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.
