Going to try and tackle my 4 year leaking problem again this spring/summer.

2/3 acre pond - dug and dammed - steep sides - 11' deep at deepest spot - hit shale when digging in an area about 1/3 the total size of the pond - covered bottom with minimum 2' clay - sides may not have gotten that much - no compaction as compaction guy didn't show and then it started raining.

Initially could see water leaking out in several spots at the toe of embankment in a 225' stretch when pond first filled.

Have tried Soilfloc in the end where we hit shale without any noticeable change. Added 624 cubic yards of clay two years ago (sides and bottom) and it helped some - but again the compaction guy did not show - so got no real compaction...... and it started raining before I could get someone else.

Pond drops rapidly after rain stops at end of winter - 6 foot in about two-three weeks - then slows down considerably and after 2 months loses very little and no leak at toe of dam. (deepest part now approx 3-4 feet)

So the question -- how do you ascertain if it it leaking out the bottom when the pressure is high (full pond) or is going down thru the sides? No noticeable interior leaking holes. So I don't know whether to concentrate efforts on the bottom or the sides ?

Might be safest to just add clay to any obvious area of shale or porus soil and recompact the entire bowl. Making sure all areas are covered adequately. Then you know for sure what you have.

Mine also leaks. The only way I can figure out where is to drain the darn thing and look.

Water seeping out the back toe of the dam suggests the dam wasn't cored properly. If that's the case, then the entire pond bottom, and up the sides, needs to have compacted clay. Or, you may able to dig a core trench, backfill, and compact it well into each end of the dam, beyond where the dam ties into the hillsides.

I'd be tempted to dig into the front side slope, above the water level, digging several feet below the water level, and see if these test holes fill with water. If so, you can resolve it with a core trench. Mike Otto wrote a story about digging a core trench after the fact and compacting it with a remote-controlled ditch compactor.

I'd be tempted to call Mike and discuss it with him.