Claudia Bingham Baker, WSDOT communications, 360-357-2789 (Tumwater)
TACOMA – Drivers trying to reach State Route 7 from Interstate 5 later this month will be taking the long way around for nine weeks.
Beginning at 10 p.m. Monday, Aug. 12, crews working for the Washington State Department of Transportation will close the southbound I-5 exit to SR 7 for nine weeks. Motorists will be detoured around the closure using Interstate 705 and State Route 509 (see map below).
To prepare for the long-term ramp closure, crews will close nearby ramps from 9 p.m. Monday, Aug. 12, to 5 a.m. Tuesday, Aug. 13, and detour motorists through the I-5/South 56th Street interchange. Those ramps include:
Construction crews will use the closed SR 7 ramp as a construction zone from which to excavate two concrete-lined vaults full of soil contaminated with petroleum products left from original Interstate 705 construction. While it is necessary to remove the vaults and material, the contaminated soil does not represent a health or safety threat to the public or the environment.
The ramp from southbound I-5 to southbound SR 7 is scheduled to reopen Oct. 11. Closing this ramp, which serves up to 1,700 vehicles per hour, is not expected to cause significant traffic backups.
The vaults to be removed measure about 100 feet wide, 230 feet long and 18 feet deep. They are buried about six feet underground in a grassy area between I-705 and SR 7. When constructed in the 1980s, they were an economic and creative means of handling the contaminated soil. By capturing and burying the soil, WSDOT avoided significant costs associated with disposing of the material at an approved site.
Since then, WSDOT has begun the Tacoma/Pierce County HOV Program, which constructs 70 miles of high-occupancy-vehicle lanes on state highways in Pierce County. Stormwater treatment standards have evolved since the 1980s that require WSDOT to use available space within existing right of way for water treatment. This plot of land was identified as a place to construct a permanent stormwater detention pond to manage runoff generated by one of those projects, entitled I-5: M Street to Portland Avenue – HOV, which will start construction in 2014.
The excavated material will be disposed of at an approved site. About 1,100 dump truckloads of material will be removed.