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..� <br /> NEW <br /> roperty, it is likely that cation adsorption, denitrification, and dilution will significantly <br /> reduce the concentration of nitrate to levels which will not approach the maximum <br /> contaminant level (MCL) (10 mg/P) for nitrate nitrogen (NO;N) in the first encountered <br /> groundwater approximately 70 to 80 feet bgs. <br /> A second approach used to calculate the nitrogen loading by four to six inhabitants <br /> in the existing residence is based on conservative assumptions of nitrogen loading per <br /> person-day. The EPA (1980) estimates that the nitrogen loading ranges from 6 to <br /> 17 grams of nitrogen per person-day (g N/person/day). Using the average value of <br /> 11 .5 g N/person-day and 45 gallons/person-day, the conservative estimate of wastewater <br /> influent from a typical household to a septic system is estimated at 67.3 mg N/P. This <br /> conservative estimate differs from the value of 38 mg/f used in Figure 2. Using the more <br /> conservative estimate of 67.3 mg N/R results in an increase of 77% in all the processes <br /> described in Figure 1 . However, the predicted concentrations in groundwater directly <br /> underneath the septic system still does not approach 10 mg N0;N/P. <br /> 6.2 PHASE 1 EXPANSION <br /> As discussed above, the Church is applying for permission to convert the existing <br /> four-bedroom residence into a facility that could accommodate 65 people for church <br /> attendance. This section will present the assumptions for liquid and nitrate loadings <br /> associated with the expansion, discuss the calculated liquid and nitrate loading rates, and <br /> present some potential septic system modifications for the Phase 1 expansion. Detailed <br /> calculations of liquid and nitrogen loading rates are presented in Appendix F. <br /> -� 6.2.1 Assumptions for the Phase 1 Expansion <br /> ,. This subsection presents assumptions for the Phase 1 expansion of the property. <br /> The assumptions were used in the liquid and nitrate loading rate calculations presented <br /> in the following subsection. The assumptions for the Phase 1 expansion are as follow: <br /> a <br /> • The liquid loading rate is 45 gallons per person-day. <br /> — <br /> • The nitrogen loading rate is 11 .5 grams N per person-day. <br /> • Two people will occupy the facility 5 days per week from 8 am to 5 pm; the <br /> associated waste will result in liquid and nitrogen loading equivalent to 0.75 <br /> day (i.e., 33.75 gallons/person and 8.625 g N/person) for that period. <br /> SAC 125.12 9 <br /> s DAMES &MOORE <br />