OAR 340-071-0280: Seepage Trench System

(1) Criteria for approval. Construction permits may be issued for seepage trench systems on lots created before January 1, 1974, for sites that meet all the following conditions. (a) Groundwater will not be degraded. (b) Lot or parcel size will not accommodate standard subsurface system disposal trenches with a design flow of 450 gpd. (c) All other requirements for standard subsurface systems can be met. (2) Design criteria. (a) The maximum depth allowed for a seepage trench is 42 inches. (b) The seepage trench system must be sized according to the following formula: length of seepage trench = 4 x (length of standard disposal trench) divided by (3 + 2D), where D = depth of drain media below distribution pipe in feet. Maximum depth of drain media (D) is 2 feet. (c) The design flow is limited to a maximum of 450 gallons.