as in double chamber tank. This may be a long shot, but given that "fosa séptica" is a "septic tank", it may work, and I'm not totally convinced by pit/trench/pool

Structure 74-This is a double chamber tank located on Coasters Harbor Island adjacent to the boiler house. The south chamber of the tank has been cleaned and filled with foam. A pump and treat system is in place. Removal of the Boiler House 86 in FY02 will trigger removal of Structure 74. Release of Violation was issued 3/22/99.

Septic tanks - Operation, design, and construction of septic tanks - Single chamber tank - Double chamber tank - Trickling filter - Combined tank and filter - Effluent drain