Subterranean plastic tank

A thin walled plastic tank for subterranean storage and transmission of materials, said tank comprising:

• a generally horizontal bottom wall having a round peripheral edge disposed generally in a horizontal plane,
• a peripheral wall connected to and extending generally upward from the peripheral edge to an apex area, the peripheral wall having a plurality of corrugations including alterating crown and root portions which extend from the bottom wall toward the apex area, the peripheral wall having a generally rounded horizontal cross section;
• the apex area including a generally horizontal top wall area;
• and
• an enlargement of one of the root portions defining a recessed indentation area integral with the peripheral wall, a sleeve integral with the indentation area to define an access opening, such that the sleeve is disposed below the outer surface of the tank for protection against damage.

A thin walled plastic tank for subterranean storage and transmission of materials, said tank comprising:

• a generally horizontal bottom wall having a round peripheral edge disposed generally in a horizontal plane,
• a peripheral wall connected to and extending generally upward from the peripheral edge to an apex area, the peripheral wall including a plurality of corrugations including alternating crown and root portions which extend from the bottom wall toward the apex area, the peripheral wall having a generally rounded horizontal cross section, the peripheral wall including a peripheral rib extending around the periphery of the tank, the peripheral rib including a plurality of rib portions disposed in the root portions, each rib portion having an outer portion which is substantially flush with the crown portions and having side portions which extend from the outer portion into the adjacent root portion;
• the apex area including a top wall area;
• and
• access means for allowing access to the interior of the tank.

A thin wall plastic tank for subterranean storage and transmission of fluids, said tank comprising:

• a bottom wall having a peripheral edge disposed generally in a horizontal plane;
• a peripheral wall connected to and extending generally upward from the peripheral edge to an apex area, the peripheral wall having a plurality of corrugations extending from the bottom wall toward the apex area, the corrugations comprising alternating crown and root portions;
• and,
• an enlargement of one of the root portions defining a recessed indentation area integral with the peripheral wall, a sleeve integral with the indentation area to define an access opening, such that the sleeve is disposed below the outer surface of the tank for protection against damage.