Laserfiche WebLink
k" KLFINFELOFR <br /> iImpacts, Hantzsche and Finnemore (1992)), which is presented below with an explanation for <br /> each factor and the 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, communications with Mr. Mike Huggins with the SJCPHS/EHD, and information <br /> provided in a report dated March 19, 1997 prepared by the Questa Engineering Corporation and <br /> authored by Mr. Hantzsche for a development in the Stockton area. <br /> Nc,=AWNw 1-D + R <br /> AW+R <br /> Where: <br /> N, = Average calculated nitrate-nitrogen in groundwater resulting from domestic sources <br /> and precipitation—mg/l, as N <br /> A — Number of dwelling units per acre on septic tanks (unit/acre) = 0.625 (estimated <br /> based on an estimated water usage of 90 gal./day, a typical water usage for 6 <br /> employees at 15 gal/employee per the SJCPHS/EHD Sewage Standards divided by <br /> 150 gal./day to obtain an equivalent number of homes, divided by 0.96 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 150gal./day/dwelling unit) <br /> Nw = Nitrate concentration of nitrified leachfield effluent (mg/1) — 70 mg/l typical <br /> (communication with Mr. Mike Huggins with SHCPHS/EHD) <br /> D = Percent dentrification of leachfield effluent = 0.25 percent (0.1 to 0.35 percent <br /> typical per Hantzsche and Finnemore ([1992]). <br /> R = Annual deep percolation of precipitation (inches) = 7.6 inches (representing 80 <br /> percent of average annual rainfall of 9.5 inches in project area. Remaining 20 <br /> percent of rainfall is assumed to drain off-site into natural or manmade drainages) <br /> Nb — Background nitrate nitrogen concentration of rainfall recharge at the water table = <br /> 0.5 mg/l (per Technical Memorandum, Hydrologic and Soil Investigation for the <br /> -Chico Urban-Area, page 6, Dames and Moore, April 1996) <br /> Our calculation is as follows: <br /> N,, = 0.625(2)(70)(1 —0.25)+0.5(7.6) = 65.6 + 3.8 = 7.84 mg/l as N <br /> 0.625(2)+7.6 1.25 +7.6 <br /> CONCLUSIONS <br /> Based on the above evaluation, we conclude that wastewater produced by the proposed leach <br /> field should not have a nitrate as nitrogen (N) concentration at the groundwater level greater than <br /> 12573/20028320 June 11,2002 <br /> ©2002 Kleinfelder,Inc. Page 3 of <br />