The City of Seattle has added some 300 buildings to its list of old brick structures most at risk of damage or collapse in the event of a major earthquake. Among the 1,160 “unreinforced masonry structures” counted in a recent report, Capitol Hill continues to have the most of any neighborhood in the city.
The latest URM survey added 16 Capitol Hill structures to the city’s 2012 list, bringing the neighborhood’s total count to 152 URM buildings — 13% of all URMs in Seattle. 44 were counted on First Hill and 24 were counted in the Central Area/Squire Park
Property owners with buildings on the list began receiving notifications this month from Seattle’s Department of Construction and Inspections. No immediate action is required, but it may be in the future.
Finalizing the inventory of URMs is an important step in the city’s goal to one day mandate all URMs undergo seismic retrofitting. Currently, property owners are only required to retrofit URMs when there is a major upgrade or change of use of their building. The city has been working on a mandate for years and the City Council is not expected to consider legislation until 2017.
The report found the vast majority of Capitol Hill’s URMs had no evidence of retrofitting, although it is possible some work was overlooked. Owners have an opportunity to challenge the URM designation or offer additional information, but they will need to hire an engineer to perform an in-depth analysis of the the building, according to the report.
That could kick off another round of Capitol Hill preservation developments and demolitions. Earthquake prevention work can be an enormously expensive, especially for individual owners who may deicide to sell in the face of such costs. It happened before at the Callahan Auto building and many fear a retrofit mandate would put many businesses and independent property owners in jeopardy. By using preservation incentives, DCI says it wants to save as many buildings as possible.
“The last thing we want to do is to encourage people to demolish these structures,” said DCI spokesperson Bryan Stevens. “Generally speaking, I think people want to see these structures preserved.”
URMs, as defined by the city, are old brick buildings that were originally built without steel reinforcements and with inadequate ties between building elements. They are considered to be vulnerable to collapse during severe earthquakes. Seattle started to ramp up efforts to identify and address URMs in the wake of the 2001 Nisqually Earthquake, although such work had been going on long before then.
The report estimates that 38% of buildings have undergone some retrofitting work already — some of those may satisfy a future mandate, but some may fall short.
In addition to historical research and canvassing neighborhoods to find URMs, DCI made extensive use of Google Streetview and Google’s “See Inside” photos to look for evidence of seismic retrofitting. Evidence of retrofitting can often be found on brick exteriors:
The report estimates that 56% of Seattle’s URMs likely qualify for a simplified and cheaper retrofit, which some already have installed. Reinforcement strategies vary. Look for tiebacks embedded into the masonry that connect the walls to the floor joints. Other buildings use steel beams to supplement the existing structure. In some solutions, the braces take the form of a large “X” while others form a chevron.
Buildings were also broken out by risk category.
Critical Risk — assigned to buildings in the Emergency and Schools occupancy groups
High Risk — assigned to buildings over three stories in poor soil areas (liquefaction and slide areas); and buildings in the public assembly group with occupancies more than 100 people.
Medium Risk — assigned to all other buildings.
Only four Capitol Hill buildings are considered at critical risk and Seattle First Baptist Church at Harvard and Seneca is the only one of the four that the city reports has no visible seismic retrofitting. Capitol Hill has 18 buildings classified as “high risk” and the rest are considered medium risk.
Following the last round of URM building designations, CHS wrote about how some building owners were proactively retrofitting while others were fighting the designation. DCI’s URM committee determined it still needed more information following the 2012 study and commissioned the more in-depth analysis in 2015.
Since 2001’s Nisqually quake, several buildings have been reinforced like the Piston and Ring preservation-friendly development. Here’s a look at how Capitol Hill’s greatest old buildings stand up, with elegance, to earthquakes.