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1. H. KLEINFELQER & ASSOCIATES File: W-2022-1/11:312 June 19, 1986 Page 12 Based on our field explorations and previous research, we estimate ground water to be at approximately 200 to 300 feet below ground surface at the landfill site. Historically, seepage from the near -surface gravels of the Corral Hollow drainage located south of the current landfill operations, has not been observed. Therefore, although ground water has been measured at a shallow depth approximately one mile west of the site, the general ground water conditions directly beneath the existing landfill do not appear effected by this limited near -surface ground water source. FINDINGS Rising water levels encountered while drilling and geologic -- profiles containing apparently extensive continuous impermeable strata appear to indicate confined, or at least semi -confined aquifer conditions. Local and laterally limited near surface perched zones of unconfined water bearing zones may exist near the site, but were not observed in our borings at the Corral Hollow Landfill. It appears that the regional aquifer in the area is overlain by a confining layer. If wells are drilled through this confining layer, water from the aquifer may rise considerable distances above the top of the aquifer. It appears that the potentiometric surface for this aquifer is considerably higher than the elevation of first encountered ground water. Based on our analyses of the referenced report and with the low natural permeability of soils beneath the site, it appears that breaching the impermeable zone would allow the water surface to rise and could potentially promote contamination of the aquifer. This report was prepared in general accordance with the accepted standard of care which exists in Northern California at the time the investigation was performed. Statements made in this report are based on the results of our firm's review of previous available reports, published information, and our understanding of the project. The geologic data used in this report was obtained from previous field investigations, existing laboratory test results, and drill logs available in the vicinity of the site. It should be recognized that definition and evaluation of geologic conditions is a difficult and inexact art. Judgements leading to conclusions and recommendations are generally made with an incomplete knowledge of the subsurface conditions present. No warranty, expressed or implied, is made.