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u � The calculated nitrate loading concentration in the recharge effluent from the Office Trailer is calculated to be under the Maximum Contaminant Level limit for nitrate in drinking water. The variables used in the calculations above are conservative. For example, the use of 103 mg NIL, is a much higher nitrogen concentration than those concentrations published from household or domestic sources. Secondly,various researchers place the nitrogen reduction occurring in septic tanks at 10%to 20%. From the May 8, 2003 Symposium"Onsite Wastewater Treatment-Nitrogen Removal,"Dr. Stuart Oakley of Chico State University states that"approximately 20%of the total nitrogen generated is removed in the septic tank." The EHD is also concerned with the total nitrate loading from the entire West Lathrop Business Park, consisting of 34.7 acres. The original Nitrate Loading Study calculations for this property(Application Numbers GP-01-13 and ZR-01-09, February 2002)demonstrated that the entire property could support 300 people. These calculations are illustrated below. Personal communications with Mr. Steve Dunn who is the Preston Pipelines Lathrop Office Manager, stated that Preston Pipelines has approximately 10 office staff and approximately 12 field personnel. Therefore,the total number of people on the entire property acreage of 34.7 acres does not currently exceed 300. THE MAXIMUM NUMBER OF PEOPLE APN 190-230-07 (34.74 Acres)CAN SUPPORT= HANTZSCHEIFINNEMORE EQUATION INµ,(1 -d)+RNb Nr= (I+R) Where: Nr= Resultant average concentration of nitrate-nitrogen in recharge water-(ppm NO,-N) I = Volume rate of wastewater entering the soil averaged over the gross developed area in inches per yr Nw= Total nitrogen concentration of wastewater in mg N/L d = Fraction(%)of nitrate-nitrogen loss due to denitrification in the soil R = Average recharge rate of rainfall -inches per yr Nb= Background nitrate-nitrogen concentration of rainfall recharge, exclusive of wastewater influences (ppm NO,-N) Values and Assumptions I=300 people x 15 eals/nerson/d x 260 work d/yr= 1,170,000 eals=total W W/vr= 156,417 cu ft= 1.24 in/yr 34.74 Ac x 43,560 sq ft/Ac x (I ft/12 in) Nw= 103 mg N/L d = Assume 20% due to a fine-grained soil R = 11 in/yr. Nb= Assumed to be 0.1 ppm NO3-N 1.24 in/yr(103 me N/L) 0 -0.20)+(11 in/yr x 0.1 mg/L) Nr = (1.24 in/yr+ 11 in/yr) Nr = 9 ppm as nitrate-nitrogen(NO3-N)or 40.0 ppm as nitrate(NO,) 9 Chesney Consulting