Changes

It does not relate to the hydraulic conductivity or permeability of filter media or planting media used within vegetated BMPs.  

It does not relate to the hydraulic conductivity or permeability of filter media or planting media used within vegetated BMPs.  

{{TOClimit|2}}

{{TOClimit|2}}

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_fc''), or 'saturated hydraulic conductivity' (''K_sat''). 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 always synonymous with 'permeability', 'field hydraulic conductivity' (''K_fc''), or 'saturated hydraulic conductivity' (''K_sat''). 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.

{{textbox|It is highly recommended that testing be conducted on site.}}

{{textbox|It is highly recommended that testing be conducted on site.}}

|

|

*[[Permeameter]]

*[[Permeameter]]

*Double ring infiltrometer

*[[Double ring infiltrometer]]

*[[Percolation test]]

*[[Percolation test]]

|

|

*[[Grain size analysis]] (Hazen)

*[[Grain size analysis]] (Hazen method)

|

|

*Single ring infiltrometer

*Single ring infiltrometer

*Soil textural classification   

*Soil textural classification   

|}

|}

==Safety correction==

==Safety correction==

The measured or calculated infiltration rate must be divided by a value between 2 and 3 before use in design<ref>Design criteria for infiltration. (2018, February 14). Minnesota Stormwater Manual, . Retrieved 00:16, March 14, 2018 from https://stormwater.pca.state.mn.us/index.php?title=Design_criteria_for_infiltration&oldid=35583.</ref>  

To apply conservatism, the measured or calculated infiltration rate may be divided by a value between 2 and 3 before use in design calcualtions<ref>Design criteria for infiltration. (2018, February 14). Minnesota Stormwater Manual, . Retrieved 00:16, March 14, 2018 from https://stormwater.pca.state.mn.us/index.php?title=Design_criteria_for_infiltration&oldid=35583.</ref>  

{| class="wikitable"

{| class="wikitable"

|+ Selecting a safety factor

|+ Selecting a safety factor

|-

|-

! 2

! Lower value (closer to 2)

! 3

! Higher value (closer to 3)

|-

|-

|Catchment < 100 m²

|Catchment < 100 m²

|Double ring infiltrometer test on site, or grain size analysis used <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>  

|Double ring infiltrometer test on site, or grain size analysis used <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>  

|-

|-

|Loamy or sandy soil

|Loamy or sandy soil texture

|Clayey soil<ref>CRC for Water Sensitive Cities. (2015). Adoption Guidelines for Stormwater Biofiltration Systems: Appendix C - Guidelines for filter media in stormwater biofiltration systems.</ref>

|Clayey soil texture<ref>CRC for Water Sensitive Cities. (2015). Adoption Guidelines for Stormwater Biofiltration Systems: Appendix C - Guidelines for filter media in stormwater biofiltration systems.</ref>

|}

|}

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

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;

#Surficial geology and underlying stratigraphy;

#Watercourses (perennial and intermittent), water bodies, wetlands and floodplains;

#Watercourses (perennial and intermittent), waterbodies, wetlands and floodplains;

#Small headwater drainage features;

#Small headwater drainage features;

#Topography, slope, and drainage patterns;

#Topography, slope, and drainage patterns;

! BMP footprint (m²)

! BMP footprint (m²)

! Test pit  

! Test pit  

! Bore hole

! Borehole

|-

|-

| < 50 || 1 || 1

| < 50 || 1 || 1

|-

|-

|rowspan = 2| 50 – 900 <br> (alternative)|| 1 || 2

|rowspan = 2| 50 – 900 || 1 || 2

|-

|-

| 2 || 0

| 2 || 0

|-

|-

| rowspan = 2|> 900 <br> (alternative)|| 1 every 450 m² || 2 every 450 m²

| rowspan = 2|> 900 || 1 every 450 m² || 2 every 450 m²

|-

|-

| 2 every 450 m² || 0

| 2 every 450 m² || 0

|}

|}

* Tests must be conducted within 10 m of the infiltration practice footprint area.  

* Tests must be conducted within 10 metres of the infiltration practice footprint area.

* Where multiple test are carried out, they should be planned equidistant and mapped accordingly.  

* Tests should be performed within 48 hours of a rain event, when the soil is already near, or at field capacity.

* Make a minimum of seven (7) measurements (i.e. tests) for each test location (i.e., each test pit or borehole).

* An additional round of tests should be conducted at 1.5 metres depth below the proposed bottom elevation of the practice if there is significant variation in geologic formation, soil texture or bulk density compared to conditions at the proposed bottom elevation.<br>

* To calculate the median infiltration rate of the native soil at the depth tested, discard the highest and lowest values obtained from each test location and calculate the median from the remaining measurements.  

'''The recommendations above are guidelines'''  

'''The recommendations above are guidelines'''  

Additional tests should be conducted if local conditions indicate significant variability in soil types, geology, water table levels, depth and type of bedrock, topography, etc. Similarly, uniform site conditions may indicate that fewer test pits are required. Excessive testing and disturbance of the site prior to construction is not recommended.<ref>Christopher B. Burke Engineering LLC. (2009). Soil Infiltration Testing Protocol SOIL INFILTRATION TESTING PROTOCOL Purpose of this Protocol Who Should Conduct Testing. Retrieved from https://www.in.gov/ocra/files/Appendix%20F%20-%20Soil%20Infiltration%20Testing%20Protocol.pdf</ref>

Keep in mind that excessive testing and disturbance of the site prior to construction is not recommended.<ref>Christopher B. Burke Engineering LLC. (2009). Soil Infiltration Testing Protocol SOIL INFILTRATION TESTING PROTOCOL Purpose of this Protocol Who Should Conduct Testing. Retrieved from https://www.in.gov/ocra/files/Appendix%20F%20-%20Soil%20Infiltration%20Testing%20Protocol.pdf</ref>

----

----

[[Category:Infiltration]]

[[Category:Infiltration]]