Modular stormwater retention system

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.

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.

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.