Agenda - Planning Commission - 08/02/2018

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North Dayton Development AUAR The USDA maps show the majority of the site consists of Lester loam, morainic, 6-12% slopes, eroded and Angus loam, 2-6 % slopes. Both Lester loam and Angus loam consist of loam overlaying clay loam. The project area will be mass graded in several phases beginning at the east side of the site. The phases will be market driven and likely exist of 20 to 80 acres in each phase. As is typical with residential site grading, the street section will be established following the existing terrain filling some lower areas and cutting the hilltops. Home pads will be graded adjacent to the roadways. Typical cut or fill depths are in the 2 to 10 ft. range. Existing topsoil in the project area is anticipated to be 1 to 3 ft. in depth with greater depths near wetland areas. Topsoil will be stripped and salvaged such that a minimum four inch topsoil layer will be provided for the project area, according to local code requirements. At this time no unusual requirements are anticipated for the site grading operations. County Well Index data was used to determine the elevation of the aquifer (see Appendix B). Based on well log data for wells located on site, the elevation of the aquifer beneath the site is approximately 65 feet below ground surface. Test wells completed on the site did not identify static water table levels. MITIGATION MEASURES (QUESTION 10): Mitigation measures that will be incorporated into the proposed project to mitigate against the potential incompatibility of surrounding land uses include: • Any vegetation, topsoil, organics, and/or soft clays should be removed from within the building footprints and oversize areas prior to construction. • Excavation bottoms should be observed by a geotechnical engineer, or their representative, to judge if excavation bottom soils are similar to those encountered within the geotechnical report. Actual depths of excavation will need to be determined in the field at the time of construction by a geotechnical engineer prior to new fill or concrete placement. • To provide lateral support of structural loads, it is recommend that oversizing (widening) excavations one (1) foot horizontally beyond the footings for each foot excavations extend below bottom -of - footing elevations. • The contractor should develop a groundwater control plan for use if groundwater is encountered during construction. • If groundwater is encountered, a dewatering permit from the Minnesota DNR may be required if the dewatering is expected to exceed 10,000 gallons per day or one million gallons per year. • In areas where site grading will be performed early in the construction phasing (i.e., where a construction delay of at least 6 months can be accommodated), backfill materials should be composed of non -organic mineral soils containing no debris and having a PI (Plastic Index) less than 20. In areas where a construction delay will not be accommodated (i.e., Building E soil corrections), it is recommend that the balance of excavation backfill greater than 10 feet in thickness below bottom of 19