Flow•Hold•Infil: Integrated Subsurface Stormwater Management Systems

Maximize land value with invisible, heavy-duty underground infrastructure. Our traffic-rated systems are engineered for global infiltration, detention, and OSD compliance.

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Core System Specifications

95–97%

Effective void ratio

200–800 kN/m²

Module Strength (Traffic Load)

DN100–800

Pipe Connections

H20–H25

AASHTO Load Rating

0.30–1.50 m

Typical Cover Depth

2–3×

Storage Capacity (vs Stone Trench)

System Flow Sequence

Pre-Treatment: Initial device (e.g., Aqua StormFilter or sumped inlet) removes pollutants, protecting the core system.

Application Layer Choice: Water is routed based on depth and use case:

Shallow Layer: Utilizes products like Integrated Shallow Geocellular Solution for rapid surface runoff interception and sub-grade drainage.
High-Volume Subsurface System: The primary structure for engineered capacity and load is chosen based on required geometry:

Primary Structure Selection:

Geocellular Tanks: (Best for H25 Load / Deep Burial / Modular, irregular plots)
Stormwater Modules:(Best for High-void crates / Scalable stacks/half-layers)
Stormwater Chambers: (Best for Low Profile Sites / Row geometry for corridors)

Functional Layering & Infiltration:

Wrap with Geotextile for infiltration basins (groundwater recharge)
Wrap with Geomembrane for watertight detention tanks.

Discharge & Overflow Control:

Controlled Release (Detention/Retention): Lined systems use orifice/vortex control to regulate outflow, enabling flood mitigation or rainwater harvesting.
Emergency Bypass (1% AEP Compliance): Defined overflow systems ensure flows exceeding the 1% Annual Exceedance Probability (AEP) design standard (100-year storm) are safely conveyed away from critical infrastructure.

Core Components of the F•H•I System

Heavy-duty modular geocellular tanks for deep underground stormwater detention

Modular Geocellular Tanks (Heavy-Duty)

High-strength (HS-25) structural tanks for heavy traffic areas, airports, and deep underground attenuation.

High-void stormwater modules for shallow infiltration dry wells and LID

Stormwater Modules (High-Void)

High-density modular crates for deep burial and urban OSD projects. 97% void ratio for maximum storage.

Open-bottom leaching chambers for septic drain fields and linear drainage

Leaching Chambers (Open-Bottom)

Open-bottom arch chambers for large-scale infiltration and septic leach fields. Cost-effective and inspectable.

Aspect	Geocellular Tanks	Geocellular Modules	Stormwater Chamber
Primary Role	High-Capacity Detention/Storage	High-Efficiency Infiltration/Attenuation	Low-Profile, High-Flow Rate
Structural / Load	H25 Heavy-Duty (Up to 800 Kn/m²)	H-20/HS-20 Medium-Duty (Up to 600 Kn/m²)	H-20/HS-20 Medium-Duty (Up to 600 Kn/m²)
Ideal Application	Heavy Traffic (Truck Lanes, Ports)	Parking Lots / Landscaped Areas	Linear Projects / Depth-Restricted Sites
Geometry / Flexibility	High Flexibility (Irregular Plots)	High Scalability (Multi-Layer Stacks)	Row Geometry (Corridors)
Key Value Summary	Extends Heavy-Duty Pavement Life	Provides Sustainable Groundwater Recharge	Reduces Excavation Depth & Costs

Pretreatment filter unit reducing sediment and hydrocarbon load

Aqua StormFilter

Cartridge/basket filtration upstream of the shallow raft to capture silt and hydrocarbons.

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Geomembrane

Creates detention zones; use welded seams and protection layers per specification.

Drainage cell panels and perforated pipe for underdrain and venting

Geotextile

Filter/separator enabling infiltration while controlling fines (select weight & AOS by soil).

Access manholes and inspection points for operation and maintenance

SN8 Pipe

Outlet conveyance or bypass; connect via shallow inspection boxes with throttled discharge.

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Quick Selection Guide: Which System Do You Need?

Feature	Modular Geocellular Tanks	Stormwater Modules	Leaching Chambers
Primary Function	Large Volume Detention (Hold)	Efficient Infiltration (Infil)	Septic & Linear Drainage (Flow)
Best Application	Commercial Parking / Heavy Traffic	LID Swales / Residential Dry Wells	Septic Leach Fields / Roadside
Load Rating	AASHTO HS-25 (Heaviest)	AASHTO HS-20	AASHTO H-20
Void Space	95%	97%	100% (Open Interior)
Cover Depth	Deep Burial Capable (up to 3m+)	Shallow to Medium	Shallow to Medium
Maintenance	Inspect via Ports / Jetting	Inspect via Ports	Isolator Row (Easy Clean)

Applications

Underground detention tanks under commercial parking lot

Parking Lots

Maximize parking revenue by moving storage underground. H-20/HS-25 rated for heavy commercial traffic

Roadside stormwater drainage chambers for highway runoff

Roads & Streets

Linear drainage for highway corridors. Reduces CSO (Sewer Overflow) by capturing runoff right at the curb.

