I was talking to a dirt contractor about a 6.5 acre pond project and here is how he deals with excess water.
IF there is excess water in the ground, he said they put a french drain around the perimeter of the work site, 10' deeper than the deepest part of the pond. They have pipe risers connecting to the french drain, and hook up large dewatering pumps to the pipe risers so they can suck the water out of the ground before it gets to the area that they are digging. They pump that water away. Sometimes there are field tiles that are available to tie into, sometimes there are ditches nearby to pump the water to.
This particular pond project will be 20' deep, so he would set the french drain at 30' below the soil level.
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