Methods and modules for an underground assembly for storm water retention or detention

1. A method for retaining or detaining storm water beneath a ground surface comprising the steps of:

placing a first level within the ground comprising a plurality of modules in a first configuration, wherein each module comprises a horizontally disposed deck portion and at least one substantially vertically disposed side portion extending therefrom, said deck portion and said side portion have respective end edges, and said side portion respectively having an edge opposite the deck portion;

placing a second level within the ground comprising a plurality of modules in a second or inverted configuration, said inverted modules being supported by the first level, wherein each inverted module comprises a corresponding horizontally disposed deck portion and at least one corresponding substantially vertically disposed side portion extending therefrom, said deck portion and said side portion of said inverted module have respective end edges, and said side portion respectively having an edge opposite the deck portion;

connecting a plurality of longitudinal channels each defined by at least a portion of a selected one of the first level and the second level; and

connecting a plurality of lateral channels each defined by at least a portion of a selected one of the first level and the second level.

2. The method of claim 1 wherein at least one deck portion of the second level includes an opening for flow of stormwater.

3. The method of claim 1 wherein the deck portion of the first level forms at least a portion of a floor and such portion is imperforate.

4. The method of claim 1 wherein the deck portion of the first level forms at least a portion of a floor and such portion is perforate.

5. The method of claim 1 wherein said longitudinal channels and said lateral channels are defined in part by the first level, which includes a plurality of elongated U-shaped modules, each module formed from a corresponding deck and two corresponding side walls extending from opposite longitudinal sides of the deck, wherein the steps of connecting said channels include installing a plurality of U-shaped modules within the ground in an upright configuration at a predetermined depth.

6. The method of claim 1 wherein said longitudinal channels and said lateral channels are defined in part by the second level, which includes a plurality of elongated U-shaped modules, each module formed from a corresponding deck and two corresponding side walls extending from opposite longitudinal sides of the deck, wherein the steps of connecting said channels include installing a plurality of U-shaped modules within the ground in an inverted configuration at a predetermined depth above the first level.

7. The method of claim 1 wherein the second level is supported by the first level in vertical alignment.

8. The method of claim 1 wherein side portions of the second level are supported on the side portions of the first level.

9. The method of claim 1 wherein said longitudinal channels and said lateral channels are each defined by respective portions of at least one substantially horizontal deck and at least one substantially vertical side wall of said first and second levels.

10. The method of claim 1 further comprising providing an outer boundary for said channels, said outer boundary being formed by a plurality of peripheral walls that include some wall portions which define no openings and other wall portions which define no openings other than at least one assembly access port located therein.

11. An assembly for retaining or detaining storm water beneath a ground surface comprising:

a first level comprising a plurality of upright modules;

a second level comprising a plurality of inverted modules;

each of said upright and inverted modules having a horizontally disposed deck portion and at least one substantially vertically disposed side portion extending therefrom, said deck portion and said side portion have respective end edges, and said side portion respectively having an edge opposite the deck portion;

a plurality of longitudinal channels each defined by a selected one of said first level and said second level; and

a plurality of lateral channels each defined by a selected one of said first level and said second level.

12. The assembly of claim 11 wherein at least one deck portion of the second level includes an opening for flow of stormwater.

13. The assembly of claim 11 wherein the deck portion of the first level forms at least a portion of a floor and such portion is imperforate.

14. The assembly of claim 11 wherein the deck portion of the first level forms at least a portion of a floor and such portion is perforate.

15. The assembly of claim 11 wherein said longitudinal channels and said lateral channels are defined in part by the first level, which includes a plurality of elongated U-shaped modules, each module formed from a corresponding deck and two corresponding side walls extending from opposite longitudinal sides of the deck.

16. The assembly of claim 11 wherein said longitudinal channels and said lateral channels are defined in part by the second level, which includes a plurality of elongated U-shaped modules, each module formed from a corresponding deck and two corresponding side walls extending from opposite longitudinal sides of the deck.

17. The assembly of claim 11 wherein the second level is supported by the first level in vertical alignment.

18. The assembly of claim 11 wherein side portions of the second level are supported on the side portions of the first level.

19. The assembly of claim 11 wherein said longitudinal channels and said lateral channels are each defined by respective portions of at least one substantially horizontal deck and at least one substantially vertical side wall of said first and second levels.

20. The assembly of claim 11 wherein each said channel has about the same cross section.