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IV. MOUND SYSTEM DESIGN CRITERIA The design of the pressurized mound disposal system for the project is based upon criteria for efficient operation,disposal field longevity,and environmental protection. An overview of the entire system as it currently exists is found on Page 2 of this document. The proposed domestic wastewater management system for the expansion, is as follows: Beginning with the two residential structures: wastewater management will continue as it currently exists with influent from the west house coming into the new second(middle)west septic tank and influent from the east house coming into the new second(middle)east septic tank,as illustrated on the Mound System Plans. A new 1,600 gallon septic tank is to be installed for the west house. Kitchen influent from the Darbar Hall kitchenette and the Langar Hall kitchen will gravity through a four-inch ABS tightline into the west,new three compartment 2,000 gallon grease interceptor(first)tank. Kitchen influent from the existing Assembly Hall will gravity flow in four-inch ABS tightline into the east,new three compartment 2,000 gallon grease interceptor(first)tank. Influent from the Darbar Hall restrooms will gravity flow in a four- inch ABS tightline into the new second(middle),west 2,000 gallon,two compartment septic tank. Influent from the Langar Hall restrooms will gravity flow in a four-inch ABS tightline into the new second(middle), east 2,000 gallon,two compartment septic tank. Effluent from both middle tanks will gravity flow into the third,or last,new 2,000 gallon septic tanks for further treatment. From these last two tanks,effluent will gravity flow 450 ft to a new 1,600 gallon,two compartment filtered pump vault(FPV)tank. As referenced, a custom four pump effluent filtered chamber will sequentially pressurize each of four cells within the mound. A. GREASE INTERCEPTOR TANKS, SEPTIC TANKS AND DOSE CRAMBER TANK Septic tanks store the accumulated sludge,scum and effluent(clear zone)volumes,which in tum affect treatment of nitrogen within the tanks. Although there are differing methods to size septic tanks for a project,tank capacity based on pump-out interval and average daily flow is as follows:For a pump out interval of every 5 years,tank volume V=3.65 Q„2 x Peaking Factor. The peaking factor is typically taken to be 2.5 for commercial projects based on a"peak day”since it is assumed the majority of flow will occur on Sundays. Additionally,to operate as a plug flow reactor, the volumetric septic tank capacity should be approximately:5x the ADF: 5 x 2,400= 12,000 gallons. Therefore,sufficient septic tank capacity exists. There must be an effluent filter in all of the septic tanks as noted on the Plans. When the tanks are pumped, only two-thirds of the tank contents should bepumped to retain ballast. Septic Tank Capacity Based on Potential Pump-out Interval of Every Other Year: 2.0(pump-out interval factor)(QAvE)x Peaking Factor(PF=2.5)=2.0(2400 gals/day)x 2.5= 12,000 gals. Total septic tank capacity=2-2,000 gallon grease interceptor tanks; 2-2,000 galloa septic tanks;2-2,000 gallon septic tanks,and one 1,600 gallon,two compartment dose tank 13,600 gallon . Detention Time: Detention Time= 13,600 gal total tank capacity x 0.70(30%volume lost to sludge/scum accumulation) ; 2.5 (Peaking factor)x 2400 gals/day(ADF) Detention Time= 1.6 days.The minimum acceptable detention time i5 1.0 day. 11