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.............. Appendix A Table 1 ............... • A Gravel, sand, sandy gravel, silty gravel, loamy sand, sandy loam GW — Well -graded gravel or well - graded gravel with sand GP — Poorly graded gravel or poorly graded gravel with sand 1.6 GM — Silty gravel or silty gravel with sand SW — Well -graded sand or well - graded sand with gravel SP — Poorly graded sand or poorly graded sand with gravel 0.8 B Loam, silt loam SM — Silty sand or silty sand with gravel 0.6 ML — Silt OL — Organic silt or organic silt with sand or gravel or gravelly organic silt 0.3 C Sandy clay loam GC — Clayey gravel or clayey gravel with sand SC — Clayey sand or clayey sand with gravel 0.2 D Clay, clay loam, silty clay loam, sandy clay, silty clay CL — Lean clay or lean clay with sand or gravel or gravelly lean clay CH — Fat clay or fat clay with sand or gravel or gravelly fat clay OH — Organic clay or organic clay with sand or gravel or gravelly organic clay MH — Elastic silt or elastic silt with sand or gravel < 0.2 Source: Minnesota Pollution Control Agency, Minnesota Stormwater Manual. Thirty guidance manuals and many other stormwater references were reviewed by the MPCA when it compiled the recommended infiltration rates. All of these sources use the following studies as the basis for their recommended infiltration rates: Rawls, Brakensiek and Saxton (1982); Rawls, Gimenez and Grossman (1998); Bouwer and Rice (1984); and Urban Hydrology for Small Watersheds (MRCS). The rates presented in this infiltration table use the information compiled from these sources as well as eight years of infiltration rates collected from various infiltration practices in the South Washington Watershed District. * U.S. Department of Agriculture, Natural Resources Conservation Service, 2005. National Soil Survey Handbook, title 430 -VI. (Online) Available: http://soils.usda.gov/technical/handbook/. ** ASTM standard D2487-00