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1 � 1 ., as kn KLEINFELDER FIELD EXPLORATIONS AND TESTING The subsurface conditions at the site were explored on February 26, 2002, by drilling one boring to a depth of approximately 10 feet below existing grade. The boring was drilled using a Simco 2400 truck-mounted drill rig equipped with 4-inch O.D. solid-stem auger. During the same time period, percolation borings were drilled to depths of about 3.5 and 4.0 feet below site grade. The location of the percolation tests is approximately 100 feet west of a private well on the project 2� site. The approximate percolation test locations are presented as P-1 and P-2 on the attached p plate. 0 Based on our findings, the subsurface soils encountered consisted of brown to gray/brown sandy , clays with gravel to a depth of about 2 feet below site grade, underlain by brown sandy clay to a depth of about 4 feet. These soils were underlain by light brown sandy clays to a depth of about ur s LPK G 8 feet, followed by sandy silts to the depth explored. The percolation tests were performed on—Marc1L6.,2 0�2, in accordance with accepted guidelines $� 91 using clear potable water. The procedure calls for first placing about 2 inches of fine gravel at the bottom of the bore hole. The hole is then pre-soaked with water at least 24 hours prior to performing the test. The test is performed by first adding about 6 inches of water per 3 foot of percolation test depth above the gravel to the hole. From a fixed reference point, the drop 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. Under the observation of a sanitarian from the San Joaquin County Public Health Services, Environmental Health Division (SJCPHS/EHD), the last 30-minute reading of the 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 signed by a representative from SJCPHS/EHD is attached. if itt, E NIC6l`atlon`Rate min./inch ,fie b P-1 3.5 63 ' y P-2 4.0 17 .U-Z) Following our percolation testing, a staff engineer with our firm obtained a sample of groundwater using clean procedures from a spigot ne eon-site wel The well was located approximately 200 feet north of that parcel's southeast corner. The same day, the water sample was submitted to Sequoia Analytical using chain-of-custody procedures for DBCP and nitrate testing. The results of our tests and a copy of the chain-of-custody are attached. 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 (NOO 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 Ground-Water Niirate-Nitrogen 12573/2002R320 April 16,2002 ©2002 Kleinfelder,Inc. Page 2 of 4