2019.02.04 CC Packet - Laserfiche WebLink

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Effective April 28, 2015 Chapter Four Subsurface Sewage Treatment System Regulations SECTION 18 TYPE II SYSTEMS 18.1 Type II Systems. Systems designed according to this Section are considered Type II systems. Systems in soils with a loading rate less than 0.45 gallons per day per square foot must not be used in a Type II system for new construction. 18.2 Floodplain Areas (1) General. SSTS must be designed under this part if the system is proposed to be located in a floodplain. A system located in a floodplain must meet or exceed the following requirements: (A) Employ flow values in Section 12. (B) Meet or exceed applicable technical requirements of Section 13, Section 14, and Section 15, except as modified in this part. (C) Meet or exceed the requirements of Sections 17.2 to 17.4. (D) Meet or exceed requirements of Section 16.2 and 16.3, except as modified in this part. (E) Meet the requirements of Section 18.2 (2) to Section 18.2 (11). (2) State and Local Requirements. The allowed use of systems in floodplains must be according to state and local floodplain requirements. (3) Location of System. An SSTS must not be located in a floodway and, whenever possible, placement within any part of the floodplain should be avoided. If no alternative exists, a system is allowed to be placed within the flood fringe if the requirements of Section 18.2 (4) to Section 18.2 (11) are met. (4) Openings. There must be no inspection pipe or other installed opening from the distribution media to the soil surface. (5) Highest Feasible Area. An SSTS must be located on the highest feasible area of the lot and must have the location preference over all other improvements, except the water supply well. If the ten- year flood data are available, the bottom of the distribution media must be at least as high as the elevation of the ten-year flood. (6) Pump. If a pump is used to distribute effluent to the soil treatment and dispersal system, provisions shall be made to prevent the pump from operating when inundated with floodwaters. (7) Raising Elevation. When it is necessary to raise the elevation of the soil treatment system to meet the vertical separation distance requirements, a mound system as specified in Section 17.3 is allowed to be used with the following additional requirements: (A) The elevation of the bottom of the mound bed absorption area must be at least on -half foot above the ten-year flood elevation, if ten-year flood data are available. (B) In no case shall the sand fill for the mound exceed 48 inches below the mound bed absorption area. (C) Inspection pipes must not be installed unless the top of the mound is above the 100-year flood elevation. (D) The placement of clean sand and other fill must be done according to any community adopted floodplain management ordinance. (8) Inundation of Top. When the top of a sewage tank is inundated, the dwelling must cease discharging sewage into it. (9) Backflow. Backflow prevention of liquid into the building when the system is inundated must be provided. If a holding tank is used, the system must be designed to permit rapid diversion of sewage into the holding tank when the system is inundated. (10) Holding Tank. If a holding tank is used to serve a dwelling, the holding tank's capacity must equal 100 gallons times the number of bedrooms times the number of days between the ten-year stage on the rising limb of the 100-year flood hydrograph and the ten-year stage on the falling limb of the hydrograph, of 1,000 gallons, whichever is greater. The holding tank must be accessible for removal of tank contents under flooded conditions. 73 Washington County Development Code