Can I leave a space for sewer drain when putting retaining wall up so, rock wont rest on top of soil where sump pump sewer pipe is?

Update with more detail:

My home has a sump pump that kicks the water out to a sewer pipe that leads underground to the back of my lot to a drain sewer. The backyard slopes so I had to dig out the area for my pool, and at the high side it was about 2ft. I am installing retaining wall blocks that are 6inches tall, 12 inches deep and 17 inches wide and hollow in the middle to be filled with crushed rock.

Because a 6 inches base is required, and minimum of 6 inches of the first row be burried, I needed to dig down another 12 inches. So I ran into this sewer pipe where I need to put the base rock, and it will sit up an inch or so higher than the base rock. I am looking to leave a small space when placing the base blocks so no weight will be directly on this pipe, and then just build the wall as usual. Is there anything I should be aware of, or is there something else I should be doing?

Currently I dug out the base and left the compacted clay covering the pipe on each side about 3 inches. Would it be better to dig out and expose the pipe within the base and just put the base rock all around it and try to tamp it as best I can? Or is it better to leave the compacted clay soil around it and work the base rock around the clay covering the pipe?

Thank you.

Diagram: enter image description here


1 Answer 1


Well, without much finding of information on this, and trying to do this project alongside a full time job, and rain delays, I moved on and did what made sense.

I just left a space where the pipe was with a couple of inches on each side to reduce side pressure, and hand tamped the base around the pipe. The hardest part was getting both sides of base rock level with each other, but got it done.

I just made sure to start the blocks at the pipe to get the right gap.

After leaving the space and filling the gap with crushed stone, and because the bottom layer is mostly burried anyway, the gap isnt noticeable, and the wall seems pretty stable.

Again, this is just a small gravity wall.

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