Is it possible that ice over the winter would compact the clay of my pond (I'm up in Maine we get a lot of ice). The reason I ask is the pond was not holding water last year. However over the winter it gradually filled, with the ice level slowly rising with the water. Now the water level is staying steady right about where it was when the ice melted. This is the most water it has held to date, when it rains it doesn't really seem to rise, but also is not really decreasing as it did last year.

Freeze and thaw cycles in the north could possibly cause some consolidation. Some settlement will occur naturally over time, with wetting and drying of clays.

+1

Also, what is the current moisture content in the soil surrounding the pond? My pond doesn't "leak" in the spring until the surrounding soil is going dry.

When the NRCS guy designed our main pond, in the design he allowed for a certain percentage of natural compaction or settling of the dam. I can't remember the amount (in the plans that are around here somewhere) but it was something like 2% or 5%. He said we might have none at all if we did a good job of compacting the dam, but he allowed for some anyway.

That tells me natural compaction and settling will occur over time.

My NRCS design calls for 10% overfill in elevation. They assume the compaction is done by a bulldozer and the dam will settle by TWO feet (on a 20 foot high dam). With a calculated total volume of 4,700 yards at $2.75 per yard, one might assume that the overfill of perhaps 400 yards would cost me $1100.

Perhaps if you could cut the overfill down to 2% if the dam was properly compacted with a sheepsfoot, paying for itself by not having to haul as much soil and having a better dam in the end.

Would one not have to move the same amount of dirt no matter whether if is compacted by a sheepsfoot or by settling?

Well duh. I guess so! But if it is compacted correctly, it shouldn't need to be built 10% over.

Yup, and it is less likely to leak. I bought a 4' wide sheepsfoot off Craig's list and used it on a wetland berm and barn pad. The barn pad still need to be leveled. I would still leave an extra foot of freeboard for settling though, but I overbuild.