Providing Affordable Housing in a Shaky World

Assessing liquefaction risk in light of Oakland’s new affordable housing plan

OAKLAND, Calif.—At 796 66th Avenue, a dilapidated parking lot sprawls across the concrete terrain North of Oakland Arena. Even the graffiti on the barriers blocking the lot’s entrance has faded. But in the cracks of the pavement, new growth is peaking through. By 2031, this site will provide affordable housing to 300 residents of Oakland.

796 66th Avenue, Oakland, as seen from Google Maps street view.

On February 17, California state housing regulators signed off on the city of Oakland’s new eight-year Housing Element, a comprehensive housing plan aiming to provide nearly 30,000 new homes to residents over the next decade. Nearly 500 sites are already confirmed for development between 2023 and 2031. Since 1969, the state has required all local governments to submit formal plans—called Housing Elements—to adequately meet the housing needs of everyone in the community. These Elements typically run for eight-year cycles. During previous cycles, most Bay Area local governments have failed to meet their low and middle-income homebuilding targets. In the 2015-2023 cycle, the amount of units Oakland built only accounted for 22 percent of the units needed by the population. This new Housing Element seeks to close that gap—and set up the city for future success—by planning 15 percent more units than what is currently needed. Oakland’s history of redlining—a discriminatory practice in which residents of neighborhoods deemed financially “hazardous” are barred from vital services—has left lasting scars on many parts of the city. Combatting and remedying those damages are among the city’s principal goals in the new Housing Element. “We know that racist housing policies in the past have divided our communities, leading to unequal access to housing, jobs, and schools,” explained Planner III Khalilha Haynes in the city’s Housing Element explainer video. “By law, the housing element must help undo these inequities by building a more inclusive Oakland.” Through hosting public events and workshops, the planning committee learned they needed to prioritize expanding opportunities for both housed and unhoused Oaklanders and addressing urgent neighborhood and community needs. Critically, Oakland officials plan to expand the range of housing options in more affluent neighborhoods and invest more resources into less affluent neighborhoods. “We already know the cost of housing is too high. Worse, we haven't built enough affordable housing to meet the needs of long-term Oaklanders, especially low-income folks.” Haynes added. “The housing element will set new goals with room to spare to make sure we not only build enough housing, but make sure it's affordable and within reach of Oakland's most vulnerable.” The lot at 796 66th Avenue is only one of the many proposed sites that will provide affordable housing options. Other sites slated for development will provide options accessible to those earning a median income and those earning an above-average income as well. Because the state approved the Element on February 17, the city has already secured the crucial funding needed for the eight-year plan. There’s only one potential problem: almost half of the proposed sites sit atop high-risk earthquake hazard zones.

Liquefaction risks endanger East Bay residents The San Francisco Bay Area is no stranger to earthquakes. The Bay is sandwiched between three active strike-slip faults, a type of boundary in which two plates slip past one another horizontally. Many of the quakes produced by these faults are small or undetectable to those living near them. Big ones like the 1906 San Francisco quake and the 1989 Loma Prieta quake, while powerful and destructive, are relatively rare in a single lifetime. However, the last major earthquake along Oakland’s neighboring Hayward Fault, estimated by the United States Geological Services to be roughly 6.8-7.0 in magnitude, was in 1868. The East Bay is due for another Big One. The California Earthquake Authority has estimated that the entire Bay Area has a 72 percent chance of experiencing a damaging earthquake of a 6.7 magnitude or greater in the next 30 years. The East Bay is at a much higher risk than the San Francisco Peninsula. For Bay Area earthquakes in particular, it's not necessarily the shaking of the earth that poses the highest risk for residents and infrastructure—it’s liquefaction. Liquefaction is a process in which loose, water-logged sediments near the ground surface lose their strength—and begin to act like a liquid— in response to intense ground shaking. Sediments that are especially susceptible to liquefaction include beach and stream deposits, soil saturated by groundwater, and artificial fill. USGS Research Engineer alex grant explains how liquefaction works on a much smaller scale:

USGS Research Engineer alex grant explains liquefaction. Animation made with Procreate by Alex Hughes.

“Liquefaction is a really esoteric topic that no one thinks about until their house is tilting over,” grant explained. One of the worst case scenarios for liquefaction is artificial fill, which in Oakland, is made up of soil, mud, and rocks from the bottom of the San Francisco Bay. “[Artificial fill] is inherently a very loose way of depositing material,” grant added, “ and if it happens to be sandy, you've created this perfect condition for liquefaction.” With the exception of its downtown area, the majority of Oakland has been deemed highly susceptible to liquefaction, and may face this reality in the near future. Of the near 500 sites slated for development in the Sites Inventory list for Oakland’s Housing Element, 40 percent sit atop land highly susceptible to liquefaction.

Future low- and median-income residents of these sites are at a higher risk of liquefaction than their higher-income neighbors. The Sites Inventory list for the Element provides data on each unit’s total capacity and how affordable these units are for future renters. While some units provide mixed-income options, most units cater primarily towards one income bracket: “low,” “moderate,” (near median for Oakland), and “above moderate” (high). 32 percent of the sites that will primarily house higher-income residents fall on liquefaction zones, whereas for median-income units, it’s 46 percent, and for low-income units, 48 percent. When accounting for each unit’s total capacity, the percentages display similar patterns.

