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k%1 KLEINFELDER <br /> a <br /> Following our percolation testing a representative with our firm obtained. a sample of <br /> groundwater using clean procedures from the well located on 10834 Copperopolis Road <br /> (northern parcel). The same day, the water sample was submitted to Far West Laboratories using <br /> chain-of-custody procedures for DBCP and nitrate testing. The results of our tests and a copy of <br /> k the chain-of-custody are attached. <br /> NITRATE LOADING CALCULATIONS <br /> Per San Joaquin County Public Health Services (SJCPHS) Department Environmental Health <br /> Division(PHS/EHD) requirements, the following summarizes our nitrate loading calculations for <br /> the proposed leach field. The drinking water standard for nitrate is 45 milligrams per'liter (NO3) <br /> and 10 mg/l as Nitrogen (N) in groundwater. In our evaluation of nitrate loading, we have used <br /> the Hantzsche mass balance equation (source: Predicting Ground-Water Nitrate-Nitrogen <br /> Impacts, 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, and information provided in a report dated March 19, 1997 prepared by the Questa <br /> Engineering Corporation and authored by Mr. Hantzsche for a development in the Stockton area. <br /> N, =AWN, (1-D,l+ (Nj <br /> AW+r <br /> Where: <br /> NC — 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) = 2.0 (estimated based <br /> on an estimated water usage of 300 gal./day for two homes (SJCPHS requirement). <br /> Typical daily water usages based on SJCPHS recommendations for a 3 bedroom <br /> residential home.) <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 = Nitrate concentration of nitrified leachfield effluent (mg/1) = 35 mg/l typical <br /> (Hantzsche and Finnemore (1992)) <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 large depth to <br /> groundwater (>75 feet)) <br /> R = Annual deep percolation of precipitation (inches) = 12.33 inches (representing 85 <br /> percent of average annual rainfall of 14.5 inches in project area. Remaining 15 <br /> percent of rainfall is assumed to drain off-site into natural or manmade drainages) <br /> 20-4684-01.G01/2011R1570 December 20,2001 <br /> ©2001 Kleinfelder,Inc. Page 3 of 4 <br />