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Riverstone South EAW Draft — December 2020 <br />b. Soils and topography - Describe the soils on the site, giving NRCS (SCS) classifications and descriptions, <br />including limitations of soils. Describe topography, any special site conditions relating to erosion <br />potential, soil stability or other soils limitations, such as steep slopes, highly permeable soils. Provide <br />estimated volume and acreage of soil excavation and/or grading. Discuss impacts from project activities <br />(distinguish between construction and operational activities) related to soils and topography. Identify <br />measures during and after project construction to address soil limitations including stabilization, soil <br />corrections or other measures. Erosion/sedimentation control related to stormwater runoff should be <br />addressed in response to Item H. b. ii. <br />The Web Soil Survey indicates the project area includes seven soil mapping units that consist of <br />mostly loamy sands (Table 4 and Figure 7). <br />Table 4. Soil Classifications <br />Symbol <br />Soil Name <br />% of <br />Area <br />% <br />Hydric <br />Hydric Category <br />Farmland Category <br />Ba <br />Becker very fine sandy loam <br />9.5 <br />7 <br />predominantly <br />non-hydric <br />prime farmland <br />D67A <br />Hubbard loamy sand, 0-2% slopes <br />20.0 <br />1 <br />predominantly <br />non-hydric <br />Not prime farmland <br />D67B <br />Hubbard loamy sand, 1-6% slopes <br />16.0 <br />3 <br />predominantly <br />non-hydric <br />Not prime farmland <br />D67C <br />Hubbard loamy sand, 2-12% <br />2.8 <br />0 <br />Non-hydric <br />Not prime farmland <br />slopes <br />DnA <br />Dickman sandy loam, 0-2% slopes <br />37.6 <br />0 <br />Non-hydric <br />Farmland of statewide <br />importance <br />DnB <br />Dickman sandy loam, 2-6% slopes <br />12.5 <br />0 <br />Non-hydric <br />Farmland of statewide <br />importance <br />NrD <br />Nyomore loamy coarse sand, 12- <br />1.7 <br />0 <br />Non-hydric <br />Not prime farmland <br />25 /o slopes <br />Five of the seven soils do not have limitations for dwelling units and local streets. Two of the soils <br />(Ba and NrD) have limitations due to factors such as flooding, depth to saturated zone, frost action, <br />and slope. Soils in the project area are generally considered slightly to moderately susceptible to the <br />sheet and rill erosion by water, as indicated by slopes and K factors that range between 0.02 and <br />0.37. <br />Grading operations for residential development construction are expected to affect about 68.0 acres <br />and involve movement of about 350,000 cubic yards of soil to construct streets, residential building <br />pads, and stormwater features. Grading is expected to avoid disturbance of trees that will be <br />preserved, which cover about 7.73 acres. <br />Elevations in the project area range from 880 feet above mean sea level at the highest point in the <br />northwestern part of the site to 858 feet at the lowest point in the southeastern part of the site. <br />Review of two -foot contour mapping indicates the northwestern part of the site includes about one <br />acre of 12-14% slopes and the site does not include any bluffs (Figure 5). Soils mapping classifies <br />the steepest part of the site, about 1.33 acre, as 12-25% slopes (Table 4, Figure 7). As shown on the <br />