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Total nitrogen concentration of the effluent wastewater after septic tank treatment was determined in the calculations above (NW- Page 7) and found to be 42 mg N/L. Therefore,to determine the assumed total nitrogen concentration of raw wastewater influent,this nitrogen concentration in septic tank treated influent must be increased by 20%to account for nitrogen reduction occurring in the septic tank, in accordance with the findings of Dr. Stewart Oakley. Consequently, the total influent(raw wastewater)nitrogen concentration can be assumed to be 42 mg N/L x 20%=50 mg N/L. Complying with the 50%reduction in nitrogen concentrations between the raw wastewater influent and treated effluent, places the effluent concentration requirement after the proposed vegetative treatment at no greater than 25 mg N/L. According to The International Plant Nutrition Institute,which is now part of The Fertilizer Institute, 0.675 tons of Fescue grass removes 25 lbs of nitrogen per ton of Fescue removed. The following calculations demonstrate that the Fescue lawn grass can theoretically uptake the effluent nitrogen to lower the effluent concentration from 50 mg N/L to 25 mg N/L: 0.1 lbs Fescue grass/sf x 750 sf filter bed=75 pounds grass/cutting. 2 cuttings per month over eight month growing season(Feb-Oct) = 18 cuttings 75 lbs. grass/cutting x 18 cuttings = 1,350 lbs grass (0.675 tons) However, 50 mg/L of total nitrogen equates to 0.000416794 pounds of nitrogen per gallon of influent. The total volume of raw wastewater flow from the second unit dwelling is estimated to be: 225 gals ADF x 365 d/yr= 82,125 gals. Pounds of nitrogen in this volume= 82,125 gals x 0.000416794 lbs nitrogen/gals= 34 lbs of nitrogen spread over 750 ft', or 0.0453 lbs nitrogen/ft'. But based on the 50%reduction in total nitrogen requirements as referenced above, only 17 lbs of nitrogen would have to be treated by vegetative uptake, not the 25 lbs as calculated. The ammonium fraction of the wastewater,which constitutes approximately 80% of the septic tank-treated effluent is immediately available for uptake by the Fescue grass. The remaining 20% organic fraction must undergo ammonification before uptake. The total nitrogen is used since it is assumed this 20%will eventually undergo ammonification. V. MONITORING PROGRAM To determine nitrate concentrations from within vadose zone water under the EZFIow tubes, a Soil Solution Access Tube (SSAT)manufactured by the Irrometer Company is proposed, as illustrated in the attached data sheets. I am proposing to use this device to sample effluent that has percolated into the vadose zone under the EZFIow tubes. As-builts must be provided by the installer specifying the depth(soil-interface depth) and the exact location of the filter bed perimeter, either by placing stakes or some other marker at the four corners, or tying a filter bed corner distance from a fixed object. A hand auger will be used to drill a boring in between the tubes. A 48" SSAT will be installed, then extraction of a vadose zone water sample from at least 1 ft below the soil-effluent interface will be obtained by suction. I Page -10- Chesney Consulting