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Final Dispersal Option: Shallow Narrow Drainfield
Shallow narrow pressure-dosed drainfields are used to disperse wastewater from innovative systems to the soil environment, and are generally used for wastewater that has been treated to meet a minimum of 30 mg/L of BOD5 and TSS. The drainfield lines are placed in the upper soil layers in order to achieve maximum wastewater treatment through processes occurring in the soil environment. This shallow placement also maximizes the vertical separation distance from the bottom of the drainfield to the groundwater table, providing greater protection of water resources.
Grass growing above the shallow narrow drainfield lines is generally very lush, as seen in the photographs above. The grass is using the moisture and nutrients that are being dispersed through the drainfield lines, and so removing nitrogen and phosphorus from the effluent. The roots of the grass also help to keep the soil aerated.
For more information on shallow narrow drainfields:
Web Links: This drainfield option has been studied in great detail, with the above-referenced results summarizing of the data obtained. See the report by S. Holden and M. Stolt for full details of the study, available here.


Copyright 2006 URI Water Quality Program