When record high flood waters caused Interstate 5 to close through Lewis County for four days in December 2007, freight and passenger travel halted and detours took travelers through state Route 7 and U.S. Highway 12.
The total lost economic output from the four-day closure reached $47.07 million, according to a 2008 report by the Washington State Department of Transportation.
Bart Gernhart, the assistant regional administrator for engineering for the Washington State Department of Transportation, said since the historic flood, DOT has worked closely with the Chehalis Basin Flood Authority to maintain build contingencies and protect the interstate during serious floods.
The Flood Authority approved an eight-year timeline last month that will dedicate at least $26.5 million to finding to a basin-wide solution, which includes a possible dam on the Chehalis River above Pe Ell.
According to the Flood Authority’s proposed timeline, over the next two years, engineers and experts will explore the feasibility of two dam models.
“We are on hold until the whole process has an outcome,” Gernhart said. “The Flood Authority is proposing a series of tasks and activities for decision by the fall of 2014.”
The four ideas still being considered by the Flood Authority and WSDOT for protecting Interstate 5 include:
• Protecting I-5 with walls and levees, estimated to cost $80 to $100 million;
• Building an I-5 express way, cost to be determined;
• Building temporary I-5 bypass lanes, cost to be determined;
• Raising and widening I-5 to six lanes using fill material, costing about $450 to $550 million.
Gernhart said while the larger plans are left to be determined in the coming years, WSDOT is working toward more short-term flooding solutions for I-5.
WSDOT introduced a new commercial vehicle passport system last month that will allow emergency freight to access U.S. Highway 12 and state Route 7 during a serious flood event on I-5.
Colin Newell, the Chehalis area engineer for the department of transportation, said the passport system will be functional by the end of this year. The system will be used when a flood event has closed I-5 for at least 24 hours and poses the risk of closing it for a full 72 hours.
If I-5 closes for at least one day, truckers will be notified and have to apply online for a special tag that will let them access the detour routes in a three-hour window on a certain day.
Tags will be awarded in varying classifications; A tags for those delivering emergency equipment, B tags for necessary or perishable goods, and C tags for all other deliveries.
The project has been in the works since 2011 and is estimated to cost $1.6 million, according to WSDOT. The majority of the money for the project came from federal funding.
Gernhart said WSDOT also has flooding solutions in mind while constructing the widening project on I-5 between Mellen Street and Blakeslee Junction in Centralia.
At the airport levee along Airport Road in Centralia, crews are installing two 84-inch culverts that will drain into the open field immediately after a flood.
The culverts will eliminate the need to breach the levee to drain floodwaters.
WSDOT Assistant Area Engineer Ty Hillebrand said the airport levee’s construction is a high priority that is expected to be finished by winter.
The $155 million, two-stage project is scheduled to be completed between late 2014 and early 2015.