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L & M OPERABLE UNIT- FIRST QUARTER 2012 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT Appendix C Page 1 STANTEC CONSULTING CORPORATION 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, if present, within each well casing is measured to the nearest 0.01 ft 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 Groundwater wells are purged by using a dedicated bailer or a groundwater pump. 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 deemed sufficient once successive measurements of pH, conductivity, and temperature stabilize to within +/- 10 percent. 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 80 percent of the pre-purge groundwater elevation. For very slow recharging wells (wells pumped dry during purging), samples may be collected after 2 hours of recharge. Groundwater Sample Acquisition, Handling, and Analysis 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, hydrochloric acid-preserved and unpreserved 40 milliliter (mL) glass vials and sealed with Teflon-lined septum, and screw-on lids for analysis of total petroleum hydrocarbons for gasoline range organics, methyl tertiary butyl ether, and benzene, toluene, ethylbenzene, total xylenes, and 5 fuel oxygenates by EPA Method 8260B. Collected water samples are also discharged directly