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GROUNDWATER MONITORING AND SAMPLING PROCEDURES Introduction The groundwater monitoring and sampling event was conducted in accordance with procedures detailed in the State of California LUFT Manual The objectives of the monitoring and sampling procedures were to determine the groundwater gradient at the site and to collect and preserve representative samples of the groundwater at the site for delivery to a State of California-certified laboratory t Samples were collected from four groundwater monitoring wells during this event Samples were analyzed by Trace Analysis Laboratory, Hayward, California, for concentrations of Benzene, ' Ethylbenzene, Toluene, and Xylenes (BETX) using the Modified EPA Method 8020, and Total Petroleum Hydrocarbons as gasoline (TPHg) using the DHS Method Sample and Data Collection ' All field parameter meters were calibrated according to the manufacturer's instructions prior to use Static depths to water and total depths of all wells were measured using a scaled electronic water level meter Water level measurements were recorded in the field log to the nearest 0 01 foot If free ' product was present, the depth to free product and the depth to water were measured using an electronic oil/water interface probe and an observation sample was collected with a clear acrylic bailer for confirmation No analytical samples were collected from monitoring wells containing more than 0 25 inch of free product Prior to collecting a sample, standing water was purged from the well using a clean Teflon bailer Care was taken during purging and sample collection to minimize the loss of ' volatile constituents from the sample Purged water was periodically monitored for temperature, pH, and specific conductance, and the values were recorded in the field log Physical characteristics such ' as color, turbidity, odor, or the presence of a sheen were noted during purging and recorded in the field log Samples were collected after stabilization of the measured parameters and recovery of the water level to at least 80 percent of its initial level Wells dewatered during purging were sampled ' after 80 percent recovery, or, when recovery to 80 percent exceeded two hours, a sample was collected when sufficient volume was available Samples to be analyzed for TPHg and BETX were decanted ' from the top of the bailer into two EPA-approved 40-m1 volatile organic analysis (VOA) bottles preserved with hydrochloric acid Sample bottles were completely filled with no observable headspace Sample bottles were labeled with the project name and number,well identification number, date, name ' of sampler,preservation method, and analysis requested Samples were immediately placed in an ice chest and maintained at VC for delivery to a State of California-certified laboratory Water generated during the purging process was stored on-site in properly labeled (Title 22 CCR §66508) DOT- approved 55-gallon drums pending disposal Du Pont Environmental Remediation Services 0511 10 Rev 0 Printed on Regded Paper r A-