Consequential Disruptions in Transportation Infrastructure

By Liz Ranieri

Having moved to San Francisco from Boston months prior to the 1989 Loma Prieta earthquake, I experienced firsthand the sudden destruction of much of the city’s infrastructure, including the irreparable damage to the elevated 50-foot-high two-level Embarcadero Freeway and the disruptions to transit access. This controversial piece of infrastructural highway, which was envisioned to create an expedited vehicular connection from the city’s Bay Bridge to the Golden Gate Bridge, bypassing the city grid, was at that point realized but only in part.

Ferry Building and Embarcadero, circa 1960. The freeway was damaged in the 1989 earthquake, and torn down between 1991 – 1994. Todd Lappin (SFGATE)

Construction from Broadway along the Embarcadero to the Bay Bridge was completed in 1958, but further pieces were halted by the community’s grassroots effort; known as “the Freeway Revolt,” this “pitted environmentalists and residents, outraged by the idea of their neighborhoods being cut in two by an expressway, against city and state planners keen to realize a modern vision of mass transit in America,” as writer Andrew Charmings put it in SFGATE earlier this year.

Fast forward 32 years: driving the U.S. 101 Highway corridor between San Francisco and Marin Counties, I have witnessed gradual, consequential disruptions in transit access in Southern Marin due primarily to storm surges from sea-level rise, though there are other factors. King Tide events have closed roads, limited access, and damaged coastal habitats on a regular basis, regardless of precipitation. This is only one geographic location that illustrates how sea-level rise will jeopardize waterfront assets, developments, ports, and infrastructure at risk in the coming century.

Water surrounds a disabled car at the southbound Highway 101 onramp in Marin City, CA 2021. (Sherry LaVars/Marin Independent Journal) Source: Marin Independent Journal

The swift destruction of the Embarcadero Freeway by earthquake and the gradual disruption of the San Francisco–Marin portion of Highway 101 by climate change both point to the necessity of preparing for adverse events, rather than waiting for deferred maintenance and environmental catastrophe to wreak havoc. In both cases, the impact spreads to multiple other pieces of essential transportation infrastructure that are linked to and rely on the portion at risk.

Embarcadero Freeway The 7.1 magnitude earthquake in 1989 critically damaged the Embarcadero Freeway’s structural integrity; however, other infrastructural systems in direct proximity to the colossal concrete freeway were impacted and/or disrupted as well: 15 streets and pedestrian/bike pathways from the city’s grid to the waterfront were blocked; the city’s main ferry hub, the historic Ferry Building, was closed due to damage and its ferry service stopped; and underground utilities, including gas and water lines, were broken, resulting in a loss of services. Closing the Embarcadero Freeway to traffic allowed the city to experience life without it, as drivers found other routes through the city. The idea of removing it no longer seemed politically impossible. Mayor Art Agnos, long a foe of the Embarcadero Freeway, presided over its demolition in 1991.

U.S. Highway 101 at Southern Marin There have been and continue to be consequential and periodic flooding episodes that halt transit access at Highway 101 in Southern Marin. Disruptions affect primary access routes from 101 to State Highway 1, Tam Junction, Almonte, West Marin, the Mill Valley-Sausalito Multi Use Path, the Manzanita Interchange, the Tamalpais business district, Marin City, numerous public schools and senior housing developments, and adjacent neighborhoods. As sea levels rise, eventually this area will be permanently underwater.

This flooding and inundation occur during heavy rains, high tides, and the seasonal King Tides; however, one of the biggest (and latent) sources of flooding is roadway subsidence. According to the Tam Valley Sea Level Rise Task Force, “[t]he roadbed underneath the freeway has subsided 4 -12 inches since 1995 due to the weight of the road compressing the mud underneath… and the culverts that enable outflow of tidal and rainwater are increasingly blocked with mud and debris.”

These roadway closures are an obvious sign that current and future sea-level rise will impact—and transform—surrounding communities. When 101’s offramps close down at these locations, other infrastructural systems are impacted, including water and sewerage utilities, pedestrian and bike paths, public bus service and shuttles to major airports (as Park & Ride lots close due to flooding), and mail and delivery services.

