Request for Proposals for Design Engineering for Beltz 9 Upgrades for Aquifer Storage and Recovery Project.

The City of Santa Cruz Water Department (City) intends to convert its existing production well, Beltz 9, to an aquifer storage and recovery (ASR) well. Pilot testing was conducted at Beltz 9 from November 2023 through June 2024 and after obtaining favorable results, the City decided to proceed with converting Beltz 9 to an ASR well.

The City is seeking proposals from qualified engineering firms interested in providing design engineering services required for this project. Services include developing construction plans, specifications, and bid documents for demolishing and/or retrofitting the existing discharge and facility piping, mechanical and electrical components and equipment, controls and SCADA integration, and associated appurtenances of the permanent ASR well facilities per City of Santa Cruz guidelines. The project will also utilize templates and guidelines that have been developed for the larger Santa Cruz Water Program. Engineering analysis will include best practices for converting an existing production well to an ASR well. The design of the Beltz 9 facility should take into consideration future growth of the City’s ASR program, joint operation with existing ASR wells (Beltz 8 and Beltz 12), and additional ASR wells that may be brought online in the future.

The City provides drinking water to a service area approximately 20 square miles in size, including the entire City of Santa Cruz, adjoining unincorporated areas of Santa Cruz County, a small part of the City of Capitola, and coastal agriculture north of the city. The City’s water supply system draws water from surface water sources on the San Lorenzo River and local North Coast streams, which make up approximately 95% of the annual supply. That amount is supplemented, primarily during the dry season, by limited production from groundwater wells in the Santa Cruz Mid-County Groundwater Basin (MCGB) in unincorporated Santa Cruz County. The City also stores water in Loch Lomond Reservoir in Ben Lomond, which is formed by Newell Creek Dam to help meet dry-season water demand and provide back-up supply during winter storms that make river diversions problematic due to turbidity issues. The City has no imported water supply from outside the region.

Based on favorable results of the feasibility investigation, the City decided to advance the ASR pilot testing program to the existing Beltz 9 well. Beltz 9 pilot testing was completed in 2024, and the City is ready to begin design. In addition to the pilot testing at Beltz 9, the City had previously conducted feasibility investigations and successfully completed ASR pilot testing at the Beltz 8 and Beltz 12 well sites. Construction of the Beltz 12 ASR upgrades are currently underway, and the City is soliciting contractors for the ASR upgrades at Beltz 8.

The pilot test program at the Beltz 9 well consisted of three repeated ASR cycles of operations and monitoring, each of larger volume and duration than the preceding cycle. The pilot testing was conducted to demonstrate injection well hydraulics and operational performance characteristics of the well and monitor the local aquifer hydraulic and geochemical responses to recharge and recovery operations. The pilot testing also examined operations and water quality to learn more about ASR impacts on ammonia, arsenic, disinfection byproduct (DBP) ingrowth and degradation during the storage period, and more. As a result of the pilot study at Beltz 9, the recommended injection rate was approximately 500 gallons per minute (gpm), the recommended extraction rate was approximately 750 gpm, and the recommended backflush rate was approximately 1,000 gpm.

The City is planning to implement its ASR program incrementally by prioritizing the optimization of existing infrastructure before expanding to include new ASR sites and infrastructure. The operation of the City’s ASR program involves the diversion of excess winter and spring flows from the City’s North Coast sources and the San Lorenzo River (SLR), treated to potable standards at the City’s only surface water treatment plant – Graham Hill Water Treatment Plant (GHWTP), and then conveyed through the existing water distribution system to be injected at ASR wells. Later extraction at the ASR wells would be used to meet peak summer demands, during drought years, and/or serve as an emergency or backup water source during maintenance activities or potential upsets at the water treatment plant. “Excess” flows are flows that exceed the City’s demands, meet in-stream flow requirements, and are within the City’s water rights. The new facilities will be constructed with the capability for groundwater extraction and surface water injection.

Groundwater modeling for long-term planning has been used to evaluate the effect of expanding the ASR project to include up to 6 ASR wells in the MCGB. This modeling evaluated well interference due to the proximity of the wells, as well as impacts to coastal water levels. The MCGB is a “critically over drafted basin” with indications of seawater intrusion. The City is planning to pump both native groundwater and ASR water from the ASR wells and will not maintain an ASR injected water buffer. A geochemical interaction analysis has been completed, and the blended water can be treated to potable water quality standards through the existing groundwater treatment systems. Therefore, it is anticipated that the groundwater treatment systems for ASR operations will remain the same as currently needed for treating native groundwater, primarily with respect to iron and manganese removal.

For further project background and information, Proposers must review the supplementary documents included in Appendix C, as listed below. Proposers will be required to agree to and sign a Non-Disclosure Agreement (NDA) to review the documents in Appendix C. NDAs shall be submitted via email to Katy Fitzgerald, kfitzgerald@santacruzca.gov .

• C.1: Beltz 9 Record Drawings
• C.2: Beltz 9 ASR Pilot Test Summary of Operations Report
• C.3: Existing 60-HP Grundfos Pump Information
• C.4: SCWD Water Program Design Submittal Checklists
• C.5: SCWD Water Program Invoice and Monthly Reporting Requirements

Please be advised that the Record Drawings included in Appendix C.1 may be outdated, so a new site survey will be necessary.