see this post Using the single handle dragline and imagine that hole with 4 or 5 inches of "hand mixed" "wheelbarrow" type concrete…
I got my walk in today… and then went to Lowes and got the bags of sacrete, blocks, and mortar to work on the other section under the stair landing… It took about 3 hours ( I ain’t fast with hand mixing)… to get the base concrete poured in that trench and now it sets and waits to get hard so I can put the blocks in there and fill up most of that hole… I got the parts ordered for the downspout diverter to run the outlet below the steps and get the water away from going under… so things are