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Rainbow MWD board learns about potential reclamation plant, recycled water system

 

Last updated 9/16/2016 at Noon



The Aug. 23 meeting of the Rainbow Municipal Water District (MWD) board included a presentation on the district's potential water reclamation plant and recycled water distribution system.

Although the future infrastructure was a non-voting item, the board agreed with Rainbow staff's recommendation that the various options should be evaluated in further detail.

"The board gave direction to take the next phase, which is to do a high-level analysis," said Rainbow general manager Tom Kennedy.

In January 2015, the Rainbow board awarded a professional services contract to Atkins to update Rainbow's water and wastewater master plans. Master plans are typically prepared every five years, although Rainbow had not prepared a master plan since 2006.

The master plans serve as the basis for infrastructure decisions and for the amount of capacity fees paid by developers to support the infrastructure the development requires. The updated plans consider both existing conditions and expected conditions through the year 2030 and assess potential water sources, including recycled water and local groundwater supply with the assessment also helping to determine whether Rainbow should build its own wastewater reclamation plant or continue to convey wastewater through the Oceanside Outfall.

In May 2015, the Rainbow board awarded a contract to the Tamayo Group to help facilitate the district's strategic plan which will provide a long-range vision to guide Rainbow's board and staff through decisions which will be made in the near future and which will help determine the best options for infrastructure investment to serve new development.

Tamayo's work allowed the district to develop goals and objectives for each strategic focus area which will allow Rainbow to monitor and measure its performance in meeting those objectives. The Rainbow board approved the strategic plan Jan. 26. The strategic plan documents Rainbow's mission statement, core values, and key focus areas and includes goals and objectives for the Rainbow staff to pursue.

In September 2015, the Rainbow board voted to approve detailed studies on a potential water reclamation plant and recycled water system. That action determined that the development of a local water reclamation plant and recycled water system is potentially feasible but that additional information is needed, and the board at that time also appropriated $200,000 from Rainbow's master planning project for the cost to develop the pre-design report. A separate vote that day authorized the application of a water recycling planning grant from the State Water Resources Control Board.

Atkins reviewed several locations for a water reclamation plant as well as methods of storing and distributing the recycled water. Two potential projects were identified, along with financial modeling for the costs of each project and the comparison of the expense with the cost to continue to send wastewater to Oceanside, including the purchase of additional capacity to meet demand. One of the options would be to construct a plant at or near the district headquarters site on Old Highway 395. The other site studied is near Lift Station 2 at the intersection of Old River Road and Gopher Canyon Road.

A recycled water plant at the Old Highway 395 site would produce approximately 0.9 million gallons per day (mgd) of recycled water with perhaps an additional 0.2 mgd if the Warner Ranch project is approved while the remaining wastewater to the west of that site would continue to be conveyed to the San Luis Rey treatment plant operated by the City of Oceanside. The potential plant near Lift Station 2 would produce about 1.6 mgd of recycled water with an additional 0.2 mgd if Warner Ranch is included while capturing more than 99 percent of all of the district's wastewater for re-use.

The 0.9 mgd project would have costs nearly identical to the "do nothing" alternative of sending water through the Oceanside Outfall, although the drought-proof water supply of more than 1,000 acre-feet per year would equate to approximately 7 percent of Rainbow's total supply and the production with the Warner Ranch project would be an estimated 1,232 acre-feet. The 1.6 mgd option would be more expensive but would produce nearly 1,800 acre-feet annually or 11 percent of the district's demands and that supply would increase to 2,016 acre-feet if Warner Ranch is built.

The pre-design report prepared by Dudek refined the alternatives and costs. Because the Old Highway 395 reclamation plant option would still require some wastewater to be conveyed through the Oceanside outfall, it was eliminated from further consideration and the two alternatives currently being considered are a reclamation plant near Lift Station 2 along with providing a recycled water distribution system and acquiring additional capacity in the Oceanside Outfall while constructing recycled water distribution infrastructure within the Rainbow boundaries.

The option of constructing a reclamation plant along with a distribution system has an estimated capital cost of $62,084,000 and estimated annual operating costs of $2.07 million. The continued use of the Oceanside Outfall would include collection system upgrades upstream of Lift Station 2 and contributions to construct tertiary treatment at the San Luis Rey reclamation facility; the estimated capital cost is $50,813,000 although an estimated annual cost of $3.01 million would make that option more expensive over a 30-year period than the Lift Station 2 alternative.

"The goal is to recover the wastewater," Kennedy said. "It's just a question of how."

The analysis will also include identifying and assessing use for recycled water customers within the Rainbow district boundaries.

"We're trying to evaluate where the best places to put these pipelines are," Kennedy said.

Those predictions will be based on existing agricultural and other irrigation customers as well as expected demand from new development.

"Recycled water makes the most sense for agricultural use," said Kennedy.

The projected demand is 1,842 acre-feet per year, or 1.65 million gallons per day, although much of the demand is associated with nurseries and avocado growers on property which might not have those crops over the 30-year timeframe of the analysis.

"We don't know if that grove is going to be there," Kennedy said.

Rainbow is working with the San Diego County Farm Bureau on issues related to future demand.

"That's one of our big challenges," said Kennedy. "It's hard to predict where the water's going to be used in the future."

The City of Oceanside is studying the potential of an indirect potable reuse option which would blend advance treated recycled water into an existing water source such as a groundwater basin which would be treated later for potable use. Such a project, which would inject treated recycled water into the San Luis Rey groundwater basin, could be complemented with a project to capture and treat imported water return flow. Rainbow would need a feasibility study to analyze the costs and risks before making any decision on participating in an indirect potable reuse project. Oceanside's water utilities department is willing to let Rainbow collaborate on the Oceanside study, although further discussions will be necessary to determine the parameters of Rainbow's participation.

"At least now we know what the basic parameters are for the recycled water side of it," Kennedy said. "The goal is to find reliable water supplies. The goal is to have reliable water at low cost."

The lack of a preferred board alternative at the Aug. 23 meeting allows for all options to be evaluated further.

"It's a long-term project to develop local water supply," said Kennedy. "We don't need to rush into it. It's important to carefully evaluate all the opportunities and options."

 

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