SPUR REPORT / ONE OF A SERIES
[ see all reports in this series ]
Adopted by the SPUR Board on January 16, July 16, September 17 and November 19, 2008
The Resilient City - Part I (condensed version)
On April 18, 1906, shortly after 5 a.m., almost 300 miles of the San Andreas Fault ruptured. The ground shaking and ensuing fires caused more than 3,000 deaths, destroyed more than 28,000 buildings and left homeless about 225,000 of Northern California's 1 million residents.
In that year, about 390,000 people lived in San Francisco and less than 1 million lived in the entire 19-county Northern California region. Today, the number of San Franciscans has more than doubled and Northern California's population exceeds 10 million. Northern California now has more than 3 million buildings with a total value of $1 trillion. San Francisco's building value exceeds $100 billion. The potential for damage today far exceeds the damage wrought by the 1906 event.
What would happen if the 1906 earthquake were to happen again in the next five, 10 or 20 years? The answer depends on what we have done to prepare for the next big event. In one scenario — the most likely one at this point — not enough special preparation has been done. A few existing buildings were retrofitted by owners voluntarily, and a few others through attrition were replaced by newer structures. The newer structures have better seismic performance than the older buildings, and very few of these buildings collapse and kill occupants. But many new structures are rendered unusable by the quake; some will not be back in service for months and some are not economically repairable and must be demolished. Breaks in water mains mean that many buildings are left without water. And the damage to surface rail lines means that Muni trains are unusable.
The damage has cascading consequences for San Francisco. People are displaced from their homes, companies and residents are forced to move out of the area, small businesses fail, and reconstruction demands overwhelm the city's damaged infrastructure. Years later, San Francisco has failed to recover and is no longer seen as the center of the region.
In another scenario — the one we advocate — San Francisco has chosen to invest the time, energy, and political and economic capital in becoming a resilient city — that is, a city that can rebound quickly from a natural disaster. Performance objectives have been established for buildings and for lifelines — those systems such as power, gas and water services, as well as communications and transportation systems. Enough homes have been retrofitted so that the vast majority of San Franciscans are able to shelter in place. A "Lifelines Council" with influence over the preparation of critical services has ensured that the city's water, gas, electricity and sewer services are strong enough to be back in use within days. Seismic Silver and Seismic Gold buildings, defined by a new voluntary rating system, perform so well that they quickly become a model for all new housing in the region. The entire city is back on its feet within four months.
What we do before the disaster determines what happens after the disaster. We cannot control or precisely predict what nature will do, but we have it within our power to take steps to make this city resilient in the face of a major earthquake. The work before us involves far more than the high-drama rescue, firefighting and medical response in the moments and days following a disaster. It involves a redesign of our buildings and infrastructure systems so that they become capable of surviving the kinds of earthquakes likely to hit San Francisco.
For the past two years, SPUR has been hard at work on its Resilient City Initiative — trying to determine what it is that we should be doing now so that we can rebound quickly from a major event. Our efforts have resulted in four major policy papers, presented in the following four setions of this report:
1. DEFINING RESILIENCE: Defining what San Francisco needs from its seismic mitigation policies
When a major earthquake strikes the Bay Area, we will face thousands of casualties, hundreds of thousands of displaced households, and losses in the hundreds of billions of dollars. Recovery will take years. The overall impact and cost of a disaster is strongly influenced by how long it takes to recover. The time needed to recover depends on the level of damage sustained by buildings, the availability of utilities, and how quickly communities can re-establish usable housing and livable environments.
This article addresses one aspect of the broader policy problem related to making San Francisco resilient in the face of a disaster — the standards we use for deciding when a structure is "safe and usable enough." The truth is that when we choose our engineering standards, we really are choosing to define how many deaths, how many building demolitions and how long a recovery time we will have for various levels of earthquakes. Currently, the City of San Francisco has no adopted performance objectives for determining these factors.
A disaster resilient San Francisco
SPUR has defined
performance goals in terms of
four "clusters" of infrastructure
(page 9), eight performance
categories and three response
and recovery phases (shown
in this table). We are not
recommending that all
facilities be upgraded without
regard to cost. Rather, our
intent is to require only those
improvements needed to
assure a quick recovery — or the level of resilience desired
for each stage of recovery.
SPUR's efforts to define San Francisco's seismic resilience come with a clear and transparent understanding of the hazards and risks we face. These are defined in terms of the earthquakes we expect to occur, the damage they will cause to the built environment, and the effects of that damage on response and recovery.
Performance goals for the "expected" earthquake
SPUR is not recommending that all facilities be upgraded to a level that would make them damage-proof without regard to cost. Rather, our intent is to clarify the level of damage that is acceptable, and require only those improvements in performance needed to assure a quick recovery — or the level of resilience desired for each stage of recovery (see page 6). We believe that most of the criteria for new buildings are adequate, and the need for strengthening existing buildings is perhaps less extensive than generally perceived. Nevertheless, some important changes are needed.
SPUR's seismic target states of recovery (see page 9) are stated in terms of general states of damage and repair over an extended recovery period, under the assumption that an "expected" earthquake has occurred. We chose to analyze the "expected" earthquake, rather than the "extreme" event, because it is a large event that can reasonably be expected to occur once during the useful life of a structure or lifeline system.
Defining the "expected" earthquake
A defined level of earthquake performance only makes sense if you also define which earthquake you're talking about. The same damage or disruption that might be forgivable in a large earthquake might be unacceptable in a small one. Earthquakes are commonly reported in the public press in terms of the Richter Magnitude. That measure was defined in the early 1940s and is useful only for quantifying the energy released overall by a single earthquake. It offers little in terms of how buildings or infrastructure will fare, or how they should be designed.
In order to evaluate an existing facility or design a new one, earth scientists and engineers today use different measures to quantify the intensity of the expected shaking at a specific site. These engineering measures account for the possible effects of different earthquakes on multiple faults, and therefore are defined in probabilistic terms. For example, a building might be designed for the level of shaking expected to occur with 10 percent probability over a 50-year time period.
A third way of defining earthquakes involves "scenario events": specific hypothetical earthquakes defined by the location of the fault rupture and the magnitude of the energy released. For example, a "magnitude 6.9 earthquake on the San Andreas fault near Santa Cruz" would be one scenario event of possible interest in San Francisco, as that would represent a repeat of the 1989 Loma Prieta earthquake. Scenario earthquakes are especially useful for citywide or regional planning. They also are easier to grasp than probabilistic measures and therefore are effective for communicating earthquake risk to policymakers and to the public. In 2003, the San Francisco Department of Building Inspection's Community Action Plan for Seismic Safety chose four scenario earthquakes as the basis for its planning and mitigation programs.
