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LIAR-24-99 16 35 From WOODWARD CLYDE + T-735 P 02/34 Job-492 EMCCICY TeStlngA FMd 09 MO [ASIS SOM099nu mas W Kabrs,BSG Douglas S Hodge,Ph D J Graydon Martz,BAG ASsTRACT Groundwater monitoring and sampling has bacorne ars integral part of site assessment and remodial efforts at facilities with chemically impacted groundwater significant efforts in boot the assessment and romedial arenas are being undertaken based on the Information generated during groundwater monitoring events Therefore, it becomes Imperative that the most reliable and accurate groundwater information be generated The reliability of groundwater sampling devices boars dimly on the reliability of groundwater monitoring data. Sampling deeviceo have boon evaluated for their capacity to provido roliabie samples(ltroalona, M J , et al , 1984) for laboratory analysts.The most reliable,to date,have boon the check-valve bailor and the gas-operati;d bladder pump These devices have their draw-backs,primarily by the targe amount of contaminated purge water croatod and the trate necessary to purge the well pnor to obtaining the sample The KABIS Sampler was tested against the check-valve bailor for over-ail accuracy in two ways The KABiS Sampler was shaven to be superior to the Check-valve Beller in all categories of the test. INTRODUCTION Until recently, groundwater sampling was performed using a handful of groundwater sampling devices,each with its individual set of sampling errors and sampling idiosyncrasies A large amount of purged groundwater was produced from each sampled well under the presumption that a sample representative of formational conditions could be collected The presumable reason for purging is to refresh the stagnant borehole water with representative formational water This Is boat-out by the early data, but is a potential misnomer because thore is widely varying scientific ovidence and opinion on the number of stagnant borehole volumes to purge.There are even varying opinions on exactly what ® constitutes a borehole or well volume The most reliable sampling devices were identified by screening fourteen different devices from five mechanistic categories(Barcelona,et a, 1954) The results of Barcolona's scresining have become the equipment protocol (TEGD)basis for nearly SM/6 of currently recommended sampling activities The KAKIS Sampler is a new adjunct to that list LITERATURE REVIEW Many articles have been published on the pmblern of obtaining representative groundwater samples from rapidly recovering ground-water monitoring wells Scan, et al I reported In a 1981 paper that bacterial activity can dramatically affect VOG analysis results Dissolved VOCs can effervesce in as little as 2 hours after sample acquisition Seanor and BrannaW note(%in their 1853 paper that water in ground water monitoring wells standing considerably above the screened interval and not in communication with formational water is stagnant This standing water is subject to dmerent chemical equilibria and often has different pH,EC,temperature, and dissolved solids Wilson and Dworkins reported in their 1984 paper that rust and scale from ground-water monitoring wells may interfere with laboratory analyses,as may the proseince of colloids and clay platelets Barcelona and Helfrich4 concluded.in 1986,that no or improper purging of a ground-water monitoring well was a greater cause for sampling error than was sampling method,well construction materials,or sampler matenals They went so far as to state that improper purging was the dominant error factor in groundwater sampling WB Puroina The universal goal of well purging is to remove°stagnant"water from the well,creating very little disturbance to the groundwater flow regime Recommended purge volumes range from one(1)to twenty(20)well bore volumos, • 1 of 14 3124199 4.21 PM