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). H. KLEINFELDER & ASSOCIAS <br /> File: S-1008-21/12 : 317 <br /> June 26, 1986 <br /> Page 2 <br /> In fact, the Labor Camp well log shows "Sand Gravel" from <br /> 126-144 feet and "Sand Water" from 144-148 feet. Water was <br /> first found at 120 feet . Static level after well completion <br /> and development was 99 feet, 8 inches. This well was cased <br /> to 160 feet and the log shows "Brown Clay" from 154-316 <br /> feet. If this clay is continuous and relatively impervious, <br /> this well has been providing ground water samples from the <br /> 316 foot depth and below. <br /> My point is that great care must be taken while drilling the <br /> new monitoring wells to determine where ground water first <br /> exists. The drilling program must be flexible enough to <br /> properly adjust to actual site conditions. They propose to <br /> use 120 to 130 feet of solid casing above 40 to 45 feet of <br /> slotted casing. Should ground water be encountered at 100 <br /> feet, for example, with a confining layer from 140 to 150 <br /> feet, they could end up creating a conduit between an upper, <br /> contaminated zone and a lower, non-contaminated zone. <br /> Response: <br /> As stated in the RWQCB's letter of 21 April 1986, nearby <br /> wells indicate a water bearing stratum may exist at depths <br /> between 125 and 165 feet. It is not uncommon to screen <br /> wells 5-10 feet above and 20-40 feet below the first <br /> encountered ground water, particularly in areas of severe <br /> overdraft. It is understood, however, that if the first <br /> ground water zone is a confined zone, the well shall be <br /> completed in the first impermeable zone. Otherwise, the <br /> well shall be screened to a depth 30-40 feet below the water <br /> table, if no impermeable zone is encountered. There will be <br /> an experienced, knowledgeable professional (geologist or <br /> engineer) present onsite to mane t1hese decisions during the <br /> well installation. <br /> Comments: <br /> 2. Without any information on the highest ground water levels, <br /> it is difficult to properly place the new wells. Plate B of <br /> the submittal isn' t much to go on. If the upper ground <br /> water gradient is to the south, southeast, or southwest, the <br /> well placement shown on Plate B appears reasonable. I <br /> suggest drilling the northernmost well first and the <br />