13.20.480 Alternative method of determining required absorption trench system area.
In lieu of calculating the absorption trench system area according to ARSD §§ 74:53:01:30 and 74:53:01:31, the following criteria in Table 5 may be used for the design of individual or small onsite wastewater systems, if the absorption trench system is of an area sufficient for at least 3 bedrooms. The absorption area shall be determined according to the following:
Percolation Rate | Minimum Absorption Trench Area |
|---|---|
(Minutes for water to drop 1 inch) | (Square feet of trench bottom per bedroom) |
1 but less than 5 minutes per inch | Not permitted–see ARSD § 74:53:01:33 |
5 but less than 10 minutes per inch | 125 square feet |
10 but less than 15 minutes per inch | 165 square feet |
15 but less than 30 minutes per inch | 200 square feet |
30 but less than 45 minutes per inch | 250 square feet |
45 but less than 55 minutes per inch | 300 square feet |
55 but no more than 60 minutes per inch | 350 square feet |
Over 60 minutes per inch | Not permitted–see ARSD § 74:53:01:33 |
The minimum absorption trench area, as shown in the above table, may be reduced in accordance with ARSD § 74:53:01:31, when the depth of fill material below the distribution pipe is 12 inches or greater. (Note: The above method refers to a Class I dwelling. For a Class II dwelling, see § 13.20.490, Table 5b.)