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OMernorandum CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD . CENITF?AL VALLEY REGION 3201 S Street Sacramento, California 95816 Phone: 445-0270 TO: Antonia Vorster FROM: Jim Eckman Senior Engineer Project Engineer DATE: 21 April 1986 SIGNATURE: —------ __V_ SUBJECT: PROPOSED HARNEY LAND LANDFILL GROUND WATER MONITORING PROGRAM I have reviewed the Kleinfelder submittal and have the following comments: 1. Regional hydrogeologic data was used to design this program. Regional ground water elevation and depth maps were used to estimate ground water flow directions. The wells that provided this data are generally cased to a depth of 150 feet or more and I 'm concerned that there may be shallower ground water which is not hydraulically connected to the levels these wells are tapping. The site elevation (undisturbed) is approximately 100 feet MSL. Ground water elevations are -15 to -36 feet MSL (or 115 to 136 feet deep). Jim Parson's 22 January 1980 memo (copy attached) says he reviewed the DWR logs of the Farm Labor Camp and Lee Hall wells. The labor camp well is cased to 164 feet depth and the Hall well is cased to 180 feet. Sand and gravel layers were found above the cased depth in each well . These layers could easily be water-bearing. In fact, the Labor Camp well log shows "Sand Gravel" from 126 - 144 feet and "Sand Water" from 144 - 148 feet. Water was first found at 120 feet. Static level after well completion and development was 99 feet, 8 inches. This well was cased to 160 feet and the log shows "Brown Clay" from 154 -316 feet. If this clay is continuous and relatively impervious, this well has been providing ground water samples from the 316 foot depth and below. My point is that great care must be taken while drilling the new moni- toring wells to determine where ground water first exists. The drilling program must be flexible enough to properly adjust to actual site condi- tions. They propose to use 120 to 130 feet of solid casing above 40 to e"5 feet of slotted casing. Should ground water be encountered at 100 feet-9 for example, with a confining layer from 140 to 150 feet, they could end up creating a conduit between an upper, contaminated zone and a lower, noncontlaminated zone. 2. Without any information on the highest ground water levels, it is difficult to properly place the new wells. Plate B of the submittal isn't much to co on. If the upper ground water gradient is to the south, southeast, or southwest, the well placement shown on Plate B appears reasonable. I suggest drilling the northernmost well first and the southernmost well