To further Bills comments, I came up with a possible plan to allow for better drainage/pumpout of the second bilge. Let me know what you think as it came to me at 2:00 am this morning. Drill the hole Bill suggested far enough to reach the area that should be the low point in the second bilge. Obvious risk in drilling through one of the existing hoses, or worse. The hole diameter should be big enough to accept a fuel hose for a typical dingy outboard motor. By using the bulb pump that is on almost every dingy fuel line, the second bilge can be pumped as dry as the hose position allows. If you seal the area with silicone where the hose penetrates the vermiculite, you don't refill the second bilge from the first. You could even pull the bulb off the hose, but leave the bulb's first check valve with the hose, then attach another hose to it that ends in the bottom of the first bilge. This way if there is a large quantity of water, or whatever, that gets into the second bilge, it may reach far enough into the hose to empty into the first bilge, and even start a siphon that sucks the second bilge dry(er). The retained check valve eliminates the risk of, again, backfilling the second bilge through the hose.
OK, does this sound like a 2:00 am save the world scenario, or what?
Any thoughts? (Or was this too painful?)