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I� A GROUND-WATER SAMPLING PROTOCOL Equipment Cleaning II I Ground-water samples are recovered in pre-cleaned disposable polyethylene or Teflon bailers. The samples are then placed in pre-cleaned laboratory supplied glassware. Sample bottles and caps remain sealed until actual usage at the site. Before and during use at the site, equipment which comes in contact with the well or ground water is thoroughly cleaned with trisodium phosphate or Alquinox and rinsed with deionized or distilled water. This procedure occurs between each sampling event. Monitoring wells are sampled in approximate order of increasing contamination. i p Prior to field activities ground-water and field monito)ring equipment are calibrated using the appropriate calibration standards. Water Level Measurements Prior to checking for floating product, purging of the well and sampling, the depth to water E is measured in each well using a sealed sounding tape)of a scaled electric sounder. Water levels are recorded in the field to the nearest 0.01 foot from a common reference point on the well casing. r Floating Product Thickness A field check for floating product is made with a clean and clear acrylic or Teflon bailer. Thickness of floating product as well as odor and color of the water is recorded. A clean I nylon or cotton cord is used in each well. The cords Flare replaced with new cords prior to the sampling event. Water Sampling Procedures ` i Prior to sampling of the ground water, a minimum o I four to ten well-casing volumes of j water are removed from the well. The volume of water to be removed is calculated from the measurements of the water level, casing diameter,acid the well depth. Water is removed by either bailer, hand pump, or submersible electric pump. During purging, temperature, k pH, dissolved solids, and oxidation-reduction potential are monitored for stabilization (t10%). Turbidity of the water is also noted either givalitatively or by means of a NTU instrument. A water sample is collected using a clean disposable polyethylene bailer when t the appropriate volume has been purged or when the parameters have stabilized and a minimum of four well-casings have been purged. If thle well is dewatered during purging, the well is allowed to recover to 80 percent of the static water level prior to sampling. If recovery exceeds a two-hour duration, the sample will be collected when a sufficient volume is available for the specific laboratory analyses., i 4203-F3 I I March 25, 1997