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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Rev.ised Supplemental Draft Environmental Assessment-Chapter 3-Affected
Environment and Environmental Consequences

Colorado River that carries water from the Government Highline Canal to the Orchard
Mesa Power Canal.

Two factors could affect these structures: 1) scouring of the riverbed and banks, and 2)
the rate of wetting or dewatering the foundations of the railroad and Interstate 70. River
scour is a function of water velocities, the size of the cobbles in the riverbed, and the size
of the riprap along the banks. If the dam is removed, the velocities of the water in the
river would increase in the vicinity of the dam. As the velocity increases, the ability of
the water to scour the banks and riverbed increases. Ifthe banks and streambed are not
adequately protected, the scour could move horizontally toward the railroad and Interstate
70. If the dam is not removed correctly, riverbed scour could extend upstream and could
expose and damage the siphon.

Wetting (saturation of) the foundations of the railroad and Interstate 70 would weaken the
foundations. If actions taken at the site raise the existing water levels, there could be
impact to these structures. Since the siphon is buried beneath the riverbed, foundation
wetting is not a concern.

Issue: Effects of alternatives on integrity and use of the highway, railroad, and
siphon.

Existing Conditions: Upstream and downstream from the Price-Stubb Diversion
. Dam, riprap protects the foundations of Interstate 70, and the railroad. The siphon is
located in a stable portion of the riverbed that has not shown significant scour. During
flood stages and the corresponding high water levels, the railroad bed has reportedly
become weakened due to foundation saturation in the vicinity of the dam. This is not a
known issue with Interstate 70. CDOT expressed concerns with fish passage
construction limiting potential future widening ofInterstate 70.

Impacts

No Action: The No Action alternative assumes the Jacobson Hydro No.1 Project
would not be built as described in the terminated FERC license. However, if constructed,
the hydropower plant would divert water for power generation. The design capacity of
the amended power plant is about 1,000 cfs. The No Action alternative would have no
effect on the foundation of Interstate 70, future widening of Interstate 70, or railroad and
Colorado River siphon foundations.

Conventional Fish Ladder: Impacts of constructing a fish ladder around the
dam would be similar to those of the No Action alternative. Ifthe Jacobson Hydro No.1
Project were constructed with the conventional fish ladder, the tailrace of the hydropower
plant would serve as an attraction flow for fish to find the fish ladder entrance. If the
hydropower plant were not constructed, an attraction flow pipe would cost about
$100,000. This alternative would have no effect on the foundation of Interstate 70, future
widening of Interstate 70, or railroad and Colorado River siphon foundations.

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