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Minnesota Stormwater Manual

Difference between revisions of "Design infiltration rates"

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{{alert|The original Manual had two different infiltration rates for B soils (0.3 and 0.6 inches per hour). In spring of 2013 the infiltration rate for all B soils was changed to 0.3 inches per hour. Following a meeting of technical experts on December 16, 2013, a rate of 0.45 inches per hour was established for SM soils.|alert-warning}}
 
  
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<font size=3>'''Design infiltration rates, in inches per hour, for A, B, C, and D soil groups. Corresponding USDA soil classification and Unified soil Classifications are included. Note that A soils have two infiltration rates that are a function of soil texture.*'''</font size><br>
+
{{alert|The table for design infiltration rates has been modified. Field testing is recommended for gravelly soils (HSG A; GW and GP soils; gravel and sandy gravel soils). If field-measured soil infiltration rates exceed 8.3 inches per hour, the Construction Stormwater permit requires the soils be amended. Guidance on amending these soils [[Guidance for amending soils with rapid or high infiltration rates|can be found here]].|alert-warning}}
 +
 
 +
<font size=3>'''Design infiltration rates, in inches per hour, for A, B, C, and D soil groups. Corresponding USDA soil classification and Unified soil Classifications are included. Note that A and B soils have two infiltration rates that are a function of soil texture.*'''<br>
 +
'''The values shown in this table are for uncompacted soils. [https://stormwater.pca.state.mn.us/index.php?title=General_relationship_of_soil_bulk_density_to_root_growth_based_on_soil_texture This table] can be used as a guide to determine if a soil is compacted. For information on alleviating compacted soils, [https://stormwater.pca.state.mn.us/index.php/Alleviating_compaction_from_construction_activities link here]. If a soil is compacted, reduce the soil infiltration rate by one level (e.g. for a compacted B(SM) use the infiltration rate for a B(MH) soil).'''</font size><br>
 
Link to this [[Design infiltration rates|table]]
 
Link to this [[Design infiltration rates|table]]
 
