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KLEINFELDER using clear potable water. The approximate depth of each percolation test below existing site grade is shown on the following table. The holes did not exhibit sloughing or caving. At the time of testing, standing water remained in the shallow hole, approximately 24 hours after presoaking. From a fixed reference point, a marked location on the side of PVC pipe inserted into each hole, the drop in water level in the deep hole was measured in approximate 30-minute intervals for four hours, refilling as necessary to maintain the prescribed amount of water over the gravel (SJCEHD Procedure #2). As specified, the last two 30-minute readings were recorded under the observation of a representative from the SJCEHD and were used to calculate the percolation rate in minutes per inch. As water remained in the shallow test hole testing was performed in accordance with SJCEHD Procedure #1. It was shown that no percolation occurred in the shallow hole over a period greater than 1%2 hours. The estimated percolation rates for both holes are summarized below. A copy of our field percolation test results signed by a representative from SJCEHD is attached. Details of each test can be found on the percolation test sheets. Test Number Performed Depth (feet) Percolation Rate (min./inch) 3.1 Did not percolate P-1 22.0 20.8 7. NITRATE LOADING CALCULATIONS Per SJCEHD 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/l as Nitrogen (N) in groundwater. In our evaluation of nitrate loading, we have used the Hantzsche mass balance equation (source: Predicting Groundwater 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 S ewage S tandards,p revious communication w ith M r. M ike Huggins w ith S JCEHD, 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. Current laws allow two homes on each parcel. Therefore, we present these calculations based on two single-family residences on the proposed 5-acre parcel. Nc=AWNW(1-D) + (NbhR AW+R Where: N, = 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) = 0.4 (based on two homes divided by 5 acres.) bw bw 51727.G01/ST04R1700 December 17,2004 ©2004 Kleinfelder,Inc. Page 4 of 6