A cubic modular subsurface stormwater unit has equal top and bottom
surfaces spaced apart by a set of four pillars, each of which runs from a
corner of the top surface to a corresponding corner of the bottom
surface. The pillars define a void having a generally cruciform cross
section, the void opening onto each of the four side faces defined
between the roof and the base. A line of units connected together in
series side to side will have a long throughway formed by the respective
voids in each unit, and a regular matrix of X- and Y-axis throughways
will be formed as units are connected laterally on all sides. The unit is
formed of identical halves which can be connected together in any
orientation due to the square configuration and to a mating connection
which has mating parts symmetrically disposed about a diagonal
corner-to-corner line.