WSP09467

• File Number: 8281.990
• Description: Colorado River Studies and Investigations -- Webster Hill Dam and Reservoir
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 6/1/2001
• Author: Brown and Caldwell
• Title: Technical Memo NO 4A: Analysis of Alternative 4 - New Storage Facility at Webster Hill Site - Mainstem Colorado River
• Water Supply Pro - Doc Type: Report/Study

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DRAFT

ANALYSIS PROCEDURES AND ASSUMPTIONS

GENERAL

The analysis consisted of two primary tasks:

· A water availability analysis was completed to determine the yield of a reservoir on the
Colorado River mainstem at the Webster Hill site immediately downstream from Rifle,
Colorado,
· More detailed opinions of probable cost were developed for a proposed reservoir at the
Webster Hill site.
· A preliminary economic feasibility analysis was completed

The following procedures and asswnptions were employed in the reservoir operations and yield
analysis of the proposed reservoir sites:

· Daily historic streamflow data for the period October 1966 through September 1997 were
obtained from HydroBase for several gages (DeBeque, Cameo, and Parachute Creek).
Specifically the feasibility of making the following releases was investigated: (1) the
20,000 acre-feet release on the peak of the spring hydrograph in those years in which it is
required for recovery of the endangered species and (2) a second 20,000 acre-feet release
during the late swnmer or early fall for purposes of the recovery program.
· The frequency of daily flows exceeding 200 cfs was determined in order to check
calculations and asswnptions employed in the Dwyer-Shepherd report (1976) with respect
to detennining hydroPQwer generation feasibility at the site.

For purposes of the determining opinions of probable cost and the economic feasibility
investigation, the calculations in the 1976 Dwyer-Shepherd study were updated to 2001 and
preliminary cost estimates for the following components were made because costs for these
components were not included in the original report:

(1) a 10 MW hydropower component,
(2) railroad relocation,
(3) Interstate 70 vertical re-alignment,
(4) gas well relocation and
(5) real estate acquisition,

USE OF STATEMOD

StateMod was not employed in this investigation.

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