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File No. 20-3239-03 kT] KLEIN FELDER August 20, 1992 Only one of the six 3-foot deep tests passed, all of the six 8- to 91/2-foot deep tests passed, and four of the 131/2- to 141/2-foot deep tests passed. In addition, the soils between approximately 8 to 12 feet deep produced the fastest percolation rates. Therefore, based on the test results and on our experience in this area, it is our opinion that approximate 12- to 15-foot deep sump pits will likely be the most effective means of disposal. Prior to construction on the parcels, San Joaquin County Environmental Health Services will require that a passing percolation test be obtained on each parcel. ITEM C-3: "The depth and gradient of the water table;" During our residence surveys on July 15, 1992, we were able to measure groundwater in two wells. Groundwater was measured at depths of approximately 93 and 98 feet below existing ground surface at locations 3 and 2, respectively. During our residence surveys on March 3, 1992, we were able to measure groundwater in wells at locations 6 and 7 at depths of approximately 92 and 89 feet, respectively. The regional groundwater depth map published by the San Joaquin County Flood Control and Water Conservation District, Plate II, indicates the depth to groundwater in the site area was between approximately 90 and 110 feet in fall 1991. On the basis of the groundwater map showing lines of equal elevation of groundwater, Plate III, we conclude that the main groundwater gradient is in roughly the northwest direction. 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 ground water 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 a maximum of seventeen additional septic systems over an approximate 200-acre site. Therefore, with groundwater at a depth of approximately 90 to 110 feet, in our opinion the likelihood of a significant change in the nitrate level of the groundwater beneath the site, because of the additional systems, is remote. If additional more-concentrated development is planned in the area, we suggest that consideration be given to completing a nitrate loading study. This completes our scope of work at this time. Based on the above information, it is our opinion that the nineteen proposed parcels are suitable for septic system use. The septic systems should be located and future wells should be constructed following County requirements. Continuous monitoring of the septic systems should be maintained throughout the duration of their use. Once this report is reviewed by Environmental Health Services, we would be pleased to furnish a proposal for providing whatever additional information they may require for their evaluation. Copyright 1992 KLeinfelder, Inc. Page 4 of 5