The entire area around the stadium is not an area you want to be digging. A lot of what was left after the fire in 1901 was dumped in the area. Lot J is entirely capped and if you look it has no inlets. It drains to the pond over by the TV station. The area also had an old paint factory and they built Liberty ships in that area as well. That is why Lot J has no inlet, the soil is not something you want to be digging into.
If you look at Lot J you will see humps on the parking lot where the old rails went to the river to launch the ships. The parking lot has settled on either side of these old rails that are on piles.
COJ just didn't have the money to take down the whole thing. The Grant they received from the Feds was the only way they had enough money to do what they did.