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Group D soils have high runoff potential. They have very low infiltration rate when thoroughly <br />wetted and consist chiefly of clay soils with high swelling potential, soils with a permanent high <br />water table, soils with a claypan or clay layer at or near the surface, and shallow soils over <br />impervious material. These soils have a very low rate of water transmission (0 -0.05 in /hr). <br />The Soil Report used in the DRMS application (Appendix 8) did not specify a HSG for this soil <br />type when generated by the USDA web soil survey. In order to determine the HSG, the property <br />Capacity of the most limiting layer to transmit water was used. The two elements of the 112 soil <br />(Cryorthents and Rock outcrop) have different value ranges for this property. The Cryorthents <br />has a range for water transmission of 0.06 to 0.20 in/hr while the Rock outcrop has a range of <br />0.00 to 0.06 in/hr. The complex is listed as being split 50% (Cryorthents), 40% (Rock outcrop). <br />This places the overall soil squarely between Group C (higher water transmission rate) and <br />Group D (lower water transmission rate) for the HSG. In order to determine the appropriate soil <br />group, more site specific details should be applied. <br />The soil map units used in the web soil survey are drawn from soil surveys conducted over large <br />regions, and therefore do not reflect the specific details at Revenue. The distribution of the sub- <br />units of map units 112 is 50% Cryorthents and 40% Rock outcrop in the regional soil survey. <br />This may not reflect the Revenue area soil types accurately. An examination of photography of <br />the area south of the Revenue Mine shows that the area the 112 soil unit covers has substantial <br />permanent vegetation including large amounts of forest and thick brush communities (Figures 1 - <br />3). These communities require soils deep enough to allow the infiltration and drainage of runoff. <br />Cryorthents has a soil depth of 10 -39 inches according to the soil survey. It is likely that the <br />vegetated areas are the Cryorthents soil type. Rock outcrop has no soil depth to bedrock, and <br />therefore would not support vegetation of the scope seen in the Figures. Based on general areas <br />from maps like Figure 1, the portion of thicker soil (Cryorthents) is closer to 90% than 50 %. <br />WestWater Engineering, while conducting wetlands examinations on site, logged soil depths of <br />20 inches just south of the old pond. As Figure 1 shows, these sample points are in the middle of <br />the 112 soil map unit. These soil depths support the idea that the vegetated areas south of the <br />Revenue Mine contain soils that are the Cryorthents type, not Rock outcrop. <br />