Commercial Shoring at Chase Center Construction

Joe Lazzaretti
Oct 5
8 min read

The Chase Center, home to the Golden State Warriors, is a $1.4 billion, 18,064-seat arena located in San Francisco. Its construction faced complex challenges like high groundwater, seismic risks, and limited urban space. To address these, engineers implemented advanced shoring systems, including H-piles

, cement deep-soil mixing walls, and a "boat" waterproofing design. Key solutions included:

Water Management: 52 dewatering wells and cement-treated soil stabilized the site.
Seismic Resilience: Tiebacks and deep foundations countered earthquake risks.
Efficient Excavation: A perimeter wall system supported a 300,000-cubic-yard excavation.

These methods ensured safety, structural stability, and compliance with strict building codes, offering practical insights for future urban construction projects.

Chase Center Golden State Warriors 4K Construction Time-Lapse

Shoring Systems and Methods at Chase Center

Building the Chase Center required a shoring strategy that could handle challenging conditions, including working 26 feet below sea level and managing frequent water intrusion. The construction team developed a set of solutions that provided solid structural support while controlling water effectively. These systems were critical in addressing issues like water discharge and seepage.

Main Shoring Systems

The project relied on a perimeter wall system that combined H-piles with cement deep-soil mixing (CDSM) cutoff walls. This hybrid setup supported a massive 300,000-cubic-yard excavation while serving as a strong barrier against water infiltration. The H-piles

, driven into stable soil layers, managed lateral loads from both soil and groundwater. Meanwhile, the CDSM cutoff walls created a continuous shield to reduce seepage from the bay and surrounding groundwater sources [1].

Waterproofing Solutions

One standout feature was the "boat" solution, which acted as a structural bathtub, sealing all foundations. This design eliminated the need for internal bracing, opening up the workspace for construction activities. To tackle groundwater issues, the team installed 52 dewatering wells across the site to keep the water table consistently low. After excavation, they stabilized the working surface by mixing bay mud with cement to create cement-treated soil. This method allowed heavy equipment to operate directly on the surface, doing away with the need for traditional rock-filled driving aisles and speeding up pile placement [1].

Tools, Technologies, and Safety Measures

Deep underground construction comes with its own set of challenges, requiring advanced tools and rigorous safety protocols to ensure success. By utilizing specialized equipment and well-planned measures, the project maintained stability and safety throughout the process. These efforts supported the shoring systems, creating a smooth path from concept to completion.

Construction Tools and Equipment

A range of equipment played a crucial role in handling the underground conditions:

Soil-mixing machines: These created continuous waterproof barriers, protecting the underground structure from water intrusion.
Pile-driving equipment: Essential for installing structural components that reinforced the shoring system.
Water pumps with monitors: Maintained controlled water levels, ensuring a stable environment for the machinery.
Soil stabilization techniques: Strengthened working platforms to handle the weight and movement of heavy construction equipment.

Planning and Communication Methods

Strong planning and communication were vital for keeping operations running smoothly. Regular meetings and the use of BIM software improved coordination among the various teams involved, particularly during shoring operations. This approach not only ensured that equipment was placed efficiently but also enhanced safety during the ever-changing site conditions. Frequent safety briefings and reliable communication systems kept everyone informed and prepared for any adjustments.

Monitoring and Safety Protocols

Safety was a top priority, supported by continuous monitoring and strict protocols. Systems constantly tracked groundwater levels and structural movements, providing early warnings of potential issues. Workers were safeguarded through measures like confined-space protocols, fall protection, and multiple emergency exits. Additionally, all personnel received specialized training, and safety gear was readily accessible. To meet environmental standards, redundant dewatering systems and water quality testing were implemented, ensuring the site remained compliant and secure.

Lessons Learned and Best Practices

The Chase Center project offered critical insights that continue to shape commercial shoring methods in urban settings. Its demanding site conditions served as a real-world proving ground for addressing intricate geotechnical and environmental challenges.

Key Lessons from Chase Center

A thorough site analysis proved to be a non-negotiable step before construction began. The project site, located on reclaimed land filled with debris from the 1906 San Francisco Earthquake, presented what engineers described as a "geotechnical nightmare" [2][5][1]. Excavations plunged to depths of 30 feet, reaching unstable bay mud and extending 26 feet below sea level [2]

[3][1]. This triggered substantial hydrostatic uplift pressures, adding another layer of complexity.

Hazardous materials, including asbestos and other contaminants, were uncovered early on, making environmental mitigation a priority from the start [2][5]. Additionally, inconsistent bedrock levels and weak soil conditions complicated the installation of deep foundations

[2][1]. These challenges highlighted the need for more refined strategies in commercial shoring.

Commercial Shoring Best Practices

The lessons learned from the Chase Center project have directly influenced best practices for future endeavors. Here are the key takeaways:

Comprehensive Geotechnical Investigations: Conducting early and detailed site analyses can help anticipate and address challenges, especially in urban areas with complex development histories.
Seismic Resilience in Design: San Francisco's seismic activity, paired with weak soils and high groundwater levels, demanded advanced engineering solutions. Incorporating seismic considerations in the design phase is essential for similar projects [2][5][1].
Water Management: Effective water control is crucial for excavations below sea level. The Chase Center's conditions underscored the importance of robust strategies to manage hydrostatic pressures [2][3][1].
Stakeholder Coordination: Urban construction sites often face tight schedules and logistical hurdles. Early collaboration with stakeholders is key to keeping projects on track [2][4][1].
Environmental Mitigation: The discovery of contaminated fill at the site reinforced the importance of integrating environmental strategies into shoring operations from the outset [2][5].

