[Update Jan 28, 2008] It appears as if the Port of Seattle is in some hot water for some alleged shady dealings with one of the contractors on the project.  More at Seattle Times. [/Update]

Erosion Control magazine has an interesting article on MSE Walls. I think the tie-in of MSE Walls with erosion control is a little questionable (they did mention wall drainage a few times), but the article highlights several interesting projects, particularly the Seattle-Tacoma Airport or Sea-Tac Third Runway Project retaining walls. The West wall for that project is the tallest MSE Wall in North America, 130-ft at its highest point. More after the break. (Photo by Sea-Tac Airport)

The article indicates that the walls were necessary to allow for the construction of an additional runway to meet federal guidelines requiring separation of runways during bad weather. Previously Sea-Tac had to operate only one runway during bad weather (about 40% of the time!) causing delays etc. Over 16 million cubic-yards of fill were needed for the project, and the walls became necessary as environmental mitigation for neighboring wetlands and a creek as the footprint for 2H:1V embankments would have covered wetland area. The overall project cost is more than $1.1 Billion!

Image copyright Hart Crowser

There are 4 tiers to the west wall, and the average wall-height is 74-ft with a total wall length of over 1,400-ft. The Reinforced Earth Company (RECo) was the designer and supplier of 5-ft by 5-ft cruciform shaped panels (Reinforced Earth^® system) with galvanized steel straps as reinforcement. One interesting thing I didn't know about the project was that for that West wall, they had poor subgrade soils, possibly because of the neighboring wetlands. They had to overexcavate and replace 20-ft of material (mostly peat)! Our local contractors grumble about 5-ft of overex and recompact. To do the excavation they needed sheet pile shoring. (Photo by Sea-Tac Airport)

Other MSE Wall projects discussed in the article include a Tensar Mesa Retaining Wall System used at a new interchange for Interstate 24 at Manson Pike in Murfreesboro Tennessee (completed in 2004), and a couple residential retaining walls in Roseville California and Atlanta Georgia.

Thanks to Geosynthetica.net for finding the article.

Related Items:

• AASHTO LRFD Bridge Design Specifications - 2008 Interims Released
• ADAMA Software Updates - MSEW and ReSSA
• Devil's Slide Tunnel Construction Kicks Off
• MSEW 3.0 - Update 7
• MSEW 3.0 - Update 7.1

• NCS Consultants, LLC

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Skip Ragsdale said:

Randy commented that he didn't understand why a wall would be in a magazine on erosion control. A wall is an erosion control Best Management Practice (BMP). Just like erosion control blankets, walls control erosion although different they are both tools in the toolbox of erosion control and sediment control professionals. For more info check out the IECA web site at www.ieca.org. Skip Ragsdale Sunshine Supplies, Inc. Birmingham, AL www.sunshinesupplies.com

Friday January 11, 2008 07:36AM

rockman said:

Thanks for the comment Skip. I am certainly no erosion control expert, just a lowly geotech. But what I meant was that the walls that the author chose to discuss in her article didn't seem to be related to erosion control. I'm not complaining, I enjoyed the article. I can see walls having their place as BMPs though. If you or anyone else come across an article about retaining walls used for erosion control, let us know. --Randy

Friday January 11, 2008 08:01AM

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