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I ' In addition to depth to water measurements, Blaes Environmental technicians collected dissolved oxygen level measurements from each well casing using a YSI-85 dissolved oxygen meter The dissolved oxygen ' meter was decontaminated before and after use at each well Dissolved oxygen level measurements were recorded on the standard field data sheet The method of dissolved oxygen measurement collection is ' described in Appendix B Measurements indicated that dissolved oxygen levels in groundwater ranged from 10% at monitor well MW-2 (deeper well zone) to 15 1% at monitor well MW-5B (middle well ' zone) Dissolved oxygen levels above 10% were observed at monitor wells MW-5, MW-5B, MW-6B and MW-8A (Table 3) 3.1.2 Groundwater Sampling-December 2000 ' On December 6 and 7, 2000, Blaes Environmental collected 18 groundwater samples from the on-site monitoring wells This included samples from the middle "B" casings and lower casings plus samples ' from MW-3A and MW-5A The drop in groundwater levels did not allow sample collection from any of the other upper"A"casing wells ' Groundwater sample collection involved purging approximately three well volumes of groundwater from • the wells and allowing the wells to equilibrate before sample collection Bailing or pumping techniques were used to purge the wells Bailing was used to purge water from the middle and lower casings No purging was performed at the upper"A"casings due to the lack of water in these wells Purging wells by bailing involved lowering new disposable bailers in and out of the well until approximately three well volumes of water had been removed The purged water was transferred from five-gallon buckets to an on-site 1,000-gallon polyethylene storage tank Purging by pumping was planned for each of the lower casings, however, the pump malfunctioned after purging five of the eight lower casing wells and balling was used for the remaining wells Purging by pumping utilized a pump and reel system that included DurhamGeo® 1 5-inch diameter submersible pump, associated hose, and control box The pump was decontaminated before and after use using a liquid Alconox® detergent wash, a tap water rinse, and a final rinse with deionized water The pump was typically lowered to approximately five to ten feet from the bottom of the well The average purge rate using the pump was approximately 2 to 3 gallons per minute, which was the maximum flow rate for the pump Purge water was temporarily stored in 55-gallon steel drums and later transferred into the on-site Ipolyethylene tank Approximately three well volumes of groundwater were purged from the wells and • o7norol Blaes Project#002-70950-02 8 bpm C 1BLAES1U-Hau1170950170950r101 doc