For the purposes of defining resilience and developing mitigation policies to achieve it, SPUR uses one of the scenario earthquakes also used by CAPSS, and refers to it as the "expected" earthquake: a magnitude 7.2 earthquake on the Peninsula segment of the San Andreas fault.
Our expectations, our goals and our recommendations are presented with this event in mind. This expected earthquake can be expected — conservatively but reasonably — to occur once during the useful life of a structure or system, and more frequently if the structure is renovated periodically (as most San Francisco buildings are) to serve more than one or two generations. Of course, this defined scenario would produce different levels of shaking at different locations, but for most of the city its effects would be similar, in probabilistic terms, to those with a 10 percent chance of occurring over a 50-year period.
We define resilience in terms of this expected earthquake. Other earthquakes are possible, of course. In a smaller, more routine earthquake, better performance would be expected. For a larger, more extreme event, lesser performance would have to be tolerated.
A defined level of earthquake performance only makes sense if you also define which earthquake you're talking about. The same damage or disruption that might be forgivable in a large earthquake might be unacceptable in a small one. Earthquakes are commonly reported in the public press in terms of the Richter Magnitude. That measure was defined in the early 1940s and is useful only for quantifying the energy released overall by a single earthquake. It offers little in terms of how buildings or infrastructure will fare, or how they should be designed.
In order to evaluate an existing facility or design a new one, earth scientists and engineers today use different measures to quantify the intensity of the expected shaking at a specific site. These engineering measures account for the possible effects of different earthquakes on multiple faults, and therefore are defined in probabilistic terms. For example, a building might be designed for the level of shaking expected to occur with 10 percent probability over a 50-year time period.
A third way of defining earthquakes involves "scenario events": specific hypothetical earthquakes defined by the location of the fault rupture and the magnitude of the energy released. For example, a "magnitude 6.9 earthquake on the San Andreas fault near Santa Cruz" would be one scenario event of possible interest in San Francisco, as that would represent a repeat of the 1989 Loma Prieta earthquake. Scenario earthquakes are especially useful for citywide or regional planning. They also are easier to grasp than probabilistic measures and therefore are effective for communicating earthquake risk to policymakers and to the public. In 2003, the San Francisco Department of Building Inspection's Community Action Plan for Seismic Safety chose four scenario earthquakes as the basis for its planning and mitigation programs.
For the purposes of defining resilience and developing mitigation policies to achieve it, SPUR uses one of the scenario earthquakes also used by CAPSS, and refers to it as the "expected" earthquake: a magnitude 7.2 earthquake on the Peninsula segment of the San Andreas fault.
Our expectations, our goals and our recommendations are presented with this event in mind. This expected earthquake can be expected — conservatively but reasonably — to occur once during the useful life of a structure or system, and more frequently if the structure is renovated periodically (as most San Francisco buildings are) to serve more than one or two generations. Of course, this defined scenario would produce different levels of shaking at different locations, but for most of the city its effects would be similar, in probabilistic terms, to those with a 10 percent chance of occurring over a 50-year period.
We define resilience in terms of this expected earthquake. Other earthquakes are possible, of course. In a smaller, more routine earthquake, better performance would be expected. For a larger, more extreme event, lesser performance would have to be tolerated.
Steps toward a more resilient city
While this paper defines the goal of an earthquake-resilient San Francisco, the following papers apply the concept of resilience to new buildings, existing buildings and lifelines. Each of those papers include near— and long-term recommendations to achieve the goal of resilience. Overall, SPUR's specific recommendations for action have been developed by considering:
(1) the goals for seismic resilience for each component of our city
(2) the gap between current seismic performance and the goal, and
(3) the cost of making the necessary improvements or retrofits.
Priority is given to those actions that provide the best improvement to seismic performance and resilience with the least amount of cost and disruption.
SPUR's recommendations for existing buildings focus on dealing with the city's most seriously deficient buildings through mandatory programs where the needs are clear, and the development of additional programs where further definition is needed. Soft-story wood frame buildings need to be retrofitted. Buildings providing shelter and other essential City services need to be evaluated and retrofitted as needed. San Francisco's non-ductile concrete buildings — structures that have frames of reinforced concrete but are unable to bend without breaking — need to be inventoried, and a program should be developed to mitigate their potential for collapse. Gas shut-off valves need to be installed to prevent massive fires from consuming the city following an earthquake. And the adequacy of the 1992 Unreinforced Masonry Building Retrofit Ordinance needs to be assessed.
SPUR's recommendations for new buildings focus on adding transparency to the building code requirements; incorporating new, near-term cost-effective improvements into the code; creating a certification system for voluntary seismic upgrades akin to the LEED system for green building standards; and adding strong incentives for owners to build to higher seismic standards. Owners and tenants need to understand what seismic performance to expect from the buildings they own, lease and construct, and the options they have for improvement.
SPUR's recommendations for lifelines begin with the formation of a Lifelines Council that brings the various owners and operators together to assess the vulnerability of the systems that serve San Francisco. The council also should develop performance standards and retrofit priorities. The City should incorporate the needed retrofits into its capital improvement plans, give specific attention to managing the city's gas system, and form partnerships with the regional and state public and private providers to secure the necessary modifications to their systems. The City also should become an advocate at all levels for the development of consistent performance standards.
Conclusion
The "x's" in this chart
indicate SPUR's best educated
guesses about current standards
for recovery times. The shaded
areas represent the goals —
targets based on clearly stated
performance measures (see next
page) — for recovery times for
the city's buildings and lifelines.
The gaps between "x's" and
shaded boxes represent how far
we are from meeting resiliency
targets.
2. THE DILEMMA OF EXISTING BUILDINGS: Private property, public risk
San Francisco has more than 120,000 buildings,2 at least 90 percent of which were erected before the adoption of modern building codes in the mid-1970s. Most of these buildings are safe even in large earthquakes, meaning they won't flat-out collapse, break apart or shed their heavy skins onto sidewalks. But there will be damage. For a Loma Prieta-sized earthquake close to the city, 30,000 buildings could be damaged beyond repair by shaking and fire.3 Even if the number is smaller, thousands of buildings will need substantial repairs, or at least inspection and clean-up, before being reoccupied.
Losing a quarter of our existing building stock, even temporarily, is not acceptable. But neither is the cost of eliminating all potential losses. For a large earthquake in our lifetime, some damage is inevitable. But how much is acceptable?
It depends on what we're trying to achieve. Would it be enough to eliminate the risk of life-threatening collapses? After all, the first goal of earthquake preparedness is to protect lives.4 But mere survival is not the only goal, especially from a citywide perspective. City policy must recognize responsibilities beyond basic safety and even beyond a simple reduction of damage. Planning for resilience means preparing our structures, networks, and organizations so that expected losses are not disproportionate or catastrophic.
So which buildings are critical to San Francisco' s resilience? We know what services will be critical to earthquake response and recovery. We also know which structure types are most prone to collapse. What we need to know for assessing resilience is which structure types the critical services are in, and which of those buildings might be safe from collapse but are still not likely to be usable right away.