<table class="sortable"><tr>
 
<table class="sortable"><tr>
 
<th>Hydrologic soil group</th>
 
<th>Hydrologic soil group</th>
 
<th>Infiltration rate (inches/hour)</th>
 
<th>Infiltration rate (inches/hour)</th>
 +
<th>Infiltration rate (centimeters/hour)</th>
 +
<th>Soil textures</th>
 +
<th>Corresponding Unified Soil Classification<sup>Superscript text</sup></th>
 +
</tr>
 +
<tr>
 +
<tr>
 +
<td rowspan="3"><center>A</center></td>
 +
<td colspan="2">Although a value of 1.63 inches per hour (4.14 centimeters per hour) may be used, it is '''''Highly recommended''''' that you conduct field infiltration tests or amend soils.<sup>b</sup> See [[Guidance for amending soils with rapid or high infiltration rates]] and [https://stormwater.pca.state.mn.us/index.php?title=Determining_soil_infiltration_rates Determining soil infiltration rates].</td>
 +
<td>
 +
gravel<br>
 +
sandy gravel
 +
</td>
 +
<td>GW - Well-graded gravels, fine to coarse gravel<br>
 +
GP - Poorly graded gravel</td>
 +
</tr>
 +
<tr>
 +
<td>1.63<sup>a</sup></td>
 +
<td>4.14</td>
 +
<td>
 +
silty gravels<br>
 +
gravelly sands<br>
 +
sand
 +
</td>
 +
<td>
 +
GM - Silty gravel<br>
 +
SW - Well-graded sand, fine to coarse sand<br>
 +
</td>
 +
</tr>
 +
<tr>
 +
<td>0.8</td>
 +
<td>2.03</td>
 +
<td>
 +
sand<br>
 +
loamy sand<br>
 +
sandy loam
 +
</td>
 +
<td>
 +
SP - Poorly graded sand
 +
</td>
 +
</tr>
 +
<tr>
 +
<td rowspan="2"><center>B</center></td>
 +
<td>0.45</td>
 +
<td>1.14</td>
 +
<td>silty sands</td>
 +
<td>SM - Silty sand</td>
 +
</tr>
 +
<tr>
 +
<td>0.3</td>
 +
<td>0.76</td>
 +
<td>loam, silt loam</td>
 +
<td>MH - Elastic silt</td>
 +
</tr>
 +
<tr>
 +
<td><center>C</center></td>
 +
<td>0.2</td>
 +
<td>0.51</td>
 +
<td>Sandy clay loam, silts</td>
 +
<td>ML - Silt</td>
 +
</tr>
 +
<tr>
 +
<td><center>D</center></td>
 +
<td>0.06</td>
 +
<td>0.15</td>
 +
<td>
 +
clay loam<br>
 +
silty clay loam<br>
 +
sandy clay<br>
 +
silty clay<br>
 +
clay
 +
</td>
 +
<td>
 +
GC - Clayey gravel<br>
 +
SC - Clayey sand<br>
 +
CL - Lean clay<br>
 +
OL - Organic silt<br>
 +
CH - Fat clay<br>
 +
OH - Organic clay, organic silt</td>
 +
</tr>
 +
</table>
 +
<font size=1><sup>1</sup>For Unified Soil Classification, we show the basic text for each soil type. For more detailed descriptions, see the following links: [https://www.globalsecurity.org/military/library/policy/army/fm/5-472/apb.pdf The Unified Soil Classification System], [https://dot.ca.gov/-/media/dot-media/programs/maintenance/documents/office-of-concrete-pavement/pavement-foundations/uscs-a11y.pdf CALIFORNIA DEPARTMENT OF TRANSPORTATION (CALTRANS) UNIFIED SOIL CLASSIFICATION SYSTEM]<br>
 +
*NOTE that this table has been updated from Version 2.X of the Minnesota Stormwater Manual. The higher infiltration rate for B soils was decreased from 0.6 inches per hour to 0.45 inches per hour and a value of 0.06 is used for D soils (instead of < 0.2 in/hr).<br>
 +
Source: Thirty guidance manuals and many other stormwater references were reviewed to compile recommended infiltration rates. All of these sources use the following studies as the basis for their recommended infiltration rates: (1) Rawls, Brakensiek and Saxton (1982); (2) Rawls, Gimenez and Grossman (1998); (3) Bouwer and Rice (1984); and (4) Urban Hydrology for Small Watersheds (NRCS). SWWD, 2005, provides field documented data that supports the proposed infiltration rates. ([[References|view reference list]])<br>
 +
<sup>a</sup>This rate is consistent with the infiltration rate provided for the lower end of the Hydrologic Soil Group A soils in the [https://dnr.wi.gov/topic/Stormwater/standards/postconst_standards.html Stormwater post-construction technical standards, Wisconsin Department of Natural Resources Conservation Practice Standards].<br>
 +
<sup>b</sup>The infiltration rates in this table are recommended values for sizing stormwater practices based on information collected from soil borings or pits. A group of technical experts developed the table for the original Minnesota Stormwater Manual in 2005. Additional technical review resulted in an update to the table in 2011. Over the past 5 to 7 years, several government agencies revised or developed guidance for designing infiltration practices. Several states now require or strongly recommend field infiltration tests. Examples include North Carolina, New York, Georgia, and the City of Philadelphia. The states of Washington and Maine strongly recommend field testing for infiltration rates, but both states allow grain size analyses in the determination of infiltration rates. The Minnesota Stormwater Manual strongly recommends field testing for infiltration rate, but allows information from soil borings or pits to be used in determining infiltration rate. A literature review suggests the values in the [https://stormwater.pca.state.mn.us/index.php?title=Design_infiltration_rates design infiltration rate table] are not appropriate for soils with very high infiltration rates. This includes gravels, sandy gravels, and uniformly graded sands. Infiltration rates for these geologic materials are higher than indicated in the table.<br>
 +
References: Clapp, R. B., and George M. Hornberger. 1978. Empirical equations for some soil hydraulic properties. Water Resources Research. 14:4:601–604; Moynihan, K., and Vasconcelos, J. 2014. [https://www.chijournal.org/Journals/PDF/C372 SWMM Modeling of a Rural Watershed in the Lower Coastal Plains of the United States]. Journal of Water Management Modeling. C372; Rawls, W.J., D. Gimenez, and R. Grossman. 1998. Use of soil texture, bulk density and slope of the water retention curve to predict saturated hydraulic conductivity Transactions of the ASAE. VOL. 41(4): 983-988; Saxton, K.E., and W. J. Rawls. 2005. Soil Water Characteristic Estimates by Texture and Organic Matter for Hydrologic Solutions. Soil Science Society of America Journal. 70:5:1569-1578.
 +
</font size>
 +
 +
<!--{{alert|The original Manual had two different infiltration rates for B soils (0.3 and 0.6 inches per hour). In spring of 2013 the infiltration rate for all B soils was changed to 0.3 inches per hour. Following a meeting of technical experts on December 16, 2013, a rate of 0.45 inches per hour was established for SM soils.|alert-warning}}
 +
 +
<font size=3>'''Design infiltration rates, in inches per hour, for A, B, C, and D soil groups. Corresponding USDA soil classification and Unified soil Classifications are included. Note that A soils have two infiltration rates that are a function of soil texture.*'''
 +
 +
'''The values shown in this table are for uncompacted soils. [https://stormwater.pca.state.mn.us/index.php?title=General_relationship_of_soil_bulk_density_to_root_growth_based_on_soil_texture This table] can be used as a guide to determine if a soil is compacted. For information on alleviating compacted soils, [https://stormwater.pca.state.mn.us/index.php/Alleviating_compaction_from_construction_activities link here]. If a soil is compacted, reduce the soil infiltration rate by one level (e.g. for a compacted B(SM) use the infiltration rate for a B(MH) soil).'''
 +
 +
'''It is Highly Recommended that soil borings be extended a minimum of 5 feet below the bottom of the proposed infiltration practice and that the most restrictive soil layer be considered in estimating infiltration rate.'''</font size>
 +
Link to this [[Design infiltration rates|table]]
 +
<table class="sortable"><tr>
 +
<th>Hydrologic soil group</th>
 +
<th>Infiltration rate (inches/hour)</th>
 +
<th>Infiltration rate (centimeters/hour)</th>
 
