PERMFILE134174

• Permit No: M2005045
• IBM Index Class Name: Permit File
• Doc Date: 8/31/2005
• Doc Name: Other Agency Materials
• From: Gravel LLC
• To: DMG
• Media Type: D
• Archive: No

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Tom Kruger -Fwd: LUR Piedras de la Florida Class II r'^~ ~"~`~S
From: Wendy Klemm
To: Nan Bedau; Tom Kruger
Date: 7/1/2005 2:52 PM
Subject: Fwd: LUR Piedras de la Florida Class
COLORADO GEOLOGICAL
SURVEY
Division of Minerals & Geology
DepaRment of Natural Resources
1313 Sherman Streel, Room 715
Denver, Colorado 80203
Phone [phone]
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Juanita Sauvage
La Plata County Planning Dept.
1060 East Second Ave.
Durango, CO. 81301
RE: Piedras de la Florida Class II
CGS Review No. LL-05-0016
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Location: S30, T34N, R8W tCr.J~r
Received re fe
Bill Owens
(~ Governor
AUG 2 ~ [i]U~ Russell George
Fxecu6ve Dire
Ronald W. Caa
Durango Field Dffice Division Directe
Dear Ms. Sauvage: Division of tdinerats 8 Geology
Vincent MatNe
Per your request, I visited the site and reviewed the site plan on June 28, 2005. The site consistss'?IF ceologis
199.39 acres and will be used for a commercial gravel mining operation. Included in the submittal were a project
narrative (undated) and a Class II plan map by Southwest Land Services, Inc. (6-6-05). The CGS 1041 Geological
Hazards map of the Loma Linda Quadrangle (January 1977) was used as a reference.
1. Commercial area.
The proposed commercial area at the east side of the property is on a relatively flat, ancient river terrace adjacent
to C.R. 309. There are no geologic hazards that would preclude development in this area.
2. Access road.
The access road from C.R. 309 to the bottom of the floodplain adjacent to the Florida River cuts across slopes of
30% or greater. These slopes are cut banks of river terraces. This slope is marked as Potentially Unstable Slopes
(PUS) on the 1041 map. The definition of PUS is "Slopes in equilibrium but subject to failure if disturbed
improperly." There are a few concerns 1 have with the construction of this road. The first is slope stability in the
vicinity of the Williamson residence. The access road is proposed to run below the residence, which sits very
close to the edge of the top of the slope. Over-steepening of the slope below the residence has the potential to
cause slope instability and possibly have a negative effect on the Williamson house. I suggest that the road be
constructed with a fill section instead of a cut section in the area below the Williamson residence. The access
road should be engineered to avoid potential slope stability hazards.
There are wet areas on the slope below the proposed access road that may be wetlands. These wet areas can
affect the slope stability, especially with over-steepened road cuts and heavy truck traffic. A slope stability
analysis should be performed on the slope crossed by the access road which includes the wet areas in the
analysis. A qualified wetlands expert should designate potential wetlands areas on the property.
Please note that the geologic hazards associated with Phase 2 of this project are not evaluated in this letter.
In conclusion, a slope stability analysis should be performed on the slopes crossed by the access road. A
wetlands evaluation should be performed prior to the slope stability analysis so that the water mass may be
included in the slope stability analysis.
If you have any further questions or concerns, please contact me at [phone], or
file://C:1Documents%20and%20SettingsUcrugertg\Local%20Settings\Temp\GW}00002.HTM 7/6/2005 ,