These insights not only addressed the unique challenges of this project but also laid a foundation for tackling similar complexities in future urban developments.

Bay Area Shoring Solutions and Applications

The Chase Center project set a new standard for commercial shoring in one of the most earthquake-prone areas in the United States. These solutions now serve as a model for similar projects throughout the Bay Area.

Seismic Challenge Solutions

The geology of the Bay Area presents unique challenges, requiring shoring systems capable of withstanding intense seismic activity. At the Chase Center, seismic forces were two to three times higher than usual due to its proximity to fault lines, weak bay mud, and historic fill [2]. These conditions amplify the effects of earthquakes, making seismic resilience a top priority in design.

To address these challenges, engineers used advanced seismic analysis techniques, including linear time-history analysis to evaluate how multiple buildings interact during earthquakes. They also conducted 360-degree seismic ground-motion simulations to fine-tune predictions of structural behavior under seismic stress [2].

One key solution involved installing up to three rows of 1,200 tiebacks, each extending as far as 100 feet. These tiebacks were strategically angled - 5° for stable fill and up to 45° for denser formations - to reduce the risk of liquefaction [2].

Adapting to Local Conditions

Beyond seismic considerations, the project required adaptations to the Bay Area's diverse ground conditions. Engineers incorporated over 1,300 deep-foundation elements, utilizing three different pile types with nine reinforcement configurations. A 3,200-foot-long, tied-back continuous DSM (deep soil mixing) wall was constructed to support excavation, protect nearby structures, and prevent groundwater intrusion [2]. These wall panels extended 25 to 75 feet below the surface, reaching stable soil layers.

Water management also played a significant role. Techniques developed during the Chase Center project, such as using deep foundation elements to counteract hydrostatic uplift pressures during construction, continue to shape best practices across the region [2][6].

Meeting Technical Standards

Shoring projects in the Bay Area must comply with some of the most rigorous building codes and seismic requirements in the country, often exceeding national standards. For the Chase Center, engineers implemented specialized detailing for deep foundations, ensuring ductile connections to pile caps while providing the lateral strength and flexibility needed to handle seismic forces [2].

All project documentation adhered to U.S. standards, with dimensions measured in feet and inches, loads in pounds and kips, and pressures in psf. Costs were tracked in U.S. dollars, and schedules followed the MM/DD/YYYY format.

The installation of the DSM wall using a triple-axis soil-mix rig required precise coordination among various disciplines - a process that has now become standard for large-scale projects in the Bay Area [2].

Conclusion: Chase Center Shoring Results

The Chase Center project serves as a clear example of how thoughtful planning, modern techniques, and precise execution can address seismic challenges in urban construction. Throughout the process, the shoring systems proved dependable, safeguarding structural integrity and ensuring nearby buildings remained protected during excavation.

Key elements like efficient installation, carefully designed support systems, effective water management, and secure deep foundations all worked together to maintain safe and steady progress. Advanced seismic analysis and close collaboration across disciplines further contributed to the project's success, offering a practical model for similar urban developments.

This case highlights the importance of well-rounded shoring strategies - not just for ensuring safety and efficiency, but also for protecting surrounding infrastructure and achieving overall project goals. The lessons learned from the Chase Center's construction provide valuable insights for future projects in dense urban environments.

FAQs

What are the benefits of using a 'boat' waterproofing design in large-scale projects like the Chase Center?

When it comes to large-scale construction projects like the Chase Center, a 'boat' waterproofing design brings some standout advantages. It forms a strong, seamless barrier that keeps water and moisture out, even in tough conditions like high groundwater levels or challenging soil. This not only safeguards the foundation but also boosts the structure's longevity.

Another key perk is its efficiency and dependability, making it a go-to option for commercial builds needing solid water management. By cutting down on water seepage and the damage it can cause, this approach helps maintain the building's integrity and saves on expensive repairs in the long run.

How were shoring systems at the Chase Center designed to handle San Francisco's seismic challenges?

The shoring systems at the Chase Center were specifically crafted to handle San Francisco's challenging seismic conditions. Two standout features are the H-pile and cement deep-soil mixing (CDSM) cutoff walls and the 1,700 tiebacks, which work together to bolster the foundation and perimeter against earthquake forces.

The design also includes a graduated pile foundation system and nine reinforced concrete cores integrated into the base structure. These elements add extra stability, reducing the likelihood of structural damage during earthquakes. Together, these strategies help ensure the arena remains secure and steady, even during major seismic activity.

What key takeaways from the Chase Center construction can guide future urban projects with challenging soil conditions?

The construction of the Chase Center offers some key takeaways for handling tricky urban soil conditions. One major lesson is the importance of early and detailed geotechnical investigations. These studies help uncover site-specific issues, like soft or unstable soils, giving engineers the insight they need to develop targeted solutions.

Another standout strategy was the use of advanced shoring techniques, such as impermeable barriers and internal bracing. These methods played a crucial role in stabilizing the site, especially given the challenges posed by Bay Mud soils. They not only reinforced the structure but also reduced internal stress on the building's framework.

By focusing on forward-thinking engineering strategies and fostering early collaboration between contractors and geotechnical experts, future projects can tackle similar obstacles and ensure stability in complex urban settings.