Issues Along I-5 at Nisqually Could Create ‘Chehalis-Level’ Flooding in Next 17 Years


The Interstate 5 crossing at the Nisqually River will need to be fixed due to “coastal squeezing” and ecological issues, and stakeholders estimate the project could cost at least $4 billion in order to prevent “Chehalis level” flooding on the heavily-trafficked interstate. 

Coastal squeezing is defined as the loss of land and habitat due to rising sea levels. 

Bill Adamson, program manager of the South Sound Military and Communities Partnership, said they plan on asking the state Legislature this January for a range of funding — anywhere from  around $7.5 million on up — in order to fix the problem stakeholders have declared a “national security risk” due to its heavy use and proximity to Joint Base Lewis-McChord. 

“It’s a multidimensional problem,” Adamson said. “The current design of I-5 restricts critical ecological functions, impacting salmon survival and is at high-risk of being overtopped by a major flooding event, and has little capacity to handle the growing South Sound economy and population. About a third of the JBLM workforce lives south of the Nisqually River.”

According to South Sound Military and preliminary findings from a United States Geological Survey (USGS) study, a combination of sea level rise, channel reorientation of the Nisqually River and more prolific rains will lead to historic 100-year floods occurring four to five times more frequently. 

Adamson said those preliminary findings estimate a similar event to the 2007 Chehalis River flood could happen at the Nisqually River I-5 crossing in the next 17 years. 

Revenue shortages are expected to be especially pronounced this January when lawmakers gather for the legislative session in order to readjust budgets thrown into disarray by COVID-19, but stakeholder groups including South Sound Military are hoping lawmakers see the immediacy needed in the project. 

“It’s a complicated situation,” he said. “We know it’s going to be a tough budget year with COVID-19, but we’ve got our fingers crossed because it’s something that needs to start happening.” 

Rep. Jake Fey, D-Tacoma, who chairs the House Transportation Committee, is one of six lawmakers Adamson has discussed the project with so far. Fey noted the project looks like a priority for the legislating body, even if the coronavirus recession has brought about a shortfall of $1.4 billion in the state’s transportation budget. 

But this unique problem will likely lead to unique funding methods, Fey said, such as going out for bond funding. 

“I get the need, I’m supportive, but we’re going to need more revenue to do this work,” said the 27th Legislative District lawmaker. 

The request, Fey said, comes also as the state aims at replacing ferry vessels, building a new bridge to replace the decrepit Columbia River bridge between Portland and Vancouver, Washington, and investing in removing fish barriers. Washington’s funky geography doesn’t help with those projects either, Fey noted. 

“The needs just keep mounting. The needs for the transportation system is more and more all the time,” he said. 

The $4 billion price tag to replace the Nisqually River corridor, which includes much-needed transportation improvements up and down the 17-mile stretch between Tumwater and Mounts Road as well as a wider and more elevated bridge, doesn’t help. 

A portion of the total request to address the immediate concern at the Nisqually River crossing could be the likely option, though the pending results from a United States Geological Survey (USGS) study, which alerted stakeholders to the flooding concern, will likely outline the options and give a broader picture. 

That study should be finished this winter, Adamson said. 

“We’re going to have to sort this out and do it in pieces,” Fey said. “Cause we couldn’t tackle it all at once … It’s a tough situation, but that doesn’t mean that you don’t do anything about it. It just makes the urgency to find funding that much bigger.” 

The project at hand is large though, Fey said. For comparison, the total cost to bring State Route 167 from Puyallup to the Port of Tacoma cost about $1.9 billion, and that’s been noted as one of the more expensive projects completed in the South Puget Sound region. 

If the state funds the low end, which is about $7.5 million, Adamson said that would take them through the phase to design and select the transportation alternative, and finish up environmental work. The full $4.2 billion would eventually allow for them to fund the construction to replace north- and southbound I-5 with elevated bridges and an additional lane in both directions.  

The hope is to start construction by 2027. 

David Troutt, the Nisqually Indian Tribe’s director of natural resources, said coastal squeeze in the Nisqually River estuary can also negatively affect the lifespan of the Chinook salmon, a major source of food for the southern resident orcas. 

With rising sea waters pushing more salt water into the delta, Troutt said that affects the salinity of the freshwater and the fish species’ ability to transfer from a freshwater to saltwater. There’s even a section of the delta near the bridge where large populations of fish stick around to make this transition. 

“Having that opportunity to change really helps their survival,” Troutt said, adding later of their native fisheries: “We are in a recovery mode with our fall Chinook, and we are estuary dependent.” 

Troutt said the main problem stems from when I-5 was constructed. The Nisqually River crossing was built on piers on the delta, then those piers were filled in during the 1970s by WSDOT. In addition to making the Nisqually River a glorified, porous dam, the bridge also disturbs the river’s natural sediment deposit. 

Because the river tends to build up at the bridge, an unnatural bend in the Nisqually River started developing near the Wa-He-Lute Indian School in the 1950s, becoming more pronounced near the turn of the century. 

Troutt, echoing preliminary findings from the USGS, said it’s more a matter of “when” and not “if” the river breaks the bend, which could happen during a “perfect storm” flood event and flood the interstate. And, according to USGS, that’s likely within the next 17 years. 

“The risk there of I-5 blowing out is pretty obvious. We’ve seen the challenges that happened at DuPont and the transportation challenges,” Troutt said. “This needs to be resolved sooner rather than later or else we’re going to see massive consequences.


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