600 RIVERSIDE RD Geotech Report 2022-10-25

1 Ll 1 1 Landau Associates Proctor). The purpose of this effort is to identify possible loose or soft soil deposits and to recompact the soil exposed during site stripping and demolition activities. Proof rolling should be carefully observed by geotechnical personnel. Areas exhibiting significant deflection, pumping, or weaving that cannot be readily compacted should be overexcavated to firm or dense soil. Overexcavated areas should be backfilled with compacted granular material in accordance with subsequent recommendations for structural fill. Proof rolling or compaction could damage exposed subgrades within 2 ft of groundwater or during periods of wet weather. Under these conditions, a qualified geotechnical engineer should observe subgrade conditions to determine if proof rolling and compaction is feasible. Construction in wet weather conditions may not allow proper compaction of the subgrade. In this case, it may be necessary to overexcavate loose and wet surficial soil and replace it with clean, well -graded sand and gravel or base -course material in paved areas. The depth of overexcavation required will depend on the condition of the soil at the time of construction, but the depth could be on the order of 6 to 12 inches. If the subgrade is particularly loose or disturbed by construction equipment during wet weather, an even thicker subbase layer or the use of a geotextile in combination with a granular base material may be needed to achieve suitable conditions for the proposed pavement sections. 3.5 Fill and Compaction Structural fill used to raise site grades for the proposed access road and trails must be properly placed and compacted. In general, any suitable, nonorganic, predominately granular soil may be used for fill material, including portions of the existing site fill, stockpiled dredge materials, and native sandy soil, provided the material is properly moisture conditioned prior to placement and compaction, and the specified degree of compaction is obtained. If the existing native onsite soil or dredge material is to be reused for structural fill, pieces of wood or other deleterious material should be removed. Excavated site material containing topsoil, wood, trash, organic or fine-grained material (including the silt unit of the alluvial deposits), or construction debris will not be suitable for reuse as structural fill and should be placed onsite in nonstructural areas where several inches of post -construction settlement is tolerable. The suitability of excavated site soil or imported soil for use as compacted structural fill will depend on the gradation and moisture content of the soil when it is placed. As the amount of fines (that portion passing the US Standard No. 200 sieve) increases, the soil becomes increasingly sensitive to small changes in moisture content and adequate compaction becomes more difficult to achieve. Soil containing more than about 5 percent fines cannot consistently be compacted to a dense, nonyielding condition when the water content is greater than optimum. Optimum moisture content is the moisture content at which the greatest compacted dry density can be achieved. The moisture content Geotechnical Engineering Report 0121030.010.011 Riverside Business Park March 22, 2018 Public Access Trails and Roadway Improvements 3-4