WSP07975

• File Number: 8278.100
• Description: Title I - Yuma Desalting Plant
• Basin: Colorado Mainstem
• Date: 10/1/1987
• Author: USDOI/BOR
• Title: Yuma Desalting Plant Operations Study - Draft Special Report
• Water Supply Pro - Doc Type: Publication

The Yuma Projects Office began analyzing modifications to the YDP
to reduce O&M costs. This effort was expanded and a planning
team was formed and charged with reevaluating YDP operations and
identifying any structural or non-structural plans with the
potential of reducing YDP operation costs. ~ew restriction were
placed on plan selection since institutional problems that would
have previously made some plans unworkable may now be resolvable
with the changing political and institutional climate of the past
few years.

EVALUATION PROCEDURE

The planning team identified 48. plans meriting consideration.
These plans are listed in three categories in Table 1. Plans in
Group A are proposed structural changes to the YDP itself, or
modifications of YDP operations which would reduce production
costs. Group B plans provide for new or. conserved water to
substitute for bypassed Wellton-Mohawk return flow which, because
of its poor quality, cannot be delivered to Mexico without being
desalted. Group B plans, therefore, reduce or eliminate YDP
production. Plans in Group C propose changes to the legal or
institutional constraints that would reduce or eliminate the need
for YDP production.

The evaluation of the plans was both subjective and objective.
Rating criteria were established to give an indication of each
plan's relative "value." Since many of the criteria could not
be directly measured, evaluation required judgment based on the
planning team's previous experience and training. A comparative
Total Value Score (TVS) was computed for each plan.

The objective portion of the evaluation was the estimated annual
costs for each plan. These costs were derived from a number of
supplementary analyses such as; estimates of water yields by
proposed plans to provide substitute water (Group B), estimates
of the frequency of YDP production, estimates of required YDP
capacity, operational requirements, and reject stream replacement
requirements.

A computer simulation model aided in estimating the impacts of
various plans on YDP production requirements. Because of the
simplifying assumptions built into the computer model, the
results are valid for comparison purposes only. Also used was
the Bureau of Reclamation's (Reclamation) Colorado River
Simulation System (CRSS) model. However, the CRSS data base is
not sufficiently defined in the lower reaches of the river to
accurately estimate the required frequency of YDP operation.

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