2019.02.04 CC Packet - Laserfiche WebLink

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Effective April 28, 2015 Chapter Four Subsurface Sewage Treatment System Regulations 13.13 Compartmentalization of Single Tanks. If septic tanks are compartmentalized, items (1) to (5) of this Section apply: (1) When septic tanks are divided into compartments, the volume of the first compartment must be equal to or larger than any succeeding compartments. Each compartment must contain at least 25 percent of the total required liquid capacity and have an inside horizontal dimension of at least 24 inches. (2) Flow between compartments can be achieved by an unbaffled transfer hole with a minimum size of 50 square inches located in the clarified liquid zone or a minimum of 12-square inch transfer hole located above the clarified liquid zone that is baffled according to Section 13.14. The final compartment of a tank that employs a transfer hole in the clarified zone shall not be used as a pump tank. (3) Septic tanks must have at least a two-inch drop between the invert of the inlet to the invert of the outlet. No liquid level drop is required between two compartments. (4) Adequate venting must be provided between compartments by baffles or by an opening of at least 12 square inches near the top of the compartment wall. (5) All compartmental walls must be designed to withstand the weight of the effluent against an empty compartment. 13.14 Septic Tank Baffles. All septic tanks must be baffled according to (1) to (7) of this Section. Effluent screens are allowed to be substituted for outlet baffles. (1) Baffles must be installed at each inlet and outlet of septic tanks. Outlet baffles are required on compartment walls if the transfer hole is at the liquid level. (2) Baffles must be resistant to corrosion or decay. Inlet baffles must not restrict the movement of solids. (3) Baffles must be integrally cast with the tank or affixed at the top and bottom with connectors that are not subject to corrosion or decay. Baffles for fiberglass reinforced polyester tanks are allowed to be either resin bonded or secured with suitable structural adhesive. Sanitary tees used as baffles must be affixed to the inlet or outlet pipes with a permanent waterproof adhesive. (4) The inlet baffle must extend at least six inches, but not more than 20 percent of the total liquid depth, below the liquid surface. The inlet baffle must extend above the liquid surface in compliance with Section 13.4 (5), and at least one inch above the crown of the inlet sewer. (5) The outlet baffle and any baffles between compartments must extend below the liquid surface a distance equal to 40 percent of the liquid depth, except that the penetration of the indicated baffles or sanitary tees for horizontal cylindrical tanks must be 35 percent of the total liquid depth. They must also extend above the liquid surface as required in Section 13.4(5). (6) There must be at least one inch between the underside of the top of the tank and the highest point of the inlet and outlet baffles. (7) The nearest point on the inlet baffles other than sanitary tees must be no less than 6 inches and no more than 12 inches from the end of the inlet pipe. The nearest point on the outlet baffle, other than sanitary tees, must not be closer than 6 inches and no more than 12 inches from the beginning of the outlet pipe of the baffle. Sanitary tees used as inlet or outlet baffles must be at least 4 inches in diameter. 13.15 Sewage Tank Access. Septic tanks shall have a minimum of two maintenance holes with a minimum diameter of 20 inches (least dimension). Maintenance holes must be placed over the inlet baffle and the outlet device (baffles or screen). The maintenance holes must be large enough to allow pumping without interference Enough maintenance holes must be provided so access can be gained within six feet of all walls for solids removal of each compartment. Inspection pipes of no less than six inches in diameter shall be provided over any baffles that are not otherwise accessible through a maintenance hole. 50 Washington County Development Code