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City of Arden Hills <br />Project B2502087 <br />June 13, 2025 <br />Page 11 <br />C.2.b. Corrosion Potential <br />Based on our experience, the soils encountered by the borings are moderately corrosive to metallic <br />conduits, but only marginally corrosive to concrete. We recommend specifying non-corrosive materials <br />or providing corrosion protection, unless project planning chooses to perform additional tests to <br />demonstrate the soils are not corrosive. <br />C.2.c. Excavation Oversizing <br />When removing unsuitable materials below structures or pavements, we recommend the excavation <br />extend outward and downward at a slope of 1H:1V (horizontal:vertical) or flatter. See Figure 3 for an <br />illustration of excavation oversizing. <br />Figure 3. Generalized Illustration of Oversizing <br />C.2.d. Excavated Slopes <br />Based on the borings, we anticipate most of the on-site soils in excavations will consist of fill sands and <br />clays. These soils are typically considered Type C Soil under OSHA (Occupational Safety and Health <br />Administration) guidelines. OSHA guidelines indicate unsupported excavations in Type C soils should have a <br />gradient no steeper than 1 1/2H:1V. Slopes constructed in this manner may still exhibit surface sloughing. <br />1.Engineered pavement embankment fill as defined in Section C.2.f. <br />2.Excavation oversizing minimum of 1H:1V slope or flatter. <br />3.Backslope to OSHA requirements. <br />4.Outside edge of existing pavement. <br />5.Outside edge of new pavement. <br />6.Unsuitable soils to be removed.