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Nftp" %%./ Isurface ATE-NITROGEN IMPACT MITIGATION 4.1,4.2 It is possible that septic effluent disposal area(leachfields) constraints m7LD, in n the subject Lots. Filter beds may be considered for design criteria imposed by thction with seepage pits, since dual septic systems will be required. Filter beds allo rized(preferably) distribution piping to be installed as high in elevation as possible to take age of evapotranspiration during favorable months of any given year. Deep-rooted grasses e planted over the disposal area to aid in evapotranspiration and take-up nitrogen in the form ate and ammonium. Deciduous and evergreen plants maybe planted no closer than 15 ft from chline to prevent root infiltration. The scientific literature suggests that denitrification may anced by placing piping higher in elevation toward the soil surface, particularly since the soils contain approximately a 20%clay soil. During the fall and winter months, seepage pits would be used to manage excess effluent volumes that could not be managed by the filter beds. Additionally, during the rainy season,November through March, nitrification is suppressed during these colder months of the year, so it would be beneficial for the effluent disposal area piping to be placed high in elevation where the soil/effluent interface is colder. SSS§ 6.8 Depending upon the final EHD design criteria for effluent management for each Lot,the septic system and disposal area parameters could be based upon the following: Two septic tanks may be required by EHD for the dual system, and each tank should have two compartments. Tank sizing will be dependent upon the number of bedrooms each residential structure will have. Effluent filters must be installed in the second compartment of each tank. A filter pump vault must be installed if the effluent is to be pumped. As noted in the Nitrate Loading Calculations on pages 9 and 10, an additional tank will theoretically decrease the nitrogen concentration in the septic effluent by an additional 10%. It is imperative to recognize that all septic systems have a lifespan. This lifespan is dependant on several factors and is therefore difficult to determine. Lifespans may be measured in months or years. Due to the indigenous clay/hardpan surface soils over the project site, most of the effluent volume will be managed by the deeper septic system structures, provided that"conventional" (leachlines and seepage pits) septic systems are installed. Consequently, three critical issues must be addressed: The first issue is limiting water use throughout the future homes as much as possible. As calculated on Page 9 of this report, the household usage for this Study has been determined to be 68 gals/resident, and should not exceed this volume. Restricting water use also includes checking for water leaks in toilets, dripping faucets, etc. on a regular monthly basis. The second factor in extending the lifespan of each system is not installing garbage grinders, commonly called sink disposals. Food products that would be ground-up by a disposal must be handled as a solid waste for this subdivision. Garbage disposals will increase the organic loading in the effluent leading to substantial biomat(clogging mat) formation. Thirdly, water softeners should also not be installed in the subdivision because the sodium from water softeners will bind the clay soil and destroy permeability. Although this phenomenon is debated in the scientific literature, it is my Lopinion that it is a distinct possibility and should be avoided since it could lead to a decrease in disposal area longevity. Page-14- Chesney Consulting