Why existing buildings are challenging
Structural engineers have tools to predict damage and assess safety. Unfortunately, they work best with individual buildings whose structural attributes are known. It's harder to draw reliable conclusions about a class of buildings such as shelters, schools or residences, for two reasons.
First, existing buildings are relevant to resilience plans because of their occupancy — that is, because of the functions they house, whether residential, office, hospital, church, jail, warehouse and so on. But engineers classify and assess buildings not by occupancy, but by structural materials (such as wood or concrete) and systems (such as frames and shear walls).Some historic correlations are helpful here. For example, most single-family residential buildings are of conventional wood construction. But the patterns are not robust enough to be consistently useful. What's needed is an inventory that breaks out the structure types within each occupancy category.5
Second, existing buildings affect resilience to the degree they remain habitable or usable after the earthquake. Engineering assessments, however, rarely look at buildings this way, as they typically focus only on safety — that is, on whether occupants will be able to escape the building uninjured.6 Using SPUR's performance categories (see sidebar), these assessments determine whether a building is in Category E, but they make little or no distinction between Categories A through D. Consider the City's recreation centers and department offices. Any previous assessments probably predict only whether these buildings might be evacuated safely, and say little about whether they might remain in service to aid response and recovery. Some buildings can take damage but remain basically functional. Others might see little structural damage but be lost to the recovery effort due to plumbing failures or broken windows, or even because the file cabinets and storage racks have toppled.
So while resilience is a function of occupancy and usability, engineers tend to look more at structure type and safety. These disconnects point to the need for more complete building inventory data: We need to know which structures house which occupancies. Absent that data, can any broad observations be made? Though the relationship is fuzzy, it's fair to say that post-earthquake usability correlates inversely with damage, and traditional building patterns do paint at least an impressionistic image of where our existing building stock might achieve or fall short of resilience goals.
Our analysis, as shown in the chart below, also allows several observations about San Francisco's current building stock:
- Despite the strong historic performance of typical wood houses, San Francisco's residential buildings will affect resilience citywide because of the prevalence of soft-story, multi-unit buildings and house-over-garage conditions. Unbraced cripple walls, though found in older houses throughout California, are relatively rare in San Francisco. Instead, our high density and narrow lots have made two-story, house-over-garage construction more common.
- Retail and commercial spaces exist in nearly every structure type. As a sector, commercial occupancies can be affected by the broadest set of potential hazards and might therefore present the toughest challenge in terms of crafting simple, effective risk reduction policies.
- Non-ductile concrete frame buildings probably house every critical occupancy. A more complete and reliable inventory will significantly inform any risk reduction program for these structures.
- Nonstructural components include everything from ceilings and windows to boilers and plumbing. Their performance is notoriously unpredictable (due to a lack of building code provisions in the past, and spotty construction quality more recently) and can affect the post-earthquake usability of almost every occupancy.
- In addition to vulnerable construction, geotechnical conditions such as the potential for landslide or liquefaction often affect performance. Though important, these factors are not listed in the above table because the vulnerability is entirely based on location and is not related to the occupancy of the building.
The "x's" in this chart
indicate SPUR's best educated
guesses about current standards
for recovery times. The shaded
areas represent the goals —
targets based on clearly stated
performance measures (see next
page) — for recovery times for
the city's buildings and lifelines.
The gaps between "x's" and
shaded boxes represent how far
we are from meeting resiliency
targets.
Near-term mitigation strategies for existing buildings
Can building-by-building mitigation improve the resilience of a city of 120,000 structures? If it's targeted to the critical services and structure types, SPUR believes it can.7 The important thing for San Francisco is to find mitigation strategies that will be feasible on a citywide scale, and to dovetail mitigation plans with response and recovery plans. If we're not prepared to mitigate, we must be prepared to respond and recover, and if we're not ready to respond and recover, we must take steps to mitigate.
Every sector of our existing building stock poses some risks and presents some opportunities to improve resilience. Ranking sectors by importance is not easy; there is no formula to balance effectiveness, cost, fairness and expedience. Setting priorities and achieving consensus also is complicated because the best strategies to increase resilience citywide might not be the ones that most serve individual citizens' interests. The City's responsibilities — and therefore its risks, too — are broader and deeper.
Mitigation programs are effective when they balance the needs and resources of all stakeholders. A mandatory program that no building owner can afford, or that causes enormous short-term disruption to achieve a hypothetical long-term result, will accomplish little. On the other hand, programs designed for the convenience or benefit of individuals don't often get the job done for the community. Political leadership and community willingness must be in sync.
Our shortfall in resilience is a problem almost a century in the making. It will not be solved in a quick decade with a short list of programs. Still, the City needs to get started with policies and initiatives that make sense in the near term, as well as commitments to stay on the job for a generation to come. There are dozens of ways to reduce our risk and increase our resilience. They are all valuable, but they cannot all be done at once. Near-term strategies should address our biggest resilience gaps and set the stage for equally important programs to come later.
SPUR has prioritized six policy recommendations for near-term mitigation of existing building risks.
SPUR RECOMMENDATIONS: EXISTING BUILDINGS
1. Mandated retrofit of soft-story, wood frame, multifamily housing.
Our current housing stock cannot provide the resilience we need. A documented history of poor performance and potentially disastrous effects on response and recovery make this a risk that deserves immediate attention. Not every residential building is a soft-story hazard (see Field Notes on page 30), but soft-story conditions probably will determine whether our housing stock as a whole can meet a high resilience objective. A major Bay Area earthquake could render 2,000 or more soft-story buildings uninhabitable, leading to the loss of housing for 50,000 residents.8
These vulnerable buildings need to be identified, and as a class they need to perform better. A mitigation program coordinated with citywide resilience goals would be consistent with existing City policy to facilitate "shelter in place" and post-earthquake damage assessment plans.9
SPUR recommends a program of mandated retrofits over a feasible compliance period as was done for unreinforced masonry buildings. Ample background work by the Department of Building Inspection and the readiness of policymakers10 will make a mandate feasible. Specific criteria, exemptions and prioritization (by building size or location, the number of units, or other factors, with buildings housing low-income or otherwise socially vulnerable tenants meriting special interest) deserve study by DBI, but should be based on data already gathered by CAPSS. Further, the City should explore a full range of financial resources and incentives, including the potential for using funds left over from the Unreinforced Masonry Bond program which distributed bond funds for the upgrade of unreinforced masonry buildings.
2. Mandated retrofit or redundancy for designated shelters.
Until the housing stock is improved, we must be ready for the effects of significant housing losses. While the City has designated certain existing buildings to serve as shelters, it has not confirmed that those facilities will be sufficient or even usable after a damaging earthquake.11
The City must make this among its highest near-term priorities. Using SPUR's terminology, these facilities must be capable of Category B performance. The Department of Emergency Management, which designates shelter facilities, should be the lead agency for this work. Following assessment of the facilities currently designated, the department should propose measures to address identified deficiencies by 2015.
