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March-26,2003 Job Number:"LG02--031 Page 7 officials but with some real limitations. In Hantzsche and Fennemore's article,published-in Ground Water, they.mention that the equation ignores dispersion,lateral'flow, and mixing . ent areas: These processes would generally contribute to., with ground water flow from up-gradi additional reduction of nitrate' concentrations in ground water to the extent that the nitrate=nitrogen concentration of ground-Water flow from up-gradient areas is lower." The Hantzsche,and Fer►nemore equation'provides"...a conservative (worst case) first . - approximation of groundwaternitrate-nitrogen concentration resulting from the combined effect; �— of on-site sewage disposal systems and precipitation,-.This(the equation and approach) is for. estimation of long-term.effect (i.e.,aver years) on ground=water quality, and is not.intended for . prediction:of seasonal changes." ` The Harntzsche and Fennemore' equation takes into account development area, soil denitrification factor,rainfall volume,.rainfall nitrate concentration,the waste effluent quantity, and waste. effluent nitrate-concentration. The formula, assuriiptions and calculations used for the analysis R. are shown'on Plates 8 and 9. The units of J.trat 'used in the mass,balahce equation are nitrate-N whose rnaximum.drinking water contaminate level is 10 xnglL. - 5.1 Nitrates from Rami Fall ' An estimate of the quantity and qualityof rainfall was required for the nitrate loading analysis. The,deep percolation of rain for the Lodi area was estimated to be.6.84:inches. The assumptions and the calculation'are shown on Plate 8. and Finnemore have used.the a concentration of rain fall for their equation of 1.O mg/L- Hantzshe . . -. }� 5.2 Nitrates from Septic System Waste Water The average total=nitrate concentration of the typical septic waste=is"normally considered to be 35 mg/L-N g. The average daily flow of influent into the septic systems on the site was determined 'by listing the:categories of occupancy; duration.of occupancy; and estimated domestic waste h water flow associated with each category. The following table lists the assumptions to determine average daily-domestic-waste waterflow. s Crites,R.,Tchobanoglous,G:, 1998,,Small and decentralized wastewater management systems:McGraw- Hill series in water resources and environmental engineering,McGraw-Hill.Boston first edition,see Table 4-14 page ,,, 191,Typical composition of untreated domestic wastewater.