Changes

This method of determining [[design infiltration rate]] is only approved for sandy native soils with d₁₀ between 0.1 - 2.5 mm (i.e. soils to which the Hazen formula is applicable)<ref>San Francisco Public Utilities Commission. (2017). Determination of Design Infiltration Rates for the Sizing of Infiltration‐based Green Infrastructure Facilities. Retrieved from http://sfwater.org/modules/showdocument.aspx?documentid=9681</ref>. This method must not be applied within areas of fill.

This method of determining [[design infiltration rate]] is only suitable for coarse-textured native soils with d₁₀ between 0.1 - 2.5 mm (i.e. soils to which the Hazen formula is applicable)<ref>San Francisco Public Utilities Commission. (2017). Determination of Design Infiltration Rates for the Sizing of Infiltration‐based Green Infrastructure Facilities. Retrieved from http://sfwater.org/modules/showdocument.aspx?documentid=9681</ref>.  

 

'''This method shall not be applied within areas of fill or in regions where hydraulic conductivity is controlled by vertical fractures in the soil matrix.'''

==Procedure==

==Procedure==

# Collect [[soil]] samples for each defined soil layer below the bottom of the proposed infiltration facility. Layers must be evaluated to the following depths, depending upon facility type:

# Collect soil samples for each defined soil layer below the bottom of the proposed infiltration facility. Layers must be evaluated to the following depths, depending upon facility type:

#* For [[bioretention]] facilities, analyze each defined layer below the proposed facility bottom to a depth of at least 3 times the maximum ponding depth, but not less than 1 m.  

#* For [[bioretention]] facilities, analyze each defined layer below the proposed facility bottom to a depth of at least 3 times the maximum ponding depth, but not less than 1 m.  

#* For [[permeable paving]], analyze each defined layer below the proposed facility bottom to a depth of at least 3 times the maximum depth of water within the base course, but not less than 1 m.  

#* For [[permeable pavements]], analyze each defined layer below the proposed facility bottom to a depth of at least 3 times the maximum depth of water within the base course, but not less than 1 m.  

#* For other types of infiltration facilities serving drainage areas up to 4 Ha, analyze each defined layer below the proposed facility bottom to a depth of at least 2.5 times the maximum depth of water in the facility, but not less than 3 m.  

#* For other types of infiltration facilities serving drainage areas up to 4 Ha, analyze each defined layer below the proposed facility bottom to a depth of at least 2.5 times the water storage reservoir depth, but not less than 3 m.  

# Submit the soil samples for laboratory testing of particle size analysis according to [https://www.astm.org/Standards/D422.htm ASTM D422].

# Submit the soil samples to a certified soil testing laboratory for grain-size, or particle-size distribution analysis according to [https://www.astm.org/Standards/D422.htm ASTM D422] Standard Test Method for Particle-size Analysis of Soils.

===Data Analysis===

===Data Analysis===

As the Soil Grain Size Analysis method is only approved for soils with d₁₀ between 0.1 and 2.5 millimeters, the Hazen formula <ref>Hazen, A. (1893). Some physical properties of sand and gravel with special reference to the use in filtration. 4th Annual Report, State Board of Health, Boston.</ref> may be used to calculate the soil permeability. The calculated soil permeability shall be considered to be the measured infiltration rate:

NB:  The Hazen formula method of estimating soil permeability based on grain size distribution analysis is only suitable for coarse-textured soils with d₁₀ between 0.1 and 2.5 millimeters <ref>Hazen, A. (1893). Some physical properties of sand and gravel with special reference to the use in filtration. 4th Annual Report, State Board of Health, Boston.</ref>. The soil permeability value estimated using the Hazen method can be considered to be the measured infiltration rate of the soil, f, in mm/h

<math>K=C\cdot {\left (d_{10}\right )^{2}}</math>

:<math>f=C\cdot {\left (d_{10}\right )^{2}}</math>

{{Plainlist|1=Where:

{{Plainlist|1=Where:

''d₁₀'' = the soil particle diameter for which 10% of all soil particles are finer (smaller) by weight (mm),

*''d₁₀'' = the soil particle diameter for which 10% of all soil particles are finer (smaller) by weight (mm), median value of all samples tested.

''C'' = is a shape factor (see below), and

*''C'' = is a shape factor (see below)}}

''K'' = permeability (mm/hr)}}

{| class="wikitable"

{| class="wikitable"

! colspan =2| Shape factors (C) to yield K in mm/hr

! colspan =2| Shape factors (C) to yield f in mm/h

|-  

|-  

|Very fine to fine sand

|Very fine to fine sand

|}

|}

==Safety Correction Factor==

==Don't forget to apply [[Design infiltration rate#Safety correction| a safety correction factor]] before beginning your sizing calculations==