PERMFILE72543

• Permit No: M2003091
• IBM Index Class Name: Permit File
• Doc Date: 10/29/2003
• Doc Name: Application
• From: Lafarge West Inc
• To: DMG
• Media Type: D
• Archive: No

~I I ~ I
J~ SCOTT, COX & ASSOCIATES, INC. consulting engineers • surveyors
M. Edward Glassgow, N, P.E. • William H. Mitzclfeld, P.E.
September 19, 2003
Lafarge
1400 W 64th Avenue
P.O. Box 21588
Denver, Colorado 80221-0588
Project: 03449
Ladies and Gentlemen:
At your request, and pursuant to the rules and regulations of the Colorado Mined Land
Reclamation Board (6.4.19 -Permanent Man-Made Structures), Mr. Ed Glassgow, P.E.,
Scott, Cox & Associates, Inc. reviewed Western Mobile's existing geologic data (boring
logs) and conducted a field inspection of Western Mobile's Duckworth Property
(located north of Weld County Road 20 'h and west of Weld County Road 7) in Weld
County, Colorado. The purpose of this inspection and data review was to provide
Western Mobile with offset recommendations between areas proposed for excavation
and existing permanent man-made structures. Additionally, we were asked to provide
an opinion regarding offset from waterways, such as Idaho Creek and major ditches.
The available boring log documentation (a total of 27 borings completed at scattered
locations across the site) shows that the soils at this site consist of an average of
approximately 3.5 feet of overburden (consisting of topsoil, clay, sand and
undifferentiated materials logged just as overburden) atop an average of approximately
14.9 feet of sand and gravel (although it is unclear if the full gravel section was
penetrated in some of the borings). The groundwater table was not on the boring logs
that we reviewed. However, the groundwater level at nearby investigations that we
have completed has ranged from depths of approximately 6 to 12 feet below the
existing ground surface. The depth of the deeper borings ranged from approximately
15 feet to 20.5 feet. We assume that the boring was terminated at the bottom of the
gravel layer, which would typically be claystone bedrock in this area. Therefore, it is
anticipated, from our review of the boring logs that the pit depth could range from 15
feet to over 20 feet. For the purposes of this report we will assume a maximum mined
depth of 20 feet.
The soils encountered at this site have varying angles of repose. The soils that will
control the stability of the slope are anticipated to be the sand and gravel. Based on our
experience in this area and reference geotechnical engineering literature
("Fundamentals of Geotechnical Analysis" by I. S. Dunn, L. R. Anderson and F. W.
Kiefer) an anticipated conservative angle of internal friction for this material is
approximately 26°. This is based on the assumption that dewatering will keep the face
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