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II. DISTRIBUTION OF EFFLUENT <br />1. BY GRAVITY FLOW OVER THE SOIL TREATMENT AREA <br />A. Level Ground <br />(1) The box shall be watertight with a removable cover and <br />shall be constructed of durable materials not subject to <br />excessive corrosion or decay. The minimum inside dimen- <br />sion shall be at least ten inches. <br />(2) The inverts of all outlets shall be at the same elevation <br />as measured from a liquid surface in the bottom of the box. <br />(3) The inlet invert shall be at least one inch above the out- <br />let inverts. <br />(4) The outlet inverts shall be at least four inches above the <br />distribution box floor. <br />(5) Each drainfield trench line shall be connected separately <br />to the distribution box and shall not be subdivided. <br />When sewage tank effluent is delivered to the distribution box <br />by pump, either a baffle wall shall be installed in the distri- <br />bution box or the pump discharge shall be directed against a <br />wall or side of the box on which there is no outlet. The baffle <br />shall be secured to the box and shall extend at least one inch <br />above the crown of the inlet flow line. <br />B. Sloping Ground <br />Where the elevation difference of the ground surface exceeds <br />28 inches in any direction within soil treatment area a drop box <br />shall be installed at the head end of each lateral line. Connec- <br />tions between drop boxes shall be by watertight pipes. <br />(See Figure 2) <br />(1) The drop box shall be watertight and constructed of durable <br />materials not subject to excessive corrosion or decay. The <br />minimum inside dimension shall be at least ten inches, un- <br />less the box is to be used as a valve box. Then each outlet <br />shall have at least eiqht inches of sidewall space and the <br />side of any outlet shall be at least six inches from any <br />corner. <br />(2) The invert of the inlet pipe shall be at least one inch <br />higher than the invert of the outlet pipe to the next <br />trench. <br />(3) The invert of the outlet pipe to the next trench shall be at <br />least two inches higher than the invert of the outlet pipe <br />of the trench in which the box is located. <br />