Soils question:
I'm going to be using some interlocking soil retaining block of 8" depth to create a 75 square foot terrace raised from grade by about 3' or so, using further instructions and materials from the supplier who made this video:
• Video Link
I like the terrace to form part of the west edge of a 9' x 5' pond (approximately 1000 gallons) with a 5' vertical depth on the terrace edge preferably made of cinderblock. The other sides of the pond will be formed at a general 1:1 slope with flexible liner and I have a pretty good idea of how to tie that in with the foundation of a concrete supporting wall.
But what kind of soil wall design would be necessary to hold back the pond, the soil, and the wall of the terrace on top?
I'm thinking a cavity wall made of 2 wythes of concrete block, with 3' of geogrid and compacted soil/gravel going into the terrace side and a thick coating of epoxy resin on the pond side, but I'm not sure about the foundation width, the cinder block width, how to specifically design the top of the wall or its sides.
Thought: 6" of reinforced cinderblock on each side with a 2 - 3" cavity on an 24" foundation, then simply lay a deeper set of blocks at the base. If I can place the epoxy coating on the interior of the pond wall, I can have a kickass permeable surface on which all sorts of things will grow on that won't leak.
I'm guessing I technically need a permit but I'd really rather not to go through it because of the costs of drawing it up and having it stamped, which would well exceed the materials cost. I'd like to build this mostly myself.