At its April 1, 2020 meeting, the Vista Irrigation District (District) board of directors approved moving forward with planning efforts to replace the 11-mile, nearly 100-year old Vista Flume (Flume). The District is reliant on the Flume to deliver treated water from the Escondido-Vista Water Treatment Plant to its service area; this includes delivery of treated local water from Lake Henshaw, which the District owns and manages. An alternative, and more expensive, source for the District is purchased treated water delivered from multiple connections along the San Diego County Water Authority’s (Water Authority’s) aqueducts.
With the Flume approaching its useful life, the District prepared a Water Supply Planning Study (Study) to evaluate whether the Flume should be replaced or retired and what other alternatives exist. The Study weighed a number of factors when comparing the two options, including costs, reliability, water quality, environmental protection, existing water supply obligations and assets. The board of directors reviewed the Study during three workshops; links to the briefing document for each workshop are provided below.
The evaluation of alternatives related to replacing the Flume sought to account for current and future cost of the District’s local water supply operation as well as the benefits to the District afforded by access to and management of its own local water supply. Likewise, the analysis of alternatives related to retiring the Flume accounted for a number of factors, including current and future costs of purchasing additional water from the Water Authority; possible additional treated water storage and/or other delivery reliability improvements required for routine 10-day Water Authority aqueduct shutdowns; the future of the Boot and Bennett service areas fed from the Flume; and options to exchange the District’s local water.
Results from the Study estimate Flume replacement to cost between $120 million and $130 million including planning, design and construction. Study results show that Flume replacement is the least costly water supply option for the District, having an estimated first-year unit water cost of $2,000 per acre-foot and total 30-year present-worth cost of $240 million. In comparison, the alternative of retiring the Flume and having complete reliance on the Water Authority has an estimated first-year unit water cost of $2,200 per acre-foot and total 30-year present-worth cost of $350 million. In addition to significant cost savings, the Flume replacement alternative also provides the advantage of increased water supply reliability and the opportunity for continued regional cooperation with other local water agencies and partners.
Flume replacement planning costs are estimated to range between $1.7 and $3.0 million; planning efforts, which will begin this summer, include preparation of an alignment study and environmental documentation and financial planning.
Water Supply Planning Study Workshop 1 Water Supply Planning Study Workshop 2 Water Supply Planning Study Workshop 3