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

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

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

1

1. INTRODUCTION

1.1 BACKGROUND INFORMATION

The DeWeese-Dye Ditch and Reservoir Company (Company) supplies water for irrigation of
approximately 1 100 acres of land located near Canon City, in Fremont County, Colorado,
Irrigation water for the land, known as Lincoln Park, is delivered through the DeWeese-Dye
Ditch, which was constructed in the late 1890's, The DeWeese-Dye Ditch diverts water from
Grape Creek, a tributary of the Arkansas River, and delivers it to the Lincoln Park area through
about 3,6 miles of canal.

In addition to the DeW eese- Dye Ditch, the Company owns DeWeese Dam and Reservoir. The
dam and reservoir are located on Grape Creek in Custer County, Colorado, about five miles
north of the town of WestcIiff, The dam is a curved, concrete, gravity structure with a masonry
downstream face. The reservoir is the Company's only water storage facility, In addition to
irrigation water storage, the reservoir provides recreational benefits, The location of the dam and
contributing drainage area are shown on Figures I and 2.

Little information is available regarding the design or construction of the original dam structure
or its subsequent raises and improvements, Based on available information, it appears that the
original dam was constructed in 1903 and consists of a concrete section with downstream
masonry facing. Sometime between 1903 and 1931, a four-foot-high concrete raise was
constructed on the crest of the original dam, A second concrete crest raise was constructed in
about 1931, extending about 8 feet above the first raise and bringing the dam crest to about
elevation (EL) 7678, Design/construction drawings for the second raise indicate that it was
reinforced with steel reinforcing bars. No information is available regarding reinforcement in
the original dam or first crest raise section.

As shown on Figure 3, the present dam has a structural height of about 63 feet and a total crest
length of about 425 feet. The crest of the dam has a width of about 2 feet; however, there is a
downstream, 4-foot-wide ledge about 2 feet below the crest, which provides pedestrian access
along the top of the dam. The upstream face of the dam is nearly vertical and the downstream
face slopes about O.3H: 1 V (horizontal to vertical), The maximum normal pool level is at the
spillway crest, about 1.7 feet below the dam crest (estimated at EL 7678,0). The reservoir
volume at the maximum normal pool is about 4020 acre-feet (ai), An uncontrolled, rock-cut
spillway is located in the right abutment. The spillway has a crest and channel width of about
60 feet with a reported capacity of abciu"f390 cubic feet per second (cfs) when the reservoir pool
is at the dam crest, Two 16-inch-diameter outlet pipes are located about 42 feet below the crest
of the dam; a third, 36-inch-diameter pipe is located below the 16-inch pipes, about 50 feet
below the dam crest. The outlet conduits are controlled by slide gates located on the upstream

%OO6\REPORTS\FEAS\TEXT.NEW

~ GEL Consultants, Inc,