On the tank list is a 1500 gallon septic tank. These (and larger) are readibly available in the U.S. but the only thing we have found is a round one that is more in the shape of the plastic water tanks. We really need something that is in a more "traditional" shape—that is, rectangular and longer than the height.
Our permiso with MARENA includes the fact that our septic system (which includes gray water separation and a bio-filter) will have a plastic rather than concrete tank. This is because of a whole host of requirements to ensure the concrete tank won't leak.
Anyone seen such animals anywhere?