The enclosure has walls (4) that are widened from bottom to top, and a lower part that is narrow in length and width directions if the enclosure is rectangle or irrespective of polygonal shape of the enclosure. A leg assembly (3) maintains a compartment and a floor (2) of the enclosure above ground such that the enclosure is raised from ground, where the assembly is constituted by a stack of wood billet sections. A frame made of porous material regulates water flow and protects the billet sections.
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