Underground tank with void-eliminating cradle

A glass fiber reinforced plastic tank including an elongated generally cylindrical body portion and a pair of end cap portions respectively closing opposite ends of the body portion, the tank being adapted to be installed underground with a longitudinal axis of the body portion extending horizontally, and void-eliminating means preventing voids beneath the tank when the tank is installed in an excavated cavity in the ground and the cavity is backfilled, said void-eliminating means comprising hardened plastic foam filling the spaces generally defined by (a) an outer surface of a lower portion of the body portion of the tank, the outer surface extending substantially the full length of the body portion between the end cap portions, (b) a horizontal plane tangent to the bottom of the tank and extending substantially the full length of the body portion, and (c) a pair of planes diverging upwardly from the horizontal plane into tangency with the body portion of the tank respectively on opposite sides of a longitudinal axis thereof and extending substantially the full length of the body portion, a glass fiber reinforced plastic casing for the hardened plastic foam, the casing being generally defined by said planes and secured to the tank at the tangency of the upwardly diverging planes with the body portion thereof, said foam being provided in the spaces between the bottom horizontal plane tanqent and the tangency of the upwardly diverging planes.