This is a solution I came up with for planting a garden above my septic system leach field. I didn't want to plant directly on the field, or even create a raised bed. I had access to 55 gallon juice drums and thought I would make use of 3 of them. The stand features the 3 drums cut in half lengthwise, supported by a series of assemblies connected by 2x4 stringers. A good solution for the leach field issue, plus it's easier on my back.
Step 1: Assemble The Assemblies
To begin, I created the 4 support assemblies that will be connected by the 2x4 stringers later on. For simplicity, I made them all identical and symmetrical. The two legs are made from 4x6 pressure treated (PT) lumber, and in my case, they measured 26-1/4" long (high). The cross members that connect each leg are 2x4 PT and connect to the legs via dadoes cut in the legs. To create the dadoes, I carefully laid them out and hogged out the material using my table saw with the blade set to 1-1/2" high and the miter gauge. With a series of kerfs cut, I turned to my chisel and hammer and cleaned the dadoes up, making sure a 2x4 would fit in snugly. Note that the legs are connected by 2 cross members. Structurally, 1 would be sufficient, but I like the symmetry of using 2 (plus I had the material handy). When the dadoes are done, cut a couple of cross members to length (31" in my case, which produces a perfect fit for the drums later on), lay on some construction adhesive and put a couple screws in each connection point. For my 6 half drums, I needed 4 assemblies. There is one more thing each assembly needs: a couple of pieces of wood that will straddle the longitudinal 2x4 that supports the underside of the drums. The inside of each piece go 3/4" off the centerline of the cross members, so as to create a 1-1/2" pocket that will hold the longitudinal piece.