3620 36TH PL NE 2018-01-02 MF Import

repair and/or modify them as appropriate. Provisions for modifications to the erosion control system based on monitoring observations should be included in the erosion and sedimentation control plan. 4.2.2 Excavation Considerations Surficial soils consisting of fill, wood chips and soft native organic silt were observed in the explorations. We anticipate that these materials can be excavated with conventional excavation equipment, such as trackhoes or dozers. However, due to the soft and wet nature of the native fine- grained soils, we recommend that the contractor use low ground pressure equipment including wide - tracked dozers, when operating over the native soils. In addition, we recommend that all excavations by excavators be accomplished using a bucket with a smooth edge to reduce disturbance to the native soils espe,:ially when performing excavations under planned structures. 4.2.3 Clearing and Grubbing The site is partially covered with thin topsoil deposits, fill soils, and wood chips. Portions of the site are also covered with grasses and shrub vegetation. Existing fill and wood chips overlie most of the central and northern portion of the site. The thickness varies significantly. As discussed in Section 3.4, the fill consists of sand and gravel, some quarry spalls, and exists across these areas and is on top of or mixed in with the wood chips in some areas. The wood chips may be up to 5 feet thick in areas. The thickest areas exist from the north edge of the central part of compost system pad Nos. 1 and 2 sou: '. to the central area of compost system pad No. 3. Topsoil, wood chips and organic debris should be removed from all planned structural areas. The wood chips should also be removed laterally beyond footprints of planned structures by a distance equal to the depth of the excavation below the bottom of the footings or slabs, whichever is deeper. In locations where fill will be placed that is greater than 2 feet thick below the pavement section subgrade, we recommend that vegetation be mowed as close as practical to the ground surface and that the cut vegetation be removed from the site prior to placing fill to raise site grades. Where fill is less than 2 feet thick below pavement section subgrade, we recommend that the topsoil and organic materials be completely stripped and removed from the pavement areas. 4.2.4 Subgrade Preparation The exposed subgrade in structure and pavement areas should be evaluated after site clearing and stripping is complete and prior to fill placement. Proof -rolling with heavy, rubber -tired construction equipment should be used for this purpose during dry weather. Probing should be used to evaluate the subgrade during periods of wet weather. Soft areas noted during proo£rolling or probing should be excavated and replaced with compacted structural fill. Evaluating subgrade conditions at the site in planned structure and pavement areas will be extremely important and will likely require much judgment based on the conditions observed and the planned improvement. We recommend that a geotextile separator (such as TC Mirafi 600X) be placed over native subgrade soils in all structural areas, including planned pavement sections. The geotextile separator will allow the granular fill soils to remain clean throughout construction and thereby maintaining the. necessary support for the structures and pavement areas. In addition, the separator will provide a better working surface for i Geo En 1t1 �} g i n e e r s File Na. 10625�WI-02/123007 � i