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File No. 20-3554-01 k%J KEEINFEEDER January 22 , 1992 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 appeared to be due to the elevation change between the north and south ends of the site. The regional groundwater depth map, Plate II, published by the San Joaquin County Flood Control and Water Conservation District, indicates the depth to groundwater in this area was approximately 35 feet in Spring 1991. We note that the map for Fall 1990, used in our referenced report, indicated groundwater was approximately 30 to 35 feet deep. 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, Plate III , showing lines of equal elevation of groundwater, we conclude that the main groundwater gradient is in roughly the north to northwest direction, which is the same direction indicated in our referenced report. 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; " Our scope of services did not include a detailed evaluation of the potential for the septic systems to affect the quality of groundwater. However, the project involves only four septic systems on an approximate 9-acre site. Therefore, with groundwater at approximately 28 to 31 feet deep in August 1991 and possibly deeper at this time, the likelihood of a significant change in the nitrate level of the groundwater beneath the site is very remote. If additional , more-concentrated development is planned in the area, we suggest that consideration be given to completing a nitrate loading study. As requested by San Joaquin County Environmental Health personnel, we collected a water sample in August 1991 from the well located on the adjacent Scott/Johnson property. The sample was delivered to FGL Environmental laboratory in Stockton for DBCP testing. A copy of the test results is included with this report. Copyright 1992 Kleinfelder, Inc. Page 3 of 4