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The assumption is made that the grass will uptake 80% of the nitrogen in the effluent since it only uses two forms of nitrogen: Ammonium and nitrate. Approximately 70%to 90%of the effluent is in the ammonium form, with the remaining concentration in the unavailable organic form. 80% of 80%(between 70% and 90%) of 88%mg N/L = 56 ppm NH4 =56 ppm x 0.612(conv. factor)=34 lbs of N/Ac ft of effluent disposed. Nitrogen uptake calculations: 160 workdays/8 mos. of the yr x 1,000 gaWday= 160,000 gals-325,851 gaWAc-ft=0.491 Ac-ft of effluent water. 34 lbs N/Ac ft x 0.491 Ac ft= 17 lbs of applied by the effluent water. Using Kentucky blue grass as a landscape ground cover example: Kentucky blue grass requires 124 lbs N/ac/yr for optimum growth. Therefore, 124 lbs.N/Ac/yr x(1,600 f12 , 43,560 112/Ac) =0.037 Ac. = 5 lbs N/yr should be applied to the grass over the filter bed area. Although the effluent will supply more than three times the nitrogen than what the grass requires(17 lbs N vs. 5 lbs N)during the growing season,it is possible for the grass to absorb more nitrogen than what it needs. Grasses will absorb readily-available-nitrogen as long as the grass is cut or mowed and the clippings disposed of. Consequently, most of the applied nitrogen(17 lbs)may be taken up by the grass. As demonstrated through the nitrogen calculations, commercial nitrogen fertilizer should not be applied to the filter bed landscape grass. From the calculations for the irrigation water requirement of the landscape groundcover grass over the filter bed area, we find that the irrigation requirement will be roughly one-third of the total theoretical effluent volume to be produced. We also find that the nitrogen requirement of the grass during the growing season (eight months of the year) will be roughly one-third of the total pounds of nitrogen in the disposed effluent. Therefore, the nitrate loading as calculated on Page 8 by the Hantzsche/Finnemore Equation may be theoretically reduced by one-third, from 8 ppm NO3-N down to 5.3 ppm NO3-N. During the winter months, nitrification may be suppressed due to the colder temperatures and was therefore, not considered in the above calculations. Nitrate Impact Mitigation Factors Summarized OO From the concentration of alkalinity found in the domestic well for the Cunha facility, it appears there may be insufficient alkalinity to support nitrification from the underlying aquifers that will provide water to the project. Alkalinity contributions from the wastewater emanating from the project are of course unknown at this time, but may supply additional, but probably deficient, alkalinity. © The upper soil profile has a fair degree of denitrification potential due to its alkalinity and a measure of cation exchange capacity. This soil type coupled with the use of peat at the soil effluent interface may have a dual action effect by suppressing nitrification and promoting denitrification. O It is known that the daily groundwater flow into Oakwood Lake is substantial. This is undoubtedly increasing groundwater flow velocity under the subject property and may be an explanation for the low nitrate concentration in the water table and underlying water bearing strata. This comparatively fast groundwater flow would be beneficial for creating a dilution effect on the percolating effluent from the project by rapidly removing any "build-up" of a nitrate concentration under the disposal area. Page -13- Ch mq Consulting