Sec. 470.307. - Absorption field.

(a) A septic tank system shall be designed so that the effluent or drainage flow from the tank is disposed of in a soil absorption field. The minimum absorption area of the absorption field is 300 square feet or, if greater: (1) For a residence and a multiple dwelling, an area determined by reference to the number of bedrooms, the results of soil and percolation tests and Table 470-3. (2) For any other building, an area determined by reference to the estimated or, if applicable, the actual, daily sewage waste flow, the results of soil and percolation tests and Table 470-4. Table 470-3 Absorption Area Requirements For Residences and Multiple Dwellings Percolation Rate Absorption Area per Bedroom (square feet) 2 or less 125 3 150 4 160 5 170 10 245 15 270   Table 470-4 Absorption Area Requirements For Other Buildings Percolation Rate Maximum Rate of Sewage Application (gallons per square foot per day) 2 or less 2.0 3 1.7 4 1.5 5 1.33 10 1.0 15 0.8   The total sewage application capacity of the absorption area shall equal or exceed the estimated sewage flow. (b) Every absorption field shall comply with the following construction standards: (1) Drain tile shall be installed in filter material of washed and screened gravel, slag, rock or similar approved material of equivalent strength and durability, and shall vary in size from one-half inch to two inches, and shall be free from fines, dust, sand and clay. (2) Filter material shall encase the tile with a minimum depth of six inches under the tile and shall have a total depth, extending throughout the width of the trench, of: (i) If a cradle or block unit is used in the absorption field, at least 14 inches with at least six inches under the unit and eight inches above the bottom on the unit. (ii) Otherwise, at least 12 inches. (3) Filter material in place shall be protected from infiltration of earth backfill by an effective barrier of building paper. (4) The maximum depth from the invert of the drain tile to the finished ground surface shall not exceed 24 inches. Minimum earth cover above the top of the drain tile shall be six inches. (5) Drain tile used in the absorption field shall be at least four inches inside diameter of vitrified clay, with one-quarter-inch open joints between each tile. The Director may approve drain tile constructed of other materials, having substantially the same characteristics, taking into consideration the intended use of the tile. (6) Cradle or block units of optional design for drainfield distributors may be used when approved by the Director and installed as required by this Chapter. (7) Drain lines shall be graded with a downward slope of one-quarter to one-half inch per ten feet, but in no case exceeding six inches per 100 feet. (8) Laterals shall not exceed 100 feet in length. If two or more laterals are used, they shall be as close to the same length as practicable, and they may be connected to produce a contiguous system. (9) The width of the trench at the bottom for drain tile shall be not less than 12 inches or more than 24 inches. If cradle or block units are used, the maximum width of the trench shall be 48 inches. (10) The minimum distance between the center line of any two adjoining trenches shall be six feet, if the trench width is 12 to 24 inches, and eight feet for block or cradle units. (11) Any replaced or relaid drain field shall be not less than 208 square feet in size and shall contain not less than three lines of tile unless, due to a space limitation, an exception to these requirements is granted by the Director. (Ord. 70-650-526; Ord. 71-435-150, §§ 4, 5; Ord. 71-397-181; Ord. 83-591-400, § 1) Note— Former § 624.307.