WSP05705

• File Number: 8407
• Description: Platte River Basin - River Basin General Publications
• State: CO
• Basin: Statewide
• Date: 3/11/1964
• Author: CWCB
• Title: Engineering and Geologic Investigation and Analysis of Alternate Proposed Dam Sites on the South Platte River - Morgan and Weld Counties-Colorado
• Water Supply Pro - Doc Type: Report/Study

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making a cutoff through the Aeolian sediments to the bedrock on

the upper abutments or through the alluvium to the water table

at any point along the axis. Below the water table we believe a

slurry trench type or grout cutoff can be reasonably made to

depths of 70 to 80 feet. This has already been demonstrated on

dams on the Columbia River under much more difficult conditions.

A cutoff through the deep inner channel would, we believe, have

to be a grout or slurry trench cutoff.

The dr i lling and seismic iuvestiga tiOI1S performed in con-

junction with this report arc, in our opinion, sufficiently firm

for the purpose intended and we believe they show that the lower

Weld County site is geologically suitable for construction of an

earth dam. They show that the seepage conditions are sufficieutly

low, that construction materials are available and that from an

engineering geologic standpoint the lower Weld County site offers

the opportunity of better seepage control than the Narrows site.

we, therefore, recommend that the comparative costs of con-

structing the two sites be re-figured by the U. S. Bureau of

Reclamation utilizing the data made available by these investiga-

tiOl1S. We believe that the previously stated cost advantages of

Narrows over the Weld County site us far as construction and secp-

age control are concerned, will be significantly reduced or offset.

By

j!)A~CleVenger

EBW:WAC:m

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(20 copies