1976.10.18 ORD 1976-132 - Laserfiche WebLink

Home

(5) Additional criteria for judging soil suitability. (a) In areas of shallow ground water, the depth of the water table shall be determined. No soil absorption system shall be installed in an area where the water table is at any time less than six and one-half (6 1/2) feet below ground level or four (4) feet below the bottom of the drain field trench. Soil absorption systems installed in areas where impermeable layers are found at depths of less than six and one-half (6 1/2) feet shall be considered to be of special design. (b) In addition to percolation test, a minimum of 2 borings penetrating not less than 7 ' shall be included as part of data to be submitted. The boring shall be of sufficient diameter to determine soil conditions and evidence of high water (mottling) . (c) A modification of the percolation test may be used where the percolation test procedure has been previously used and knowledge is available on the character and uniformity of the soil. (6) Construction of disposal trenches . (a) All trenches in a disposal field shall be constructed in accordance with the following standards : (1) Minimum number of lines per field 2 (2) Maximum length of individual lines 100 feet (3) Minimum bottom width of trench -- 18 inches (4) Minimum depth of cover of tile lines 18 inches (5) Preferred depth of cover of tile lines 24 inches (6) Maximum depth of cover of tile lines 36 inches (7) Maximum uniform grade of tile lines 6 inches per 100 ft. (8) Preferred uniform grade of tile lines 2 to 4 inches per 100 feet (9) Size and spacing of trenches - Conform to Table 3 (10) Minimum filter material under tile 6 inches (11) Preferred depth of filter material under tile 12 to 24 inches (12) Minimum filter material over tile-- 2 inches -13-