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118 <br /> nodes emit the same flowrate. The drainfield is broken into multiple zones to facilitate <br /> the distribution of the effluent to the drainfield. Pumping to the drainfield is done <br /> repeatedly over short intervals during the day. <br /> An especially attractive aspect of SSDD systems is that they can be located in wooded <br /> areas with just the removal of underbrush and saplings. By contrast, standard drainfields <br /> require tree removal and trenching to a depth greater than the diameter of the discharge <br /> pipe. Drip drainfields are segmented into zones of, say, 3000 linear feet per zone. There <br /> is much latitude for how zones are combined or distributed to work with the layout of <br /> residential pods and other components of the community, so that wastewater discharge <br /> can "fit in" rather than be "worked around". Another important consideration to <br /> emphasize is that drainfields can be used for other purposes and they can be located in <br /> otherwise undisturbed areas such as meadows and forests. Within reason, I believe we <br /> could locate walking trails over portions of the drainfield if desired. <br /> Several companies manufacture systems for subsurface drip discharge, including <br /> Geoflow and Netafim. They vary slightly in the details of their systems, but the basic <br /> design and functioning is similar for all companies. The main idea is for the majority of <br /> the water discharged to go into the atmosphere through evaporation and transpiration by <br /> virtue of the overlying plants, typically grass or trees. This contrasts with conventional <br /> systems that are designed for infiltration of discharge down through the subsoil earth. <br /> Determination of the area needed for discharge has been calculated for the system as <br /> follows. Final buildout would be 150 units at 2 bedrooms/unit. An unreduced design flow <br /> is calculated to be 150 x 2 x 120 gpd per bedroom= 36,000 gpd. However, given the <br /> characteristics of the community, a flow reduction to 90 gpm per bedroom appears <br /> warranted for the drainfield portion of the design. At 27,000 gpd and a conservative <br /> loading rate (based on using treatment) of 0.15 gpd/sq.ft. yields an area required for one <br /> field at 180,000 sq.ft. A factor of 3 times this quantity is used to account for the repair <br /> field and also the fanning out that occurs due to topography (the drainlines have to be <br /> installed on contour). This gives us a planning area of 540,000 sq. ft. or 12.4 acres. This <br /> would fit into the two effluent discharge areas that are currently reserved for this purpose. <br /> The current plan shows areas of 9.5 acres and 12.7 acres allocated to SSDD primary and <br /> repair. <br /> It is possible to reduce these areas and put the treated water to useful purposes using <br /> reclaimed water methods. Further study and planning will be devoted to water reuse for <br /> watering lawns, fields, and ornamental plants to the greatest extent possible. <br /> Please let me know if there are any questions or comments on this summary. Please feel <br /> free to contact me at 919-367-6310 or via email at kdavidsonO,agriwaste.com <br /> Regards; <br /> Kevin Davidson, P.E. <br /> V.P. of Engineering <br />