20.1 The following procedure shall be used to determine the minimum surface area required for drip dispersal system.

20.2 The depth and duration of the seasonal water table shall be determined.

20.3 The sizing and loading rate chart found in Table 1, 2 and 3 of this manual shall be used to determine the amount of surface area required for installation.

20.4 The spacing between drip tube laterals shall not be less than two (2) ft. center to enter. Drip tube laterals spacing may be greater than two (2) ft. however, for the purpose of determining the length of tubing required for a dispersal field, all length calculation shall be two (2) ft. center to center.

20.5 The effective area of the dispersal field shall be calculated by dividing the daily wastewater flow rate (DWF) in gallons per day (gpd) by the soil loading rate (SLR) in gallons per foot square per day (g/ft ft² / d). [Area of the dispersal field (DF) = design wastewater flow (DWF) / soil loading rate (SLR).]

20.6 The length of the drip tubing shall be determined by dividing the dispersal field (DF) required by the drip tube spacing (DT) of two (2) Ft. [Drip tube length (DTL = dispersal field area (DF) / drip tube spacing (DT) of two (2) ft.]

20.7 The number of emitters required shall be determined by dividing the drip tube length (DTL) by the emitter spacing (E) ft. [Drip line lateral length (ft.) / emitter spacing (ft.) = Number of emitters.]

20.8 The loading rate for a soil which has a rock substrata (consolidated or fractured) and no seasonal water tables present above the rock substrata shall be sized as a moderate seasonal water table.