Heavy-duty infiltration system for logistics yard drainage

Logistics & Yards

Engineered for heavy industrial loads. Manages massive roof runoff from warehouses and distribution centers.

Shallow LID stormwater storage under urban plaza paving

Urban Hardscapes

Shallow-cover solutions for plazas and podiums. Supports permeable paving and tree pit irrigation (LID).

Large scale rainwater harvesting tank for university campus

Campuses & Healthcare

Create quiet, invisible detention zones under green spaces. scalable for phased campus expansions.

Subsurface drainage modules under sports field

Sports & Recreation

Keep playing fields dry. Rapid infiltration systems installed under turf or tracks to prevent waterlogging.

Backyard dry well and septic drain field installation

Residential Dry Wells

DIY-friendly soakaways. Simple, lightweight modules to manage roof gutter runoff and prevent soggy backyards.

Transit & Park-and-Ride

High-efficiency drainage for transport hubs. Connects easily to municipal storm sewers with flow control.

6-Step Installation Overview

1) Site Prep & Safety

Verify utility locations and survey data. Confirm seasonal groundwater tables (GWT) and prepare the layout plan.

2) Excavation

Excavate to design level. Remove soft spots and proof-roll the subgrade. Keep the pit dry (dewatering) during installation.

3) Base Preparation

Lay a level base of clean, angular crushed stone (6″ / 150mm min). Compact to specification to ensure a stable foundation for the tanks.

4) Assembly & Wrapping

Infiltration: Wrap units in non-woven geotextile.
Detention: Seal with geomembrane liner + protective fleece.
Assemble modules/chambers according to the interlocking diagram.

5)Connections & Accessories

nstall inlet/outlet manifolds and inspection risers. Fit any flow control devices (orifice plates) or pre-treatment isolator rows.

6) Backfill & Finish

Backfill with approved stone in even lifts. Do not drive directly on the units until full cover depth is achieved. Reinstate pavement or landscaping.

FAQ — Engineering & procurement

What is the difference between Infiltration (Soakaway) and Attenuation (Detention) systems?

It depends on your site’s hydrology and local discharge regulations.

Infiltration (Soakaway): The system is wrapped in a permeable non-woven geotextile. This allows collected runoff to percolate slowly back into the surrounding soil, recharging the groundwater. Ideal for LID (Low Impact Development) and complying with “Zero Discharge” mandates.

Attenuation (Detention): The system is sealed with a watertight geomembrane (impermeable liner). It holds peak storm volumes and releases them at a controlled rate to the municipal sewer. This is essential for flood mitigation and meeting SuDS (Sustainable Drainage Systems) flow control limits.

Can these geocellular modules support heavy traffic loads (Trucks/HGVs)?

Yes. Our modular systems are engineered for high structural integrity. They are compatible with major international loading standards, including AASHTO H-20/HS-25 (USA) and equivalent Eurocode traffic loads. When installed with the correct cover depth and compacted backfill, they are suitable for use under commercial parking lots, fire access roads, and logistics yards globally.

How do these plastic crates compare to traditional gravel trenches or concrete tanks?

They offer superior efficiency and lower carbon footprint.

Void Ratio: Gravel only offers ~40% storage capacity, whereas our polypropylene modules provide 95% void space. You store 2.5x more water in the same excavation footprint.

Installation: Unlike heavy concrete culverts requiring cranes, our lightweight stackable crates can be hand-assembled. This reduces transport costs, machinery usage, and on-site labor time, making them a preferred choice for green building projects.

Are these systems suitable for high groundwater tables or shallow bedrock?

Yes, the modular design is fully adaptable. For sites with vertical constraints (high water table or rock), you can configure the system as a “flat” single-layer structure. This spreads the storage volume horizontally, keeping the base above the groundwater level while ensuring sufficient earth cover for surface traffic.

Can I use this underground system for Rainwater Harvesting (Reuse)?

Absolutely. By encapsulating the tank in a welded geomembrane liner, the system functions as a high-capacity underground cistern. It can be integrated with pumps and filtration units to harvest non-potable water for landscape irrigation, toilet flushing, or industrial cooling—helping projects achieve BREEAM, LEED, or Green Star credits.

What maintenance is required to ensure long-term performance?

Pre-treatment and sediment management are critical. We recommend installing upstream silt traps or hydrodynamic separators. Inside the tank, an “Isolator Row” (or sediment channel) wrapped in geotextile should be included. This concentrates debris for easy extraction via inspection risers using standard high-pressure jetting (Jet-Vac), preventing the main infiltration field from clogging.

Do your products meet international environmental standards?

Yes. Our modules are manufactured from 100% recycled polypropylene (PP), which is chemically resistant to naturally occurring soil salts, acids, and alkalis. The material is robust, durable, and fully recyclable at the end of its life, supporting circular economy principles in construction.

How do I calculate the required number of modules for my project?

We provide engineering support. Simply provide your required storage volume (m³ or ft³) based on your local rainfall data and catchment area. We will calculate the optimal tank layout (length x width x depth) and provide a comprehensive material takeoff, including the number of crates, connector clips, and the total area of geotextile/geomembrane required.

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