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KLEINFELDER FIELD EXPLORATIONS AND TESTING The subsurface conditions at the site were explored on April 5, 2001, by drilling one boring to a depth of approximately 15 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 in the northeast and southwest corners of the lot at depths of about 3.5, 9 and 13 feet below site grade. The approximate percolation test locations are presented on the attached plate. Based on our findings, the subsurface soils encountered consisted of interbedded strata of silty and clayey sands, sandy and silty clays, and sandy silts. The silty sands encountered at the approximate 2.5 to 3.5-foot depth were weakly cemented. A log of boring that describes the subsurface conditions encountered is attached. The percolation tests were performed in accordance with accepted guidelines 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 is then added 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 Department (SJCPHD), 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 at each test location are as summarized below. A copy of our field percolation test results for test numbers P-1 and P-2 is attached. The percolation test result for P-3 is not attached and was mistakenly not witnessed by the SJCPHD representative. At the time the test was performed, the pre-soak water had not percolated into the soils and it was judged that soils at the 3.5-foot depth were non-percolating. Test Number Depth, ft. Percolation Rate min./inch P-1 12.5 10 P-2 9.5 23 P-3 3.5 Non-percolating Following our percolation testing, on April 16, 2001 a staff engineer with our firm obtained a sample of groundwater using clean procedures from a well located at an adjacent rural commercial/industrial property to the east. The following 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 San Joaquin County Public Health Services (SJCPHS) Department Environmental Health Division (PHS/EHD) requirements, the following summarizes our nitrate loading calculations for the proposed leach field. The drinking water standard for nitrate is 45 milligrams per liter (NO3) and 10 mg/1 as Nitrogen (N) in groundwater. In our evaluation of nitrate loading, we have used 204585-OI.GOI/201IR602 November 21,2001 ©2001 Kleinfelder,Inc. Page 2 of 4