Update: This blog was updated on July 12, 2019 to reflect commercial loading zone changes for large trucks which are about to take effect.
In early May, we announced new safety restrictions for large vehicles traveling through Pioneer Square. Vehicles weighing more than 10,000 pounds are no longer allowed to park or drive in the lane closest to the sidewalks on First Ave in Pioneer Square due to concerns about the underground road support structures. Previously announced commercial load zone changes for large trucks will take effect on the week of July 15.
A quick history lesson
As you probably know if you’ve taken a tour underneath Seattle’s historical Pioneer Square district, many of the sidewalks in this part of town are built on top of empty spaces called areaways dating back to when the streets were rebuilt after the Great Seattle Fire of 1889 burned down 25 city blocks.
Residents decided to rebuild in the same location. New buildings were built over those that had been damaged by the fire, one to two stories above the original elevation.
As a result, many of the sidewalks in the area, especially along First Avenue, are built on top of empty spaces that date back to when the street was rebuilt. Over time, many of these areaways were turned into basements and cellars for buildings in Pioneer Square while others are still empty space.
Today, the weight of Pioneer Square roads and sidewalks are still being held up by support walls right under the outer edge of the sidewalk.
Underground support walls hold up the weight of cars and people above
Many of these street support walls were built from brick, rubble, and mortar over 100 years ago. These underground walls were not designed to support the weight of today’s large trucks and buses or to meet modern earthquake safety standards.
We have been monitoring the condition of underground areaways and street support walls for many years. Recently, when the SR 99 Viaduct closed and several bus routes moved onto First Ave, we conducted a new comprehensive analysis in order to identify safe locations for new bus stops. This led us to find new structural vulnerabilities which we had not identified before.
We found that the street support walls were all safe to support the weight of normal cars, but in some cases could not continue to hold the weight of large trucks and buses parking and driving next to the curb.
New rules for large vehicles on First Ave to keep everyone safe
In May, we added safety restrictions for large vehicles traveling through Pioneer Square to ensure the safety and integrity of the road. Vehicles weighing more than 10,000 pounds are no longer allowed to park or drive in the lane closest to the sidewalks on First Ave between Marion St and Railroad Way S.
Beginning on the week of July 15, commercial load zones throughout Pioneer Square will be relocated, so large trucks may need to park on another part of the street than they are used to. These changes will ensure that large vehicles are parked at safe areas which are not near these kinds of underground areaways and support walls.
Over the past few months, we have been speaking with the community and responding to concerns about these commercial load zone locations. The new parking rules will take effect as soon as we install new weight-limit signs.
There is no change to for the rules about normal sized cars.
Pioneer Square roads are still completely safe
Our engineers routinely monitor underground areaways and street support walls and are confident that the streets and sidewalks are safe to use, as long as large vehicles over 10,000 pounds remain in the inside lanes.
We’re also completely confident that the Pioneer Square sidewalks are safe for everyday activities (such as walking, sidewalk dining, and moving furniture). We’ve also checked to make sure that the tours underneath the sidewalks are completely safe too.
What’s the repair plan?
We are continuing to conduct a thorough inspection of every underground areaway and road support wall in Pioneer Square.
We have also been working with local businesses to assess the condition of underground support walls throughout Pioneer Square and to install monitoring equipment.
We’re committed to doing everything possible to keep you informed. In partnership with the Alliance for Pioneer Square and other City departments like the Office of Economic Development, we will work closely with the neighborhood to provide ongoing information about the safety assessment and repair work.