Difference between revisions of "Infiltration chambers"

Revision as of 14:03, 6 March 2019

Overview

As their name suggests infiltration chambers work exclusively to infiltrate stormwaterSurface runoff from at-grade surfaces, resulting from rain or snowmelt events.. They are an underground facility and are often used beneath parking lots or playing fields to treat flow routed from other areas.

The fundamental components of an infiltration gallery are:

• Structurally reinforced chambers
• Layers of coarse aggregate to bed the chambers and redistribute water.
• Pipe

System type	Pipe	Vaults	Arched chambers	Crates
Materials	Plastic	Concrete	Plastic/concrete	Plastic
Footprint	Medium	Small	Large	Small
Stackable	Not usually (can be without infiltrationThe slow movement of water into or through a soil or drainage system.Penetration of water through the ground surface.)	Yes	Not usually (can be without infiltrationThe slow movement of water into or through a soil or drainage system.Penetration of water through the ground surface.)	Yes
Onsite assembly	Some	No	Yes	Yes
Void ratioThe void ratio (e) of a mixture is the ratio of the volume of void-space to the volume of solids. It is closely related to the concept of porosity (n) where porosity is the ratio of the volume of void-space to the total or bulk volume of the mixture. e = Volume of voids/Volume of solids = n/(1-n)	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 lower bedding layer of angular stone to permit infiltrationThe slow movement of water into or through a soil or drainage system.Penetration of water through the ground surface., 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 the gallery are then filled with more 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 for most applications. Where this cover is (irrigated) topsoil this can support turf grass. Deeper soil is required to support more complex plants.

Design

Sizing

Infiltration: Sizing and modeling

Modeling

Materials

Chambers

Plastic chambers

Chambers should be compliant with:

• CSA B184 SERIES-11 (R2015) "Polymeric subsurface stormwater management structures".
• ASTM F2418-16a “Standard Specification for Polypropylene (PP) Corrugated Wall Stormwater Collection Chambers”.

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:

• CSA A23.3-14 "Design of concrete structures",
• CSA A23.1-09/A23.2-09 (R2014) "Concrete materials and methods of concrete construction/Test methods and standard practices for concrete", and
• ASTM C858 - 10e1 "Standard Specification for Underground Precast Concrete Utility Structures".

AggregatesA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations.

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 aggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations. to be used to store water for infiltrationThe slow movement of water into or through a soil or drainage system.Penetration of water through the ground surface.. This is usually called 'clear stone' at aggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations. yards.

To see an analysis of Ontario Standard Specifications for granularGravel, or crushed stone of various size gradations (i.e., diameter), used in construction; void forming material used as bedding and runoff storage reservoirs and underdrains in stormwater infiltration practices. materials, see OPSS aggregates.

For advice on decorative surface aggregatesA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations. 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 porosityThe porosity (n) of a mixture is the ratio of the volume of void-space to the total or bulk volume of the mixture. It is closely related to the concept of void ratio (e) where void ratio is the ratio of the volume of void-space to the volume of solids. n = Volume of voids/Total volume of mixture = e/(1+e) of 0.4^[1].

The clean wash to prevent rapid accumulation of finesSoil particles with a diameter less than 0.050 mm. from the aggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations. 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 porosityThe porosity (n) of a mixture is the ratio of the volume of void-space to the total or bulk volume of the mixture. It is closely related to the concept of void ratio (e) where void ratio is the ratio of the volume of void-space to the volume of solids. n = Volume of voids/Total volume of mixture = e/(1+e)). PorosityThe porosity (n) of a mixture is the ratio of the volume of void-space to the total or bulk volume of the mixture. It is closely related to the concept of void ratio (e) where void ratio is the ratio of the volume of void-space to the volume of solids. n = Volume of voids/Total volume of mixture = e/(1+e) 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 aggregatesA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations. are maintained by ASTM D2940

• 

  The highest porosityThe porosity (n) of a mixture is the ratio of the volume of void-space to the total or bulk volume of the mixture. It is closely related to the concept of void ratio (e) where void ratio is the ratio of the volume of void-space to the volume of solids. n = Volume of voids/Total volume of mixture = e/(1+e) is found in uniformly graded aggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations., as there are no smaller particles to occupy the inter-particle pores. ^[2]
• 

  Higher permeability is found in larger, angular, uniformly graded aggregateA broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations.. This is due to larger pore sizes and lower tortuosity. ^[2]

Other

• Geotextiles
• Pipes

Construction

Construction

Gallery

• 

  Infiltration chambers being installed.

• 

  Chamber systems can be very large, both in terms of depth and footprint...

• 

  ...or very small as this residential soakawayAn underground water storage reservoir into which stormwater is directed and allowed to percolate into the underlying native subsoil.An excavated area lined with geotextile filter cloth and filled with clean granular stone or other void forming material, that receives runoff and allow it to infiltrate into the native soil; can also be referred to as infiltration galleries, French drains, dry wells or soakaway pits./dry well.

• 

  Parking lot stormwater detentionThe temporary storage of stormwater to control discharge rates, and allow for sedimentation. system, partially installed. Photo credit: Arbitrarily0

• 

  Contractors construct an underground soakawayAn underground water storage reservoir into which stormwater is directed and allowed to percolate into the underlying native subsoil.An excavated area lined with geotextile filter cloth and filled with clean granular stone or other void forming material, that receives runoff and allow it to infiltrate into the native soil; can also be referred to as infiltration galleries, French drains, dry wells or soakaway pits. on the runway extension of Taxiway Alpha as shown here Oct. 5, 2012, at RAF Mildenhall, England. Photo credit: Karen Abeyasekere

• 

  Infiltration chambers being installed.

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

• ADS chambers design tool
• Armtec
• Echelon
• Cultec
• Nilex
• Triton

Concrete chambers

• Stormtrap