Plural liquid- and gas-tight, large capacity upright cylinders having closed tops and bottoms are positioned connected together resting on the bottom of a body of water. A first cylinder, initially filled with water, is loaded with waste (potentially consisting of various types of trash including solids of different specific gravity, oil and other liquids and entrapped gases created by decomposition). Liquid displaced by the trash is pumped to the next cylinder. A third cylinder may be fabricated on site or transported to the site in time to replace the second cylinder as it is being filled after the first is completed. Displaced gases are accumulated in the tops of the cylinders pipe to a location where they may be filterted or otherwise purified or burned.