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III. NITRATE LOADING STUDY FINDINGS A. WASTEWATER FLOW VOLUME PROJECTIONS AND CHARACTERISTICS Wastewater Flow Volume Projections To determine nitrate-nitrogen loading from any project, wastewater flow volumes must be determined as accurately as possible. The future Restroom building is assumed to be a Men's and Women's Restroom with toilets, urinals and lavatories. A toilet flush+hand washing total approx. 1.78 gallons (1.28 gals-New CA standard)+0.5 = 1.78 gals) Assume there are on average three flushes each hour, for two toilets+lavatories, 8 hrs per day: 1.78 gals/toilet flush x 3 flushes/hr x 8 hrs/day x 2 toilets= 85 gpd ADF x 365 d/y= 31,025 gpy. Alternatively, a proposed demographic of 15 people are assumed to be onsite daily: 15 people (per the CDD CUP) x 1.78 gals/toilet flush = 27 gpd ADF x 365 d/y= 9,746 gpy. The more conservative factor of 31,025 gpy will be used in the nitrate loading calculations below. Wastewater Characteristics The domestic wastewater generated from the restroom building will be composed primarily of blackwater from toilets and graywater from hand washing. There will be no high organic loading such as food preparation in a cafeteria. Consequently, a nitrogen concentration of 90 mg N/L is used below and is based on septic tank effluent analysis from similar facilities. B. CALCULATED NITRATE-NITROGEN LOADING NLS§3.0. The calculated nitrate-nitrogen impact to the soil and ultimately to the groundwater is difficult to determine due to the large number of variables involved and variables unknown at this time. These include: 1.) Nitrate impact from upgradient agricultural sources, 2.) Variability in wastewater flows, effluent nitrogen concentrations and dilution effects, 3.) Changes in groundwater directional flow and elevation, 4.) The denitrification potential of the indigenous soils. HAN17SCHFIFINNEMORE SQUAT/ON IN,,,0 -d)+RNb Nr= (I+R) Where: Nr = Resultant average concentration of nitrate-nitrogen in recharge water-(ppm NO3-N) I = Volume rate of wastewater entering the soil averaged over the gross developed area in inches/yr Nw = Total nitrogen concentration of wastewater in mg N/L d = Fraction(%)of nitrate-nitrogen combined loss in the soil due to denitrification. R = Estimated Annual Rainfall Recharge in inches/yr. Nb = Background NO3-N concentration of rainfall recharge, exclusive of wastewater influences. Page -4- Chesney Engineering, Inc.