3. A mitigation program for essential City services.
Essential post-earthquake services are those needed to implement a sufficient response and recovery plan. They include certain City department operations, as well as medical and social services. While the City's latest planning documents acknowledge these needs, there does not appear to be a coordinated effort to identify and address critical vulnerabilities, even for City-owned or City-leased facilities.12
Of particular concern are medical and social services, which in San Francisco are provided in part by non-governmental organizations. If the City is relying on NGOs to make its emergency plan viable, it should allocate resources to help those organizations prepare. The Department of Emergency Management and the Department of Public Health should jointly engage the NGO community, coordinate the City's emergency plan with those NGOs' resources, and propose measures committing City resources to bridge the gaps those organizations — most of which are cash-poor — cannot fill on their own. Using SPUR's terminology, these facilities — if not backed up by alternatives — must be capable of Category B performance.
A coordinated analysis of combined public and private capacity, overlain by estimates of service demands, is doable by 2010. The analysis will inform the selection of mitigation strategies that should be implemented by 2015.
4. A mitigation program for critical non-ductile concrete buildings.
Mitigation starts with inventory. By 2010, DBI should know how many of these obsolete and dangerous buildings are in the City, where they are, what services they house, and what effects their expected performance will have on response and recovery. As critical City-owned buildings are identified, DBI and the Department of Public Works should take steps to require seismic evaluations. DBI should also consider changes to San Francisco Building Code Chapter 34 to trigger seismic evaluations of privately owned concrete buildings. Together with a growing body of technical and cost data, we will then be in a position to move forward with a program that targets the unacceptable risks with the most appropriate and effective strategies.
5. Mandated and triggered retrofit of gas lines and gas-fired equipment.
Fire can turn a manageable earthquake emergency into catastrophe. Since broken gas lines often are involved in earthquake-related fires, the best solution is to prevent ruptures by bracing equipment such as water heaters and using flexible lines and connections. If the structure itself is a collapse hazard, or if the gas line passes through a damageable building wall, then a different solution is needed. An excess-flow gas-shutoff device can be installed upstream of the potential rupture location. But there's a problem: The damageable building is the owner's responsibility, while the line upstream of the meter belongs to the gas company.
SPUR's recommendation is for mandated retrofit, guided by a coordinated study. The Department of Building Inspection must determine which City buildings are at risk of collapse or rupture. PG&E must determine where individual ruptures will do the most damage and where excess-flow shutoffs will be effective (they do not work well on low-pressure lines), based on knowledge of its own distribution system. From the combined data, DBI should develop a retrofit mandate for selected existing buildings, to be implemented jointly by PG&E and building owners.
Meanwhile, DBI and the Public Utilities Commission should work with PG&E, insurers and business associations to reach building owners and assist them in eliminating hazards voluntarily. DBI should consider requiring excess-flow shutoffs or seismic-triggered shutoffs on all new installations, and should develop code provisions to trigger upgrades when properties are sold or altered.
6. Assessment of the unreinforced masonry program.
Retrofits of the City's unreinforced masonry buildings, mandated by a 1992 ordinance, are nearly complete. While unquestionably beneficial, these retrofits were minimal, intended only to prevent wholesale collapse. The effort so far will save lives, but it will not keep buildings usable, and unreinforced masonry buildings as a group remain a significant source of potential losses. Using SPUR's terminology, most of them have been improved only from Category E to Category C or D. DBI should now assess the completed program, draw lessons from it, and estimate the remaining risks in resilience terms.
Conclusion
Can building-by-building mitigation improve the resilience of a city of 120,000 structures? If it's targeted to the critical services and structure types, SPUR believes it can.7 The important thing for San Francisco is to find mitigation strategies that will be feasible on a citywide scale, and to dovetail mitigation plans with response and recovery plans. If we're not prepared to mitigate, we must be prepared to respond and recover, and if we're not ready to respond and recover, we must take steps to mitigate.
Mitigation strategies for existing buildings: An à la carte menu
Even where mitigation is necessary, it does not always have to involve an immediate mandate for structural retrofit. Effective risk reduction policies adopt and combine a variety of strategies:
Inventory and planning. Inventories and studies do not reduce risk. But they do make risk reduction programs viable by building consensus around objective data. Knowing what's at risk is always sound policy. From an inventory, the effort can progress to planning, then to implementation.
Mandated retrofit. Generally enacted by legislation, mandated programs require work on specified buildings regardless of an owner's intent. Mandates tend to address otherwise intractable conditions with long records of poor performance and sizable remaining inventories still at risk, especially where the mitigation would have a broad public benefit. Examples of mandated retrofit programs include the improvements to California hospitals and programs for unreinforced masonry buildings in accord with California's 1986 URM Law.
Voluntary retrofit. Where mandates are not viable, a policy of voluntary retrofits can be effective. Driven only by owners' knowledge and risk sensitivity, with minimal outside requirements, voluntary work can range from bracing a water heater to a complete structural upgrade. In booming economies, owners retrofit to limit business disruptions. In slower times, they have other priorities. Institutional owners do voluntary work to fulfill management responsibilities to their constituents. Voluntary work also can be encouraged by education, and by incentives such as fee or assessment waivers or grandfathering with respect to future mandates.
Triggered retrofit. Seismic improvements can be required, or triggered, by the scope of repairs, additions, alterations, changes of occupancy or even changes in ownership. San Francisco has upgrade triggers in Chapter 34 of its Building Code. The work often is driven by business decisions to otherwise improve a property, so triggers can be effective if they apply when new funds are available. On the downside, an owner's intended project might be scaled down or skipped completely in order to avoid triggering additional seismic requirements.
Insurance and risk transfer. If an unacceptable risk cannot be actually removed, its financial component sometimes can be transferred through insurance or reinsurance. This strategy works best when expected losses are otherwise repairable, and when quick recovery or continuity of operations is not needed.
Redundancy. Backup, or redundant, facilities don't reduce damage, but they can shorten the time needed to recover normal operations. Redundancy planning can save retrofit costs and avoid the service disruptions that sometimes come with retrofitting. The strategy also makes sense when the vulnerable facility is deficient in other ways as well, so that rebuilding makes more sense than retrofitting. It is not an effective strategy where relocation cost and delay will interfere with critical post-earthquake operations.
Occupancy resumption planning. When other risk reduction strategies are not feasible, or while they are being implemented, a plan to speed up re-occupancy (often as part of a broader continuity of operations plan) can at least aid recovery when the building remains habitable, even if it does not reduce damage or actual risk.
