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r. stainless steel, 2) a pneumatic-airlift pumping system, 3) a centrifugal pumping system, or 4) a Teflon or stainless steel bailer. The type of equipment chosen is based upon well size, depth, location, accessibility, chemical constituents, and client or regulatory recommendations. As a general rule, 3-5 well casing volumes are typically purged prior to sampling. Wells which de-water or demonstrate low-yield will not be sampled unless at least 80% of the previously measured water column has been replaced by recharge, or as required by a pre-arranged protocol with the client. Temperature, pH and specific conductance readings are monitored to determine stability. Temperature values are considered stable once two or more consecutive reading agree within + 1 degree Fahrenheit. The pH units are stable when two or more concecutive readings agree within + 0.1 unit, and specific conductance agrees within + 10%. Field Sampling Because groundwater samples collected by Gettler-Ryan are analyzed at the parts-per- billion (ppb) range, utmost care is taken to avoid the possibility of cross-contamination and loss of volatile analytes. Sampling personnel shall wear a clean pair of gloves for each new sample location. Where previous chemical analytical data are available, samples are first obtained from the least contaminated wells, to the greatest contaminated wells. Groundwater samples are collected with clean bailers or bladder pumps. Decontamination consists of an Alconox/potable water high-pressure wash followed by two water rinses and a final distilled water rinse. Samples are collected in laboratory-prepared containers for transport or shipment to the laboratory. A. schematic of field monitoring procedures can be found in Appendix B. Sample Packaging and Shipment Coolers containing glass sample containers are lined..with bubble-pak or vermiculite. Coolers will contain ice or an ice substitute to keep samples chilled during shipment. If regular ice is used it will be double bagged to prevent leakage. Samples are delivered by G-R personnel, courier, or Federal-Express. Appendix C lists typical analytical methods, sample containers, preservatives, and analytical holding times. Section 4.0 Recordkeeping Field data collected during gauging, purging and sampling activities shall be entered onto a G-R Field Data Sheet as shown in Appendix D, or onto forms supplied by the client. Field Data Sheets are reviewed for accuracy and completeness prior to inclusion in the Quarterly. Monitoring Report. Sample labels are completed in the field, and placed on each sample container immed- iately following sample collection. Label information shall include: (1 ) sample point designation, (2) sampler's identification, (3) project number, (4) date/time of ' collection, and (5) sample preservation. Gettler-Ryan's sample label can be found in Appendix D.