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Sewage di.~sal systen~ <br /> <br />§ 8.80 <br /> <br /> Filter material for a soil treatment unit using gravity <br /> distribution of effluent shall not be placed in contact with <br /> original soils having a percolation rate faster than 0.1 <br /> minute per inch. <br /> <br /> For coarse soils having a percolation rate faster than 0.1 <br /> minute per inch, at least 12 inches of loamy sand textured <br /> soil having a percolation rate between 6 az~d 15 minutes per <br /> inch at the original site shall be placed between the filter <br /> material and the coarse soil along the excavation bottom and <br /> sidewalls. The size of the soil treatment; system must be <br /> based on the required treatment area for a soil having a <br /> percolation rate of 16 to 30 minutes per inch as specified in <br /> Table II. <br /> <br /> For soils with percolation rates between 0.1 and 5 minutes <br /> per inch, at least one of the following treatment techniques <br /> shall be used: <br />a) Distribute the sewage tank effluent by pressure flow over <br /> the treatment area as specified in this chapter. <br />b) Divide the total soil treatment area into at least four <br /> equal parts connected serially;, or <br />c) Provide at least 12 inches of loamy sand textured soil <br /> with a percolation rate between 6 and[ 15 minutes per <br /> inch in situ between the drainfield rock and the coarse <br /> soils. Trenches must be used with this liner system. <br /> The size of the soil treatment system faust be based on <br /> the required treatment area for a soil having a <br /> percolation rate between 16 to 30 minutes per inch as <br /> specified in Table II. <br /> <br />~Iotmds. <br />1. <br /> <br />Mounds may be constructed on soils having the site or soil <br />conditions specified in §8.30.04 Subd. 7. <br /> <br />The soft percolation rate in all layers of the natural or fill soil <br />to a depth of at least 24 inches below the sand shall be faster <br />than 120 minutes per inch. <br /> <br />The allowable absorption area loading rate must be <br />determined according to Table III by the percolation rate of <br />the 12 inches of original or fiI1 soil immediately under the <br />sand layer. <br /> <br />Printed 19.2/28/90 <br /> <br />Page 255 <br /> <br /> <br />