Thanks CTM1 - the spot was picked for a couple reasons. It is an area that is quite often wet - but I didn't understand why until I started reading about ponds. the field is right on a 1700 ft contour line and the crest of the hill looking down the valley. The wet spot is down the hill a bit (originally this was a 15 acre field that we've split up). The spot drains at least 3-4 acres of the old field. Where the soil is wet - is where the old farm lane transects the field - for the last 100+ years. What we found is that the farm lane through the field is like a Dam because its compacted. ALL the soil on this hill top has clay 1-2 feet down tops, and the rainwater that makes its way down the hill through the thin topsoil - hits the compacted roadway and pools there - and the soil always seems wet as a result, sometimes it gets so saturated that it comes up and out of the ground and runs on top the ground over the old roadway. Not because of a spring - and that's a good thing in my opinion.
so the plan here was to dig away the topsoil up the hill from the farm lane and use the clay soil from the bottom of the dug pond to build the dam core. This will stop the water from leaking under and/or through the dam. Now - its hard to know if you really got all the topsoil away- especially when you are newbie pond builder like me. So there is is a chance the dam could leak, so far - the bottom is solid - the water in the pond is only from a couple rains -so we did good with the placement and drainage.
The pipe you see is for drainage if/when it fills. That way if it over fills it doesn't come up and over the dam. I did build a lower section in the dam that is an emergency spillway - I cannot imagine ever needing it - but should the pipe plug and we get a monsoon - the water will run over the dame on one compacted edge and go around the dam instead of over it. If I don't get the pond fill like I want - I might lay some tile to divert runoff more directly into the pond, Its hard to catch it all with such a small pond.
I'm not worried about stagnation - we have beaver ponds, and vernal pools around - some of which are pretty stagnant -and its never been an issue. We do not have EHD issues here historically either. This pond will put water right at the food source - which we've never had before - already we can see the deer relating to it. The closest creeks/ponds are not real close by - and most are all the way off the property - so this has been a goal for a while.
