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AVRES ASSOCIATES MEMORANDUM To: Chris Kronser, Planning Associates, Inc. 0 From: Robert W. Whitmyer, CPSS, CSTM Date: July 30, 1997 Re: Land Use Effect on Leachable Nitrogen Because of concern for increased pollutants, you asked us to compare the amount of leachable nitrogen generated by the current and proposed land uses of a 46-acre parcel along the south side of Oncken Road in the Town of Westport. Leachable nitrogen is defined as the amount of nitrogen that has potential to impact groundwater, and is typically in the nitrate (NO3) form. This memorandum provides you with that information and includes summarization of computations and supporting literature citations for the figures used in those computations. The parcel described as the southeast % of the southwest % of Section 29, Township 8 North, Range 9 East, is currently being used for agricultural purposes and is proposed to be used as the site of the Madison Country Day School. Current and past use of this parcel has been for growing row crops. Field corn and soybeans or alfalfa have been grown on a rotational basis for a number of years with two years of corn being grown for every year of soybean or alfalfa growth. The proposed school will initially consist of pre-kindergarten through third grade and maximum 300-person population (275 students and 25 staff). As demand increases and classes pass to the next level, it is anticipated the school will expand to include fourth through twelfth grades and a maximum student population of 800; with staff, total maximum building population is projected to be 875. Periods of operation will be the same as other schools, eight hours per day five days per week September through May except holidays. Total number of days in session per year will be approximately 185. Leachable nitrogen is produced by both land uses. Fertilization during corn cropping adds nitrogen to the soil in greater quantities than is used. The recommended rate of fertilization is 160 pounds of nitrogen per acre per year (lb N/ac/yr) for the soil series mapped on the propertyl. Corn uptake of fertilizer nitrogen rarely exceeds 40 percent of that applied2. Soybeans and alfalfa are legumes, which are normally not supplemented with nitrogen fertilizers. Because the site is rural and not served by a municipal sewer, wastewater generated at the proposed school would be treated and dispersed on site. Urine and feces are the source of greater than 90 percent of the nitrogen in domestic wastewater, which consists of toilet, food preparation, and cleaning wastes3. At the school, no food preparation wastes would be generated as meals would be catered. Total nitrogen generated per person per year is estimated to range from 4.5 kilograms (kg) to 5.8 kg4. Up to 80 percent of the nitrogen discharged to an onsite wastewater treatment and dispersal system is leachable5. Chris Kronser Memorandum d:\bobw\data\rwwproj\private\wi\cntryday\ckmo01.doc Engineers/Architects/Scientists/Photogrammetrists 52-0167.11 2631 West Superior Street,Suite 105, Duluth,MN 55806-1811,(218)722-7131,FAX(218)722-7165 Page 1 of 2