ARCHIVED REPORTS_XR0005851 CASE 2

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UIRS • '( Mr Mike Infuma Page 2 San Joaquin County Environmental Health Department May 3, 2004 CaVEPA Representative Samj)ling of Ground Water for Hazardous Substances dated July 1995 page 6 Most reports on low-yielding wells recommend purging them to dryness and obtaining the sample after water levels have recovered sufficiently to allow collection of the required sample volume, a recommendation with which CaIIEPA agrees EPA — Environmental Response Team Groundwater Well Sampling SOP# 2007 dated January 26 1995, pages 2-3 For wells that can be pumped or bailed to dryness with the equipment being used, the well should be evacuated and allowed to recover prior to collecting a sample If the recovery rate is fairly rapid and time allows, evacuation of more than one volume of water is preferred If recovery is ' slow, sample the well upon recovery after one evacuation Well Purging Procedures at ARCO Station 6020 The purging procedures used by Blaine Tech Services, Inc , at ARCO Station 6020 are in compliance with both the Cal/EPA and U S EPA well-purging guidance documents An excerpt from the Blaine procedures is cited hereafter, a full copy of the Blaine Standard Procedures for Well Monitoring is lieincluded in Attachment III Blaine Tech Services, Inc Standard Procedures for the Routine Monitoring of Groundwater Wells, BP/ARCO Northern California Sites, pages 4-5 Normal purging activities remove no less than three case volumes of water from the well However, less water may be removed in cases where the well dewaters and does not immediately recharge Wells that dewater will be sampled once they have recharged to 80%of their original static water level or when we are prepared to leave the site provided at least one hour has passed ' URS hopes that this alleviates any concern you had concerning Blaine's well purging procedures Blaine will continue to follow this policy for the purging of ARCO sites in San Joaquin County