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`i �■ KLEINFELDER GROUNDWATER DEPTH AND TESTING According to the "Lines of Equal Depth to Groundwater" published in the sprung of 1999 (most current edition) by the San Joaquin County Flood Control and Water Conservation District, the depth to groundwater at this location is between 60 to 70 feet. There is an existing well at the Atwood residence located in Heather Moor Estates - Unit No. 1, just east of the study area. A water sample obtained from this well on September 10, 2001 was submitted to Sequoia Laboratories for analytical testing of Nitrate as (N). The result, which is attached, indicates a concentration of 5.7 milligrams per liter (mg/1). For your information, in June of 2000, our firm obtained a water sample from the existing well at the Pollardville Restaurant located south of the site. The water sample was also tested by Sequoia Laboratories, which found a nitrate concentration of 2.25 mg/1 (N). PERCOLATION TESTS Attached to this letter are the results of percolation tests observed by representatives of San Joaquin County, Public Health Services Department, Environmental Health Division. A total of thirty-two percolation tests were initially installed on the 12 remaining lots of Unit No. 2. All tests were located in the designated drain field areas toward the back of each lot. As expected, all of the shallow (approximately 3 feet) tests failed except for those which appeared to have been effected by rodent activities. Attempts were made to terminate the remaining deeper percolation holes in strata consisting of either silty sand or sandy silt. These types of soils were encountered in relatively thin lenses rather than thick layers. The depth of the deeper percolation holes varied from 7 to 16 feet. The percolation tests were performed between September 4 through September 10, 2001, and the results generally vaned between 5 to 16 minutes per inch. An exception was lot 18 where the measured percolation rates for the last 30 minutes was approximately 50 minutes per inch. For deep percolation holes, the maximum allowable percolation rate is 30 minutes per inch. Since an engineered system is being required due to nitrate loading concerns, according to our discussions with Mr. Huggins, no retest is required. Based on our experience at the other 16 lots of Unit No. 2 we are confident that additional probing on lot 18 would disclose a soil stratum where a passing test could be obtained. All seepage pits will be extending to at least the 20-foot depth, which is deeper than any of the percolation tests. A summary of the selected deep percolations tests is presented below. LOT NUMBER APPROXIMATE DEPTH OF PERCOLATION RATE 6NAL SOADIU)SIOX) TEST ft. min/in 8 9 6.3 9 9 9.2 10 10 5.2 12 9 7.5 13 9 5 14 14 2.8 15 9 6.4 18 7 50. 19 10 8.3 21 10 13.2 -2e--?.* LZ, 10 8.3 -'A3 2,q 14 11.4 9 8.3 20-2921-02/201181169 Page 2 of Copyright 2001 Kleinfelder,Inc. September 25,2001