Difference between revisions of "Design infiltration rate"

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This article discusses the determination of a suitable infiltration rate to describe the native soils surrounding a proposed infiltration practice. It does not relate to the hydraulic condcutivity or permeability of filter media or planting media used within relevant BMPs.
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The design infiltration rate (''f''') is used in all sizing calculations for [[bioretention]] and [[bioswales]], [[dry ponds]], [[infiltration trenches]] and [[infiltration chambers|chambers]], and [[exfiltration trenches]]. It is related to, but not synonymous with 'permeability', 'field hydraulic conductivity' (''K<sub>fc</sub>''), or 'saturated hydraulic conductivity' (''K<sub>sat</sub>''). Before application a safety correction factor (''SCF'') is incorporated into the figure, depending upon the source of the raw data, and the risk of failure of the finished practice.
The design infiltration rate (''f''') is used in all sizing calculations for [[bioretention]] and [[bioswales]], [[dry ponds]], [[infiltration trenches]] and [[infiltration chambers|chambers]], and [[exfiltration trenches]]. It is related to, but not synonymous with 'permeability', 'field hydraulic conductivity' (''K<sub>fc</sub>''), or 'saturated hydraulic conductivity' (''K<sub>sat</sub>''). Before application a safety correction factor (''SCF'') is incorporated into the figure, depending upon the source of the raw data, and the risk of failure of the finished practice.


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! On site testing methods
! On site testing methods
! Off site testing methods
! Off site testing methods
! '''Unacceptable methods'''
|-
|-
|  
|  
*Guelph permeameter
*Guelph permeameter
*Double ring infiltrometer
*Cased borehole (percolation test)
|-
|  
|  
*[[Grain size analysis]] (Hazen)
*[[Grain size analysis]] (Hazen)
|-
|
*Single ring infiltrometer
*Soil textural classification 
|}
|}



Revision as of 14:25, 8 March 2018

This article discusses the determination of a suitable infiltration rate to describe the native soils surrounding a proposed infiltration practice. It does not relate to the hydraulic condcutivity or permeability of filter media or planting media used within relevant BMPs.

The design infiltration rate (f') is used in all sizing calculations for bioretention and bioswales, dry ponds, infiltration trenches and chambers, and exfiltration trenches. It is related to, but not synonymous with 'permeability', 'field hydraulic conductivity' (Kfc), or 'saturated hydraulic conductivity' (Ksat). Before application a safety correction factor (SCF) is incorporated into the figure, depending upon the source of the raw data, and the risk of failure of the finished practice.

It is highly recommended that testing be conducted on site.

Caption: example table
On site testing methods Off site testing methods Unacceptable methods
  • Guelph permeameter
  • Double ring infiltrometer
  • Cased borehole (percolation test)
  • Single ring infiltrometer
  • Soil textural classification

Planning for testing[edit]

Background Evaluation[edit]

Prior to performing testing and developing a detailed site plan, existing site conditions should be inventoried and mapped including, but not limited to:

  • Surficial geology and underlying stratigraphy;
  • Watercourses (perennial and intermittent), water bodies, wetlands and floodplains;
  • Small headwater drainage features;
  • Topography, slope, and drainage patterns;
  • Existing land cover and land use;
  • Natural heritage conservation areas; and
  • Other man-made features or conditions that may impact design such as existing nearby structures (buildings, infrastructure, etc.).

A sketch plan or preliminary layout plan for the proposed development should be evaluated, including:

  • The preliminary grading plan and areas of cut and fill;
  • The location and water surface elevation of all existing, and location of proposed water supply sources and wells;
  • The location of all existing and proposed on-site wastewater (septic) systems;
  • The location of other features of note such as utility rights-of-way, water and sewer lines, etc.;
  • Existing data from borehole, well and geophysical testing; and
  • Proposed location of development features (buildings, roads, utilities, etc.).