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LID SWM Planning and Design Guide β

Infiltration chambers

Revision as of 22:24, 21 April 2020 by Dean Young (talk | contribs) (Planning Considerations)


As their name suggests infiltration chambers work exclusively to infiltrate stormwater. They are an underground facility and are often used beneath parking lots or playing fields to treat flow routed from other areas.

Infiltration chambers are an ideal technology for:

  • Installing below any type of surface or landscape
  • Receiving and infiltrating large volumes of water

The fundamental components of an infiltration gallery are:

  • Structurally reinforced chambers
  • Coarse aggregate to embed the chambers and temporarily store water.
  • Pipe
System type Pipe Vaults Arched chambers Crates
SWM Pipe.jpg SWM Vaults.jpg SWM Arches.jpg SWM Crates.jpg
Materials Plastic Concrete Plastic/concrete Plastic
Footprint Medium Small Large Small
Stackable Not usually (can be without infiltration) Yes Not usually (can be without infiltration) Yes
Onsite assembly Some No Yes Yes
Void ratio 60-65% 75-85% 50-65% 95%
Maintenance access Moderate Excellent Moderate Difficult
Standard strength H-20 H-25 H-20 H20-HS25

Planning Considerations

Both modular systems require a bedding of angular clear stone to permit infiltration, and provide a foundation for the installation:

  • Plastic modules usually have a parabolic shape to resist the load above. The spaces between the rows of modules are filled with clear stone to support the overlying infrastructure.
  • Concrete modules are often box shaped and can, in some circumstances, be employed without any additional cover. However, a minimum of 20 cm cover is recommended for most applications. Where this cover is planting soil this can support turf grass. Greater planting soil depths are required to support more deeply rooting plants like perennials and shrubs (45 to 60 cm) and trees (85 to 100 cm).




Plastic chambers

Chambers should be compliant with:

Allowable loads for the chambers must be determined in accordance with ASTM F2787-13 “Standard Practice for Structural Design of Thermoplastic Corrugated Wall Stormwater Collection Chambers”.

Concrete vaults

Concrete vault-type systems should be compliant with:


Note the uniform size and angularity of this clear stone sample. Note also that the fragments all appear to have a film of fine particles adhering; this material would be improved by being washed prior to use.

This article gives recommendations for aggregate to be used to store water for infiltration. This is usually called 'clear stone' at aggregate yards.

To see an analysis of Ontario Standard Specifications for granular materials, see OPSS aggregates.

For advice on decorative surface aggregates see Stone

Gravel used for underdrains in bioretention, infiltration trenches and chambers, and exfiltration trenches should be 20 or 50 mm, uniformly-graded, clean (maximum wash loss of 0.5%), crushed angular stone that has a porosity of 0.4[1].

The clean wash to prevent rapid accumulation of fines from the aggregate particles in the base of the reservoir. The uniform grading and the angularity are important to maintain pore throats and clear voids between particles. (i.e. achieve the porosity). Porosity and permeability are directly influenced by the size, gradation and angularity of the particles [2]. See jar test for on-site verification testing protocols.

Gravel with structural requirements should also meet the following criteria:

  • Minimum durability index of 35
  • Maximum abrasion of 10% for 100 revolutions and maximum of 50% for 500 revolutions

Standard specifications for the gradation of aggregates are maintained by ASTM D2940




External links

In our effort to make this guide as functional as possible, we have decided to include proprietary systems and links to manufacturers websites.
Inclusion of such links does not constitute endorsement by the Sustainable Technologies Evaluation Program.
Lists are ordered alphabetically; link updates are welcomed using the form below.

Plastic chambers

Concrete chambers

  1. Porosity of Structural Backfill, Tech Sheet #1, Stormtech, Nov 2012, accessed 16 October 2017
  2. 2.0 2.1 2.2 Judge, Aaron, "Measurement of the Hydraulic Conductivity of Gravels Using a Laboratory Permeameter and Silty Sands Using Field Testing with Observation Wells" (2013). Dissertations. 746.