I know you mentioned if we hit clay, its probably not ground water. But I just dont see where else the water can come from?
I should have clarified that statement a little more to "if you hit dense, hard-packed clay".
However, even with THAT clarification, there still may be little channels of sand within the clay that are capable of both storing AND conveying water! Those are typically very difficult to observe in wet, sloppy clay. Therefore, if you have not had recent rains, then I think you have proved this is ground water that builds up in your pond basin.
What happens to the water after it fills your blue catch basin?
Further, I assume the water flow rate into the catch basin is still less over the course of a day, than what your sump pump is ejecting?
Right now, I suspect you have a gigantic amount of water held in the aquifer surrounding your basement. Running a second little outlet (to your catch basin) is NOT going to drain that ocean any time soon.
However, it may help in the long run. Eventually your sump pump will get caught up with the ground water. After that, the next rain will start to recharge the aquifer. If you keep draining your little pond basin, then you will slow the recharge rate of the aquifer. If you get your drainage outlet at a low enough elevation, you may really pull down the aquifer water level during a hot, dry summer. In that case, the next few rains would have to go to filling back up a depleted aquifer. Hopefully, that will significantly decrease the work required by your basement sump pump.
Hope that helps a little more.