Oakland’s retrofit ordinance and its potential loopholes While both renters and homeowners can purchase earthquake insurance to cover losses and damages from a potential damaging quake, a more preventative protection is seismic retrofitting. A seismic retrofit bolts a home to its foundation, and can be done either when a building is first constructed or as a modification to an older building. This procedure helps mitigate some of the damages caused by earthquake-induced shaking, landslides, and liquefaction. In January 2019, the city of Oakland enacted the Soft Story Retrofit Ordinance to ensure multi-story and older residential buildings are retrofitted up to current standards. “Soft story” describes a specific type of collapse-prone building. Under the city’s ordinance, this applies to buildings constructed before 1991, containing five or more dwelling units, and with vulnerable lower stories or crawl spaces. Each subject building is assigned to three different tiers depending on building use and structure. Each tier includes a specific timeline for which an evaluation must be conducted, a retrofitting permit obtained, and retrofitting work is completed and approved. Regardless of the tier, the total time allowed between evaluating a property and completing the retrofit is roughly two years. Oakland’s retrofitting program is comprehensive and thorough, and will prove crucial in the development of the proposed sites in the Housing Development. It will ensure that the future residents of 796 66th Avenue—a future multi-story building—will have proper structural protection in the event of a major earthquake. However, the burden of financing these pricey retrofits falls squarely on landlords and property owners. Several loopholes in the ordinance could potentially be used by landlords to financially burden or endanger tenants. Luckily, there are limitations placed on rent increases used to fund seismic retrofits. Property owners must first petition Oakland's Rent Adjustment Program to increase rents. Up to 70 percent of actual costs may be passed onto tenants, but over the course of 25 years. The ordinance also states that the rent increase “cannot exceed 10 percent per a 12-month period or 30 percent per five years for a particular unit.” While it's for the benefit of safety, this rent increase could still be extremely burdensome for lower-income tenants. Property owners can also request for an extension of compliance deadlines. While there are strict limitations on extensions, further delaying seismic retrofitting could endanger tenants in the event of an unexpected rupture of the Hayward Fault. Perhaps even more concerning is the exemption clause; if a building does not meet all the requirements for buildings subject under the ordinance or the owner has a prior exemption approved by the city, they may apply for an exemption. While the city still has to inspect the property and approve an exemption, this clause provides another potentially dangerous loophole that could endanger future tenants. Potential methods of mitigating liquefaction risk While these structural fixes help to strengthen buildings and lower the extent of damages, they do not completely remediate liquefaction risks. The entire Bay Area is also grappling with the future implications of climate change. A 2018 study by the California Ocean Protection Council predicted up to seven feet of sea level rise by 2100 if current emission levels aren’t curbed. State and local governments are under additional pressure to protect their citizens from inevitable geologic processes that could be worsened by the effects of climate change. Significant sea level rise will also increase coastal groundwater levels, expanding and exacerbating pre-existing liquefaction zones. Aside from enacting stricter retrofitting requirements, what can Oakland—and the entire Bay Area—do to protect its residents while continuing to expand affordable housing? “Liquefaction is happening one or five or ten meters below the surface, so if you wanted to explicitly do seismic retrofitting or remediation for the potential for liquefaction, you would need to think about the causes of liquefaction,” USGS’ grant explained. There are three primary variables to think about. One is earth shaking—which we can’t do anything about. The other two are possibly within our control: water and soil. Liquefaction can’t occur in unsaturated soils. To control the water variable, Oakland would need to lower its regional water table. However, this would require constant pumping and would be incredibly costly. With projected sea level rise, this potential solution could create more problems than it solves. Liquefaction also can’t occur in dense, tightly packed soils, so one potential solution would be to invest in methods of soil strengthening. A study team at the University of California-Davis, led by industrial ecologist Aisha Faruqi, has been researching the effectiveness of a process called microbially induced desaturation (MID). MID involves feeding calcium nitrate and calcium acetate to soil microbes so that they produce enough gas to desaturate the soil and prevent liquefaction. This method of hazard mitigation is both more cost-effective and environmentally sustainable than its current alternatives, as it does not require the addition of cement or water not already in the ground. Precedent for other Bay Area cities Oakland is undoubtedly setting a historic precedent for Bay Area cities on the grounds of affordable housing. Including Oakland, only five Bay Area cities met the January 31 housing plan approval deadline and have received final approval from state officials, according to The Mercury News. Despite potential loopholes in the Soft Story Retrofit Ordinance, the city is also taking critical first steps in protecting its residents from the impending dangers of earthquake-induced liquefaction. In the event of the extreme sea level rise that is predicted according to current emission levels, widespread retrofitting will prove even more important in saving lives, reducing damages, and preventing widespread displacement. The continued development of sustainable liquefaction mitigation methods, like MID, will lower those risks even further. The horrifying truth is that the entire Bay Area is scarred with fault lines and needs to act with the same urgency. Almost all the region’s coastal land is prone to liquefaction, landslides, or flooding—expanding housing options on vulnerable land is inevitable. Oakland’s Housing Element and paired Retrofit Ordinance needs to be the blueprint other Bay Area cities emulate and improve upon to ensure the safety of its residents in the wake of an uncertain future.