Rainbow approves $1.2 million contract for design of Beck Reservoir UV disinfection facility

The Rainbow Municipal Water District will use Arcadis as the consultant firm which will handle the permitting and design activities for the Beck Reservoir’s ultraviolet disinfection facility.

The Rainbow board voted 5-0 Nov. 19 to authorize staff to enter into negotiations with Arcadis for a professional services contract for a price not to exceed $1,232,246.

“This is an important project for the district because it is our principal emergency storage reservoir,” said Rainbow general manager Brian Brady. “It is important that we install this new equipment and reactivate the reservoir as soon as possible.”

Beck Reservoir was constructed in 1983 and has a capacity of approximately 204 million gallons. The earthen embankment reservoir was initially built for fire suppression and emergency purposes and to improve water reliability for the Beck pressure zone.

Current U.S. Environmental Protection Agency surface water treatment rules require that the reservoir must either be covered or provide disinfection treatment. The Rainbow district received a compliance order for the Beck Reservoir and other uncovered reservoirs, and after building the 6 million gallon Pala Mesa Tank, the Beck Reservoir was removed from service while district staff completed studies analyzing the best long-term use.

The Rainbow board was presented with several options at board meetings earlier this year. Ultraviolet disinfection was deemed the most feasible of the various options which also included abandoning the reservoir, using it for raw water or recycled water storage, and installing floating covers. On May 28, the board directed staff to move forward with a plan to use ultraviolet disinfection for treated water storage, and on June 25 the board called for the UV disinfection to be considered an urgent project and set a goal to complete the project as quickly as possible.

The estimated cost for the ultraviolet treatment option is $10.4 million including additional localized piping changes. Chloramination and other chemical facilities will be required to increase the chlorine residual from the water. The primary operations and maintenance cost would involve instrument and analyzer calibration and the cleaning of the UV reactors when the facility is in service. The Beck Reservoir could be monitored remotely.

On June 27, Rainbow submitted a request for California Department of Public Health (CDPH) approval for the installation of an ultraviolet disinfection system at Beck Reservoir. Rainbow and CDPH staff met on Aug. 8, and on Oct. 24 CDPH district engineer Sean Sterchi sent Brady a letter providing conditional approval. The conditions included a permit amendment application to allow CDPH to review the proposed design and construction. During the process, Rainbow also provided a draft request for proposals for CDPH to review, and CDPH recommended the addition of a subtask involving coordination between the contractor and CDPH.

Rainbow’s final request for proposals was sent to three firms which were deemed pre-qualified due to their design expertise and their expertise in UV disinfection. Arcadis, Black and Veatch, and Carollo all responded. Rainbow’s staff reviewed and ranked the proposals and conducted interviews with two finalists before determining that Arcadis was the most qualified firm to work with the district.

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