Rainbow MWD approves design for Weese interconnect

The Robert A. Weese Filtration Plant is owned by the City of Oceanside and operated by Oceanside’s Water Utilities Department, but the facility is located off of Silverleaf Lane in the Gopher Canyon area and is within the boundaries of the Rainbow Municipal Water District. The Rainbow Municipal Water District will be commencing the staff portion of the design phase for a permanent connection to the Weese treatment plant.

A 5-0 Rainbow board vote Aug. 22 authorized district staff to proceed with the design for an interconnection with the Weese Filtration Plant.

“The savings will pay for the project costs,” said Rainbow general manager Tom Kennedy.

The City of Oceanside purchases untreated water from the San Diego County Water Authority and treats that supply at the Weese Filtration Plant. The SDCWA conveys untreated water from Lake Skinner through Pipeline 3 and Pipeline 5 on the Second Aqueduct while providing treated water through Pipeline 1 and Pipeline 2 on the First Aqueduct and Pipeline 4 on the Second Aqueduct.

The CWA supply is interrupted during annual shutdowns for maintenance reasons, and each year the Rainbow district rents and sets up a temporary pump near Rainbow’s Gopher Canyon Tank while working with Oceanside’s Water Utilities Department to change operation valves to boost pressure so that Rainbow can pump water from the Weese Filtration Plant into the Gopher Canyon Tank. That temporary connection provides a significant source of water for that Rainbow service zone during the shutdowns.

The annual cost to rent, set up, monitor, maintain, and fuel the temporary pump varies depending on water demand but ranges from $10,000 to $20,000. Fuel tanks are stored adjacent to the site in secondary containment, which creates the potential risk of spillage and having to refill the storage.

A permanent Rainbow connection to the Weese Filtration Plant would eliminate the labor and costs needed to set up the temporary pump on an annual basis. Such a connection would also streamline the process of purchasing water from the City of Oceanside, and city representatives have indicated that if Oceanside has excess capacity in the plant the city could sell treated water to Rainbow.

Rainbow’s board voted 5-0 March 28 to award a design services contract to Infrastructure Engineering Corporation for up to $186,272. IEC, which has an Oceanside office, was tasked with preparing a full set of plans and specifications for an eventual construction contract bid.

The improvements will include connection piping, a recommended meter device, installation for a prefabricated pump station along with a foundation, and electrical service to the site. The total estimated project cost including design, construction, project management, and inspection is $850,000.

The design work will provide the engineering details which are needed to complete contract negotiations with the City of Oceanside, and terms of an excess treated water agreement with the city will be negotiated before the district spends any money on the construction phase.

The specific excess capacity would depend on weather conditions, although the City of Oceanside expects to supply Rainbow with approximately 1,400 acre-feet annually during the winter months. The city is also in the process of expanding its recycled water system which would decrease Oceanside’s reliance on the Weese plant and provide additional excess capacity available to Rainbow. The excess capacity under the condition of an Oceanside recycled water system is expected to exceed 3,000 acre-feet annually.

“We can get access to that water at a discount,” Kennedy said.

Initial discussions with the City of Oceanside indicate that the city would provide a treatment discount of $100 per acre-foot, which would equate to annual savings of $140,000 without Oceanside’s recycled water system and $300,000 if the recycled system is operational.

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