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( The backfilled trench should be well tamped and be 'over--filled with <br /> 4 inches to 8 inches of earth to prevent depressions due to settling <br /> of earth (trench line depressions may collect storm water, leading <br /> to premature saturation of the absorption field and possibly to <br /> trench washouts). Trucks and heavy grading equipment shall be <br /> excluded from the disposal area unless special provision is made • <br /> to support the weight. •See Figure 2. <br /> Sections of disposal fields located on hillsides at different <br /> elevations shall be separated by undisturbed earth dams at least <br /> 2 feet across at the ground surface. There shall be a pipe transfer <br /> from the .terminus of the trench at one elevation to the inlet of the <br /> ztrench at a lower elevation. <br /> Section connecting lines or pipe transfers shall be 4-inch tight-joint <br /> sewers with connections to the distribution tiles in ,adjacent sections <br /> or to:a-drop box. The crown of the transfer shall be at least 2 inches •• <br /> below the top of the gravel. <br /> Transsfe-r.--lines•shall be so constructed as to insure an undisturbed <br /> �l block of earth between sections. The trench connecting the transfer <br /> =pipe and the preceding asborption section shall be dug no deeper • <br /> than the top of the soil gravel interface. The transfer line shall <br /> rest on undisturbed earth and backfill shall be carefully tamped. <br /> Inspection. wells consisting of four inch pipe placed vertically • <br /> in 'the trench from the bottom to the surface of the ground and <br /> provided with a cap or plug shall be placed at the terminus of each <br /> trench or/and at such other points as will make possible a check <br /> of the water table elevation within the trench at the inspection <br /> well points. These sampling wells shall be adequately marked to permit <br /> ready location and provide protection from damage. <br /> 3. Dosing Chamber: The dosing chamber where employed shall be constructed . <br /> of concrete or masonry units and may be an independent structure or <br /> a third compartment of the septic tank structure. It -shall have smooth <br /> finished walls and bottom at least 4 inches thick. When concrete block <br /> or other than approved interlocking blocks or masonry units are used, <br /> • <br /> -4- • <br />