Even where mitigation is necessary, it does not always have to involve an immediate mandate for structural retrofit. Effective risk reduction policies adopt and combine a variety of strategies:
Inventory and planning. Inventories and studies do not reduce risk. But they do make risk reduction programs viable by building consensus around objective data. Knowing what's at risk is always sound policy. From an inventory, the effort can progress to planning, then to implementation.
Mandated retrofit. Generally enacted by legislation, mandated programs require work on specified buildings regardless of an owner's intent. Mandates tend to address otherwise intractable conditions with long records of poor performance and sizable remaining inventories still at risk, especially where the mitigation would have a broad public benefit. Examples of mandated retrofit programs include the improvements to California hospitals and programs for unreinforced masonry buildings in accord with California's 1986 URM Law.
Voluntary retrofit. Where mandates are not viable, a policy of voluntary retrofits can be effective. Driven only by owners' knowledge and risk sensitivity, with minimal outside requirements, voluntary work can range from bracing a water heater to a complete structural upgrade. In booming economies, owners retrofit to limit business disruptions. In slower times, they have other priorities. Institutional owners do voluntary work to fulfill management responsibilities to their constituents. Voluntary work also can be encouraged by education, and by incentives such as fee or assessment waivers or grandfathering with respect to future mandates.
Triggered retrofit. Seismic improvements can be required, or triggered, by the scope of repairs, additions, alterations, changes of occupancy or even changes in ownership. San Francisco has upgrade triggers in Chapter 34 of its Building Code. The work often is driven by business decisions to otherwise improve a property, so triggers can be effective if they apply when new funds are available. On the downside, an owner's intended project might be scaled down or skipped completely in order to avoid triggering additional seismic requirements.
Insurance and risk transfer. If an unacceptable risk cannot be actually removed, its financial component sometimes can be transferred through insurance or reinsurance. This strategy works best when expected losses are otherwise repairable, and when quick recovery or continuity of operations is not needed.
Redundancy. Backup, or redundant, facilities don't reduce damage, but they can shorten the time needed to recover normal operations. Redundancy planning can save retrofit costs and avoid the service disruptions that sometimes come with retrofitting. The strategy also makes sense when the vulnerable facility is deficient in other ways as well, so that rebuilding makes more sense than retrofitting. It is not an effective strategy where relocation cost and delay will interfere with critical post-earthquake operations.
Occupancy resumption planning. When other risk reduction strategies are not feasible, or while they are being implemented, a plan to speed up re-occupancy (often as part of a broader continuity of operations plan) can at least aid recovery when the building remains habitable, even if it does not reduce damage or actual risk.
3. BUILDING IT RIGHT THE FIRST TIME: Improving the seismic performance of new buildings
Improving the seismic performance of new buildings (that is, projects not yet built) is an important part of improved earthquake resilience for San Francisco. While older buildings are more likely to be damaged than new structures, the cost to retrofit older buildings is relatively high. In contrast, improving the seismic safety of new structures costs relatively little and thus has a relatively good benefit-cost ratio. Equally important, improving the safety of new structures helps arrest the growth of earthquake threats in San Francisco. We should be building new buildings that will be reusable after major earthquakes and will not need costly repairs or subsequent seismic improvements.
The most effective strategy for achieving SPUR's overall targets for building performance that help create a resilient city is to set a target for new buildings higher than the overall target, and to accept a target for existing buildings somewhat lower than the overall target.
Seismic performance currently provided by the Building Code
The level of seismic performance provided by the current Building Code is not explicitly defined. The Structural Engineers Association of California is intentionally vague in its description of expected performance — buildings are expected to "possibly" experience "some" nonstructural damage in a moderate level of earthquake ground motion, and "some" structural as well as nonstructural damage in a major level of earthquake ground motion. This qualified language recognizes the variability in the observed performance of buildings in earthquakes. The variability in performance comes from the inherent randomness of earthquake and material phenomena, and from the limitations in our knowledge of the best methods and assumptions to use in all the steps of predicting seismic performance.
Although the descriptions of the seismic performance intentions of the Building Code are vague, they undoubtedly define an expectation that is less ambitious than the targets proposed by SPUR (see page 8). If the SPUR targets are to be met, new buildings in San Francisco should be designed for enhanced seismic performance rather than merely allowed to meet the default of the building code.
Clear communication of seismic performance expectations
In parallel with improving seismic performance, SPUR advocates a clearer communication of what seismic performance is expected from each building in our community. On page 10, we propose five categories of seismic performance.
For ordinary buildings, current building codes promise no better than Category D performance (safe, but not repairable) in the expected earthquake. That is, they will be safe but will be so damaged they might be unrepairable. There will be, however, variability in the resulting performance, and while some buildings designed to the code will only provide Category D performance, a large number of buildings will happen to perform much better. Thus, even though all buildings are designed to the same overall Building Code seismic criteria, they all will perform differently in the same earthquake.
Although the descriptions of the seismic performance intentions of the Building Code are vague, they undoubtedly define an expectation that is less ambitious than the targets proposed by SPUR (see page 8). If the SPUR targets are to be met, new buildings in San Francisco should be designed for enhanced seismic performance rather than merely allowed to meet the default of the building code.
SPUR RECOMMENDATIONS: NEW BUILDINGS
To help create a city that remains resilient in the face of the inevitable earthquake crisis, SPUR has developed one long-term and three near-term recommendations:
1. Establish seismic performance targets for new buildings that allow the City to recover quickly from the inevitable strong earthquake.
SPUR has defined seismic performance goals according to an intended timetable for the city's recovery. The targets are ambitious and will take proactive efforts and incentives to achieve. The targets are long-term goals, to be achieved over the next two or three decades. Among the efforts necessary to achieve these earthquake resilience targets, SPUR recommends beginning with the following three near-term actions outlined below.
2. Make improvements to the San Francisco Building Code to provide cost-effective improvements in seismic performance.
Improvements can be made to the San Francisco Building Code that should have little cost impact on construction, but should lead to improved seismic performance for new buildings. The San Francisco Department of Building Inspection should support this effort, with the goal that the City should adopt new requirements within two years. The types of changes envisioned include things such as better quality and reliability in the inspection of fire sprinkler installations and their seismic bracing, increased seismic design forces for elevator rails and better column strength requirements in tall moment frame buildings.
The overall seismic
performance targets for
buildings result from the
combination of performance
targets for new and existing
buildings. In all cases,
SPUR’s overall performance
targets require a substantial
improvement in seismic
performance compared to the
current situation.
One way to communicate expected seismic performance, and to advocate for improved performance, is to use a certification system that defines different levels of seismic resistance measures in terms of how usable or repairable a building will be after an earthquake. Potentially, a rating system could make seismic performance more transparent and allow the marketplace to push for improved seismic performance. With this understanding, owners may choose to comply with a higher standard of such seismic measures — or "provisions" — because of their own desire for improved seismic performance, or because such improved seismic certifications have been shown to appeal to buyers or tenants.
