INFO: Overflow volume (monthly or annually, in kL) If inputs to a disposal area consistently exceed outputs, no surface area (for irrigation) or no trench volume is large enough to contain and dispose of applied wastewater. If inputs exceed outputs some of the time, overflow may occur if the storage capability of the facility is insufficient. The aim of Table 5 is to choose trench dimensions (or an irrigation area) so that this never happens for the inputs/outputs you have chosen. Table 5 warns you if overflow occurs in one or more months, and you cannot proceed further until you have eliminated it. The overflow is the combined volume of retained rainfall (if any) and wastewater (expressed in kilolitres). Therefore, it is possible for the overflow for any month or year to exceed the total volume of wastewater applied to the system. The overflow might be surface flow from a trench/bed or irrigation area, or the volume discharged from a treatment lagoon. INFO: Average annual depth of effluent (in mm) The average depth of effluent is only calculated if every month has no wastewater overflow. If overflow occurs in any month you cannot calculate a trench length in the Next section, or the size of the disposal area. IMPORTANT: Various depths can be used as the 'wetted depth' in order to calculate trench or bed length. Click Options on the summary page (after Table 5) to alter the wetted depth, or wetted width, or both.