A. An absorption system shall have at least 2 absorption trenches of approximately equal length. The length of a trench with gravity flow may not exceed 100 feet, the width of a trench may not exceed 3 feet. The bottom of the trench shall be at least 18 inches below the ground surface, but the depth may not exceed 3 feet. The trench shall be constructed with a fill material consisting of washed gravel, crushed stone, slag, or clean bank run gravel ranging in size from 1/2-inch to 2-1/2 inches in diameter. An absorption line shall be placed within each trench and shall run along the length of the trench. All absorption lines shall have the ends capped. The fill material shall be at least 6 inches deep below the bottom of the absorption line, and 2 inches deep above the top of the line. The bottom of the trench shall be uniformly graded to a slope from a minimum of 1/2-inch to a maximum of 4 inches per 100 feet. There shall be at least 6 feet of undisturbed soil between trenches. A closed-loop absorption trench system shall be level. To minimize sidewall compaction, trench excavation shall be made with bucket equipment having side cutters or raker teeth. When the soil does not exceed the plastic limit, the trench walls and bottoms shall be scarified before graded material is added.

B. (Note: All absorption lines shall be centered within the excavated trenches. Piping shall be laid out so as that no particular run is longer than 100 feet either as a single run or consecutive runs. Any run over 100 feet in length shall be dosed as described in Article VII. Any excavation greater than 36 inches wide shall be considered a seepage bed.)

C. (Note: If effluent is distributed by gravity, it shall not be loaded above the natural ground surface and the rock below the pipe must be in contact with original soil and gravity distribution must be designed to load effluent the entire depth of the rock below the pipe.)