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--- ---- -- — -- – — -- h� KLEINFELDER impact on groundwater over a large area, we have assumed that the usage of the church by 20 to 40 people over the course of 5 hours per week would constitute approximately I/_ f a typical household. In otherwords, there would be no bathing, laundry, dish_ e As noted in the attached letter, the proposed meetings are relatively short, between 1 and 1'/2 hours. Even if a quarter of the attendees used the restroom facilities and used 5 gallons per visit, this would still amount to only 125 gallons per week compared to a typical residence of 1,058-gallons (7 days x 15 gal/day/residence). In our opinion, the assumption equating the church usage to '/4 a normal household is conservative. The property encompasses approximately 1.2 acres, therefore `A' (the number of dwelling units per acre on septic tanks) would equal to .25 dwelling units divided by 1.2 acres or .2. The selection of other parameters were based on previous studies by our firm as well as a report dated March 19, 1997 by Questa Engineering Corporation and authored by Mr. Norman Hantzsche. Mr. Hantzsche prepared a report for a subdivision in north Stockton -� that had similar fine-grained silt and clay soils. For these reasons, we have chosen to use the same values considered appropriate by Mr. Hantzsche for this project. — The equation is as follows: N,=AW x NW(1-D)+(Nr AW+r Where: Nc = calculated nitrate concentration in groundwater resulting from domestic sources and precipitation—mg/l, as N A = number of dwelling units per acres on septic tanks (unit/acre)_ .002 W = annual wastewater loading per dwelling unit per acre (inches) _ .2 inches (from Questa Report) N„ = nitrate concentration of nitrified leachfield effluent (mg/1) = 60 mg/l as N (conservative assumption according to the Questa report) D = percent dentrification of leachfield effluent=0.25 ` r = annual deep percolation of precipitation (inches) = 3.0 inches (based on 13.5 inches precipitation, 2 inches runoff and 8.5 inches ET) Nb = background nitrate concentration of the deep percolating precipitation—mg/1=2.2 mg/1 as N Our calculation is as follows: Low Estimate NC _ .2 (.2) (60) (1 - .25 +2.2� _(3) = 24.6 = 7.2 mg/1 as N .2 (2) +3 3.4 When combined with the measured value for nitrogen in groundwater of between 2.35, it is our opinion that the proposed church facility will not cause a rise in the nitrate levels above the state standard of 10 mg/1. 20-3168-36.G01/2000L581 Page 3 of 4 Copyright 2000, Kleinfelder, Inc. June 21,2000