitat, deer escape devices along the canal, and voluntary on-farm

development of habitat along laterals. Final recommendations may include

a combination of land acquisition with the implementation of items

discussed above.

Geology and Construction Materials

Geology

The Mancos Shale is often overlain by various forms of alluvium;

however, it is either exposed or covered by only a few feet of soi 1,

especially in the western portion of the unit area.

The surficial

deposits are composed of fine-grained alluvium along washes and streams,

gravelly pediment materials, thin slopewash, residual soils, and a rather

extensive river channel deposit--the cobble aquifer.

Much of the proposed canal and lateral lining construction would

involve the weathered Mancos Shale.

This shale is hard and dense at

depth but near the surface is often fractured and jointed or weathered

into a lean clay or silty soil.

All excavation required during con-

struction along the canal and laterals, whether in soil or bedrock, would

be common excavat ions.

The shale contains secondary mineralization in

the form of gypsum and calcite and often slakes and cracks upon exposure

to the air. The upper weathered shale often contains ground water which

moves principally through joints, fractures, and open bedd ing planes.

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