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E. SURFACE WATER INFORMATION The only body of surface water will be a detention basin which will be located sufficient distance away so as to not be impacted from septic effluent. III. NITRATE LOADING STUDY RESULTS A. WASTEWATER FLOW CALCULATIONS AND CHARACTERISTICS To adequately determine nitrogen loading from the proposed conventional leachfield,wastewater flows must be determined as accurately as possible. These wastewater flow determinations are based on current and particularly long-term growth projections. The following calculations demonstrate flow projections: It is assumed there will be no cooking within a kitchen or office area and therefore no use of a garbage disposal. This will prevent heavy organic loading. The characteristics of the wastewater flow will be predominately blackwater from toilets,with a comparatively small volume of graywater from sinks and a possible shower. Other wastewater constituents may consist of coffee,juices or other similar type liquids to the system. B. CALCULATED IMPACT FROM NITRATE-NITROGEN LOADING From the anticipated wastewater characteristics described, the nitrogen emanating from the project may be at a slightly higher concentration than what would normally be found in a typical domestic or household system. This can be attributed to the lack of a dilution effect which graywater would provide. The scientific literature cites nitrogen concentrations in septic effluent (residential)typically ranging from 17 mg N/L for basins, sinks, etc. to 140 mg N/L for toilet wastes. Therefore, considering a 70/30 percent usage for toilet water volume and sink water volume, respectively, a value of 103 mg N/L of septic effluent will be used to calculate nitrate- nitrogen loading for this project. The loading projection is based on the maximum anticipated number of employees who may use the toilet/sink, etc. on a daily basis and is projected to be 10 people. Although the actual number of people using the system per day may be half this, by using 10 people in the calculations creates a "safety factor." Each person is assigned 10 gallons per day: 10 people X 10 gals/person/day= 100 gals/day X 3.79 L/gal=379 L/day X 103 mg NIL = 39 grams N/day X 260 days/yr(5 days/wk-52 wks/yr)= 10 kg N/yr X 2.2 lb/kg=22 lbs N/yr When an areal contribution is considered,the nitrate-nitrogen concentration is projected to be: 22 lbs N/yr- 3 ac = 7 lbs NO3-N. The following reductions in the nitrate-nitrogen loading from above are anticipated, according to the scientific literature: Septic tank(as designed) removes 50%N x 22 lbs= 11 lbs 4 Na!!ey Ag Research