I-405: MSE Retaining Wall Aesthetics Blend with Natural Surroundings

I-405: MSE Retaining Wall Aesthetics Blend with Natural Surroundings


Ashlar Stone Panel Finish with Stepped Coping
Reinforced Earth Product in Field
Location: 
Renton, WA

The Seattle area is a majestic and awe inspiring place to live or visit. With an incredibly varied terrain, interesting weather patterns, rivers, lakes, streams, bays, and about any other way to describe bodies of water, it might be one of the more challenging places to build the modern highway.  The Washington Department of Transportation (WSDOT) is doing just that. 

 

The Reinforced Earth Company was contracted to design and supply 22,000 sf of Reinforced Earth® walls for Phase 1 of this challenging project in April 2008.  Due to the beauty of the natural surroundings the aesthetics of this project were a priority to WSDOT.  An ashlar stone panel finish was chosen since it would inherently blend with the environment.  In order to maintain continuity, it was anticipated that all phases of the project would use the same ashlar stone pattern, but WSDOT allowed two smaller projects that followed to proceed with variations of the original finish.  In September of 2009 RECo was contracted by I-405 Corridor Design Builders to design and supply the final phase of the project, which included 32,000 sf of Reinforced Earth retaining walls.  Although the original finish supplied by RECo in 2008 and proposed on this section adhered to the project specifications it was required by WSDOT to match the variation of the ashlar finish as supplied in two most recent projects.  The issue was quickly rectified by RECo contracting with Fitzgerald Formliners to produce a matching product, allowing the project to proceed without delay.

 

Another unique aspect of the project was the use of custom precast coping.  Instead of the more traditional coping, which would follow the top of wall grade, WSDOT requested a stepped top of wall appearance for both the Reinforced Earth and cast-in-place walls.  RECo’s engineers meticulously designed a symmetric stepping pattern which would be incorporated into the topout for all of the walls.  The detailing of the formwork had to integrate a method to allow close ended vertical up or down steps, without jeopardizing the finished appearance of the structures. In addition, a “shingled” look on the front face of the coping was required.  The final specialized coping forms were constructed by Helser Industries and incorporated inserts which could be switched in and out of forms to allow for the creation of varying shaped faces.  The completion of this project marks yet another architectural challenge that was conquered by RECo’s team of professionals.