Assembly for detaining or retaining liquid beneath a ground surface

1. A modular assembly for detaining or retaining a liquid beneath a ground surface comprising:

a plurality of precast unitary concrete modules each having a solid deck portion having outer edges and a plurality of spaced-apart load-bearing legs, a first portion of the plurality of legs extending perpendicular to the deck portion, wherein the first portion of at least two of the legs of a module are spaced inwardly from the nearest outer edge of the deck portion of the same module so that portions of the deck overhang each of the first portion of said legs;

at least two of the plurality of legs being integrally joined together by a transverse section directly below an underside of deck portion between the deck portion and the first portion of said at least two legs, said transverse section and said at least two legs forming an integral support;

wherein the legs and deck portions define flow paths with respect to each module, the flow paths including flow paths outside the first portion of the legs and flow paths between the first portion of the legs, all of the flow paths being in fluid communication with one another; and

wherein each module is to be positioned with its deck portion being horizontally adjacent to the deck portion of another module, with the deck portion of each module extending in a horizontal direction, the first portion of the plurality of legs extending in a vertical direction, and the flow paths within each module being parallel to the deck portion.

2. The assembly of claim 1 wherein each module includes pairs of parallel deck portion outer edges.

3. The assembly of claim 2 wherein the flow paths include lateral and longitudinal flow paths.

4. The assembly of claim 3 wherein at least some of the lateral and longitudinal flow paths extend through centers of the respective modules.

5. The assembly of claim 4 wherein the deck portions are rectilinear and the outer edges of the deck portion are straight.

6. The assembly of claim 2 wherein each module that is within an interior of the assembly is positioned with at least two of its deck portion outer edges adjacent to at least two deck portion outer edges of another module.

7. The assembly of claim 6 wherein some of the modules are interior modules within the interior of the assembly and some of the modules are outer modules that are positioned around the interior modules and around an outer periphery of the assembly, wherein each said outer module includes a solid outer wall that extends from the deck portion;

wherein the outer wall and legs extend substantially the same distance;

wherein the outer modules include a flow path between the outer wall and the legs, and

wherein the interior modules do not have an outer wall.

8. The assembly of claim 1 wherein some of the modules are positioned to constitute a lower layer and others of the modules are positioned to constitute an upper layer located above the lower layer;

wherein the deck portions in the lower layer modules are oriented below the legs of the lower layer modules and the legs extend upward from the deck portions;

wherein the deck portions in the upper layer modules are oriented above the legs of the upper layer modules and said legs of the upper layer modules extend downward from the deck portions;

wherein the legs of the lower layer modules support the legs of the upper layer modules;

wherein each lower layer module is paired with an upper layer module.

9. The assembly of claim 8 wherein the flow paths are lateral and longitudinal flow paths.

10. The assembly of claim 9 wherein each module includes pairs of parallel deck portion outer edges.

11. The assembly of claim 10 wherein at least some of the lateral and longitudinal flow paths extend through centers of the respective modules.

12. The assembly of claim 11 wherein the deck portions are rectilinear.

13. The assembly of claim 10 wherein each module that is within an interior of the assembly is positioned with at least two of its deck portion outer edges adjacent to at least two deck portion outer edges of another module.

14. The assembly of claim 13 wherein some of the modules are interior modules within the interior of the assembly and some of the modules are outer modules that are positioned around the interior modules and around an outer periphery of the assembly, wherein each said outer module includes a solid outer wall that extends from the deck portion;

wherein the outer wall and legs extend substantially the same distance;

wherein the outer modules include a flow path between the outer wall and the legs, and

wherein the interior modules do not have an outer wall.

15. The assembly of claim 1 wherein one of the legs of each module in the assembly is parallel to and aligned with one of the legs of an adjacent module in the assembly.

16. The assembly of claim 15 wherein the modules are configured so that imaginary parallel, spaced apart lines pass through parallel legs of said adjacent modules in the assembly.

17. A modular assembly for detaining or retaining a liquid beneath a ground surface comprising:

a plurality of modules each comprising a precast concrete unitary structure having a solid deck portion having outer edges and a plurality of spaced-apart load bearing legs, a first portion of the legs extending perpendicular to the deck portion, the legs being spaced apart from one another, wherein the first portion of at least two of the legs of a module are spaced inwardly from the nearest outer edge of the deck portion of the same module so that a portion of the deck overhangs the first portion of said legs;

at least two of the plurality of legs being integrally joined together by a transverse section directly below an underside of deck portion between the deck portion and the first portion of said at least two legs, said transverse section and said at least two legs forming an integral support;

wherein some of the modules are positioned to constitute a lower layer and others of the modules are positioned to constitute an upper layer located above the lower layer;

wherein the deck portions in the lower layer modules are oriented below the legs and the legs extend upward from the deck portions;

wherein the deck portions in the upper layer modules are oriented above the legs of the upper layer modules and said legs extend downward from the deck portion;

wherein the legs of the lower layer modules support the legs of the upper layer modules;

wherein each lower layer module is paired with an upper layer module;

wherein the legs and deck portions define substantially horizontal flow paths within each module, the flow paths including a flow path outside the first portion of the legs and another flow path between the first portion of the legs, all of the flow paths being in fluid communication with one another; and

wherein each upper layer module is to be positioned with its deck portion being horizontally adjacent to the deck portion of another upper layer module and each lower layer module is to be positioned with its deck portion being horizontally adjacent to the deck portion of another lower layer module, the deck portion of each module extending in a horizontal direction, the at least first portion of the plurality of legs extending in a vertical direction, and the flow paths within each module being parallel to the deck portions.

18. The assembly of claim 17 wherein each module includes pairs of parallel deck portion outer edges.

19. The assembly of claim 17 wherein the deck portions are rectilinear and the outer edges of the deck portion are straight.

20. The assembly of claim 17 wherein the flow paths include lateral and longitudinal flow paths.

21. The assembly of claim 17 wherein some of the modules are interior modules within an interior of the assembly and some of the modules are outer modules that are positioned around the interior modules and around an outer periphery of the assembly, wherein each said outer module further comprises a solid outer wall that extends from the deck portion;

wherein the outer wall and legs extend substantially the same distance;

wherein the outer modules include a flow path between the outer wall and the legs, and

wherein the interior modules do not have an outer wall.

22. A modular assembly for detaining or retaining a liquid beneath a ground surface comprising:

a plurality of precast unitary concrete modules each having a solid deck portion having outer edges and at least one load bearing support integrally extending from an underside of the deck portion;

the support having a bottom surface opposite the deck portion, at least two spaced apart legs and a transverse section therebetween, the transverse section integrally joining at least two spaced apart legs;

the at least two legs having a first portion extending perpendicular to the deck portion, the first portion of the at least two legs being spaced inwardly from the nearest outer edge of the deck portion of the same module so that portions of the deck overhang each of the first portion of said legs;

wherein the at least two legs and deck portions define flow paths with respect to each module, the flow paths comprising a flow path outside the first portion of the at least two legs, a flow path through the support between the first portion of the at least two legs and the transverse section and a flow path between the first portion of the at least two legs and a first portion of at least two additional legs of said module, all of the flow paths being in fluid communication with one another; and

wherein in an ordinary condition of use each module is to be positioned with its deck portion being horizontally adjacent to the deck portion of another module, with the deck portion of each module extending in a horizontal direction, the first portion of the plurality of legs extending in a vertical direction, and the flow paths within each module being parallel to the deck portion.