South Spokane Street Viaduct, Seattle, WA


Mid Mountain Contractors, Inc. for the Seattle Department of Transportation

White Shield is supporting for Mid Mountain Constructors and SDOT with construction survey services on this $17.2 million project creating a new two-lane eastbound off-ramp leading to Fourth Avenue South as a portion of the widening and improvement of the South Spokane Street Viaduct. The existing structure is a 60-year-old elevated roadway that carries 65,000-70,000 vehicles daily between I-5 and the West Seattle Bridge.

The project scope included survey for grading and demolition work including 7750 linear feet of saw cut, 3400 cubic yards of roadway excavation, grading, and sub-grade preparation; roadway paving including 12,000 cubic yards of concrete and 5600 cubic yards of asphalt paving; bridge superstructure construction including 10 spans of T-beam girder and 4 spans of box girders, 22 drilled shafts and columns; site utilities including storm sewer, sanitary sewer and 30” water main; 7700 linear feet of curbing, 23,000 linear feet of pavement markings, 59 luminaires, 1 cantilever sign and other roadway and safety features.  Significant project challenges included tying the new construction into an existing structure while maintaining drivability and constructability of the final roadway.

Work to complete the new off-ramp from I-5 is ahead of schedule. Originally set to open for use by December 2010, the new ramp is likely to open in late summer or early fall.

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