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SECOR INTERNATIONAL INCORPORATED STANDARD PROCEDURE FOR GROUNDWATER SAMPLING Depth to Groundwater/LPH Thickness Measurements Prior to purging each of the wells, the depth to groundwater and thickness of liquid phase hydrocarbons (LPH), if present, within each well casing is measured to the nearest 0 01 foot using either an electronic Solinst water level Indicator or an electronic oil-water Interface probe Measurements are taken from a point of known elevation on the top of each well casing as determined in accordance with previous surveys Groundwater Monitoring Well Purging Where purging is conducted prior to sampling wells that do not contain LPH, a dedicated 1- Inch diameter polyvinyl chloride (PVC) "stinger," bailer, or groundwater pump may be used to purge the wells During purging a minimum of three (3) well volumes, measured as the annular space of the well casing below the groundwater surface, are removed from each well However, in the case of very slow recharging wells, purging is deemed sufficient If the well contents are completely evacuated during purge operations Unless recharge takes more than two hours, wells are sampled once the well Is recharged to within In 90 percent of pre- purge groundwater elevation For very slow recharging wells (wells pumped dry during purging), samples may be collected after two hours of recharge To help assure that the collected samples are representative of fresh formation water, the conductivity, temperature, and pH of the delivered effluent are monitored and recorded using a Cambridge Hydac meter, or another meter similar in nature during purge operations Purge operations are determined to be sufficient once successive measurements of pH, conductivity, and temperature stabilize to within +/- 10 percent Groundwater Sample Acquisition and Handling Following purging operations, groundwater samples are collected from each of the wells, using pre-cleaned, single-sample polypropylene, disposable bailers The groundwater sample is discharged from the bailer to the sample container through a bottom emptying flow control valve to minimize volatilization Collected water samples are discharged directly into laboratory provided, pre-cleaned, 40 milliliter (ml) glass vials and sealed with Teflon-lined septum, screw-on lids Labels documenting sample number, well Identification, collection date and time, type of sample and type of preservative (If applicable) are affixed to each sample The samples are then placed Into an ice-filled cooler for delivery under chain-of-custody to a laboratory certified to perform the specified tests by the State of California Department of Health Services Environmental Laboratory Accreditation Program • 11ConocoPhdhps\Retatl Sites1111931QMR14QMR04 Final doc