I am still looking for causes of my leak. The NRCS guy gave me a number of possibilities:

1. Roots left in the dam after tree removal. He said, after roots rot, the voids never fill in on their own, at least not over reasonable periods of years, unless heavy wheeled equipment is regularly driven along the top of the dam to make clay collapse into the voids.

2. Wet weather springs, somewhere in the basin, making it a "water table" pond.

3. Pond sludge that is piled and graded against the back side of the dam, which causes the dam to be saturated from both sides, causing wicking through the dam. He recommends sludge from pond clean out be pushed well away from the dam.

4. Insufficient compaction on the side opposite the dam, allowing water to wick under the topsoil into un-compacted clay.

He said if it's roots under the dam, I should probably dig a new core trench just above the toe of the dam, and fill and compact it.

I asked about Soil-floc, he is not super familiar with it but the pond is so clear there are few clay particles suspended for the Soil-floc to grab onto.

I think I will wait until next summer to decide. It's about 31 inches low right now, still has about 7.5 to 8 feet of water over most of the flat part of the basin.

I would have never thought about #3. I did that when I cleaned out my sons pond and never thought anything about it.

I can sure see where #4 could be a problem, especially in areas where the topsoil is deep. We have such shallow topsoil here that usually the water hardly makes it up to the topsoil level in lots of ponds. That would be a good situation to push some clay up from the bottom of the pond and cover the topsoil area around the top as the pond is being built and compacted.

I wish I had a heavy wheeled piece of equipment to drive all the way around the pond a couple times a week. My little tractor only weighs about 2,500 pounds. I don't think that would help at all. I think my problem is most likely #1 (roots left in). It's a strange pond.

John,
I hope you get it figured out. I think I may still have a small leak, but not much. I was up there yesterday, checking on game cameras, and looked at neighbor's ponds compared to mine. It looks like most are down almost as much as I am. Maybe they all leak, but a few years ago, I used to be down twice the rate as others. I think maybe the soilfloc helped my leak. I've got a little left, I may try to dig out, and put it in around my overflow pipe. I think it's still the source of some water loss. I seem to lose the first 18" of water a little quicker, then it really slows down.

John, when you formed the dam, did you notice the amount of sand, clay, and rocks/gravel ratio during the development of the dam? #1 to #4 all plays a critical role in defining what happened to the water, but NRCS forgot to mention that the voids also increased when you have rocks/gravels within that dam, generating higher seepage volume through the soil medium.

I live right across from the 131,000+ acre feet lake that our office oversees the seismic retrofit of the lake's dam. There must be a non-gravel/rock mixture barrier in the first half (required) to 3/4 (highly recommended) compacted soil medium to prevent seepage. Horizontal hydrological migration is always a factor for the so called "water table" seepage. Compact of clay layer is standard to minimize hydrological migration. But, rock/gravel contents within that compact/non-compacted layer plays a critical role in determining the seepage load.

Geologists and soil engineers in my office would not let me off the hook if I don't mention this to you.

All the clay around here has a few small rocks in it. It's totally unavoidable. There are ponds around here with more rock in the clay than mine has, and most do not leak as much as mine does. I think I have rotting roots in the dam causing the majority of the leakage, but again, I may be wrong. "It's a strange pond."