Improper water management is a leading cause of wall failures. To help mitigate this potential problem, proper water management is critical throughout the life of your retaining wall. In an earlier post, we touched upon the planning that must be done in order to direct water away from your retaining wall using swales, berms, and other grading.
In addition to these suggestions, the secondary line of defense is the minimum 1 ft (0.3 m) of clean stone behind the wall. This drainage column allows incidental water to migrate downward to the base of the wall. Once the water makes it to the base of the wall, it enters the drain pipe. The water is then expelled to daylight through a vent. As noted on the Water Management page of the Allan Block website, the details require a toe drain for walls over 4 feet (1.2 m) tall.
Once the wall is built correctly with proper drainage, the owner must assume responsibility for the water management for the life of the structure. If future site improvements involve grading the site differently, keep in mind how water may flow and ensure that it does not flow directly toward the wall. If new gutters are put on the house, or a new sprinkler system is installed, avoid having this water pool near the top of the wall. Taking care to avoid water management issues will prolong the life of the retaining wall and keep it maintenance free.