Wow, sounds like your pond conditions are about opposite of ours. We have no groundwater at that depth and the most common is red or gray solid clay. Occasionally we might run into an old creek bed, some shale, or a sandstone outcrop that can cause leakage problems in certain areas, but mostly clay, clay, clay. So we rarely have problems with the bottom of the pond sealing and in fact our NRCS guy told me that most of our topsoil actually had enough clay content to seal water up but to always put our best material (clay) in the middle of a dam for structural strength and extra sealing.
A lot of the old quarter or half acre cow ponds around here are nothing more than the topsoil scuffed off to the clay (about 6" to 24" down usually unless in a silted in area) and the dam pushed up to dam up an old wash. They held, although it was not uncommon to have an occasional slight dam seep. Quite a different deal than building a bigger pond with higher dam heights and length. We had to go down to six feet in our core to get to clay in our new pond because the dam backside is up against a small seasonal creek and the area undoubtedly had silted in for eons.
We are all surface water.
Interesting the different problems and positives different areas of the country run into building ponds.
snrub
Last edited by snrub; 11/03/13 11:27 AM.
