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| <br /> � <br /> � <br /> 502.02' Sewage treatment mounds' On sites having soil <br /> conditions which do not permit installation of a Standard System, a <br /> sewage treatment mound may be considered . Proposed mounds shall <br /> require engineered design (conforming to the following conditions) to <br /> be submitted for review and approval prior to any permit issuance or <br /> construction . <br /> ( 1 ) General conditions. <br /> a. The soil Percolation Rate in all layers of the <br /> natural or fill soil to a depth 'of at least <br /> twenty-four (24) inches below the sand shall be <br /> faster than one hundred twenty ( 120) minutes per <br /> inch. <br /> b. Below the sand layer there shall be at least one <br /> ( 1 ) layer of soil , at least twelve ( 12) inches in <br /> depth, which has a Percolation Rate slower than <br /> five ( 5) minutes per inch. <br /> c . Mounds shall be located on flat areas or crests of <br /> slopes. Mounds shall not be installed on natural <br /> slopes exceediog three (3) .percao± where the <br /> Percolation Rate is slower than sixty (60) minutes <br /> per inch in the twenty-four (24) inches below the <br /> sand layer. <br /> d . Mounds shall not be located on slopes exceeding � <br /> six (6) percent where the Percolation Rate is ^ - <br /> slower than thirty (30) minutes per inch in the <br /> twenty-four (24 ) inches below the sand layer . <br /> (2) Soil surface preparation . <br /> a. The discharge pipe from the pump to the mound area <br /> shall be installed prior to soil surface <br /> preparation . The trench shall be carefully <br /> backfilled and compacted to prevent effluent <br /> seepage. <br /> b' The total area selected for the mound , including <br /> the dikes, shall be plowed to a minimum depth of <br /> eight (8) inches or the sod layer broken and <br /> roughened by back hoe teeth. Furrows shall be <br /> thrown up slope and no dead furrow shall be <br /> permitted under the mound . The soil shall be <br /> plowed or broken only when soil moisture to a <br /> depth of eight (8) inches is below the plastic <br /> limit. <br /> c . Where soils in the top eight (8) inches of the -` <br /> natural surface have percolation rates faster than <br /> fifteen ( 15) minutes per inch, disking may be used <br /> for surface preparation ' <br /> 30 <br />