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� I I File No. 20-3514-01 K L E I N F E L D E R September 11 , 1991 percolation rate of 60 minutes per inch, or faster, at the 3-foot depth. The 3-foot deep tests performed passed and the percolation rates are presented in the following table. The County approved percolation test sheets are included with this report. PERCOLATION TEST RESULTS Depth Percolation Rate Test/Parcel No. feet (Mins/In) 1 3 30 2 3 4 3 3 60 4 3 60 D. ITEM C-3 • "The depth and gradient of the water table; " During our residence surveys on August 13 , 1991, we were able to measure groundwater in four wells. The groundwater was measured at approximately 31 feet below existing ground surface at the three locations on the north side of the site and at approximately 28 feet at the one location south of the site. This difference appears to be due to the elevation change between the north and south ends of the site. The regional groundwater depth map published by the San Joaquin County Flood Control and Water Conservation District, Appendix, Plate A-9 , indicates the depth to groundwater in this area was approximately 30 to 35 feet in Fall 1990. Based on County requirements for a small project such as this, we are not required to establish an on-site groundwater gradient by drilling test borings. We are providing a general estimate of the groundwater gradient based on the published map. Based on the groundwater map showing lines of equal elevation of groundwater, Appendix, Plate A-10, we conclude that the main groundwater gradient is in roughly the north to northwest direction. E. ITEM C-5• "Other information as required by the San Joaquin Local Health District to determine the cumulative effect of the existing and the proposed development on groundwater contamination; " Copyright 1991 KLeinfelder, Inc. Page 10 of 13