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s _ 4 ..( C. WASTEWATER FLOW CALCULATIONS AND CHARACTERISTICS Domestic wastewater flows managed by ori-site septic systems have been studied for decades with various data published in the scientific literature. Wastewater flows for this project will be assessed on a"f iture"basis whereby it will be assumed each'household will have four persons per house (husband; wife.and two children). HOUSEHOLD PERSONAL USE 25 gal for,laundry; 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 gal/person/day x number of persons/home). s The daily wastewater flow rate can'be estimated at: 40 gals+ (35 gals x 4 people/home)= 180 gals/day for an average flow per resident of 45 gals. As a safety 'i. factor, the total daily wastewater flow per house and average daily flow per resident will be increased 1.5x to 270-gals/day and 68 gals/resident,respectively. The peaking factorfor individual residences on septic tanks will vary with the day of the week and usage. Peak hourlyrates 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, thus a 1.5 safety factor. 1 The characteristics or composition of septic tank effluent is dependent upon several parameters due to idiosyncrasies within each household. Certain appurtenances change the characteristics of the ( wastewater effluent such as filter vaults within.septic tanks and kitchen food-waste grinders. In-determining nitrogen concentrations of septic influent and effluent,per capita intake of nitrogen per day must be estimated. The average American consumes between 70 and 140 g of N/day. Since nitrogen comprises 16% of the weight of the average protein, 16% of 70 g N= 11 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 f theoretical influent: - The.concentration of nitrogen in septic system effluent is nonnally specified in the scientific literature _ as units of mg NIL (milligrams total nitrogen per Liter of effluent). Unfortunately, these units superimpose wastewater flow variability onto nitrogen influent variability, thus creating even greater variability. One researcher(Bauman), has averaged the means from 20 other studies to arrive at a concentration of 62 21 mg N/L in septic tank effluent. If the above figure for wastewater discharge is estimated at 68'gals/resident/day(257 liters) and using the figure of 17 g N/cap/day excreted= 17 g 257 L=66 mg N/L/day estimated for the proposed Sorrenti project. This concentration will be the estimatedd-N loading in the-effluent discharged from each of the potential dwellings on the six Parcels. Page -6- Chesney Consulting