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2) Soil borings shall extend to a depth of at least 7 feet below the water table. The borings shall <br />be Ieft open for a time sufficient to determine the stabilized water level in the borehole. The <br />water level shall be measured with reference to a known bench mark that can relate the water <br />table elevation to the proposed floor elevation. Soils at or immediately below the water table <br />shall be sampled and texturally classified using an approved classification method. <br />Water levels measured during dry summer months or during the winter may be lower than water <br />levels during the spring. The applicant should be required to make an effort to determine the likely <br />amount of seasonal fluctuation in the water table in the area. Water level records from wells <br />completed in the area could be used. If information is unavailable, the applicant should be required to <br />add a value to the measured water table elevation. One suggestion would be to assume 25% of the <br />total annual precipitation (29 inches), divided by the average effective porosity for non -cohesive soils <br />(0.3), which is: <br />(29 inches/4) x (1 foot/ 12 inches)/0.3 = 2 feet <br />If the seasonally adjusted maximum water -table elevation is eight (8) feet or below the bottom of the <br />slab of the lowest floor, it is unlikely that temporary flood conditions in the pond will cause the water <br />table to rise to the level of the floor! <br />Determining Soil Type at the Water Table <br />The textural classification from the soil borings will be necessary for determining the expected rise in <br />the water table caused by an increase in pond elevation. At a minimum, the soil should be classified <br />as one of the following: <br />1) Sandy or gravely soils — consisting of predominantly sand or gravel, with minor amounts of <br />silt and clay <br />2) Silty soils — consisting predominantly of silt <br />3) Clayey soils — consisting predominantly of clay <br />1 This assumes that the pond level begins to return to normal within about 30 days and the pond level's <br />increase is not greater than 6 feet. <br />J <br />