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' k` ■ KLEINFELDER On May 5, 1999, three percolation tests were performed on the top of the completed leach field area. The data sheets are attached and indicate percolation rates of 10, 20, and 30 minutes per inch. These tests were performed beginning at a depth of 3 feet below the completed pad pursuant to a letter dated April 30, 1999 'from Mike,I3uggins. Essentially;the percolation tests were performed in the zone of processed native material. We were also requested by Mr. Mike Huggins of the EHD to calculate the nitrate loading for the proposed leach field. As you etre aware, the drinking water standards for nitrate is 45 milligrams per liter (NO3) and 10 mg/I as Nitrogen (N). In our evaluation of nitrate loading, we have used the mass balance equation which is presented below with an explanation for each factor and the value used in our study. We note that the Hantzsche mass balance equation, as well as the literature available for our review. are primarily for residential type structures versus a commercial facility such as the clubhouse. Since the intent of this mass balance equation is to evaluate the impact on groundwater over a large area, we have used the approved flow rate for the clubhouse. which is 7,380 gallons per day, and calculated an equivalent number of dwelling units over the 200-acre golf course. We have assumed nominal flow from the maintenance building and the driving range restroolns. Combined, these facilities amount to approximately 50 dwelling units at 150 gal/day/Unit. N,-AW x N,,, H-D)+(Nbh AW +r Where: N, = calculated nitrate concentration in groundwater resulting from domestic sources and precipitation—mg/I, as N A = number of dwelling units per acres on septic tanks (unit/acre)= 0.25 W = annual wastewater loadinIg per dwelling unit per acre (inches) = 2.0 inches (based on 150 gpd/residence) N,,, = nitrate concentration of nitrified leachfield effluent (mg/I)=40 mg/I to 60 mg/I as N D = percent dentrification of leachfield effluent=0.25 annual deep percolation of precipitation (inches) = 3.0 inches (based on 13.5 inches precipitation,2 inches runoff and 8.5 inches ET) NI, = background nitrate concentration of the deep percolating precipitation—mg/l =2.2 Ing/] as N In our selection of parameters for this equation, we have made use of previous studies by our firm,, as well as a report dated March 19, 1997, by Questa Engineeriuv Corporation and authored by Mr. Norman Hantzsche. Mr. Hantzsche prepared a report for a subdivision in the Morada area which has somewhat similar Fine grained silt and clay soils as encountered at the golf course site. Because of the similarities in soil conditions and rainfall, we have chosen to use the same values considered appropriate by Mr. Hantzsche for the project in Morada with the following exceptions. For the value of.D, which is the percent denitrification of the leach field effluent, we have used 0.25, which is the higher range, since denitrification is highest where the soils are wet and fine textured and have high amounts of organic matter. We note that the results of water sampling indicates very low values for nitrate as both N and NO3. This confirms the ability of the bacterial process in these soils to utilize the oxygen in the nitrate NO; and release the nitrogen gas N2 to the atmosphere, especially considering the amount of fertilizer applied to the site. 20-1096-15/20191.293 Page 2 of 3 I Copyright 1998 Kleinfelder. Inc. May 13,1999 i