WSPC112

• File Number: 8240.200.49.J
• Description: Colorado River Threatened-Endangered - RIPRAP - Price-Stubb Fish Passage - Environmental Studies
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 4/19/2004
• Author: DOI-BOR
• Title: Revised Supplemental Draft Environmental Assessment and Notice of Public Meeting - RE- Providing Endangered Fish Passage at the Price-Stubb Diversion Dam on the Colorado River - 04-19-04
• Water Supply Pro - Doc Type: Report/Study

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Revised Supplemental Draft Environmental Assessment-Chapter 3-Affected
Environment and Environmental Consequences

Downstream Rock Fish Passage: This alternative would also have no effect on
existing structures. The fish passage would protect the left bank of the river with
additional riprap. Ifthe Jacobson Hydro No. 1 Project as described in the terminated
license agreement were constructed, an extended discharge pipe would be needed to
attract fish to the fish passage entrance. To address CDOT's concerns with future
Interstate 70 widening, the fish passage channel was offset 20 feet from the left river
bank to accommodate future widening projects. Reclamation would raise the elevation
between the fish passage channel and left river bank with suitable material to protect the
fish passage channel during high flow events. Additional fill material to accommodate
future Interstate 70 widening would be the responsibility of CDOT.

Downstream Rock Fish Passage with Whitewater Recreation Features:
Effects under this alternative would be similar to the Downstream Fish Passage
Alternative. This alternative also incorporates the 20 foot fish passage channel offset to
accommodate future Interstate 70 widening. Boaters would likely use Colorado River
State Park-Island Acres located about 3 miles upstream to access the whitewater features.
Without public access through E.R Jacobson and CDOTproperties downstream of the
dam, unauthorized access to the river upstream of the dam may occur. Parking on
Interstate 70 is not permitted and additional enforcement may be necessary to discourage
unauthorized river access. Fencing and signs along Interstate 70 could assist to
discourage unauthorized river access. If E.R. Jacobson and CDOT granted public
recreation access below the dam, this would further reduce unauthorized access from
Interstate 70.

Dam Removal: Dam removal would cause an increase in the water velocity
upstream from the dam. Reclamation's Technical Service Center conducted a hydraulic
and scour analysis of the pr<?ject (Collins, 1999). Analysis results presented in Figures 10
and 11 show the estimated river velocities with and without the dam. Figure 10 shows
the velocities for a 100-year flood; Figure 10 is for comparison at lower peak flow of
10,500 cfs.

The velocity increase would be greatest at the dam and would gradually diminish
upstream. Existing angular riprap on the west bank of the river would be sufficient to
protect the railroad embankment from scour due to increased velocities upstream of the
dam (Collins, 1999). Additional riprap would be placed along the Interstate 70 side of
the river. At the Colorado River Siphon, the difference in velocity is negligible.
Downstream from the dam, no change in river velocity is expected, and no increase in
scour should result.

Railroad and Landslide Stability

Approximately 1,000 feet upstream of the Price-Stubb Diversion Dam, on the Wests ide
of the Colorado River, is a historically active landslide. This landslide is a small portion
of a very large inactive landslide mass that extends upstream about 1 'l4 miles to the
Cameo Power Plant and about 1 mile west to Mount Lincoln. The active portion of the
landslide lies between the Colorado River and the steep sandstone cliffs forming the west

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