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). This method is not allowed within areas of fill.

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 is not allowed within areas of fill.

==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 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.  

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

==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 (below) may be used to calculate the soil permeability (K).  

# As the Soil Grain Size Analysis method is only approved for soils with d₁₀ between 0.1 and 2.5 millimeters, the Hazen formula (below) may be used to calculate the soil permeability (K).