We consulted on four large retaining walls at the Costco Wholesale in Springdale, Ohio and provided construction review services.  These unique walls totaled more than 54,000 sq. ft. and had a maximum height of 42 feet.  MESA Standard blocks and TENSAR geogrids were used with two mechanical comb connectors per block.

One of the unique features of the walls is that they were constructed without a drainage column of stone immediately behind the wall blocks.  Usually wall designs call for a drainage column of stone to provide:  Compaction, Connection, Filtration, Freeze-thaw protection and Water pressure build up prevention. 

Free-draining SAND was used in the entire geogrid zone and a layer of geotextile was installed to keep the sand from leaking out from between blocks. 

The sand was placed all the way up to the back of the block and provided Compaction, Freeze-thaw protection, and protection against pore water pressure build-up.  The geotextile provided Filtration so that sand was not lost through the wall.  And finally, Connection capacity was obtained using the MESA mechanical connectors!