Conjunctive Use Water Distribution System

Semitropic Water Storage District near Bakersfield encompasses approximately 225,000 acres, of which over 135,000 acres are developed to irrigated agriculture.

Semitropic has three major developments, all planned and designed by GEI Consultants (as Bookman-Edmonston).

In the 1970s, we planned, designed, and supervised the construction of the irrigation distribution system. We also negotiated for financing from the U.S. Bureau of Reclamation. The project included an 8 mile long, unlined intake canal with a maximum capacity of 570 cfs. Two 38 mile long transmission canals, with pumping plants, and distribution systems were constructed to serve about 42,000 acres. A financing arrangement was developed to maintain equity between growers using imported water and those on groundwater. This project reversed the groundwater overdraft in Semitropic (as shown in the figure below).

In the early 1990s, Semitropic developed a one-million acre-foot groundwater storage bank to take advantage of wet-year supplies. To use this wet-year water, the canal system was increased in capacity and 20,000 acres of distribution system added, including 60 miles of pipeline up to 78 inches in diameter. Facilities were also constructed to return water to the California Aqueduct. An element of this project was an 11,000-foot long, 78-inch pipeline supplied by a 5,000 horsepower pumping plant, which can return banked groundwater to the California Aqueduct in a unique “pumpback” arrangement. GEI provided planning, CEQA/NEPA compliance services, mitigation plans, design, and construction management for the banking and exchange program and provided planning, feasibility report, arrangements for financing, preparation of plans and specifications; acceptance, evaluation, and recommendation for award of bids for construction and equipment; right-of-way engineering; contract administration; inspection, testing and acceptance of construction and equipment; development of operational organization; operational start-up; and continued consulting advice.

The third element of the Semitropic development is currently being developed. The new unit will include a well field and system capable of returning up to 200,000 acre feet per year to the California Aqueduct. Facilities will include 65 new wells, two large pumping plants, a seven mile long 96-inch diameter two-way pipeline to both take water and return water to the California Aqueduct, and an added distribution system to take advantage of wet-year water.

Semitropic’s canal system includes eight check structures with pumpback facilities and approximately 13 miles of canal lining, which GEI designed.

A recent example of GEI’s work is the South Pumping Plant Expansion.

In this just-completed project, GEI was responsible for the design and construction management of a pump sump structure to house three 42-inch, 80 cfs pumps, with manifold piping, return flow piping, and a 66-inch discharge pipeline. The outlet works into the Buttonwillow Ridge Canal was expanded, a new 84-inch flap gate were installed, and the headworks and canal lining were raised two feet to increase the capacity. A pumpback structure and 48 inch pump discharge line were constructed at another location on the canal, and a steel canal plug was fabricated to be used in canal reverse flow scenarios. The South Intake Canal was cleaned, riprap was placed on the reconstructed areas near the new pump station, and approximately 14,000 yards of dry material was removed from the cut area of the canal and stockpiled for use in raising a section of the canal liner. As planned, two of the structures were completed during a short winter canal shutdown period with no delays.

The total project cost was $80 million. GEI was responsible for $9 million, for the design and construction management of the project.