I've seen seepages in ponds built in good clay
soils. The leaks are usually seen as wet areas
below the dam, and I was of the assumption that
the seepage occurred at grade level where vegetation was not adequately removed. However,
I'm now thinking that at least 70% of the leaks
occur in the upper 2 feet of dam area below the
permament water line. The soils there are less compacted and certainly the dam has less soil
mass as it nears the crown. The water seeps through, and without proper coring, gravitates
downward to grade level on the dam backside.
Maybe sodium bentonite worked into the soil in
the mentioned area could be a viable fix.
However, if seep rates below the first couple
of feet don't lessen or the soils are too
permeable, this is all just so much conjecture.
