2019.02.04 CC Packet - Laserfiche WebLink

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Effective April 28, 2015 Chapter Four Subsurface Sewage Treatment System Regulations SECTION 14 DISTRIBUTION OF EFFLUENT 14.1 General. Distribution of effluent for SSTS must meet or exceed the requirements of this Section and Minnesota Rules, Chapter 7080.2050. 14.2 Supply Pipes. (1) The supply pipe extending from the septic tank to the undisturbed soil beyond the tank excavation must meet the strength requirements of American Society for Testing and Materials (ASTM), Schedule 40 Pipe, contained in Standard Specifications for Poly(Vinyl Chloride)(PVC) Plastic Pipe, Schedule 40, 80, 120, ASTM D1785 (2006). The schedule is incorporated by reference, is available through the Minitex interlibrary loan system, and is not subject to frequent change. (2) Supply pipes must: (A) Be made from materials resistant to breakdown from sewage and soil. (B) Be watertight, including all joints. (C) Be durable throughout the design life. (D) Not deflect, buckle, crush, or longitudinally bend. (E) Be resistant to pressures, fatigue, and strain for the application. (F) Be installed according to American Society for Testing and Materials, Standard Practice for Underground Installation of Thermoplastic Pipe for Sewers and Other Gravity -Flow Applications, ASTM D2321 (2005). The standard is incorporated by reference, is available through the Minitex interlibrary loan system, and is not subject to frequent change. (G) Be designed, installed, and protected to minimize the danger of freezing in the pipe. (H) Not be closer than six inches from final grade. Pipes susceptible to freezing shall be insulated. (I) Be setback from the water supply wells and water service pipes according to Minnesota Rules, Chapters 4715 and 4725. (3) The minimum slope for gravity supply pipes is one percent ('/8-inch per linear foot). There is no maximum slope. Pipe restraints must be used for slopes greater than 20 percent or where fluid velocities in the pipe exceed 15 feet per second. For pressure systems, a minimum slope of one percent for drainback or other frost protection measures must be employed. (4) Access to each supply pipe must be provided for cleanout. The access point must be accessible from final grade. 14.3 Gravity Distribution (1) Serial distribution must be used to distribute effluent to individual trenches in a soil treatment and dispersal system. If the necessary elevation differences between trenches for serial distribution cannot be achieved by natural topography or by varying the excavation depths, parallel distribution must be used. Serial distribution must not create a pressure head on trenches at lower elevations. (2) If drop boxes are used for serial distribution, Subitems (A) to (F) apply. (A) The drop box must be watertight and constructed of durable materials not subject to corrosion or decay. (B) The invert of the inlet supply pipe must be at least one inch higher than the invert of the outlet supply pipe to the next drop box. (C) The invert of the outlet supply pipe to the next drop box must be no greater than two inches higher than the crown of the distribution pipe serving the trench in which the box is located. (D) When sewage tank effluent is delivered to the drop box by a pump, the pump discharge must be directed against a wall or side of the box on which there is no outlet or directed against a deflection wall, baffle, or other energy dissipater. The discharge rate into the drop box must not result in surfacing of sewage from the drop box. The supply pipe must drain after the pump shuts off. 55 Washington County Development Code