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APR. 8.2005 8:15AM P•ENV. SERVICES • N0.234 P.4 <br /> Mr. Duane White <br /> March 18, 2005 <br /> Page 2 <br /> 2) The increasing concentrations of acenaphthene in the B zone groundwater at <br /> downgradient well MW-26R may be indicative of downward migration of this <br /> contaminant to the C zone. <br /> RECOMMENDATION <br /> To determine if the C zone has been impacted as a result of downward vertical <br /> gradients it is recommended consideration be given to installing a C zone well at <br /> the location of the new proposed B zone monitoring well (MW-27). Otherwise an <br /> adequate explanation needs to be given as to why the C zone cannot be impacted <br /> by acenaphthene at this location. <br /> 3) Page 10, third paragraph: It is indicated that the new well will be developed by <br /> surging and bailing or pumping. The GSU believes the most efficient method to develop <br /> a monitoring well is to utilize bailing surging and pumping. Bailing allow for causing <br /> sediment on the bottom of the well to become susponded in the water column and <br /> removal of sand size material prior to pumping. Pumping allows for the removal of clays <br /> and silts to reduce the turbidity in the well water. <br /> RECOMMENDATION <br /> Develop new monitoring wells by utilizing bailing,surging and pumping. <br /> 4) Page 10, Groundwater Sampling and Analysis: It is indicated the micropurging <br /> procedures will be utilized to collected groundwater samples. It is my understanding the <br /> peristaltic pumps are only good for pumping from depths of approximately 20 to 35 feet <br /> below ground surface. The B zone well screen will be much deeper than this. As such, <br /> monitoring well purging may currently be done with pump intakes significantly above the <br /> top of well screens, This would not be acceptable for micropurging procedures as <br /> during this type of groundwater sampling approach the intake of the pump needs to be <br /> within the screen to obtain a representative sample. <br /> RECOMMENDATION <br /> Please verify to the GSU where pump intakes have been placed during <br /> groundwater micropurging procedures, If pump intakes have been well above the <br /> screen Interval during micropurging procedures then a change must be made to <br /> the groundwater monitoring procedures to ensure that pump intakes are within <br /> screen intervals during micropurging. <br /> 5) Page 10, Groundwater Sampling and Analysis: It is indicated that the groundwater <br /> sample from MW-27 will be analyzed for PAI-Is after being filtered in the laboratory. <br /> Samples from properly developed wells that were obtained during a micropurging <br /> Process should be representative of aquifer water, During the filter process colloidal <br />