California’s recent atmospheric river storm brought heavy rain, flash floods, and mudslides, underscoring the vulnerability of retaining walls. Streets and highways were flooded, canyon roads were blocked by mud and rocks, and burn areas faced heightened risks of debris flows and landslides. (1,2,3) A significant landslide also closed Thousand Steps Beach in Laguna Beach, highlighting the growing dangers to communities across the state. (4) Unlike other high-profile assets, retaining walls in every sector, from private homes to critical public corridors, are increasingly jeopardized by age, outdated engineering, and new geological threats. Their failure can trigger catastrophic mudslides, destroy properties, sever transportation arteries, and put lives at risk. These events demonstrate the urgent need for proactive retaining wall maintenance and reinforcement.
As unprecedented storms and earthquakes test the limits of aging infrastructure, Alpha Structural urges immediate action to identify and reinforce the most vulnerable areas across the state. “For almost 100 years, retaining walls have made it possible to develop property that would otherwise be unusable. But if a retaining wall collapses, the use of that property is effectively rendered inert, with devastating consequences,” explains Kyle Tourjé, Executive Vice President of Alpha Structural. “Today, many of California’s existing retaining walls, especially older mid-century or turn-of-the-century walls , lack the seismic reinforcement and modern foundation design needed for the risk profile we now face. When these structures fail, the results are not just costly-they endanger lives and critical property.”
Image Courtesy of: Alpha Structural
The Crumbling Foundation of California
Across California, the legacy of early, mid20th-century construction is evident-and it is becoming a source of growing risk. Retaining walls built during this period were commonly designed without adequate geotechnical input and typically ignored seismic forces, ground motion, or liquefaction, which are now known to be critical in this region. The result is a vast inventory of walls that are not only old but also ill-prepared to withstand today’s environmental challenges.
The state’s recent natural disasters underscore this threat. In Rancho Palos Verdes, heavy rains dramatically accelerated a long-standing landslide, shearing apart homes, cutting gas and power lines, and displacing entire communities as the land shifted at rates up to a foot per week. (5) The collapse of a retaining wall supporting Interstate 580 near Livermore, following historic atmospheric river rains, forced long-term lane closures and crippled a major transportation lifeline. (6) These high-impact events expose the systemic vulnerabilities of retaining walls and graded developments statewide, as well as the outsized dangers of ignoring early warning signs.
From Costly Reaction to Proactive Prevention
Alpha Structural challenges the prevailing tendency to wait for disaster before acting-a cycle that leads to outsized cleanup costs, collateral damage, and sometimes irreversible losses. The firm advocates for a strategy grounded in regular, affordable structural and geotechnical assessments, enabling early detection of vulnerabilities and strategic investment in reinforcements. This proactive approach is not only more cost-effective but also critical for safeguarding property and infrastructure before emergencies strike.
Stakeholders across every sector must be vigilant for the early warning signs of retaining wall distress:
- Bowing or Bulging Walls: Noticeable curvature or deformation can signal a loss of structural integrity and precede collapse.
- Cracking: Look for significant or widening cracks on the wall or ground surfaces, which often indicate internal pressure or foundation shifting.
- Out-of-Plumb Walls: Any leaning or tilting away from vertical suggests foundational instability requiring urgent attention.
- Ground Fissures: The presence of visible fissures or splits in the soil near or behind the wall may indicate active soil movement.
- Soil Cracking or Depressions: Cracks or depressions forming in the earth above or immediately behind the retaining wall often reveal subsurface instability and increased risk of failure.
- Sagging in Adjacent Areas: Roads, sidewalks, or landscape features that begin to dip, sag, or settle near retaining walls are major red flags of underlying ground movement.
Early identification of these symptoms is essential. Left unchecked, these red flags can escalate swiftly, especially following heavy rainfall or drainage failures-bringing about sudden and catastrophic wall collapse. Tourjé underscores, “Monitoring and acting on subtle distress signals is the most effective way to prevent massive repair bills and irreversible losses, whether you’re responsible for hillside neighborhoods or vital transportation corridors.”
Securing the Future: A Prevention-First Approach
Alpha Structural stands at the forefront of disaster mitigation for retaining wall failures, with an unmatched capability to analyze, design, and reinforce these essential assets across California’s complex geography. Their expertise reveals why a prevention-first mindset-embracing routine inspections, periodic engineering reviews, and targeted upgrades-is now indispensable for safety and resilience.
“When disaster strikes, repairs are always more expensive and disruptive,” says Tourjé. “Routine engineering assessments are a low-cost investment that not only highlight hidden weaknesses but empower property owners and agencies to plan improvements on a realistic timeline. The longer we rely on hope or wait for visible failures, the greater the costs to our communities, our infrastructure, and our safety. Now is the time for public officials, insurers, and property owners to prioritize preventative action and ensure California’s retaining walls can meet the challenges ahead.”
This renewed focus on proactive maintenance, updated engineering standards, and cross-sector responsibility will determine whether California’s next storm brings disruption or resilience.
About Alpha Structural, Inc.
When he saw geological challenges trigger catastrophic building collapses, Dave Tourje, founder of Alpha Structural, Inc., immersed himself in construction repairs and mitigation facing the iconic hillside homes and buildings throughout Los Angeles in the 1980s. He recognized a lack of skilled tradesmen and the need for repairs or upgrades to be engineered and constructed successfully. Today Alpha Structural is Southern California’s premier structural repair and engineering firm. With over 30 years of experience in foundation repair, hillside stabilization, and seismic retrofitting with challenges of earthquakes, wildfires and landslides, Alpha Structural distinguishes itself by being dual-licensed and authorized by the State of California to both engineer and build in-house—an integration that eliminates miscommunication and cost overruns seen when engineering and construction are handled separately. Alpha Structural is trusted by homeowners, municipalities, and commercial partners alike. For more information visit Alpha Structural.
