Harry Tracy Water Treatment Plant

Water is the life blood of the Bay Area. We are much safer today as a result of this project.

— Dan Wade, WSIP Director

In 2002, recognizing the need for major upgrades to its aging water system, the San Francisco Public Utilities Commission (SFPUC) launched the $4.8 billion Water System Improvement Program (WSIP) to provide improvements necessary to meet level of service goals established for seismic and delivery reliability, water quality and water supply.

“… for 30 years, KJ has provided highly effective engineering, design, construction support, and start-up services to SFPUC, delivering several successfully completed projects for the SFPUC. This project was no exception.

— Dan Wade, WSIP Director

Under the WSIP, the Harry Tracy Water Treatment Plant (HTWTP) Long Term Improvements Project (LTIP) was implemented to upgrade the existing plant to allow the plant to sustainably deliver a minimum of 140 million gallons per day (mgd) within 24 hours after a major earthquake. The HTWTP is situated less than 1,000 ft. away from the San Andreas Fault. Additionally, two previously unidentified traces of the lesser-known Serra Fault cross the HTWTP property.

In 2008, SFPUC retained KJ to provide predesign, design, and construction phase services for a new 11 million gallon (MG) Treated Water Reservoir (TWR) to resist high vertical and lateral seismic forces, as part of the HTWTP LTIP.

Unique Combination of Advanced Civil and Structural Engineering Techniques

The design of the new 11 MG TWR developed by KJ for the HTWTP site represents a unique combination of advanced civil and structural engineering techniques that when combined create a feasible site for the reservoir, which requires high seismic and delivery reliability. The challenges at the site included its close proximity to the San Andreas Fault and fault strands from the Serra Fault, as well as a steep hillside that required extensive cut and fill to create a suitable foundation pad for the reservoir. These challenges resulted in solutions such as soil nail and mechanically stabilized earth walls, a pile-supported foundation, and a prestressed tank designed with anchored flexible and seismic cable connections. This combination of solutions was developed to provide a stable and seismically robust design for this critical facility.

Solutions to Improve Water Reliability

The design and construction of the new TWR at the HTWTP represents a substantial improvement in the reliability of the water system for millions of people in the San Francisco Bay Area. The combination of structural techniques utilized in the design of the TWR allowed the project to proceed in a high seismic risk area near the San Andreas Fault, making such projects more feasible for future engineers. Since its construction, this project has been toured by neighboring agencies facing similar challenges to provide reliable water storage and delivery facilities in areas of high seismic risk. In addition, the advanced structural engineering technologies and the resulting design that meets the higher level of service goals that require sustainable delivery of a minimum of 140 mgd within 24 hours after a major earthquake has greatly enhanced the public perception of the water system as a reliable resource in a post-seismic environment.