OAR 340-071-0310: Steep Slope Systems

(1) General conditions for approval. Construction-installation permits may be issued for steep slope systems serving single-family dwellings on slopes in excess of 30 percent if all the following requirements can be met. (a) Slope does not exceed 45 percent. (b) The soil is well-drained with no evidence of saturation to a depth of 60 inches. (c) The soil has a minimum effective soil depth of 60 inches. (2) Construction requirements. (a) Seepage trenches must be installed at a minimum depth of 30 inches and a maximum depth of 36 inches below the natural soil surface on the downhill side of the trench and must contain a minimum of 18 inches of drain media and 12 inches of native soil backfill. (b) The system must be sized at a minimum of 75 linear feet per 150 gallons sewage flow.