Laserfiche WebLink
North Oaks Company LLC <br />Project B2402335 <br />August 22, 2024 <br />Page 22 <br />C.8.b. Corrosion Potential <br />Based on our experience, the sandy soils encountered by the borings are moderately corrosive to <br />metallic conduits, but only marginally corrosive to concrete. We recommend specifying non -corrosive <br />materials or providing corrosion protection, unless project planning chooses to perform additional tests <br />to demonstrate the soils are not corrosive. <br />C.9. Stormwater <br />Based on laboratory tests run on selected samples from the borings we estimated infiltration rates for <br />the soils we encountered, as listed in Table 13. These estimated infiltration rates represent the long-term <br />infiltration capacity of a practice and not the capacity of the soils in their natural state. Field testing, such <br />as with a double -ring infiltrometer (ASTM D3385), may justify the use of higher infiltration rates. <br />However, we recommend adjusting field test rates by the appropriate correction factor, as provided for <br />in the Minnesota Stormwater Manual or as allowed by the local watershed. We recommend consulting <br />the Minnesota Stormwater Manual for stormwater design. <br />Table 13. Soil Infiltration Rates <br />Infiltration Rate <br />Soil Type <br />Hydrologic Soil Group <br />(inches/hour) <br />Sands <br />A <br />0.8 <br />(SP-SM) <br />Silts, very fine sands, silty or clayey <br />fine sands <br />C <br />0.2 <br />(ML, SM, SC) <br />Sandy clay, silty clay, lean clay, fat <br />clay <br />D <br />0.06 <br />(CLS, CL-ML, CL, CH) <br />*From Minnesota Stormwater Manual. Rates may differ at individual sites. <br />Fine-grained soils (clays and silts), 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 />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 />BRAUN <br />INTERTEC <br />