<th>Soil textures</th>
 
<th>Soil textures</th>
 
<th>Corresponding Unified Soil Classification</th>
 
<th>Corresponding Unified Soil Classification</th>
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<td rowspan="2"><center>A</center></td>
 
<td rowspan="2"><center>A</center></td>
 
<td>1.63<sup>a</sup></td>
 
<td>1.63<sup>a</sup></td>
 +
<td>4.14</td>
 
<td>
 
<td>
 
gravel<br>
 
gravel<br>
Line 25: Line 128:
 
<tr>
 
<tr>
 
<td>0.8</td>
 
<td>0.8</td>
 +
<td>2.03</td>
 
<td>
 
<td>
 
sand<br>
 
sand<br>
Line 37: Line 141:
 
<td rowspan="2"><center>B</center></td>
 
<td rowspan="2"><center>B</center></td>
 
<td>0.45</td>
 
<td>0.45</td>
 +
<td>1.14</td>
 
<td></td>
 
<td></td>
 
<td>SM - silty sands, silty gravelly sands</td>
 
<td>SM - silty sands, silty gravelly sands</td>
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<tr>
 
<tr>
 
<td>0.3</td>
 
<td>0.3</td>
 +
<td>0.76</td>
 
<td>loam, silt loam</td>
 
<td>loam, silt loam</td>
 
<td>MH - micaceous silts, diatomaceous silts, volcanic ash</td>
 
<td>MH - micaceous silts, diatomaceous silts, volcanic ash</td>
Line 48: Line 154:
 
<td><center>C</center></td>
 
<td><center>C</center></td>
 
<td>0.2</td>
 
<td>0.2</td>
 +
<td>0.51</td>
 
<td>Sandy clay loam</td>
 
<td>Sandy clay loam</td>
 
<td>ML - silts, very fine sands, silty or clayey fine sands</td>
 
<td>ML - silts, very fine sands, silty or clayey fine sands</td>
Line 54: Line 161:
 
<td><center>D</center></td>
 
<td><center>D</center></td>
 
<td>0.06</td>
 
<td>0.06</td>
 +
<td>0.15</td>
 
<td>
 
<td>
 
clay loam<br>
 
clay loam<br>
Line 70: Line 178:
 
