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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Figure 4 is ~ geologic cross-section along the line of the

proposed axis, with interpretation based on field exploration

results.

Figure 5 is a plan drawing of the location of impervious

borrow investigations.

P igures G, 7, and 8 arc log sheets of the borrow area samples.

Figure 9 is a very simple sketch of the assumed Course of the

ancient deep channel of the South Platte Biver in the Weld County

Karrows area.

Figure 10 is a sketch showing a dam section, which we feel

is reasonable, and results of foundation seepage assumptions and

calcu la tions.

GENERAL GEOLOOY OF THE ABEA

BedroCk in the Hardin-Fort Morgan area consists of formations

of Cretaceous and older age. Those formations lying immediately

below the overburden are the Laramie, Fox Hills and Pierre forma-

tions, the latter being the oldest. These formations have, in

this area, a general, gentle, westward'dip but occasional flat-

telling and steepening have created a mildly undulating attitude

of the formations which, together with lensing stratigraphic

conditions, has created the present subsurface structure.

E.""cept

for the basal sandstone layer of the Laramie formation and thc

sandstone section of the Fox Hills formation, the bedrock through-

out the area is an impervious, gray to blac]" carbonaceous, silty

to sandy and clayey shale. The Laramie and Fox Hills sandstone

layers arc somewhat shaly, very fine grained and dense and though

more pervious than the shale layers above and below them, they
are still of vcry low permeability.

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