SITE INFORMATION AND CORRESPONDENCE

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Mr. Anthony Sa0ara • Page 3 April 14, 1988 The Department would like to limit the use of phosphate detergents (because of possible introduction of heavy metals into the samples) and, therefore, we require the use of a nonphosphate type (ie. Alconox) . 11 . Figure 3 . The Department's policy on monitoring wells limits the screen length to the minimum that will intercept the water table and provide for seasonal fluctuation of the ground water. Refer to the California Site Mitigation Decision Tree Manual . At this time of year, the length of screen below the water table should be 10 feet. We will leave to your judgement the length of screen above the water table. Include a bentonite seal between the filter pack and the cement-grout seal . This seal should be from 2 to 3 feet thick. All bentonite used must be of the unbenificiated type. We recommend that either 8-20 mesh granules or chipped bentonite be used above the water table. The Department does not believe that a sump is necessary because it is important to remove any sediment from the well when it is purged. We suggest that a tremie be used to install the filter pack and the grout seal . 12 . Page 12 , section 2 . 2 . 1 (b) . As a check on the sampling effort at each well, the pH should be checked after samples have been taken. The elevations of the top of the well casings are to be surveyed by a licensed surveyor. 13 . Page 13 , section 2 .2 . 1 (b) . Temperature, pH and electrical conductivity should be constant (within 0. 1 degree C, 0 . 1 of a pH unit, and 10% of the last sample for EC) before purging is terminated. 14 . Page 13 , section 2 . 2 . 1 (b) , Filtering samples for metals analysis requires the use of a positive displacement pump and an in-line 0. 45 micron filter. If this type of equipment is not available, you must take additional unfiltered samples to assess the amount of metals on the particulates that may be in the water sample. If the filtering equipment is available, the analysis of samples for total metals may not be necessary. Use type II water for field blanks (obtain from laboratory that will be analyzing the samples) , not distilled water. We suggest that equipment blanks be obtained as a check on the cleaning of sampling equipment between sampling stations. 15. Page 17 . Although there may be no difference, the Department uses PEL's found in Title 8 of the California Code of Regulations (formerly known as the California Administrative Code) .