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Andy, You should backfill against the wall using some type of course aggregate such as sand, gravel or crushed stone. Excavate as low as possible along the wall while maintaining enough fall for a drain pipe to drain. Install about 6 inches of aggregate. Install a 4" perforated pipe along the entire length of wall and drain over the hillside. (A large percentage of retaining wall failures are due to water pressure building against the wall.) Continue backfilling the trench with aggregate until about 12 inches from the top. The top 12 inches should be similar to the remainder of your dirt floor. If your dirt is real sandy, it would be best to use a filter fabric around the aggregate backfill. Theoretically, the aggregate need not be more than 18 inches or so in width for the entire length of the wall. Practically, it may be easier to backfill the entire excavation with aggregate. I prefer a course aggregate in which 100 percent of the stone will pass thru a 1" sieve with minimal fines. For the most part, it is self compacting and does not require the use of a mechanical tamp. I do not like to use river gravel, unless it is well confined at the perimeter, because it has a tendency to "flow" and does not make a stable surface. Another option, if you do not have a place to run the drain pipe, is to backfill as described above while omitting the pipe. Using a 3/4" masonry bit, drill holes through the concrete wall about 6" above the bottom of the aggregate installed on the back side of the wall. Drill the holes about every 2 to 3 feet apart. These holes will also serve as weep holes to relieve any water pressure that builds. The down side is, they are going to drain on the "basement" floor. Hope this helps. Chooch
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