Agenda - Council - 04/11/2017 - Laserfiche WebLink

Home

Pearson Farm Residential Development EAW Draft—March XX,2017 Sinkholes and karst lands are not known to occur in western Anoka County where the project is located. Minnesota Karst Lands and Sinkhole Mapping prepared by Calvin Alexander and others (2006)does not shows karst lands or sinkholes in or near the project area. b. Soils and topography-Describe the soils on the site, giving NRCS(SCS)classifications and descriptions, including limitations of soils. Describe topography, any special site conditions relating to erosion potential, soil stability or other soils limitations, such as steep slopes, highly permeable soils. Provide estimated volume and acreage of soil excavation and/or grading.Discuss impacts from project activities (distinguish between construction and operational activities)related to soils and topography. Idents measures during and after project construction to address soil limitations including stabilization, soil corrections or other measures. Erosion/sedimentation control related to stormwater runoff should be addressed in response to Item 11.b.ii. The Web Soil Survey indicates the project area includes five soil mapping units that consist of mostly loamy sands (Table 4,Figure 9). Table 4. Soil Classifications Symbol Soil Name % of % Hydric Category Farmland Category Area Hydric D20A Isan-Isan,frequently ponded, Predominantly complex,0-2%slopes 8 1 95 hydric Not prime farmland D67A Hubbard loamy sand,Mississippi 55.1 1 Predominantly Not prime farmland /o River Valley,0-2 slopes non-hydric D67B Hubbard loamy sand,Mississippi 5.7 3 Predominantly Not prime farmland /o River Valley,2-6 slopes non-hydric D67C Hubbard loamy sand,Mississippi 13.4 0 Non-hydric Not prime farmland River Valley,6-12%slopes Dp Duelm loamy sand,0-2%slopes 17.7 7 Predominantly Not prime farmland non-hydric These soils have varying levels of limitations for dwelling units and local streets due to factors such as depth to saturated zone,frost action,ponding, and slope. Depth to saturation limitations are often associated with wetlands,which are addressed under Item II.a.i below. Soils in the project area are generally considered slightly to moderately susceptible to the sheet and rill erosion by water, as indicated by slopes and K factors that range between 0.0 and 0.50. Grading operations for residential development construction are expected to affect about 87 acres and involve movement of about 475,000 cubic yards of soil to construct streets,residential building pads, and stormwater features. Grading is expected to avoid disturbance of wetlands and trees that will be preserved,which cover about two acres within the project area. Elevations in the project area range from 887 feet above mean sea level at the highest point in the northeast part of the project to 868 feet at the lowest onsite wetland. Review of two-foot contour mapping indicates the site has less than an acre of slopes that equal or exceed 12%and the site does not include any bluffs. Soils mapping does not classify any parts of site as having slopes of 12%or more (Table 4,Figure 9). 9