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r. <br /> i k9 KLEINFELDER <br /> I <br /> I <br /> NITRATE LOADING CALCULATIONS <br /> Per SJCEHD requirements, the following summarizes our nitrate loading calculations for the <br /> proposed leach fields. The state drinking water standard for nitrate is 45 milligrams per liter <br /> (NO3) and 10 mg/1 as Nitrogen (N) in groundwater. In our evaluation of nitrate loading, we have <br /> used the Hantzsche mass balance equation (source: Predicting Groundwater Nitrate-Nitrogen i <br /> Impacts, Hantzs& and Finnemore (1992)), which is presented below with an explanation for <br /> each factor and th'e value used in our study. The-selection of parameters was based on previous <br /> studies and investigations performed by our firm and others, San Joaquin County Sewage <br /> Standards, communication with Mr. Mike Huggins with SJCEHD, and information provided in a <br /> report dated March 19, 1997 prepared by the Questa Engineering Corporation and authored by <br /> Mr. Hantzsche for a development in the Stockton area. <br /> N, =AWN,, (1-D) + (Nb) R <br /> AW+R <br /> Where: <br /> Ne — Average calculated nitrate-nitrogen in groundwater resulting from domestic sources <br /> and precipitation—rngll, as N. <br /> A = Number of dwelling units per acre on septic tanks (unit/acre) = 0.9.5 (estimated <br /> based on 15 gallons ver full-time employee (4) divided by 150 gallons per dwelling <br /> unit divided by 0.42 acres.) <br /> W = Annual wastewater loading per dwelling unit per acre (inches) = 2.0 inches (per year <br /> per dwelling unit assuming a flow of 150 gal./day/dwelling unit.) <br /> NW = <br /> =ore <br /> concentration of nitrified leachfield effluent (mg/1) = 70 mg/i (Hantzsche and <br /> (1992)). Percent denitrification selected based on past discussions with <br /> Mr. Mike Huggins of SJCEHD. <br /> ' 1 <br /> D = Percent dentrification of leachfield effluent = 0.35 percent (0.1 to 0.35 percent <br /> typical';per Hantzsche and Finnemore (1992). 0.35 selected given the deep depth to <br /> 1 groundwater. <br /> C <br />' R = . Annual deep percolation of precipitation (inches) = 14.4 inches (representing 80 1 <br /> percent of average annual rainfall of approximately 18 inches in project area. <br /> Remaining 20 percent of rainfall is assumed to drain off-site into natural or <br /> manmade drainages.) <br /> Nb = Background nitrate nitrogen concentration of rainfall recharge at the water table = i <br /> 0.5 mg/l (per Technical Memorandum, Hydrologic and Soil Investigation for the <br /> j Chico Urban Area, page 6, Dames and Moore, April 1996) <br /> r <br /> 35025.G01/ST03R1509 October 10,2003 <br /> ©2003 Kleinfelder, Inc. Page 4 of 6 <br /> j <br /> ...-_. a ... <br />