SPUR envisions a certification system for new buildings that is based on developing targeted seismic design provisions, in Building Code language, that give an option for designing for improved performance. The certification system could have two levels, beyond the ordinary Building Code requirements:
- "Seismic Silver" describes a building meeting the minimum seismic and structural requirements of the Building Code, plus additional specific provisions, written in Building Code language, that have been developed to provide improved seismic performance. The target performance for this level might be as shown on page 10 — 85 percent of buildings designed to the Silver provisions would achieve Category C or better seismic performance. That is, they would require significant repairs, but afterward would be safe and usable.
- "Seismic Gold" would be similar to Seismic Silver, except that there would be more stringent provisions that would provide further improvement to seismic performance. The target performance for this level might be as shown on page 10 — 80 percent of buildings designed to the Gold provisions would achieve Category B or better seismic performance. That is, they would need some repairs but could be used safely while those repairs were made.
It may be advantageous to also define a "Seismic Certified" category (below Seismic Silver) that can be applied to buildings that meet the 2007 San Francisco Building Code. The reason is that the rating of new buildings as Seismic Certified would raise awareness of the seismic rating system, and ultimately could help create a market-based incentive for Seismic Silver and Seismic Gold buildings as project sponsors and prospective homebuyers become aware of the new rating system.
Implementing a rating system
The idea of targeted improvements to the Building Code grouped under categories such as Seismic Silver and Seismic Gold is a refinement of a concept that already exists in the code.
The national building standard for structures requires more restrictive earthquake designs for certain building types. The more restrictive requirements depend on a categorization of the use that occupies a building and the relative hazards to people if the building fails. Occupancy Category II refers to ordinary buildings, Occupancy Category III includes buildings such as schools, jails, utility stations, chemical facilities and assembly buildings, and Occupancy Category IV includes critical buildings such as hospitals and fire and police stations. Category I includes buildings that aren't regularly occupied by people or that represent a low degree of hazard if they fail.
Ideally, all Occupancy Category IV buildings will be fully operational and safe after a large earthquake although currently their expected seismic performance is not explicitly checked to verify that the Building Code requirements will provide the desired performance.
SPUR recommends a two-phased approach to implementing a rating system. Phase I makes use of the Occupancy Category requirements as a starting point for targeted provisions for improved performance. Phase II requires the development of targeted specific optional code provisions for improved seismic performance.
In Phase II, SPUR recommends that a group of experts develop specific optional code provisions for improved seismic performance. These provisions would define the voluntary Seismic Silver and Seismic Gold certifications. Requirements similar to those already in the Building Code for Occupancy Category III and Category IV buildings can be used as a starting point, although SPUR also recommends more targeted provisions.
4. Develop strong incentives that encourage building to higher seismic standards.
In parallel with the development of Building Code options for improved seismic performance, San Francisco should develop strong incentives to encourage developers to implement higher performance standards for buildings. Potential incentives SPUR has identified include density bonuses, tax abatement, reductions in insurance costs and the deferred payment of public benefit fees.
The cost of improved seismic provisions
in new buildings
SPUR asked contractors to estimate the percentage increase in construction cost that is likely to occur if a building is to be designed to the requirements for Occupancy Categories III or IV rather than Occupancy Category II (see explanation of categories on page 17). The contractors estimated that hard cost increases were an average of 5.5 percent for an increase from Occupancy II to Occupancy III and about 11 percent for an increase from Occupancy II to Occupancy IV13.
The components of development cost are threefold: construction costs (or hard costs), indirect costs (or soft costs), and land cost. While the proposals in this paper stand to add significantly to the hard costs of a project, there are also many soft costs that we, as a city, have decided are important to layer on development. These include exactions for parks, childcare facilities, libraries and affordable housing.
How much is too much? This is a difficult question to answer. If fees are set too high, we don't get new development, thereby propelling new growth into less costly parts of our region. If fees are set too low, we lose out on public benefits we might otherwise have been able to receive.
While there is no "bright line" where all development ceases to occur, it is possible to make some gross judgments about how new fees and regulations will affect the market as a whole. And that is where decision makers — such the mayor and the Board of Supervisors — have to start weighing policy options. Can we afford both green building requirements and new seismic performance requirements? How strict can those requirements be before the hard costs become too costly to bear? Should we reduce our fee burden for public benefits in favor of increasing our seismic requirements?
Potentially, increases in construction cost could cause developers to decide not to build projects, or could make building in San Francisco less favorable than building in neighboring cities. It is already significantly more expensive to build in San Francisco than in many neighboring locations because of higher land costs and higher government fees. In the current economic climate, demand for housing and office space has declined and the economy is uncertain. Many new development projects are not financially feasible, even without any increase in construction cost.
SPUR believes that we cannot achieve the goal of enhanced seismic performance by simply layering on yet one more cost. We believe that resiliency is an important enough goal that the City should make some hard choices to obtain it. This means either rolling back some exactions, changing the timing of payment of exactions or creating other forms of economic incentives that neutralize the added cost of building more resilient buildings.
SPUR asked contractors to estimate the percentage increase in construction cost that is likely to occur if a building is to be designed to the requirements for Occupancy Categories III or IV rather than Occupancy Category II (see explanation of categories on page 17). The contractors estimated that hard cost increases were an average of 5.5 percent for an increase from Occupancy II to Occupancy III and about 11 percent for an increase from Occupancy II to Occupancy IV13.
The components of development cost are threefold: construction costs (or hard costs), indirect costs (or soft costs), and land cost. While the proposals in this paper stand to add significantly to the hard costs of a project, there are also many soft costs that we, as a city, have decided are important to layer on development. These include exactions for parks, childcare facilities, libraries and affordable housing.
How much is too much? This is a difficult question to answer. If fees are set too high, we don't get new development, thereby propelling new growth into less costly parts of our region. If fees are set too low, we lose out on public benefits we might otherwise have been able to receive.
While there is no "bright line" where all development ceases to occur, it is possible to make some gross judgments about how new fees and regulations will affect the market as a whole. And that is where decision makers — such the mayor and the Board of Supervisors — have to start weighing policy options. Can we afford both green building requirements and new seismic performance requirements? How strict can those requirements be before the hard costs become too costly to bear? Should we reduce our fee burden for public benefits in favor of increasing our seismic requirements?
Potentially, increases in construction cost could cause developers to decide not to build projects, or could make building in San Francisco less favorable than building in neighboring cities. It is already significantly more expensive to build in San Francisco than in many neighboring locations because of higher land costs and higher government fees. In the current economic climate, demand for housing and office space has declined and the economy is uncertain. Many new development projects are not financially feasible, even without any increase in construction cost.
