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GEOMATRIX water along the inside of the well casing. Procedures for purging slowly recharging wells are discussed in Section A3. A minimum of four well casing volumes or one saturated borehole volume,whichever is greater,will be removed to purge the well prior to collection of groundwater samples if the well will be purged with non-dedicated equipment. If a low-flow capacity pump is dedicated in the well,the micropurge method described in Section AA may be used to reduce the purge volume. If the well goes dry before four casing volumes are removed, the procedure discussed in Section A.3 will be followed. The saturated borehole volume is the volume of water in the well casing plus the volume of water in the filter pack. For a well with a dedicated pump and packer,a casing volume is defined as the volume of water in the well casing below the inflated packer. Periodic observations of turbidity and measurements of temperature,pH,and specific electrical conductance(SEC)will be made with field equipment during purging to evaluate whether the water samples are representative of the target zone. Samples will be collected when: (1)a minimum of four sets of parameter readings have been taken; and(2)the temperature,pH, and SEC reach relatively constant values, and the turbidity has stabilized. A.2 Sampling Monitoring Wells The sampler will wear clean gloves appropriate for the chemicals of concern while collecting the sample. Samples will be collected directly in laboratory-prepared bottles from the sampling device. Each sampling episode or day should generally begin with the well having the least suspected concentrations of target compounds. Successive wells should generally be sampled in sequence of increasing suspected concentration. A Teflon bailer,new disposable bailer, stainless steel positive displacement Teflon bladder pump with Teflon tubing,or a clean electric submersible pump with low-flow sampling capacity will be used to collect the water samples for laboratory chemical analysis. If a bailer is being used to collect the sample, it will be gently lowered into the well below the point where the purge device was located. Samples will collected in the following order: (1) volatile organic compounds; (2)semi-volatile organic compounds;(3)metals; (4) other analytes. L\Doc_SafeTROTOCOUPROTO-MWAoc SAMPLTNGOFGROUNDWATER MONITORTNGWELLS AND WATER SUPPLY WELI2 Page 2 of 9 Revision Date: March 1996