1318 37TH ST 2018-01-02 MF Import

�. JN 97072 James Pirie Page 10 March 18, 1997 Beneath pavements 95% for upper 12 inches of subgrade, 90% below that level Where: Minimum Relative compaction is the ratio, expressed in percentages, of the compacted dry density to the maximum dry density, as determined in accordance with ASTM Test Designation D 1557-78 (Modified Proctor). Use of On -Site Soil If grading activities take place during wet weather, or when the silty, on -site soils are wet, site preparation costs may be higher because of delays due to rain and the potential need to import granular fill. The on -site soils are generally silty and therefore moisture -sensitive. Grading operations will be difficult during wet weather, or when the moisture content of these soils exceeds the optimum moisture content. The moisture content of the silty, on -site soils must be at, or near, the optimum moisture content, as the soils cannot be consistently compacted to the required density when the moisture content is significantly greater than optimum. The moisture content of the on -site soils was generally near the estimated optimum moisture content at the time of our explorations. The on -site silty sands underlying the topsoil could be used as structural fill, if grading operations are conducted during hot, dry weather, when drying the wetter soils by aeration is possible. Proper compaction of the silty sands during wet weather will generally not be possible. During excessively dry weather, however, it may be necessary to add water to achieve the optimum moisture content. Moisture -sensitive soils may also be susceptible to excessive softening and "pumping" from construction equipment, or even foot traffic, when the moisture content is greater than the optimum moisture content. it may be beneficial to protect subgrades with a layer of imported sand or crushed rock to limit disturbance from traffic. Ideally, structural fill that will be placed in wet weather should consist of a coarse, granular soil with a silt or clay content of no more than 5 percent. The percentage of particles passing the No. 200 sieve should be measured from that portion of soil passing the three -quarter -inch sieve. LIMITATIONS The analyses, conclusions, and recommendations contained in this report are based on site conditions as they existed at the time of our exploration and assume that the soil encountered in the test pits is representative of subsurface conditions on the site. If the subsurface conditions encountered during construction are significantly different from those observed in our explorations, we should be advised at once so that we can review these conditions and reconsider our recommendations where necessary. Unanticipated soil conditions are commonly encountered on construction sites and cannot be fully anticipated by merely taking soil samples in test pits. I l�20 GEOTECH CONSULTANTS, INC.