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Climatic Data: Rainfall versus Evapotranspiration NLS§ 3.2. It is generally and scientifically accepted that when precipitation exceeds evapotranspiration (Eto), deep percolation of surface rainwater may occur. Evapotranspiration refers to water evaporation that takes place both at the soil surface and transpiration by plants. Since the leachfield is to be constructed at -grade, evapotranspiration will be a significant factor. The CIMIS Data for Station 248 in Zone 14 indicates an evapotranspiration yearly total of 57 inches. The average yearly rainfall is 10 inches. Consequently, there is a significant probability that effluent will evaporate from the three leachlines during most months of the year. III. NITRATE LOADING STUDY FINDINGS A. WASTEWATER FLOW VOLUME PROJECTIONS AND CHARACTERISTICS Wastewater Flow Volume Projections Wastewater flow volumes from the project are anticipated to be very low, possibly as low as 5-10 gpd. Given that Water Use Computation Tables assign 150 gals/fixture for stores, and the facility will have two unisex restrooms (one for customer use; one for owner's personal use), this number will be used in the calculations and discussions below and provides a significant safety factor. The yearly wastewater flow volume is as follows and is based on the facility only operating on weekends, federal and Islamic holidays, from 8:OOAM to 5:OOPM: 150 gpd ADF x 2 d/wk x 52 wks/yr =15,600 g/yr. + 10 federal holidays x 150 gpd = 1,500 gals + 3 Islamic holidays x 150 gpd = 450. Total = 17,550 gallons. This figure will be used in the nitrate loading calculations below. Wastewater Characteristics The domestic wastewater generated from the facility will be composed of blackwater from toilets/urinals and greywater from hand washing. There will be no high organic loading from any additions to the septic system such as offal and blood. Additional wastewater constituents may consist of other liquids to the system such as low strength cleaning liquids, etc. No industrial or commercial chemicals, solvents, etc. should ever be introduced into the wastewater treatment system. It is imperative that low strength and low volumes of cleaners are used in the restrooms since they can disrupt the septic tank biology. The scientific literature cites nitrogen concentrations in domestic septic effluent ranging from 17 mg N/L for basins, sinks, etc. to 140 mg N/L for toilet wastes. A value of 62 mg N/L is typically used for domestic calculations, as indicated in the literature (See Kaplan - Septic Systems Handbook, Pg. 147). Page -5- Chesney Consulting