Also serving the communities of De Luz, Rainbow, Camp Pendleton, Pala and Pauma

Rainbow MWD approves groundwater development study contract

Joe Naiman

Village News Reporter

The Rainbow Municipal Water District awarded Hoch Consulting a contract to evaluate groundwater recharge return flow from the Lower San Luis Rey Valley Groundwater Basin.

Rainbow’s board voted 4-0 July 26, with Michael Mack absent, to award a professional services contract to Hoch Consulting for $600,000. The board also made findings that the contract and study itself would not constitute a project subject to California Environmental Quality Act review, although any implementation of groundwater development would likely be subject to CEQA.

“Essentially what we’ll be doing is revising the hydrogeologic model,” said Rainbow general manager Tom Kennedy.

One of Rainbow’s long-term goals is to diversify the district’s water supply. Rainbow currently purchases all of its potable water supply from the San Diego County Water Authority; most of that water is treated in Riverside County at the Skinner Water Treatment Plant owned by the Metropolitan Water District of Southern California and a portion of the SDCWA supply is treated at the CWA’s Twin Oaks Valley Water Treatment Plant in San Marcos.

Because groundwater in the Rainbow service area is considered to be a subterranean stream, water rights are managed as river diversions. The San Luis Rey River is fully appropriated in the area, so no new diversion permits can be issued.

“Rainbow doesn’t hold any water rights,” Kennedy said.

Because Rainbow imports water from outside the watershed, the district has the legal right to recover imported water which returns to the groundwater system through the use of the water by Rainbow’s customers. The returned water enters the ground through irrigation and from septic systems. For Rainbow to obtain the right to that water, the district must firmly establish the quantity of return flow.

In November 2013, the Rainbow board approved a contract with West Yost to study the amount of groundwater available to the district from the San Luis Rey Basin. Earlier in 2013, Rainbow staff completed an alternative water source feasibility study which evaluated various alternatives for the district to develop additional water supplies.

The feasibility study caused Rainbow staff to determine that the top two priorities to pursue would be evaluating groundwater supply development in the San Luis Rey Basin and evaluating development of recycled water service in conjunction with the Valley Center Municipal Water District and/or the Fallbrook Public Utility District.

The feasibility study indicated that up to 2,900 acre-feet of additional groundwater supplies could be developed (that amount does not include any additional contribution from FPUD imported water flows if Rainbow and FPUD collaborate).

West Yost estimated that between 2016 and 2046, water users within the Lower San Luis Rey Valley Groundwater Basin would be recharging the basin at a rate of 7,200 to 7,600 acre-feet per year. The 2016 estimate was based on the water use of the Rainbow, FPUD, and Valley Center customers within the watershed contributing to the Lower San Luis Rey Valley Groundwater Basin.

West Yost concluded that median annual pumping rates of 5,700 acre-feet per year could be supported without significant impacts to the hydrologic conditions which would exist in the absence of imported water. West Yost prepared preliminary project planning for a conceptual groundwater extraction and treatment project sized at 4,000 acre-feet per year (3.6 million gallons per day).

In May 2017, a technical memorandum was completed which compared a baseline groundwater extraction and desalination project against three alternatives which supplemented the groundwater supply with indirect potable reuse.

The memo concluded that Rainbow should implement the baseline groundwater desalination project while preserving the indirect potable reuse alternatives for possible implementation in the future.

Rainbow contracted with Dudek to update the 2016 West Yost groundwater model, use the model to verify production well yields in the Bonsall Basin, confirm imported return flow water rights and regulatory structure, collect groundwater quality data, perform exploratory borings for production well sites, and facilitate property acquisition and private property contracts and agreements.

Dudek developed a feasibility study, which was later paused due to unfavorable findings. Dudek’s report indicated treatment of the imported water return flow for potable use would require a substantial capital investment to construct extraction wells, a brackish water desalter, and a brine disposal line or brine treatment plant with zero liquid discharge.

The estimated 1,300 acre-feet per year supply from imported water return flows was determined not to be substantial enough to warrant moving forward with a project because a smaller scale project would result in a higher unit cost of water.

After ongoing coordination with local stakeholders including the San Luis Rey Indian Water Authority, Rainbow decided to resume its investigation for a potential return flow recovery project in close coordination with local tribes. The coordination with the tribes will ensure that tribal water rights are not compromised. “We have to make sure we’re not going to impact those rights,” Kennedy said.

The findings from the previous study indicate that opportunities may exist in the eastern portion of the Bonsall Basin due to lower total dissolved solids and options to avoid cost-prohibitive demineralization procedures. The water produced from an imported water recovery project may be competitive with or even less expensive than water from the CWA, which is expected to approach $2,500 per acre-foot in the next five years.

On Feb. 11, Rainbow advertised a Request for Proposals for hydrogeologic and engineering services to revisit the possibility of identifying and implementing an imported return flow project. The proposals were due March 25, and Rainbow received proposals from Geosyntec and Hoch Consulting.

A review committee consisting of Rainbow staff and Engineering and Operations Committee members scored the proposals based on approach to work, project manager and team qualifications, and project experience. Hoch Consulting had the higher score, and the fee in the Hoch proposal was $1,316,959.

Representatives from the two firms were invited to an interview May 4 to discuss why they believed they were the best fit for the project and to provide added value to each proposal by showcasing team qualifications, expertise, and experience. The interview panelists concurred after the two interviews that Hoch Consulting was the better choice for the project based on the team’s understanding of the scope of work, the team’s local expertise in the San Luis Rey watershed, work on similar types of projects, and willingness to negotiate fees.

“They’ve kind of assembled a dream team,” Kennedy said.

Rainbow staff then entered negotiations with Hoch and obtained a 12% decrease to the proposed fee estimate. The process also incorporated measures into the scope of services for Rainbow to assess findings and determine whether to proceed to the next task. Those measures will ensure that should early results be unfavorable, additional funds will not be expended.

The original scope of work was broken into two phases with a stopping point incorporated between the feasibility study (Phase I) and the plans, specifications, and estimate (Phase II). A restructured scope incorporates two additional stopping points; stakeholder and tribal coordination will follow Phase I and construction inspection and reporting would follow Phase II. Hoch restructured their proposal while also removing the monitoring of well work and telemetry from the scope in order to reduce the fee.

The amount with the 12% negotiated reduction is $1,158,183 and Hoch will receive that amount if the subsequent tasks are approved. The $600,000 approved July 26 covers the preliminary evaluation and project planning task; Rainbow’s board will be consulted on the findings of the feasibility study and will be presented with recommendations on how to proceed prior to any approval of subsequent task authorization and payment to Hoch.

“We’re excited to get it going,” Kennedy said.


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