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KLEINFELDER A staff engineer with our firm obtained a sample of groundwater using clean procedures from a spigot from a well located at 17390 Kroll Road, across Highway 12 from the subject property. That same day, the water sample was submitted to Sequoia Analytical using chain-of-custody procedures for DBCP and nitrate testing. As of the date of this report, the laboratory results were not available. As requested, these results and a copy of the chain-of-custody will be forwarded to you and the SJC/EHD as soon as they become available. NITRATE LOADING CALCULATIONS Per SJCPHS/EHD requirements, the following summarizes our nitrate loading calculations for the proposed leach field. The State drinking water standard for nitrate is 45 milligrams per liter (NO3) and 10 mg/1 as Nitrogen (I) in groundwater. In our evaluation of nitrate loading, we have used the Hantzsche mass balance equation (source: Predicting Ground-Water Nitrate-Nitrogen Impacts, Hantzsche and Finnemore (1992)), which is presented below with an explanation for each factor and the value used in our study. The selection of parameters was based on previous studies and investigations performed by our firm and others, San Joaquin County Sewage Standards, communication with Mr. Mike Huggins with SJC/EHD, and information provided in a report dated March 19, 1997 prepared by the Questa Engineering Corporation and authored by Mr. Hantzsche for a development in the Stockton area. Nc =AWNw_ 0-D) + (Nb)R AW+R Where: Nc = Average calculated nitrate-nitrogen in groundwater resulting from domestic sources and precipitation—mg/l, as N A = Number of dwelling units per acre on septic tanks (unit/acre) = 0.51 (estimated based on 12 homes divided by 23.6 acres) W = Annual wastewater loading per dwelling unit per acre (inches) =2.0 inches (per year per dwelling unit assuming a flow of 150 gal./day/dwelling unit) Nw = Nitrate concentration of nitrified leachfield effluent (mg/1) = 35 mg/l typical (per Mike Huggins) D = Percent dentrification of leachfield effluent = 0.25 percent (0.1 to 0.35 percent typical per Hantzsche and Finnemore (1992). 0.25 selected given the large depth to groundwater and the presence of low permeable, interbedded soil strata.) R = Annual deep percolation of precipitation (inches) = 13.6 inches (representing 85 percent of average annual rainfall of 16 inches in project area. Remaining 15 percent of rainfall is assumed to drain off-site into natural or manmade drainages) 23814.G01/ST02R814 November25,2002 ©2002 Mcinfelder,Inc. Page 3 of 4