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KLEINFELDER t 6. PERCOLATION TESTING 1 A shallow percolation test hole was installed adjacent to the existing leach field with the same drill rig used for the soil profile boring, only equipped with a 6-inch diameter auger. The approximate percolation test location is presented on Plate 1. Following drilling, the sides of ti the hole were scored, and significant loose material was removed from the bottom of the hole. The hole was drilled and prepared before noon on December 13, 2004, in accordance with SJCEHD criteria. Approximately 2 inches of fine gravel was placed at the bottom of the test t hole. The test hole was presoaked at the time of drilling with at least 12 inches of water. The percolation test was started at about 10:30 AM in overcast and foggy conditions on December 14, 2004, in accordance with accepted guidelines using clear potable water. The approximate depth of the percolation test below existing site grade is shown on the following table. The hole did not exhibit sloughing or caving. From a fixed reference point, a marked location on the side of PVC pipe inserted into the hole, the drop in water level was measured over an L approximate four-hour period. Due to initial rapid drops in the water level, readings were taken in approximately 15-minute intervals, refilling as necessary to maintain the prescribed amount L of water over the gravel. The last several readings were recorded under the observation of a representative from the SJCEHD and were used to calculate the percolation rate in minutes per inch. We note that the 15-minute intervals used are not in accordance with SJCEHD iL procedures. However, the percolation rates observed throughout the test are passing rates. A copy of our field percolation test results is attached. Details of the test can be found on the percolation test sheet. Test Number Performed Depth (feet) Percolation Rate (i4p4 ch) P-1 3.1 28.3 L 7. NITRATE LOADING CALCULATIONS Per SJCEHD requirements, the following summarizes our nitrate loading calculations for the d proposed leach field. The state drinking water standard for nitrate is 45 milligrams per liter {L (NO3) and 10 mg/1 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. IL Ne =AWN w G-D) + (Nb) R AW+R The selection of parameters used in the equation was based on previous studies and investigations performed by our firm and others, San Joaquin County Sewage Standards, previous communication with Mr. Mike Huggins with SJCEHD, 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. !r. 6 52251.GO1/ST05R192 - February 17,2005 ©2005 Kleinfelder,Inc. Page 4 of 8 a