1999-04-21_PERMIT FILE - M1999024

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U. s. UEPARTNENT OF AGRIiULTUkErAGE i OF 2 NATURAL RESUURCEo UUNSERVATIUN sERVIGE • • UAj[11g8 sUII FEATURES Endnote --sGIL FEATURES This report gives estimates of various soii features. The estimates are used in land use planning that involves engineering considerations. Depth to bedrock is given if bedrock is within a depth of 5 feet, The depth is based on many sail borings end on observations during soil mapping. The rock is either 'Soft' or 'Herd'. If the rock is 'Soft' or fractured, ezcavations can be made with trenching machines, backhoes, or small rippers. If the rock is 'Hard' or massive, blasting or special equipment 9enerallr is needed for ezcevetion. Cemented pans ere cemented or indurated subsurface layers within a depth of 5 feet. such Oans cause difficulty in ezcavation. Pans ere classified as 'Thin' or 'Thick'. A 'Thin' pan is less than 3 inches thick if continuously indurated or less then 18 inches thick if discontinuous or fractured. Ezcavetions Can be made br trenching machines, backhoes, or small rippers. A 'Thick' pen is more than 3 inches thick it continuously indurated or more then 18 inches thick if discontinuous or fractured. such a pan is so thick or massive that blasting or special equipment is needed in ezcavation. Subsidence is the settlement of organic soils or of saturated mineral soils of very low density, subsidence results from either desiccation and shrinkage or ozidation of organic materiel, or both, following drainage. subsidence takes place gradually, usually over a Period of several years. This report shoes the ezpected initial subsidence, which usually is a result of drainage, end total subsidence, which usually is a result of ozidation. Not shown in the report is subsidence caused by an imposed surface load or by the withdrawal of ground water throughout en extensive area as a result of lowering the voter table. Potential frost action is the likelihood of upward or lateral expansion of the soii caused by the formation of segregated ice lenses (frost heave) and the subsecuent collapse of the soil and Loss of strength on thawing, Frost action occurs when moisture moves into the freeiing lone of the soil. Temperature, tezture, density, permeability, content of organic matter, end depth to the water table are the most important factors considered in evaluating the potential for frost action. It is assumed that the soil is not insulated br vegetation or snow and is not artificially drained. 'silly and highly structured clayey soils that have a high eater table in winter ere the most susceptible to frost action. Yell drained, very gravelly, or very sandy soils ere the least susceptible. Frost heave and low soil strength during chewing cause damage mainly to pavements and other rigid structures. Risk of corrosion pertains to potential soil-induced electrochemical or chemical action that dissolves or weakens uncoated steel or concrete. the rate of corrosion of uncoated steel is related to Such factors as soii moisture, particle-site distribution, acidity, and electrical conductivity of the soil, The rate of corrosion of concrete is 6esed mainly on the sulfate end sodium content, tezture, moisture content, and acidity of the soil. Special site ezeminetion and design may be needed if the combination of factors creates a severe corrosion environment. The steel installations that intersect soil boundaries or soil lacers is more susceptible td corrosion than steel in installations that are entirely within one kind of soii or within one soii later. For uncoated steel, the risk of corrosion, ezpressed as 'Lou', 'Haderate', or 'High', is based on soil drainage class, total acidity, electrical resistivity near field capacity, end electrical conductivity of the saturation extract. For concrete, the risk of corrosion is also ezpressed as 'Lau', 'Moderate', or 'High'. It is based on soil tezture, acidity, end amount of sulfates in the saturation eztract.