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S E C 0 R ATTACHMENT G FFIELD AND LABORATORY PROCEDURES Fil 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 was measured to the nearest 0.01 foot using either an electronic Solinst water level indicator or an electronic oil-water interface probe. Measurements were 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 Purging was conducted prior to sampling wells that do not contain LPH, a dedicated 1-inch diameter PVC "stinger," bailer or groundwater pump was used to purge the wells. Purge water was discharged directly to a vacuum truck via the "stinger', or contained on-site in 55-gallon DOT-approved drums. To assure that the collected samples were representative of fresh formation water, the conductivity, temperature, and pH of the delivered effluent was monitored and recorded using a Cambridge Hydac meter or another meter similar in nature during purge operations. Purge operations were determined to be sufficient once successive measurements of pH, conductivity, and temperature stabilize to within +1- 10 percent. During purging a minimum of three (3) well volumes, measured as the annular space of the well casing below the groundwater surface, was removed from each well. However, in the case of very slow recharging wells, purging was deemed sufficient if the well contents were evacuated during purge operations. Unless recharge takes more than two hours, wells were sampled once the well recharged to within in 90 percent of pre-purge groundwater elevation. I For very slow recharging wells (wells pumped dry during purging), samples were collected after 2 hours of recharge. Groundwater Sample Acquisition and Handling � Following purging operations, groundwater samples were collected from each of the wells, G 14 using pre-cleaned, single-sample polypropylene, disposable bailers. The groundwater sample was discharged from the bailer to the sample container through a bottom emptying flow control rr valve to minimize volatilization. E � Collected water samples were discharged directly into laboratory provided, pre-cleaned, 40 milliliter (ml) glass vials and sealed with Teflon-lined septum, screw-on lids. Labels F, documenting sample number, well identification, collection date and time, type of sample and type of preservative (if applicable) were affixed to each sample. The samples were 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 4 1 Environmental Laboratory Accreditation Program. F ,Containment and Disposal of Generated Water/LPH Wastewater, purge water and LPH (if present) generated during the field activities are retained on-site in appropriate containers (i.e. DOT-approved drums or bulk tanks) for future tl