</tr>
 
</tr>
 
</table>
 
</table>
−
<font size=1>*NOTE that this table has been updated from Version 2.X of the Minnesota Stormwater Manual. There are no longer two different infiltration rates for B soils and a value of 0.06 is used for D soils (instead of < 0.2 in/hr).<br>
+
<font size=1><sup>1</sup> For Unified Soil Classification, we show the basic text for each soil type. For more detailed descriptions, see the following links: [https://www.globalsecurity.org/military/library/policy/army/fm/5-472/apb.pdf The Unified Soil Classification System], [https://dot.ca.gov/-/media/dot-media/programs/maintenance/documents/office-of-concrete-pavement/pavement-foundations/uscs-a11y.pdf CALIFORNIA DEPARTMENT OF TRANSPORTATION (CALTRANS) UNIFIED SOIL CLASSIFICATION SYSTEM]<br>
 +
*NOTE that this table has been updated from Version 2.X of the Minnesota Stormwater Manual. The higher infiltration rate for B soils was decreased from 0.6 inches per hour to 0.45 inches per hour and a value of 0.06 is used for D soils (instead of < 0.2 in/hr).<br>
 
Source: Thirty guidance manuals and many other stormwater references were reviewed to compile recommended infiltration rates. All of these sources use the following studies as the basis for their recommended infiltration rates: (1) Rawls, Brakensiek and Saxton (1982); (2) Rawls, Gimenez and Grossman (1998); (3) Bouwer and Rice (1984); and (4) Urban Hydrology for Small Watersheds (NRCS). SWWD, 2005, provides field documented data that supports the proposed infiltration rates. ([[References|view reference list]])<br>
 
Source: Thirty guidance manuals and many other stormwater references were reviewed to compile recommended infiltration rates. All of these sources use the following studies as the basis for their recommended infiltration rates: (1) Rawls, Brakensiek and Saxton (1982); (2) Rawls, Gimenez and Grossman (1998); (3) Bouwer and Rice (1984); and (4) Urban Hydrology for Small Watersheds (NRCS). SWWD, 2005, provides field documented data that supports the proposed infiltration rates. ([[References|view reference list]])<br>
 
<sup>a</sup>This rate is consistent with the infiltration rate provided for the lower end of the Hydrologic Soil Group A soils in the Wisconsin Department of Natural Resources Conservation Practice Standard: Site Evaluation for Stormwater Infiltration.</font size>
 
<sup>a</sup>This rate is consistent with the infiltration rate provided for the lower end of the Hydrologic Soil Group A soils in the Wisconsin Department of Natural Resources Conservation Practice Standard: Site Evaluation for Stormwater Infiltration.</font size>
  
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<noinclude>[[category:table]]</noinclude>
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-->
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<noinclude>
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[[Category:Level 3 - General information, reference, tables, images, and archives/Tables/Soil and soil properties]]
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[[Category:Level 3 - General information, reference, tables, images, and archives/Tables/Hydrology and geology]]
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[[Category:Level 3 - General information, reference, tables, images, and archives/Tables/Models, modeling, model applications and examples]]
 +
[[Category:Level 2 - Technical and specific topic information/soils and media]]
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</noinclude>

Latest revision as of 15:23, 5 April 2023

Caution: The table for design infiltration rates has been modified. Field testing is recommended for gravelly soils (HSG A; GW and GP soils; gravel and sandy gravel soils). If field-measured soil infiltration rates exceed 8.3 inches per hour, the Construction Stormwater permit requires the soils be amended. Guidance on amending these soils can be found here.

Design infiltration rates, in inches per hour, for A, B, C, and D soil groups. Corresponding USDA soil classification and Unified soil Classifications are included. Note that A and B soils have two infiltration rates that are a function of soil texture.*
The values shown in this table are for uncompacted soils. This table can be used as a guide to determine if a soil is compacted. For information on alleviating compacted soils, link here. If a soil is compacted, reduce the soil infiltration rate by one level (e.g. for a compacted B(SM) use the infiltration rate for a B(MH) soil).
Link to this table

