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Y � <br /> John Johnson <br /> Page 2 <br /> To reduce overall monitoring costs,you may submit a modified sampling plan to PHS/EHD for review and <br /> concurrence. The modified sampling plan should address, at a minimum, the following requirements: <br /> All wells on the site must be monitored on a quarterly basis for depth to water data to determine <br /> groundwater flow direction, for visual and olfactory evidence of contamination, and to ensure that <br /> the wells remain sealed and in good repair. <br /> The downgradient well, monitoring well #4, must be monitored for contaminants on a regular <br /> basis to detect any potential impact and migration by contaminants in the groundwater. <br /> All remaining wells on site must be monitored for contaminants at least on a yearly basis. This <br /> sampling should be scheduled when the groundwater is expected to be at its highest level, usually <br /> during the spring quarter. <br /> Please note that as site conditions change,an increase in the sampling (additional to the modified <br /> sampling plan frequency) of the wells at this site may be warranted toprovide the needed data to <br /> substantiate the reduction, or possibly the absence, of risk to groundwater. For example, sampling the <br /> wells when the water table is elevated may give an indication of the risk the residual soil contamination <br /> poses to the groundwater by providing data on the relationship between the increasing water levels and the <br /> contaminant concentrations. It must be shown, by actual data over time, that the groundwater does not <br /> become impacted by any residual soil contamination when the water table is elevated. <br /> If the groundwater becomes re-impacted as a result of an increase in the water table, the data may indicate <br /> what form of remediation would be necessary to effect a closure within a reasonable time period for this <br /> site. <br /> Please be advised that although a reduction in the frequency of sampling may be granted, a status report <br /> must still be submitted to PHS/EHD on a quarterly basis in order to remain in compliance. <br /> It is hoped that this letter will clarify the concerns that still must be addressed,with physical data, before <br /> PHS/EHD can concur with a closure recommendation for this site. If you have any questions, please <br /> contact Linda Turkatte, REHS, of my staff at (209) 468-3441. <br /> Jogi Khanna, Iv..D., M.P.H. <br /> Health Officer <br /> i <br /> urie A. Cotulla, REHS, Program Manager <br /> Environmental Health Division <br /> ( /LAC/L,T:lb <br /> V <br /> c: CVRWQCB-Beth Thayer <br /> c: Parker Environmental-Jim Parker <br />