Jeff,

My pond also loses the 1/4" to 1/2" a day and I have always contributed that to evaporation. My pond also has an intermittent wet area below the dam, but I am confident that it is from a rising shallow water table. I have the strangest water table that anyone has ever seen. The water in the brick lined, hand dug well, below my dam always has water in it that is several feet above the floor elevation of my basement which is only 50 yards away. The water table is very near the surface at the pond dam base, but slopes downward and goes beneath the basement under the house (thank goodness).

My point is, it is possible to have ground water surface below the dam that is NOT leaking from the pond. I'm not really saying that this is your situation, but worth investigating. Can you move over from your suspected seep at a similar elevation and dig a hole to see if there is ground water there too? If I dig a hole that is deeper than the brick well water level anywhere below the dam, it fills with water. When the weather gives us a lot of rain, the water in the well is higher than the ground around it. It's a bit spooky.

Fish on!,
Noel