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Project Title & Location
SR 518-Sea-Tac airport to I-5/I-405 interchange, in Tukwila
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Project Description
This project provides improvement of SR 518 by widening lanes and
shoulders; widening a bridge; building retaining and noise walls;
removing and replacing sign bridges; installing bridge rail; concrete
barrier; guardrail; drainage items, and installing water quality systems.
The SR 518 Westbound transition from freeway to city streets will be planted.
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Contractor/Consultant
Tri-State Construction, Inc.
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Recent Progress
The work began on August 31, 2007. The contractor has been granted substantial completion on the SR518 / SR509 interchange portion of the project. The re-alignment of the SW Tributary has been completed and accepted by regulatory agencies. Excavation and shoring for the MSE wall 1 has been completed and 78 percent of the Panels and backfill is complete. The installation of the noise wall panels has been completed for wall 2 and has started for wall 2A. The electrical work is ongoing and will be through the beginning of next spring.
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Design Construction Impacts
The MSE wall (1) that begins in the vicinity of SR99 ramp has increased cost associated to construction from miscalculated quantities of fill and shoring needed to construction the wall. Soils along the MSE wall for the 3rd lane are very poor and require additional excavation and placement of suitable materials to build the wall. Wall 3 has been deleted due to the unstable slope and associated bridge. These have impacted both schedule and budget.
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Environmental Impacts / Compliance
Maintenance of the compost socks, silt fence, and other BMPs are ongoing. This project has been identified as HIGH RISK by HQ Environmental Services. Stockpiles and exposed surfaces have been covered. The slope just prior the 51st off ramp has an abundant amount of groundwater that is high risk for turbidity. There will be three years of Plant Establishment.
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Impacts to Traffic
There have been minimal impacts to traffic to date. The contractor has been very conscientious about maintaining an even flow and minimizing any impacts to the driving public.
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