Overview

Paonia Dam is on Muddy Creek about 1 mile upstream of its junction with Anthracite Creek, which in turn forms the North Fork of the Gunnison River. The dam is an earthfill structure containing 1,302,000 cubic yards of embankment with an interior impervious zone, blanketed upstream and downstream by zones of sand, gravel, and cobbles. The upstream face is protected by a layer of riprap and the downstream face by a layer of rockfill. The crest of the dam is 35 feet wide and 770 feet long; the structure stands 199 feet above foundation.

The outlet works on the right abutment of the dam consists of a concrete intake tower, concrete-lined tunnel, gate chamber near the dam axis, and a combination stilling basin for both the outlet works and spillway. The outlet works also includes a concrete shaft house and concrete-lined shaft and add it between the gate chamber and access shaft. The capacity of the outlet works is 1,250 cubic feet per second at maximum water surface elevation.

The spillway, also on the right abutment, consists of an uncontrolled ogee crest and open chute having a design capacity of 12,500 cubic feet per second. The chute joins the combined outlet works-spillway stilling basin.

Paonia Reservoir has a surface area of 334 acres with a total capacity of 20,950 acre-feet and an active capacity of 18,150 acre-feet.

Geology

The damsite is located in a narrow V-notch section of Muddy Creek. On the right abutment, a thin mantle of soil blankets the Mesaverde formation. There are outcrop exposures of sandstone along this abutment about 60 feet above the stream. Accumulation of slope wash was found along the base of this abutment. This soil is generally sandy in texture with some fragments of sandstone distributed throughout. These fragments of sandstone vary in size from one foot to five feet in diameter. The left abutment of the dam is a steep North Slope covered with a mantle of sandy boulder soil. The depth of overburden on both abutments varies considerably and is influenced by alternating beds of sandstone and shales. The overburden blanketing the sandstone lenses is very shallow; the depth of overburden over the shale is deeper. The stream channel is made up of lava and granitic cobbles and boulders intermixed with the stream gravels. Slope wash and out wash fan accumulations have crowded into the channel. The depth of the channel gravel varies from 10 to 19 feet below the elevation of the stream surface through the damsite area. The stream has done some undercutting especially along the base of the left abutment and caused the slumping of the slope wash diverting the channel back to the right abutment.

General

Dimensions

Hydraulics & Hydrology