Hydrologic soil group Infiltration rate (inches/hour) Infiltration rate (centimeters/hour) Soil textures Corresponding Unified Soil ClassificationSuperscript text
A
 Although a value of 1.63 inches per hour (4.14 centimeters per hour) may be used, it is Highly recommended that you conduct field infiltration tests or amend soils.b See Guidance for amending soils with rapid or high infiltration rates and Determining soil infiltration rates.

gravel
sandy gravel

GW - Well-graded gravels, fine to coarse gravel
GP - Poorly graded gravel
1.63a 4.14

silty gravels
gravelly sands
sand

GM - Silty gravel
SW - Well-graded sand, fine to coarse sand
0.8 2.03

sand
loamy sand
sandy loam

SP - Poorly graded sand

B
 0.45 1.14 silty sands SM - Silty sand
0.3 0.76 loam, silt loam MH - Elastic silt
C
 0.2 0.51 Sandy clay loam, silts ML - Silt
D
 0.06 0.15

clay loam
silty clay loam
sandy clay
silty clay
clay

GC - Clayey gravel
SC - Clayey sand
CL - Lean clay
OL - Organic silt
CH - Fat clay

OH - Organic clay, organic silt

1For Unified Soil Classification, we show the basic text for each soil type. For more detailed descriptions, see the following links: The Unified Soil Classification System, CALIFORNIA DEPARTMENT OF TRANSPORTATION (CALTRANS) UNIFIED SOIL CLASSIFICATION SYSTEM

  • NOTE that this table has been updated from Version 2.X of the Minnesota Stormwater Manual. The higher infiltration rate for B soils was decreased from 0.6 inches per hour to 0.45 inches per hour and a value of 0.06 is used for D soils (instead of < 0.2 in/hr).

Source: Thirty guidance manuals and many other stormwater references were reviewed to compile recommended infiltration rates. All of these sources use the following studies as the basis for their recommended infiltration rates: (1) Rawls, Brakensiek and Saxton (1982); (2) Rawls, Gimenez and Grossman (1998); (3) Bouwer and Rice (1984); and (4) Urban Hydrology for Small Watersheds (NRCS). SWWD, 2005, provides field documented data that supports the proposed infiltration rates. (view reference list)
aThis rate is consistent with the infiltration rate provided for the lower end of the Hydrologic Soil Group A soils in the Stormwater post-construction technical standards, Wisconsin Department of Natural Resources Conservation Practice Standards.
bThe infiltration rates in this table are recommended values for sizing stormwater practices based on information collected from soil borings or pits. A group of technical experts developed the table for the original Minnesota Stormwater Manual in 2005. Additional technical review resulted in an update to the table in 2011. Over the past 5 to 7 years, several government agencies revised or developed guidance for designing infiltration practices. Several states now require or strongly recommend field infiltration tests. Examples include North Carolina, New York, Georgia, and the City of Philadelphia. The states of Washington and Maine strongly recommend field testing for infiltration rates, but both states allow grain size analyses in the determination of infiltration rates. The Minnesota Stormwater Manual strongly recommends field testing for infiltration rate, but allows information from soil borings or pits to be used in determining infiltration rate. A literature review suggests the values in the design infiltration rate table are not appropriate for soils with very high infiltration rates. This includes gravels, sandy gravels, and uniformly graded sands. Infiltration rates for these geologic materials are higher than indicated in the table.
References: Clapp, R. B., and George M. Hornberger. 1978. Empirical equations for some soil hydraulic properties. Water Resources Research. 14:4:601–604; Moynihan, K., and Vasconcelos, J. 2014. SWMM Modeling of a Rural Watershed in the Lower Coastal Plains of the United States. Journal of Water Management Modeling. C372; Rawls, W.J., D. Gimenez, and R. Grossman. 1998. Use of soil texture, bulk density and slope of the water retention curve to predict saturated hydraulic conductivity Transactions of the ASAE. VOL. 41(4): 983-988; Saxton, K.E., and W. J. Rawls. 2005. Soil Water Characteristic Estimates by Texture and Organic Matter for Hydrologic Solutions. Soil Science Society of America Journal. 70:5:1569-1578.

Retrieved from "https://stormwater.pca.state.mn.us/index.php?title=Design_infiltration_rates&oldid=67978"

This page was last edited on 5 April 2023, at 15:23.