The Strand Project • City of Coronado

The Strand Project is aimed at bolstering the water supply resilience for the city of Coronado, California.

Bocci is addressing a longstanding issue with a vital pipeline running along the Silver Strand, a narrow isthmus connecting Coronado, CA to the mainland. With a history dating back to 1910, the existing infrastructure is now outdated and unable to meet the current demands of the population in Coronado. This case study explores the challenges, solutions, and benefits of this project as we work to ensure the reliable delivery of water to this unique coastal community.

PROJECT BACKGROUND

The Strand is a seven-mile-long isthmus, only about two miles wide at its broadest point, connecting the city of Coronado with San Diego. Coronado, located at the far end of this sandbar, depends on two critical pipelines for its water supply: the Trans Bay Pipeline, which runs under San Diego Bay, and another pipeline that runs up the Strand itself. The Strand pipeline, originally installed in 1910, is now over a century old and inadequate for serving the city's current population in the event of an emergency.

The primary objective of The Strand Project is to replace a long-unused pump located within an underground vault along this pipeline. The existing pump has not been operational for over 30 years due to its excessive size, which caused damaging pressure surges and water main breaks when last used. The new pump must be sized appropriately to maintain adequate water flow and pressure along the entire seven-mile stretch of the Strand, especially in emergencies where the Trans Bay Pipeline might be unavailable.

CHALLENGES

PRESSURE + FLOW

One of the major challenges we identified was ensuring the new pump would provide sufficient water pressure and flow for the entire city of Coronado without causing issues for customers upstream or downstream. Preliminary hydraulic models indicated that the existing pipeline will struggle to handle the pressure requirements needed to serve the city effectively. This discovery led us to reevaluate the project's initial assumptions and required close coordination with a pipeline replacement project already underway.

LEAVE NO TRACE

Environmental and regulatory hurdles further complicate the project. The pump is housed in an underground vault located in a sensitive coastal area, which falls under the jurisdiction of the California Coastal Commission and the California Environmental Quality Act (CEQA). Any changes to the vault or its surroundings would trigger a host of regulatory requirements, potentially delaying the project and increasing costs.

POWER’S OUT

Additionally, there is no existing power supply at the site, necessitating coordination with San Diego Gas & Electric to secure a reliable power source for the new pump. This challenge is further complicated by the site's proximity to state-owned land and infrastructure, and any construction will require permits and approvals from multiple agencies.

SOLUTIONS

To address these challenges, we are working closely with hydraulic modeling experts to refine the design specifications for the new pump. The focus is on selecting a pump that can efficiently operate within the pressure and flow parameters required while fitting within the existing vault. The design team is considering advanced speed control technologies to optimize pump performance and reduce energy consumption.

Environmental considerations are being carefully managed by keeping the project footprint within the existing vault to minimize impact and avoid breaches in regulation. Bocci is collaborating with local authorities to streamline the permitting process and ensure compliance with all relevant regulations.

To address the power supply issue, Bocci is exploring options for tapping into a nearby power line to minimize disruption to the surrounding area. This approach will provide a stable and reliable power source for the new pump, ensuring it can operate effectively in both routine and emergency situations.

BENEFITS

The successful completion of the Strand Project will significantly enhance the resilience of Coronado's water supply system. By replacing the outdated pump with a modern, efficient unit, Bocci will help California American Water meet its mandate to provide uninterrupted service to the city. This improvement is crucial for maintaining public health and safety, particularly in the event of a major disruption to the Trans Bay Pipeline.

The project also exemplifies our commitment to sustainable and responsible design. By working within the existing infrastructure and minimizing environmental impact, the team ensures the solution is both effective and environmentally conscious.

Conclusion

As of now, The Strand Project is at the 30% design stage, known as the design memorandum phase. This phase involves refining key design decisions and solidifying the project's direction. Bocci is actively engaging with pump vendors to finalize the specifications and ensure the selected pump meets all operational requirements. The team continues to collaborate with subconsultants, particularly those focused on hydraulic modeling, to adjust the design and address any remaining challenges.

The Strand Project represents a critical effort to revamp Coronado's water supply infrastructure while preserving the unique environmental context of the region. As with every project, we are committed to excellence, to thoroughness, and to getting the job done right so that the city of Coronado has a reliable and resilient water supply that will take them far into the future.