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Bremer Financial Corporation <br />Project B2008939 <br />November 17, 2020 <br />Page 22 <br /> <br /> <br />Table 9. Estimated Design Infiltration Rates Based on Soil Classification <br />Soil Type <br />Infiltration Rate * <br />(inches/hour) <br />Silty sands, silty gravelly sands 0.45 <br />Clayey sands and clays 0.06 or less <br />*From Minnesota Stormwater Manual. Rates may differ at individual sites. <br /> <br /> <br />Fine-grained soils (silts and clays), topsoil or organic matter that mixes into or washes onto the soil will <br />lower the permeability. The contractor should maintain and protect infiltration areas during <br />construction. Furthermore, organic matter and silt washed into the system after construction can fill the <br />soil pores and reduce permeability over time. Proper maintenance is important for long-term <br />performance of infiltration systems. <br /> <br />This geotechnical evaluation does not constitute a review of site suitability for stormwater infiltration or <br />evaluate the potential impacts, if any, from infiltration of large amounts of stormwater. <br /> <br />C.10. Equipment Support <br /> <br />The recommendations included in the report may not be applicable to equipment used for the <br />construction and maintenance of this project. We recommend evaluating subgrade conditions in areas of <br />shoring, scaffolding, cranes, pumps, lifts and other construction equipment prior to mobilization to <br />determine if the exposed materials are suitable for equipment support, or require some form of <br />subgrade improvement. We also recommend project planning consider the effect that loads applied by <br />such equipment may have on structures they bear on or surcharge – including pavements, buried <br />utilities, below-grade walls, etc. We can assist you in this evaluation. <br /> <br /> <br />