WSP07325

• File Number: 8443.600
• Description: Narrows Unit - Studies
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 6/17/1977
• Author: Dames And Moore
• Title: Proposal Safety review of Foundation and Embankment Narrows Dam, South Platte River Fort Mortan, Colorado
• Water Supply Pro - Doc Type: Report/Study

DAMES 8 M~OAE

Mr. Felix L. Sparks
June 17, 1977
Page 5

Site Visit

The site will be visited and inspected thoroughly by walking the

area. If deemed necessary, we will charter an aircraft for further

reconnaissance of the areal geology. The surface materials at the site

consist of weathered shale outcrops and alluvium. It is not expected

that a surface reconnaissance will yield much significant geologic

data but such a site visit is necessary to complement the drill logs

and published data. Exposed rock outcrops will be inspected for joint

pattern, joint spacing, width of joints and structure. Spot checking of

the surface geology maps prepared by the USBR will be performed.

Particular attention will be paid to the dam abutments and to searching

for evidence of the presence of sandstones or other pervious formations

in the area.

The soils at the project site and in the proposed borrow areas which

are considered potential construction materials will be inspected.

Detailed Evaluation of Subsurface Conditions

Using data obtained by the USER during their field exploration program,

a detailed check of the interpretation will be performed. Geologic

surface mapping and geologic cross-sections of the project site will be

checked against the drill hole logs and data published by other organizations

such as the U. S. Geological Survey. The drill cores will be inspected

if available and the USBR logs reviewed in light of the inspection. The

right abutment area will be given special attention and the adequacy of

data to define subsurface conditions at this critical area will be evaluated.