What started as a peaceful day in February quickly turned into one of stress and panic as the Nisqually earthquake shook the state of Washington. Suddenly, roads trembled and broke apart, buildings crumbled and fell to the ground and thousands of Seattle residents found themselves scrambling to mend broken homes and roadways.
Over a decade later, the effects of Nisqually are still being seen. And, though we have come far in our plight to protect our city from future damage, we still have a long way to go.
Alaska Viaduct under construction 1951. Image Courtesy of the Seattle Municipal Archives
The Nisqually Earthquake and the Damage it Caused
Over ten years ago, the Nisqually earthquake shook Washington and parts of Oregon in ways that the area hadn’t experienced in centuries. The 6.8 magnitude quake injured over 400 people and caused over $ 4 billion in damage.
The city of Seattle was put on hold directly following the Nisqually earthquake so that necessary repairs could be made to transit ways, specifically the Seattle viaduct, the Magnolia bridge and the runway at Boeing Field. And, though these roadways have since been deemed safe, damage caused by the quake continues to corrode the areas.
The Alaska Viaduct today. Image Courtesy Flickr User: Cliff
Over a Decade Later, the Damage is Still Present
According to the Seattle Times, new cracks have been found and existing ones have lengthened and widened. This indicates that damage from the quake is still present below the surface. If allowed to go unaddressed, the damage get worse with time. Though the city plans to rectify the damage, the need to reinforce and protect against future disasters remains prevalent.
Long-Term Effects of Untreated Damage
Water is especially troublesome when it comes to structure stability because water seeks to level itself off, filling every nook and cranny it can find until it is level with underground water resources. If a burst water main goes undetected, it will continue to saturate the ground until it either has leveled off or run into the ocean.
For buildings, this means that if water penetrates the ground near foundations, it will likely find its way inside. It also means that, as more and more water saturates the area, the building’s foundation will become weaker and more susceptible to future damage. Unfortunately, the longer a leak goes undetected or unrepaired, the higher the final price tag will be to get it fixed. The Alaska Way viaduct is an example of high repair costs.
The viaduct has sagged more than about 5 1/2 inches since Nisqually, and has settled even more during this last winter showing multiple cracks. While it is unknown exactly what is causing this damage, it is well known what water does to loose soil and foundation cracks area that is regularly exposed to water erosion. The Seattle waterfront is exposed to both ocean elements from Puget Sound and the frequent Pacific Northwest rains.
Bertha the tunnel borer getting ready for construction for the viaduct repairs. Image Courtesy Flickr User: Ben Brooks
Repairing the Damage Caused by Niqually
Despite the eventual replacement of the viaduct roadway with a newer passthrough, the area must be safely maintained until construction can be finished. To repair the viaduct, the entire area will have to be excavated to reach the root of the damage. This will result in the closing of the viaduct in order to assess the extent of the damage, but could result in more time-consuming repairs depending on the results of the tests. While the official cause of the damage is still under debate, it is believed to not be due to tunnel work being conducted half a mile southwest. Possible repairs could include sealing the cracks with epoxy which will require a longer closing.
Repairing water damaged buildings is also a complicated process. When the foundation of a building is compromised — resulting in cracks and leaks — this damage must be either be repaired or rebuilt. To do this, new footings must be installed at a depth much greater than the originals then anchored to existing footings. Afterwards, new walls will need to be built. This is a necessary process if the property is to remain secure but unfortunately can get rather pricey.
Additional interior repairs include wall braces, epoxy injections and the installation of drain tiles. Repairs to the exterior of a building may require excavation of the area, leveling of the home and waterproofing of all materials used. It has also become standard practice to replace clay fill with a mixture of at least fifty percent sand to avoid the sponge-like effect of clay.
Protecting Structures Against Future Damage
There are many things that can be done to increase the longevity of a structure’s foundation. Some of the most important things one can do is to waterproof the building’s foundation is by adding a sealant to the concrete and by installing drainage systems and sump pumps.
All gutters and drainage systems should also remain clean and water should always flow away from a building’s foundation. Adding additional grading can also be effective, but must always be performed by a licensed professional.
We cannot avoid natural disasters, but we can help protect structures against their damage. Detecting and repairing issues as soon as possible is of the utmost importance. Because, if Nisqually has taught us anything, it is that water damage that goes uncorrected can have very costly consequences in the future.