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These impermeable surfaces will be traded for potential point sources of nitrate: on-site septic systems, lawns, landscaping and retention basins. Domestic irrigation recharge can account for 250 to 1,500 gallons of water/day/SFR during the spring and summer months (-6 mos.out of the yr). Therefore, careful nitrogen fertilization of lawns and landscaping must be done. C. WASTEWATER FLOW CALCULATIONS AND CHARACTERISTICS Domestic wastewater flows have been studied for decades with variable data published in the scientific literature. Wastewater flows for this proposed project will be managed by on-site septic systems, with the possibility of City of Manteca water and sewer hookups in the future. The total daily water use is a combination of household and personal uses, as itemized below: HOUSEHOLD PERSONAL USE 25 gal for laundry £43;x '' 2 gal for drinking and cooking 10 gal for dishwashing 3 gal for oral hygiene 5 gal for misc. use 14 gal for bathing 16 gal for toilet flushing/sink washing FLOW RATE in gals/home/day= 40 gals/household/day+(35 gallpersonlday x number of persons/home). Assuming the average household for the project will have 4 persons per house (husband, wife and two children), the daily wastewater flow rate is estimated to be: 40 gals + (35 gals x 4 people/home) = 180 gals/day for an average flow per resident of 45 gals/d. Although the residences will be built with water saving devises, the occupants will probably be of a higher income level. This normally translates into higher water usage for various reasons (e.g., indoor spas, increased entertaining, etc.). Therefore, as a peaking factor, the total daily wastewater flow per house andaverage Bail flow e ei�lent wa15 be increased 2 5x to 450 gals/house and 13 a s/ esident_res ective . The peaking factor for individual residences on septic tanks will vary with the day of the week and usage. Peak hourly rates are normally associated with the discharge of clothes wash machines, dishwashers and shower/bath water. The ratio of the peak day to the average day can vary from 1.5 to >5, depending upon the time of the year and usage, with 2.5 an acceptable peaking factor for single family residences. The characteristics or composition of septic tank effluent is dependent upon several parameters because of idiosyncrasies within each household. Certain appurtenances change the characteristics of wastewater effluent such as kitchen food-waste grinders and filter vaults within septic tanks. Since this study is concerned with nitrogen, this constituent is quantified in the wastewater effluent, as demonstrated in the calculations below: In determining nitrogen concentrations of septic influent and effluent, per capita intake of nitrogen per day must be estimated. The avera e American consumes between 70 and 140 0 . N/day. Since nitrogen comprises 16% of the weight of the average protein, 16%of 70 g N = I 1 g N/capita/day and 16% of 140 g N= 22 g N/capita/day. The average of these two values is 17 g N/capita/day of theoretical influent. 7 Vaffey AB Re-5earck