Design infiltration rate as a function of soil texture for bioretention in Minnesota
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
Soil texture (USDA classification) | Corresponding Unified Soil Classification1 | Corresponding hydrologic soil Group (HSG) | Design Infiltration Rate (in/hr) |
---|---|---|---|
Gravel, sandy gravel | GW – Well-graded gravel, fine to coarse gravel
GP – Poorly graded gravel |
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. |
Silty gravels, gravelly sands, sand | GM – Silty gravel SW – Well-graded sand, fine to coarse sand | A | 1.63 |
Sand, loamy sand, sandy loam | SP – Poorly graded sand | A | 0.8 |
Silty sand | SM – Silty sand | B | 0.45 |
Silt loam, loam | MH – Elastic silt | B | 0.3 |
Sandy clay loam, silt | ML – Silt | C | 0.2 |
Clay, clay loam, silty clay loam, sandy clay, and silty clay | CL – Lean clay
CH – Fat clay OH – Organic clay, organic silt OL – Organic silt or organic silt with sand or gravel or gravelly organic silt GC – Clayey gravel SC – Clayey sand |
D | 0.06 |
For 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