Underground Stormwater Modules: Modular Detention & Infiltration System

High-void, stackable units for LID stormwater management. AASHTO H-20/HS-20 load rated for parking lots, roadways, and green infrastructure.

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Why Choose This Modular Geocellular System

Engineered to replace traditional gravel trenches and concrete vaults. Our HS-20 rated modules provide 95% void space for maximum water storage in a smaller footprint.

Rated for H-20/HS-20 Traffic Applications

Suitable under parking lots and access roads; engineered for long-term structural performance with the specified cover, geogrid reinforcement, and compacted subbase.

AASHTO HS-20 load rated underground stormwater detention modules for parking lots

High Void Ratio = Maximum Storage

Geocellular modules deliver more storage per excavation than many vault types—ideal for constrained footprints and retrofits.

High void ratio (95%) modular stormwater tanks compared to gravel trenches

Modular, Stackable, Space-Efficient

Build Single to Pent stacks and half-layers. Create irregular underground basins with minimal waste.

Stackable stormwater storage modules for flexible underground basin design

Made from 100% Recycled Polypropylene

Eco-friendly material with excellent strength, chemical resistance, and long-term durability.

Recycled polypropylene (PP) material for sustainable LID stormwater systems

Flexible Configurations: Infiltration or Detention

Configure for infiltration trenches, detention systems, or combined reuse applications.

ersatile configuration for infiltration dry wells or detention tank systems

Serviceable & Low-Maintenance

Pretreatment (leaf baskets, silt traps, first-flush) and inspection risers keep the system clean and easy to maintain.

Stormwater system inspection ports and sediment traps for easy maintenance

Configurations: Infiltration & Detention for Reuse

Infiltration System

Wrap the module array in high-permittivity non-woven geotextile on all faces.

Set on a level, free-draining granular base compacted to spec.

Use vent and inspection risers; connect roof and yard drains.

Detention / Retention + Rainwater Reuse

Line with continuous geomembrane (HDPE/TPO) protected by geotextile.

Add orifice/vortex flow control and a pump well for irrigation or toilet flushing.

Seal pipe penetrations with boots; pressure-test per manufacturer.

Pretreatment

Install leaf baskets, silt traps, and first-flush bypass upstream.

Reduce sediment loading and keep the detention basin clean.

Diagram of shallow vs deep underground stormwater detention and infiltration systems

Specifications & Capacities — Geocellular Stormwater Modules

Two module families with identical assembly logic. Tables show gross tank volume and net water volume at high void ratio for accurate stormwater sizing.

Geocellular Module 8045

Stack	Size (mm)	Tank Volume (ft³)	Tank Volume (gal)	Net Water (ft³)	Net Water (gal)
Single	Single — 26.8 × 16.1 × 17.7 in (680 × 410 × 450 mm)	4.44	33.22	4.31	32.21
Double	Double — 53.5 × 16.1 × 17.7 in (1360 × 410 × 450 mm)	8.89	66.44	8.63	63.05
Triple	Triple — 80.3 × 16.1 × 17.7 in (2040 × 410 × 450 mm)	12.93	97.62	12.54	93.81
Quad	Quad — 107.1 × 16.1 × 17.7 in (2720 × 410 × 450 mm)	17.17	128.47	16.65	124.58
Pent	Pent — 133.9 × 16.1 × 17.7 in (3400 × 410 × 450 mm)	21.42	160.21	20.78	155.41

Geocellular Module 8053

Stack	Size (mm)	Tank Volume (ft³)	Tank Volume (gal)	Net Water (ft³)	Net Water (gal)
Single	Single — 31.5 × 19.3 × 20.9 in (800 × 490 × 530 mm)	6.02	45.12	5.84	43.76
Double	Double — 63.0 × 19.3 × 20.9 in (1600 × 490 × 530 mm)	12.04	90.24	11.68	87.52
Triple	Triple — 94.5 × 19.3 × 20.9 in (2400 × 490 × 530 mm)	18.06	135.36	17.52	131.28
Quad	Quad — 126.0 × 19.3 × 20.9 in (3200 × 490 × 530 mm)	24.08	180.48	23.36	175.04
Pent	Pent — 157.5 × 19.3 × 20.9 in (4000 × 490 × 530 mm)	30.10	225.60	29.20	218.80

Material & Compliance

100% recycled polypropylene (PP)

AASHTO LRFD cover sections; H‑20,HS-20

Resistant to molds, algae, soil‑borne chemicals, bacteria & bitumen

Temperature tolerance: −22 to 248°F (−30 to 120°C)

Hydraulic Pertormance & Flow

High void ratio for efficient storage

Detention, attenuation, and reuse configurations

Flow control via orifice/vortex; reuse with pump well

Branding & lmages

Standard color: black

Recommended media: product renders, trench installs, liner & geotextile details

Need a stamped layout and cover design for H-20/HS-20?

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Assembly Guide — Geocellular Crate Build

Tool‑assisted snap assembly using large and small plates. Use a 2×4 and dead‑blow hammer to ensure positive engagement. Verify full peg insertion.

Insert the large pegs of a small plate into the holes of a large plate to form the first side.

Repeat with remaining small plates along the large plate, creating the vertical sides.

Place the second large plate on top to complete the side frame.

Rotate the unit so large plates are on the sides (top & bottom open).

Align a large plate to the pegs of the vertical small plates and tap into place using a 2×4 and dead‑blow hammer.

Flip the unit and tap the final large plate to close the crate (Single complete).

For multi‑stack (Double/Triple/Quad/Pent): flip, align the next crate with open end, and repeat; confirm engagement.

EQUIPMENT

FAQ — Geocellular Tank Systems

Can these modules be installed under parking areas or driveways (H-20/HS-20)?

Yes. The system is H-20/HS-20 capable when the structural section is engineered correctly—cover, compacted subbase, geogrid where specified, and pavement per AASHTO LRFD.

What is the recommended maintenance plan?

Focus on pretreatment: maintain leaf baskets and silt traps to keep sediment out of the module array. Inspect via risers; clean interval depends on debris load and local guidance.

Which liner or geotextile should I specify?

Use non-woven geotextile for infiltration. For detention/retention and reuse, use a geomembrane (HDPE/TPO) with protective geotextile; weld and test per manufacturer.

How do I size the number of modules?

Divide the required storage by the net water volume in the tables. Our engineering team can optimize shape, cover, and outlet control for your site.

Do you support half layers and custom depths?

Yes. Half-layer plus Single to Pent stacks enable precise depth control across site constraints.

Is this system suitable for rainwater harvesting?

Yes. Use the detention/retention configuration with a pump well, filtration, and disinfection as required by local regulations.

Project Gallery — Underground Stormwater Storage Examples

Real-world installation examples of modular geocellular systems for stormwater detention,infiltration,and reuse.

Large scale underground stormwater detention basin installation for commercial site

Wrapping modular infiltration tanks with non-woven geotextile fabric

Assembling modular stormwater storage units for residential drainage

Underground water retention system installation for flood mitigation

HS-20 rated stormwater modules installed under roadway infrastructure

Finished underground stormwater tank system ready for backfill

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