Pond Boss Forums POND CONSTRUCTION Building a dam If your dam is wide enough...?

You core to make sure there isn't a seam or layer that water could seep through.
If there aren't any seams or porus materials below where you start adding fill it shouldn't leak.
Part of coring a dam is exploring. Digging down and looking for porus layers.
Borings offer guidelines into whether there are porus layers or not. Keep in mind that a million year old gravel stream channel that's not all that wide (might be missed by borings) might be under there. Or might not be.
Not being familiar with your area I wouldn't say whether you should core or not, just wanted to offer some general info.