SPUR believes that we cannot achieve the goal of enhanced seismic performance by simply layering on yet one more cost. We believe that resiliency is an important enough goal that the City should make some hard choices to obtain it. This means either rolling back some exactions, changing the timing of payment of exactions or creating other forms of economic incentives that neutralize the added cost of building more resilient buildings.
Conclusion
It is crucial that San Francisco start
preparing now for the inevitable earthquake. SPUR has defined overall
goals that would help San Francisco's buildings and infrastructure
remain resilient in such a disaster. The effort requires a view of
longer-term goals as defined by SPUR, as well as specific actions that
should be started now. These actions include declaring and clearly
communicating the expected seismic performance of buildings, giving
options for quantifiably improved seismic performance, making near-term
improvements to the Building Code, and developing strong incentives
such as increased height limits for buildings that meet higher seismic
standards. Building new buildings right the first time is an important
step toward creating a resilient city.
The above graph illustrates
the concept of introducing
enhanced "Seismic Silver"
and "Seismic Gold"
levels of design to reflectmeasures taken to improve
resistance to earthquakes.
4. LIFELINES: Upgrading infrastructure to enhance San Francisco's earthquake resilience
In disaster planning, much attention is paid to the role of buildings: How will they perform in a major earthquake? How long will they take to repair? Will people be able to stay in their homes after a quake, or will they need temporary shelter? Less attention is paid to the role of the infrastructure systems that support urban life, which we call our "lifelines."
By "lifeline," we mean the utility systems that bring us our water, electricity and natural gas; and the transportation systems that allow us to get around, including public transit, ports and airports, and road infrastructure. As with buildings, lifelines are critical to our ability to recover from an earthquake. If our buildings are not serviceable, nobody can live or work in them. San Francisco's capabilities for response to, and recovery from, an earthquake are highly dependent on the condition of lifelines in the wake of such a disaster.
The importance of reducing the risk to lifelines cannot be understated. Imagine what would happen if even one of our lifelines seriously failed in an earthquake. How would people be able to shelter in place without drinking water? What happens if our natural gas lines cease to work — or worse, stoke the flames of a massive fire? How will emergency workers get to our city if the bridges fail? How will we regain our economic activity if our public transportation system ceases to work and if we can't move people or goods around the region?
Lifeline owners in both the public and private sectors have made significant investments in designing, constructing and retrofitting their networks to reduce the risk of damage in an earthquake and to facilitate the restoration of services to their customers. However, the seismic performance standards for lifelines vary widely and are not tied to generally applicable public policies for reducing risk or for ensuring community resilience in the face of a major earthquake.
We need to know how our lifelines are going to perform in an earthquake. And we need to set performance targets based on resilience. To promote the city's recovery from an earthquake, the services provided by lifelines should be restored as quickly as possible — within hours or days. However, as things now stand it may take months or even years for some systems to be restored to operation, due to the uncertainties associated with potential damage, the lack of clearly articulated goals for restoration, and the lack of standards for achieving those goals.
Why is lifeline recovery important?
There are a number of reasons why the ability of lifelines to survive or recover from an earthquake is of the highest importance:
- Because lifeline systems spread across the region, they are vulnerable to site-specific weak links that increase the risk of partial or complete system shutdowns.
- The impact of damage to lifelines is compounded by the interdependency among lifeline sectors, both within San Francisco and in the region as a whole.
- In addition to supporting first responders, the expedient restoration of lifelines reduces the need for evacuation and sheltering of victims who would otherwise be without critical services.
- The recovery of communities and the economic base is dependent on the re-establishment of lifelines. If the services provided by these systems cannot be restored expeditiously, the recovery will be delayed as residents and businesses struggle with the lack of critical services and the inability to move people and goods around the region.
Seismic performance of lifelines
Each kind of infrastructure faces its own set of risks and each is governed by its own set of codes and standards. Most sectors have progressed to system-based approaches in order to assess risk and reduce disruptions in the performance of systems and the delivery of services to customers. Nonetheless, achieving a consistent level of resilience is complicated by the many different regulating bodies to which system operators must answer. The general tendency toward sector— and hazard-specific development of standards has resulted in lack of commonly understood definitions for acceptable seismic performance, different standards for performance among different sectors and a lack of inter-sector coordination for the development of standards. Furthermore, there is limited understanding among political leaders and the general public of the potential performance of lifelines during an earthquake.
The recovery of communities
is dependent on the reestablishment
of lifelines. If the
services cannot be restored
expeditiously, recovery efforts
will be delayed as business
and residents struggle with the
lack of critical services and the
inability to move people and
goods throughout the region.
Resilience in the context of lifelines
SPUR recommends the establishment of clear, readily understood performance goals that define resiliency in infrastructure. Goals for the restoration of service are expressed in terms of what percentage of customers have service after an earthquake.
Categorizing lifelines in a meaningful way will require an assessment of those lifelines that are most critical to response and recovery. This categorization may take into account the partial restoration of systems necessary to achieve the performance goals, rather than the complete restoration of those systems. For example, backup systems may be implemented to restore services to critical facilities within the desired time frame, and redundancies or bypasses in areas where ground failure is likely would allow for the restoration of services once control of the system has been established.
To identify practical measurements for lifeline performance, acceptable levels of damage should be identified and requirements should be developed to improve performance to achieve the desired level of resilience.
SPUR RECOMMENDATIONS: LIFELINES
SPUR recommends that the City implement a seismic mitigation program for lifelines through the following measures.
1. Establish a "Lifelines Council" to provide a mechanism for comprehensive planning.
The mayor should convene a Lifelines Council to:
- establish standards for resilience in cooperation with the lifeline providers; prioritize actions related to lifelines; coordinate planning across sectors
- develop a comprehensive approach to coordinating the recovery of lifelines following an earthquake
- foster partnerships with regional, state and private sector entities to improve lifeline performance in the city and across the region
- lead City efforts to pursue changes at the state and national levels regarding standards and requirements for lifeline performance and
- develop a funding plan for modifications to City-owned systems and for assisting other system owners with modifications in areas of overwhelming public interest.
2. Conduct a seismic performance audit of lifelines in San Francisco and establish priorities for lifeline mitigation.
With the guidance of the Lifelines Council and with the cooperation of lifeline system owners, the City Controller's Office should conduct an assessment of the expected performance of lifelines, using performance during the "expected earthquake" as the standard. This published study should inform the planning work being undertaken by the Lifelines Council. The assessment in each sector should be predicated on the concept of resilience. It should be conducted according to procedures set by the applicable standards organization or regulatory agency, account for ongoing programs for seismic mitigation, and result in a preliminary report to the Board of Supervisors within six months, with a full report to follow within two years.
The audit should enable San Francisco to establish priorities for modifications necessary to improve the seismic performance of lifelines. The council should present these priorities to the Board of Supervisors and to the City's Capital Planning Committee.
