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NITRATE LOADING STUDY FINDINGS <br /> WASTEWATER FLOW VOLUME PROJECTIONS AND CHARACTERISTICS <br /> Wastewater Flow Volume Projections <br /> To determine nitrate-nitrogen loading from any project, wastewater flow volumes must be <br /> determined as accurately as possible. Domestic flow volumes have been approximated from the <br /> USEPA Onsite Wastewater Treatment Systems Manual, Pg. 3-4. However,the EHD has <br /> promulgated residential flow volumes pertaining specifically to Nitrate Loading Studies. Under <br /> EHD guidelines,the first bedroom of a structure is assigned 100 gpd and all remaining bedrooms <br /> of the subject structure are assigned 50 gpd, 365 dpy. As referenced,the proposed house will <br /> have four bedrooms. Therefore,total flow volume projection= 100+ 50+50+50=250 gallons <br /> wastewater/day. <br /> Wastewater Characteristics <br /> The USEPA OWTS Design Manual states residential nitrogen concentrations in domestic septic <br /> effluent typically ranging from 35 to 100 mg N/L. A starting concentration of 45 mg N/L will be <br /> used. An accounting for the loss of nitrogen within the septic tank of between 10% - 30%has <br /> been described in Dr. Stewart Oakley's paper(See Ref. 10, Pg. 10). A removal percentage of <br /> 20%will be used to calculate nitrate-nitrogen loading for this project: <br /> 45 mg N/L -20%= 36 mg N/L. <br /> CALCULATED NITRATE-NITROGEN LOADING <br /> NLS§3.3,3.4,3.5,3.6. The calculated nitrate-nitrogen impact to the soil and potentially to the <br /> groundwater is difficult to determine due to the large number of variables involved and variables <br /> unknown at this time. These include: 1.) Impact from upgradient agricultural and septic system <br /> sources, 2.)Variability in wastewater flows, nitrogen concentrations and dilution effects from <br /> irrigation and stormwater recharge, 3.) Changes in groundwater directional flow and elevation, 4.) <br /> Denitrification potential within the clay soil fractions, and within confined and/or unconfined <br /> aquifers. <br /> The Hantzsche/Finnemore Formula is used below to predict the average resultant concentration of <br /> nitrate-nitrogen in effluent recharge water. As calculated below,the property has been assessed on a <br /> total areal loading basis correlated with the total projected yearly wastewater flow volumes <br /> calculated above. These two factors primarily estimate the average resultant concentration of <br /> nitrate-nitrogen in the recharge water. This concentration should not exceed 10 ppm nitrate-nitrogen <br /> (45 ppm as nitrate). <br /> Page -6- <br /> Chesney Consulting <br />