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6. %two, k`■ KLEINFELDER L The Soil Survey of San Joaquin County, California published by the U.S. Department of Agriculture, Soil Conservation Service (1992) refers to the near-surface soils within the project area as belonging to the Bisgani soil series (Map Symbol 109). The soils are described as having b severe percolation characteristics, an available water capacity of 0.06 to 0.08 inches per inch, a pH ranging from 7.4 to 8.4, and an organic content of 1 to 3 percent. L 6. PERCOLATION TESTING �. The 6-inch diameter percolation holes were drilled with the same equipment as the soil profile boring. Three percolation holes, one adjacent to the leach lines at each septic system, were drilled on the subject property. The holes had scored sides and no significant loose material in the bottom of the hole. All of the holes were drilled and prepared before 9:35 am on August 18, 2003 in accordance with SJCEHD criteria. The preparation procedure calls for first placing about 2 inches of fine gravel at the bottom of the borehole. The hole is then pre-soaked with a r10 minimum of 12 inches of water at least 24 hours prior to performing the test. The percolation tests were started at 10:00 am on August 19, 2003, under sunny and warm weather, in accordance with accepted guidelines using clear potable water. All holes were still intact with no Ir significant sloughing or caving noted. The approximate depth of each percolation test below existing site grade is shown on the following table. The holes were dry prior to testing. From a fixed reference point, a marked location on the side of PVC pipe inserted into the hole, the drop 6" in water level is measured in approximately 30-minute intervals for four hours, refilling as necessary to maintain the prescribed amount of water over the gravel (SJCEHD Procedure #2). Under the observation of a representative from the SJCEHD, the last 30-minute reading of the bw four-hour period is recorded and used to calculate the percolation rate in minutes per inch. The estimated percolation rates are summarized below. A copy of our field percolation test results 6. signed by a representative from SJCEHD is attached. Details of each test can be found on the percolation test sheet. Test Number Depth,feet Percolation Rate (min./inch) P-1 3.3 5 P-2 3.1 8 P-3 3.5 7 7. NITRATE LOADING CALCULATIONS Per SJCEHD requirements, the following summarizes our nitrate loading calculations for the proposed leach fields. 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 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 Sewage 31917.G01/ST03R1695 November 11,2003 ©2003 Meinfelder,Inc. Page 4 of 7 L