CORRESPONDENCE_1994-1998 - Laserfiche WebLink

Home Browse Search

Water Level and Total Well Depth Measurements Immediately before a monitoring well is purged, the water level and total well depth will be measured using an electric sounder as described in the previous section "Groundwater Elevation Survey." The electric sounder will be decontaminated by being rinsed with deionized water after each use. Well Purging Before sampling occurs, standing water in the casing and gravel pack will be purged from the monitoring well using a dedicated Well Wizard® bladder pump, pneumatic displacement pump, or a polyvinyl chloride or Teflon® bailer. Monitoring wells will be purged according to the protocol presented in Figure A-1. In most monitoring wells, the amount of water purged before sampling will be equal to or greater than four casing volumes. Some monitoring wells are expected to be evacuated to dryness after the removal of less than four casing volumes. These low-yield monitoring wells will be allowed to recharge for up to 24 hours. Samples will be obtained as soon as the monitoring wells have recharged to a level sufficient for sample collection. If insufficient water has recharged after 24 hours, the monitoring well will be recorded as dry for the sampling event. Field measurements will be recorded in a waterproof field logbook. Figure A-2 shows an example of the Water Sample Field Data Sheet on which field data are recorded. Field data sheets will be reviewed by the sampling coordinator after the sampling event is completed. The pH, specific conductance, temperature and turbidity meters will be calibrated each day before beginning field activities. The calibration will be checked once each day to verify meter performance. Field meter calibrations will be recorded on a Field Data Sheet (see Figure A-2). Well Sampling A Teflon bailer or bladder pump will be the only equipment acceptable for well sampling. When samples for volatile organic analysis are being collected with a bladder pump, the pump flow will be regulated to approximately 100 milliliters per minute to minimize pump effluent turbulence and aeration. Glass bottles of at least 40 milliliters volume and fitted with Teflon-lined septa will be used in sampling for volatile organics. These bottles will be filled completely to prevent air from remaining in the bottle. A positive meniscus forms when the bottle is completely full. A convex Teflon septum is placed over the positive meniscus to eliminate air. After the bottle is capped, it is inverted and tapped to verify that it contains no air bubbles. The sample containers for other parameters will be filled, filtered as required, and capped. SAC/pjft93M9390011.8a1-94/1fc:9 Rev.0, 10/17/94 0939-001.18 A-3