I'm new to this forum, and you have been recommended as a resource for my construction project.

WHAT: Building a pond

WHERE: On a hillside. To level the pond, I must remove three feet from the upper edge of the 20' wide oval pond, and berm up 3 feet on the downhill side.

SPECIAL PROBLEMS: We're in Zone 4B, which can see -20 degree temps. 0 degrees, sustained, is common. The freeze/thaw factor can push an incorrectly built retaining wall down such a steep bank in just a few years. So, ice expansion on a pond is a definite concern.

SOIL: We live entirely in Loess soil -- which exists in only two places on Planet Earth... the only other place being in the Gobi Desert, in Mongolia! This soil is fine, similar to clay and is somewhat unstable. The grade which will support this pond is common to our neighborhoods, but I don't see any ponds which vary six feet from "upper" edge to "lower" edge. The yard "below" the pond gradually drops off, and is well treed, grassed, etc. It is unthinkable [!] to have failure below the pond [methinks!].

MY PROPOSAL: To construct a double-wall on the downhill 180-side of the pond.

The inner wall would be concrete block on a 6"d poured footer. The outer wall would be of 24 lb interlocking retaining wall blocks.

In between would be filled with spoil, up to 24" between concrete "pond" wall and top of perimeter retaining wall.

So, this would be, from uphill to downhill: water [4' deep in center, shaped basin bottom] - conrete block - soil berm - retaining blocks.

I know how to build ponds... I am unsure how to construct the downhill support for the pond.

QUESTIONS: First of all -- will this work? Is my thinking even in the right "neighorhood?"

Second -- Should the concrete block be cemented together, or dry-stacked?

Third -- And/or, is it overkill to fill the blocks with rebar and 'rete?

SUMMARY: I am quite experienced in building interlocking block retaining walls [& drains] for this climate in this soil. If I were in Zone 9, I sure wouldn't be worrying about ice expansion.

What I don't know is what to expect [and what is overkill] with foot thick ice pushing towards the downhill side of the pond.

I'd sure appreciate any advice, suggestions, warnings, etc.

~ Broc

PS: Local code allows me to build up to 3' without inspection.

Thanks!

~ B