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STEFFEN ROBERTSON AND KIRSTEN <br /> Consulting Engineers and Scientists <br /> March 18, 1993 <br /> Ms Margaret Lagorio, Senior REHS <br /> San Joaquin County Public, Health Services <br /> P O Box 2009 <br /> Stockton, California 95201 <br /> SRe Diamond Lumber, 151 Main Street, Manteca, California <br /> Dear Ms Lagorio <br /> Steffen Robertson and Kirsten (U S) Inc, (SRK) is submitting this correspondence on behalf of our <br /> client,650 Management Corporation,in response to written comments (dated February 10, 1993) made <br /> by the San Joaquin County Public Health Services, Environmental Health Division (PHS/EHD) <br /> regarding site observations made by the PHS/EHD on February 5, 1993 during the quarterly monitoring <br /> ' event at the above referenced facility <br /> "PHS/EHD staff observed that a submersible pump was being used to purge monitoring <br /> wells SRK MW 1, SRK MW 2, and SRK MW 3 and that the pump and tubing were <br /> not being decontaminated between uses in the three monitoring wells In addition <br /> water samples were being collected using the submersible pump and the discharge rate <br /> was too high for water sample collection " <br /> "While it is desirable to be able to use the same equipment for purging and sampling <br /> it is important that the discharge rate of the pump be very low (approximately 100 <br /> ml/minute) to minimize sample aeration and degassing when collecting water samples " <br /> The following responsive actions are proposed during upcoming sampling events at the above <br /> 1 referenced facility, and will be implemented pending additional comments from the PHS/EHD <br /> • A submersible pump equipped with reinforced tygon tubing will continue to be used to purge <br /> or remove the necessary quantity of water from monitoring welts SRK-MW1, SRK-MW2 and <br /> SRK-MW3, prior to collecting analytical groundwater samples The purging sequence will <br /> proceed from known uncontaminated to known contaminated wells, i e , from clean to dirty <br /> ' The pump and tubing will be thoroughly steam cleaned before and after each purging event <br /> in accordance with PHS/EHD guidelines The proposed decontamination procedures include <br /> steam cleaning the exterior surface of the pump and tubing, and cleaning the interior surface <br /> areas by circulating a non-phosphate solution followed by a deionized rinse <br /> • After the three deep wells (SRK-MW1, SRK-MW2, and SRK-MW3) have been purged using <br /> a submersible pump, the analytical groundwater samples will be collected using a clean <br /> disposable teflon bailer equipped with clean nylon rope A new disposable bailer wall be used <br /> l to collect water samples from each well This procedure will minimize sample aeration and <br /> degassing when collecting water samples <br /> Steffen Robertson and Kirsten (U S ) Inc <br /> 15311 fd E 90th Street Redmond Washington 98052 U S A <br /> Tel (206) 881-2233 Eac&mile (206) 881-1581 <br /> Other offices in U S A Canada UnEted Kingdom and Africa <br />