The sudden impact of the Loma Prieta earthquake on the Embarcadero Freeway and the flooding from a combination of factors in southern Marin are, admittedly, unique  situations that require specific and different actions. However, some of the impacts to access and other infrastructural systems are similar.

In terms of resilience, the primary question for both the Embarcadero Freeway and Highway 101 is how to allow them to continue functioning when challenged by adverse events. According to the Victoria Transport Policy Institute’s Transportation Demand Management Encyclopedia, “resilience tends to increase if a system has diversity, redundancy, efficiency, autonomy and strength in its critical components. This allows the system to continue functioning if a link is broken, if a particular resource becomes scarce, if a particular decision-maker is unavailable, etc..” Enabling resilience, however, requires a plan that can change over time to respond to future needs – what the Victoria Transport Policy Institute calls “contingency-based planning”. Despite their similarities, do the differing conditions of the Embarcadero Freeway and Highway 101 require different approaches?

In the case of the Embarcadero Freeway, a robust CBP process, had it been  implemented prior to the earthquake, could have identified ways to increase the freeway’s resilience to reduce certain vulnerabilities such as structural integrity, given that the seismic codes had evolved. It could also have  incorporated resilience principles into the planning and management of the freeway’s critical components. Additionally, a  CBP approach might  have allowed for a process to evaluate and change  the structural plan over time in response to future needs, and may have even concluded that, for the greater good of reconnecting the city back to the waterfront, the freeway should be demolished, given its age and poor urban placement,. Finally, it could have initiated more sustainable public transit options, such as increased ferry services and new, accessible streetcars. In the end, all these options came to be, but only after disaster struck. The lack of planning necessitated an emergency response that depleted  valuable resources and, in the aftermath of disaster, required unnecessarily complex engagement with the public to restore confidence going forward.

In the case of the U.S 101 Highway’s periodic flooding at Southern Marin, it’s helpful to note that, according to a 2008 report from the Pew Foundation, “[a] third of the country’s major roadways are in substandard condition…[and] traffic jams waste 4 billion hours of commuters’ time and nearly 3 billion gallons of gasoline a year.” In addition, as climate change increases the intensity of precipitation, highways and roadways are more vulnerable than ever.

The site conditions at Southern Marin present a “perfect storm” of climate change impacts in tandem with much-deferred maintenance on the highway, off-ramps, and roads. To move forward on such a challenging process is further complicated by the difficulty of securing funding and by the decentralized and asymmetrical investment of multiple stakeholders from both the public and private sectors, including Marin County’s board of supervisors and its flood control district, Caltrans, and the Transportation Authority of Marin. To add to this complexity, other stakeholders include  Marin County Parks, the Army Corps of Engineers, the Environmental Protection Agency, the San Francisco Regional Water Quality Control Board, the California Department of Fish and Wildlife, the Bay Conservation and Development Commission, and private property owners. Though these various stakeholders have overlapping agendas, they can also differ substantially in their priorities and approaches.

Our infrastructure has been designed to withstand storms that have a probability of occurring only once or twice every 100 years. However, due to climate change, historical climate data is no longer a reliable predictor of future risk; it may be that  all we can do to predict future risk is plan for the worst-case scenario. Regardless, maintaining our aging infrastructure and bringing our systems up to current building codes is a critical defense in protecting the assets we do have against natural disasters such as earthquakes and ensuring public safety.

As Dr. Ed McCormack, MIPM Transportation Systems Instructor Emeritus at the University of Washington, said in a 2019 interview about emerging issues in transportation, going forward we will need to make transportation more resilient. This requires engaging with emerging technology to make transportation more robust and redundant, and to explore advanced sensor technologies for real-time data collection; being transparent about disruption and providing alternative means of travel; and, given how little time we have to reverse the impacts from climate change, advocate for top-down planning initiatives and regulations, in parallel with local stakeholder engagement to ensure we design, fund, and implement the most resilient solutions.



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