PROJ00454

• Contract/PO #: C153832
• Contractor Name: DeWeese-Dye Ditch and Reservoir Company
• Contract Type: Loan
• Water District: 12
• County: Custer
• Bill Number: HB 98-1189
• Loan Projects - Doc Type: Feasibility Study

4

Feasibility Report for Dam Safety Modifications to DeWeese Dam
April 22, 1997

inspection and engineering reports; preliminary stability analyses of the upper 12
feet of the dam; and recommendations for further investigative studies,

Conclusions of this evaluation confIrmed the concrete deterioration and stability
problems associated with the Crest raise sections as identifIed by the SEO and
discussed in Section 1.1 of this report.

2. Inflow Design Flood Report for DeWeese Dam, near Westcliff, Colorado
(April 7, 1995) [4]. A new estimate of the inflow design flood (IDF) for DeWeese
Dam and Reservoir was developed based on the runoff resulting from 50 percent
of the (PMP) in accordance with HMR55A [7]. The 50 percent PMP is the inflow
design flood required by the SEO for Intermediate, Class II dams, The IDF has
a runoff volume of about 57,000 af and a peak inflow to the reservoir of
approximately 144,000 cfs,

Results of the IDF study showed a peak discharge at the dam of 126,000 cfs with
17,9 feet of overtopping at the dam crest.

3. Field Investigations at De Weese Dam, near WestclifJ, Colorado (April 11, 1996)
[3]. Two borings were drilled through the dam crest and into the original dam to
obtain additional information regarding the strength and physical properties of the
concrete in the dam, This info1TI1ation was used in the development of the dam
safety modifIcation alternatives presented in this report. Laboratory testing of the
core samples included unconfined compressive strength, moist unit weight, direct
shear strength of the contact between the fIrst crest raise section and the original
dam, and petrographic analysis,

~ GEl Consultants, lnc,

96006\REPORTS\FEAS\TEXT.NEW

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