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.r-• 1. � '" '� $ Wig.. tl 7 •�J. _ €•'w _ � ,� �'i" A�' s A-1 Y 1.0 GROUND«ATER AND FREE-FLOATING PRODUCT'DFPTTT DETERMINATION A water/petroleum product interface.prole was used to determine the free product thickness,if prevent,and a water level indicator wa;used to measure she ground water depth in monitoring wells that do not contain free product. Depth to ground water was measured from the top of the monitoring well casing,which has been surveyed to within 0.01-foot relative to Of,City of Lodi bench mark with an elevation 51.70 feet above mean sea level,(Firjre 2). The tip of the wa•,er level indicator was subjectively analyzed for product sheen. All measurements and physical observations were r corded in the field on separate data sheets presented in Enclosure B. 2.0 SU13JFCI'IVE ANALYSIS OF GROUND WATER Prior to purging a water sample was collected from the monitoring wells for subjective analysis. The sample Ws retrieved by gently lowering a clean,disposable bailer to approximately one-half the bailer'-ength past the air/liquid interface. The bailer Nvas then retrieved. and tip: sample contained within the bailer was examined for floating product and the appearance of a petroleum product sheen. :y 3.0 MONITORING WELL DEVELOPMENT PURGING AND SAMPLING Monitoring wells were purged of three to four well volumes of water using a centrifugal pump or bailer. Ground water removed from the wells was stored in 55-gallon barrels at the site. The barrels were labeled with corresponding monitoring well numbers and the date of purging. After purging,ground water levels were allowed to stabilize. A water sample was then removed form eac4 of the wells using a disposable bailer. If the well was purged dry, it was allowed to sufficiently recharge and a sample was collected. Samples were collected in air-tight vials,appropriately labeled,and stored on ice from the time of collection through the time of delivery to the laboratory. A chain-of-custody form was completed to ensure sample integrity. Ground water samples were transported to the laboratory and analyzed within the EPA-specified holding times for the requested analyses. Purge water will be collected from the storage barrels in a vacuum truck and transported to an appropriate facility for treatment and/or disposal. LRP001.JDM ;r.