Changes

#* 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.  

#* 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 maximum depth of water in the facility, 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].

===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 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)

{| class="wikitable"

{| class="wikitable"