3. Require improvements to City-owned and regulated systems necessary to meet performance goals and develop a funding program to make those improvements happen.
The City has direct control of several major lifeline systems, such as the water and wastewater systems, port, airport and Muni. Consequently, the Lifelines Council should recommend to the Board of Supervisors that the departments that operate these systems incorporate into their capital improvement plans the mitigation measures necessary to achieve performance goals. For those systems that the City regulates through code requirements or other mechanisms, the Lifelines Council should recommend that the governing body require the improvements necessary to meet system-specific performance goals.
4. Require the design and implementation of improvements to the gas distribution system that reduce the risk of post-earthquake ignitions.
Protection of gas systems is critical to reducing the risk of secondary impacts — ignitions and explosions — that could cause significant damage and loss of life. However, a complete shutdown of the gas distribution following an earthquake is not practical, given that the resumption of service could take months, significantly delaying the City's recovery. Similarly, an unnecessary shutdown of the system in a moderate earthquake would have a devastating effect on the city's economy.
Consequently, the City must undertake both near— and long-term actions to ensure that the gas distribution system ultimately incorporates features that reduce the risk of secondary impacts without compromising the continued operation of the system after earthquakes. In the near term, buildings posing a significant risk of collapse need to be identified and retrofitted with shutoff valves. In addition, areas of significant risk of ground failure need to be identified, and automatic shutoff systems installed to quickly isolate them when needed. In the long term, the City should work with PG&E to develop and implement a fully automated monitoring and control system that protects the city both from fire following earthquake and from unnecessary shutdowns.
5. Establish partnerships with regional, state and private sector entities to address multijurisdictional and regional systems.
The multijurisdictional and regional nature of many of the lifeline systems that serve the Bay Area will compel San Francisco to work with other local jurisdictions, regional entities, state agencies and private sector entities. Examples include the Metropolitan Transportation Commission; the Golden Gate Bridge, Highway and Transportation District; BART; Caltrain; the Water Emergency Transportation Authority; and PG&E. In some cases, San Francisco has representation on the governing bodies that oversee these systems, but in other cases it will be necessary to develop these partnerships.
6. Establish a program for communications and outreach to regional, state, federal and private sector entities to drive change.
San Francisco does not have the authority or capability to regulate many of the lifeline systems that are critical to achieving resilience. Consequently, the City should establish a communications and outreach program to advocate for those changes that are in the City's self-interest while at the same time setting the standard for a comprehensive approach to addressing lifeline performance. Elements of this program, which would be coordinated by the Lifelines Council, should include raising the profile of public expectations for the seismic performance of lifelines; enhancing cross-sector communication in planning for and responding to earthquakes in San Francisco; developing recommendations for sector-specific organizations and state and federal regulatory agencies; and influencing the development of requirements at the state and national levels.
Endnotes
1Shelter in place is used by emergency response professionals to mean the place in a building where people can seek safety during a life threatening incident. SPUR uses "shelter in place" to mean that a building is disaster resilient enough for people to safely remain in their home during both the earthquake itself and subsequent needed repairs, even though the utility systems may not be working.
2Applied Technology Council , "San Francisco's Earthquake Risk: Report on Potential Earthquake Impacts in San Francisco," March 1, 2005 (draft), Table 4.
3ATC, Table 15.
4Code Advisory Committee, Department of Building Inspection, City and County of San Francisco, "Policy Statement: San Franciscans have the right to occupy buildings that will not collapse in future earthquakes," Nov. 16, 2005. The committee in this statement called for a program of phased mandatory retrofits for "collapse-hazard" buildings, including soft-story wood buildings and non-ductile concrete buildings.
5The Department of Building Inspection's Community Action Plan for Seismic Safety study has made some nominal distinctions among residential and commercial occupancies (see ATC, Tables 8 through 11), but CAPSS deals only with private buildings and does not address hospitals, schools, fire stations and so on. By contrast, the City's 2008 draft Hazard Mitigation Plan lists public facilities, but does so by occupancy only, ignoring the structure types and the variations in earthquake performance. Section 6.3 of the draft plan acknowledges the value of SPUR's approach, but Section 8 fails to assign a priority to such a study.
6Loss estimation tools such as HAZUS (used for the CAPSS study by the Applied Technology Council) predict damage somewhat differently from basic safety assessments, but they still do not predict directly or reliably whether a building might remain in service.
7It's also a tenet of California policy that proactive risk reduction and loss prevention make response and recovery more feasible. See the California Management Agency (formerly the Governor's Office of Emergency Services), "State of California Multi-Hazard Mitigation Plan," October 2007, sections 1.1 and 2.3.2.
8Robert Selna, "S.F. ‘soft-story' buildings at risk in quake," Dec. 11, 2008. This article cites preliminary data from the Department of Building Inspection's Community Action Plan for Seismic Safety study showing the city has 2,800 buildings of three or more stories and five or more units in which the ground floor openings are substantial enough to indicate a soft-story condition.
9City and County of San Francisco, "All-Hazards Strategic Plan," 2008. Strategic Goal 15 calls for the development of plans to shelter or evacuate at-risk populations. Strategic Goal 19 is explicit about passing legislation to strengthen soft-story buildings, in the context of a general call to develop resources for the post-earthquake safety assessment of buildings and the resumption of their occupancy.
10Soft-story mitigation is already explicitly noted in the City's 2008 "All-Hazards Strategic Plan" and in its draft Hazard Mitigation Plan. In July 2008, Mayor Gavin Newsom directed the DBI to develop a soft-story ordinance with incentives for voluntary retrofitting (Executive Directive 08-07). Those incentives were not approved, in part because voluntary work was not expected to be effective, and in December 2008 the Mayor's Office noted its openness to mitigation programs that might include mandated retrofit of certain buildings (see Selna, "S.F. ‘soft-story' buildings at risk in quake").
11While the City's Emergency Response Plan and All-Hazards Strategic Plan anticipate the need to provide post-earthquake shelters and to coordinate City departments to administer them, its draft Hazard Mitigation Plan does not list designated shelters as critical facilities (Section 6.1.3). It does list San Francisco Unified School District buildings, the Civic Auditorium and Moscone Center as critical, but it does not place any priority on taking measures to protect them (except to derive replacement values for asset management purposes). The City's branch libraries and recreation centers are listed as noncritical facilities.
12For example, the 2008 Emergency Response Plan relies on Department Operations Centers for the coordinated provision of emergency functions including mass feeding, housing, public health and so on, and the All-Hazards Strategic Plan describes several related strategic goals. Yet the draft Hazard Mitigation Plan, while it lists more than 50 "critical" City-owned government and care facilities, does not appear to set priorities for risk reduction for any of them.
13Some contractors estimated construction cost increases for OccCategory II to OccCategory IV to be as high as 20 percent.
