North America’s Tallest MSE Retaining Wall
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 EarthÂ® 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.