Difference between revisions of "Design infiltration rates"
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| Line 6: | Line 6: | ||
<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>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 27: | ||
<tr> | <tr> | ||
<td>0.8</td> | <td>0.8</td> | ||
| + | <td>2.03</td> | ||
<td> | <td> | ||
sand<br> | sand<br> | ||
| Line 37: | Line 40: | ||
<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> | ||
| Line 42: | Line 46: | ||
<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 53: | ||
<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 60: | ||
<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> | ||
Revision as of 12:31, 22 August 2016
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.*
Link to this table
| Hydrologic soil group | Infiltration rate (inches/hour) | Infiltration rate (centimeters/hour) | Soil textures | Corresponding Unified Soil Classification |
|---|---|---|---|---|
| 1.63a | 4.14 |
gravel |
GW - well-graded gravels, sandy gravels |
|
| 0.8 | 2.03 |
sand |
SP - gap-graded or uniform sands, gravelly sands |
|
| 0.45 | 1.14 | SM - silty sands, silty gravelly sands | ||
| 0.3 | 0.76 | loam, silt loam | MH - micaceous silts, diatomaceous silts, volcanic ash | |
| 0.2 | 0.51 | Sandy clay loam | ML - silts, very fine sands, silty or clayey fine sands | |
| 0.06 | 0.15 |
clay loam |
GC - clayey gravels, clayey sandy gravels |
*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).
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 Wisconsin Department of Natural Resources Conservation Practice Standard: Site Evaluation for Stormwater Infiltration.