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Water and Environment :: Environmental Planning and Compliance

I-5 Widening Environmental and Regulatory Compliance at Blakeslee Junction to Grand Mound

Lewis County, WA

DEA was the lead consultant on this $170 million project to widen I-5 from four to a minimum of six through-lanes from Mellen Street to Grand Mound. Work included reconstructing and realigning 7 miles of I-5 including two interchanges, replacing two bridges at the Skookumchuck River and one bridge at Blakeslee Junction, widening I-5 from four to six lanes, seismic retrofitting the 216th Avenue bridge across I-5, constructing off-site stormwater mitigation, and updating on-site stormwater facilities and utilities along the route.

DEA prepared the environmental analysis, National Environmental Policy Act (NEPA) documentation, and archaeological studies, and participated in a value engineering study and a cost risk assessment. The DEA team developed 13 environmental discipline reports that included compliance with Section 106 of the National Historic Preservation Act and Section 7 of the Endangered Species Act. This work led to environmental compliance approval from the Federal Highway Administration as a Documented Categorical Exclusion (DCE). DEA also assisted the Washington State Department of Transportation (WSDOT) with all federal, state, and local permitting.


  • WSDOT Excellence in Environmental Design Environmental Improvement Project Category, Southwest Region for Wetland Enhancement


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