Modular stormwater retention system

1. A modular water retention system comprising:

a plurality of modular fluid retention units positioned adjacent to one another, each retention unit comprising:

a bottom portion defining at least a first and a second opening;

a top portion connected to the bottom portion, the top portion is substantially horizontal and having a support surface positioned at the retention unit top portion, the top and bottom portions defining an interior water retention chamber volume in communication with the at least first and the second openings defining a first through passage, the plurality of retention units forming interstitial volume spaces between the adjacently positioned retention units, the plurality of adjacently positioned retention units collectively defining a cumulative interior water retention chamber volume;

a connector adapted to selectively connect the plurality of modular retention units to extend the first through passage to define the cumulative interior water retention chamber volume; and

a plurality of modular trays, each modular tray engageable with at least one retention unit support surface, the plurality of modular trays operable to substantially prevent backfill material from entering the interstitial volume spaces between the plurality of adjacently positioned retention units.

2. A method of constructing a storm water retention system for use in a below ground level excavation defining a void space volume, the method comprising the steps of:

positioning a plurality of independent modular fluid retention units having a support surface in an excavation void space volume, the retention unit support surfaces are positioned on a top portion of the respective retention units and oriented substantially horizontal;

selectively positioning the plurality of retention units in the void space volume adjacent to one another defining an interior fluid chamber volume, the positioned retention units defining interstitial volume spaces between the adjacently positioned retention units within the void space; and

positioning a plurality of modular trays to respectively engage the horizontal support surfaces of the plurality of retention units positioning the respective trays above the retention units, each modular tray engaging two adjacently positioned retention units to at least partially cover one of the interstitial volume spaces between the two adjacent positioned retention units, the plurality of trays supporting backfill material on a top surface of the trays without allowing substantial backfill material to enter the interstitial volume spaces, the engaged plurality of trays further preventing relative movement of the two engaged retention units.

3. The method of claim 2 further comprising the step of:

connecting the adjacently positioned retention units together defining the interior fluid chamber volume.

4. The method of claim 2 wherein each modular tray engages four adjacently positioned retention units whereby each modular tray covers the interstitial volume space between the four adjacent retention units.

5. The method of claim 2 where each of the plurality of modular trays includes a top surface and side walls connected to the top surface, the step of positioning the plurality of modular trays further comprising positioning the side walls of adjacently positioned modular trays in adjacent close proximity to one another to preventing substantial backfill material to enter the interstitial volume spaces.

6. A modular stormwater retention system comprising:

a plurality of modular fluid retention units positioned adjacent to one another in a void space positioned below ground level, each retention unit comprising:

a bottom portion defining at least a first and a second opening;

a top portion connected to the bottom portion, the top portion having a horizontal support surface, the top and bottom portions defining an interior water retention chamber volume in communication with the first and the second openings defining a first through passage, the plurality of adjacently positioned retention units forming interstitial volume spaces between the adjacently positioned retention units, the plurality of adjacently positioned retention units collectively defining a cumulative interior water retention chamber volume; and

a plurality of modular trays, each modular tray having a top surface and sidewalls connected to the top surface, each modular tray engageable with the respective retention unit top portion horizontal surface of at least two adjacently positioned retention units positioning the modular tray top surfaces above the retention unit support surfaces, the plurality of modular trays operable to substantially prevent backfill material from entering the interstitial volume spaces between the plurality of adjacently positioned retention units.

7. A modular water retention system comprising:

a plurality of modular fluid retention units positioned adjacent to one another, each retention unit comprising:

a bottom portion defining at least a first and a second opening;

a top portion connected to the bottom portion, the top portion is substantially horizontal and having a support surface positioned at the retention unit top portion, the top and bottom portions defining an interior water retention chamber volume in communication with the at least first and the second openings defining a first through passage, the plurality of retention units forming interstitial volume spaces between the adjacently positioned retention units, the plurality of adjacently positioned retention units collectively defining a cumulative interior water retention chamber volume; and

a plurality of modular trays, each modular tray engageable with and extending above at least one retention unit support surface, the plurality of modular trays operable to substantially prevent backfill material from entering the interstitial volume spaces between the plurality of adjacently positioned retention units.

8. The retention system of claim 7 wherein at least one of the plurality of modular trays engages at least two of the plurality of retention units positioned adjacent to each other.

9. The retention system of claim 8 wherein each modular tray further comprises:

a top surface having a plurality of upwardly angled panels extending toward an apex;

a plurality of sidewalls connected to the angled panels and engaging the respective retention unit support surface, the modular tray further operable to prevent relative movement between the adjacently positioned retention units.

10. The retention system of claim 9 wherein each modular tray sidewall further comprises two opposing corner legs selectively engagable with a respective adjacently positioned retention unit support surface, the modular tray further operable to prevent relative movement between the adjacently positioned retention units.

11. The retention system of claim 9 wherein the plurality of upwardly angled panels comprises four upwardly angled panels.

12. The retention system of claim 11 wherein the four upwardly angled panels further define a plurality of through holes in communication with the water retention chamber volume.

13. The retention system of claim 8 wherein each retention unit further comprises:

a connector adapted to selectively connect the plurality of modular retention units to extend the first through passage between connected retention units and increase the size of the interior chamber volume.

14. The retention system of claim 7 wherein each retention unit horizontal support surface defines a plurality of recesses, each of the plurality of recess having a lower support surface.

15. The retention system of claim 14 wherein each modular tray further comprises a top surface and a plurality of legs extending below the top surface, each of the plurality of tray legs extending through one of the plurality of recesses and abuttingly engaging one of the plurality of retention unit lower support surfaces thereby preventing relative movement of the adjacently positioned and engaged retention units with respect to one another.

16. The retention system of claim 7 wherein at least one of the plurality of trays engages four retention units positioned adjacent to one another.

17. The retention system of claim 7 wherein each of the plurality of modular trays further comprises:

peripheral sides, the plurality of modular trays positioned adjacent to one another having one peripheral side in close proximity to an adjacent tray peripheral side operable to substantially prevent backfill material from entering the interstitial volume spaces between the plurality of adjacently positioned retention units.

18. The retention system of claim 17 wherein each of the plurality of trays further comprises:

a modular key slot defined in each of two of the plurality of modular trays positioned adjacent to one another; and

a locking key selectively positionable in the respective key slot in each of the adjacent modular trays to selectively connect the adjacent modular trays.

19. The retention system of claim 7 wherein the retention unit at least first and second openings comprise a first, a second, a third and a fourth opening, and wherein

the retention unit bottom portion comprises four legs defining a first, a second, a third and a fourth side orthogonally positioned with respect to one another and respectively defining the first, the second, the third and the fourth openings, wherein

two of the first, the second, the third and the fourth openings positioned along a first chamber axis defining the first through passageway and the other two of the first, the second, the third and the fourth openings positioned along a second chamber axis defining a second through passageway.

20. The retention system of claim 19 wherein each of the first, the second, the third and the fourth sides comprise an arch defining the respective first, the second, the third and the fourth openings, the unit further comprising a connector integral to each of the respective arches adapted to selectively connect the plurality of modular retention units to extend the first through passage between connected retention units and increase the size of the interior chamber volume.

21. The retention system of claim 7 wherein each modular tray further comprises:

a top surface having a plurality of upwardly angled panels extending toward an apex; and

a sidewall connected to each angled panel, at least two of the sidewalls engaging the respective retention unit support surface.