I-5: A Whirl of Changes


Editor’s note: This is the first of a four-article series dissecting an upcoming Interstate 5 project in Centralia. Today The Chronicle provides an overview of the project and the changes it will make. Future articles will discuss why the Mellen Street interchange is designed as it is and how construction of the project will impact residents and drivers. The series will conclude with how the new freeway interchanges will affect traffic and other issues in Centralia and Chehalis.

There’s lots of good news and a little bad news regarding the upcoming widening of Interstate 5 in Centralia. The good news is local traffic will be able to travel between Harrison Avenue to Mellen Street without getting on the freeway. It will also improve access to and from Providence Centralia Hospital and mitigate flooding that has prevented access in the past. 

The bad news is it will take three years to complete, and the changes will take some getting used to. 

Interstate 5 is “the most significant freight freeway on the West Coast,” according to the Washington State Department of Transportation. 

The project, officially called I-5, Mellen Street to Blakeslee Junction, is the third in a 40-mile series of projects intended to improve safety and mobility between the Toutle River rest area in Cowlitz County and the Maytown interchange in Thurston County. The Mellen Street project will be followed at some time in the future by a another project between Mellen Street and the 13th Street interchange in Chehalis.

The Mellen Street project will essentially pull local traffic off the freeway via collector distributor, or C-D lanes, that will parallel the mainline freeway between the Harrison and Mellen interchanges. The C-D will reduce freeway congestion and open up the interstate to commercial thru-traffic by keeping local traffic on local roadways.

“We’re more into throughput and not designing the interstate exclusively for local use,” Gernhart said. “That’s not the purpose of the interstate. Its for throughput of goods and services up and down the west coast.”

To say the I-5 is an important commercial arterial is an understatement. According to WSDOT, I-5 has the highest roadway fright hauling classification in the state. Ten million tons of goods and services are hauled up and down the freeway annually. Put in context, a 2008 WSDOT study estimated $47 million in revenue was lost when flooding shut the facility down in 2007, along with $3.81 million in sales tax revenues, 460 jobs and $23.15 million in personal income. Congestion has similar economic effects.

Here's How It Works

The upcoming changes to Mellen, Harrison and Interstate 5 will take some getting used to. Here’s what to expect:

Accessing the Hospital from Southbound I-5

For freeway drivers to access Providence Centralia Hospital from the north, they will need to exit the interstate at Harrison and get on the new C-D lanes to Mellen. There will be no direct access to the Mellen Street interchange as presently exists.

Driving From Harrison Avenue to Providence Centralia Hospital and Back

This is how the new freeway will work for local drivers once completed. A driver from, say, Fords Prairie who wants to travel to Providence Centralia Hospital currently accesses the freeway to travel from Harrison Avenue south to Mellen Street. The process is reversed when they return. That trip will look much different when the Mellen Street project is complete.

Rather than getting on the mainline, drivers on Harrison will access new southbound C-D lanes from the same intersection they access the freeway from now, following drivers who exited the freeway to get to Mellen. The C-D will parallel the freeway but be separated from the freeway mainline. Drivers wishing to access the freeway will essentially take the same route they do now. But to get to the hospital our driver will continue along the C-D, crossing a new bridge over the Skookumchuck River and on to a signalized intersection at Mellen Street.

The return trip will be much different.

Driving From the Hospital to Harrison Avenue and Northbound I-5

Currently there are four intersections within a short, 800 foot distance between Ellsbury Street and Airport Road along Mellen Street at interchange. According to Gernhart, that short space doesn’t allow enough room to store vehicles between each traffic signal. WSDOT’s solution? Get rid of two intersections on Mellen — Ellsbury and Airport Road — and make westbound Mellen Street traffic one-way under the existing I-5-Mellen Street overpass. The upside is the remaining intersections — the on and off-ramp intersections of the interchange — won’t need to handle as many turning movements at the signals, making them more efficient, Gernhart said. 

So how do motorists who want to return from the hospital get back to Harrison if they can’t go under the freeway overpass? Southbound along a realigned Airport Road, then over a new structure crossing the freeway about one-quarter mile south of Mellen Street. Here’s how it will work for drivers coming from the hospital:

The current southbound freeway on and off-ramp intersection on the west side of the Mellen Street interchange will become the new Airport Way intersection. (The Airport Road park-and-ride will remain, as will access to it from Mellen, but the existing Airport Road will be cut off and access to it relocated west. The old Airport Road will be used only for emergency access.) 

The new Airport Road intersection — the current freeway on and off-ramp intersection — will handle four directions of traffic: southbound C-D traffic, southbound Airport Road traffic, and motorists who want to get across to the east side of the freeway. Southbound freeway on-traffic will break off from Airport Road at a new freeway on-ramp. 

Remaining traffic will continue along Airport Road toward Chehalis, or turn left at the new overcrossing structure to return to Mellen. 

After crossing over the freeway they will turn left again, merging with traffic exiting from the northbound freeway. Together they will travel north to a signalized intersection at Mellen, at the same location it exists today. This is the beginning of the northbound C-D.

The northbound C-D will eliminate Ellsbury Street south of Mellen, providing direct access to businesses currently served by Ellsbury, a potential economic boon for them. It will also allow motorists direct access to neighborhoods behind the businesses on Alder and Bostick Streets. 

No Northbound Freeway Access from Mellen Street

After crossing over the freeway, the Fords Prairie driver coming back from the hospital will need to negotiate two signalized intersections to get back onto Harrison Avenue and home. Here is another major revision from what currently exists: drivers will no longer be able to access the northbound freeway at the Mellen Street interchange. Instead, they will need to drive along the entire length of the C-D through Harrison Avenue before crossing the signalized intersection and speeding up to merge with northbound I-5 mainline traffic.

Back at Mellen Street, the new intersection on the west side of the interchange will be controlled by a quicker and more efficient two-phase signal; quicker because it will only need to accommodate motorists heading west on Mellen toward the hospital, or those on the one-way C-D who want to turn left, go straight toward Harrison, or right onto eastbound Mellen toward downtown Centralia.

Moving forward along the C-D, the Ford’s Prairie driver will pass Plummer Lake, which will be partially filled in to accommodate the new C-D lanes. Just before crossing another new structure over the Skookumchuck River, C-D traffic will merge with another set of cars exiting northbound I-5 onto the C-D. The C-D will then pass Hayes Lake before it splits into four lanes at the signalized intersection at Harrison Avenue.  

Other than adding additional turn lanes, the intersections at Harrison Avenue will remain essentially the same. Once turning left onto Harrison from the C-D, the driver from Ford’s Prairie will be back in familiar territory. The biggest difference between the Mellen and Harrison interchanges is drivers will be able to access southbound I-5 from Harrison without traveling the entire length of the C-D, at least temporarily. Likewise, northbound drivers will be able to exit directly to Harrison from the freeway. Those on and off-ramps were a concession made to the Port of Centralia and the Outlet Malls, according to Gernhart.


If you have questions or comments about the project, contact reporter Lee Hughes at 360-807-8239 or by email at lhughes@chronline.com


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