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Groundwater Sampling Prior to groundwater sampling, each well is purged of "standing" groundwater. Either a bailer, hand pump, or submersible pump is used to purge the well. The amount of purging is dependent on the well yield. In a high yield formation, samples will be collected when normal field measurement, including temperature, pH, and specific conductance stabilize, provided a minimum of three well -casing volumes of water have been removed. Field measurements will be taken after purging each well volume. In low yield formations, the well is purged such that the "standing" water is removed and the well is allowed to recharge. (Normal field measurements will be periodically recorded during the purging process.) In situations where recovery to 80% of static water level is estimated, or observed to exceed a two hour duration, a sample will be collected when sufficient volume is available for a sample for each parameter. At no time will the well be purged dry so that the recharge rate causes the formation water to cascade into the well. In wells where free -phase hydrocarbons are detected, the free -phase portion will be bailed from the well and the volume removed recorded. A groundwater sample will be collected if bailing reduces the amount of free -phase hydrocarbons to the point where they are not present in the well. Well sampling will be conducted using one of the aforementioned methods depending on the formation yield. However, if free -phase hydrocarbons persist throughout bailing, then groundwater samples will not be collected. Groundwater sample containers are labeled with a unique sample number, location, product name and number, and date of collection. All samples are logged into a chain -of -custody form and placed in a chilled ice chest for shipment to a laboratory certified by the State of California Department of Health Services. ENSCO ENVIRONMENTAL SERVICES, INC. Groundwater Sampling Protocol Latest Revision: April 20, 1989