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Active Groundwater Sampling Standard Operating Procedure SWE-FSOP-401;Revision 1 Ahtna Southwest Environmental Operations For bailer and submerisible sampling techniques, a single measurement is collected after three well volumes have been purged or the well drys and recovers. Using a cup provided by the manufacturer (or similar). Allow the parmaters to stabilize before loging the readings. Note. Some project work plans specify water quality measurements after each well volume. Consult the PL or FTL for the project specifications. If the project requires downhole parameters to be measured, lower the probe to the well screeen midpoint; once readings stabilize, one set of parameters are recorded. Well water stability criteria (EPA, 2017): DO ± 10 percent or±0.2 mg/L, depending on units of measure Specific conductance ±3 percent(microsiemens per cm) ORP ± 10 millivolts pH ±0.1 units Turbidity ± 10%or less than 10.0 NTU (Nephelometric turbidity unit) Temperature +3%°C Turbidity stabilization can be problematic. If other parameters have stabilized but not turbidity, the FTL may determine that the purging meets the objectives of obtaining a representative sample and terminate the need for additional purging volume. 4.3 Bailer Sampling 1. Measure groundwater level, then depth to bottom if needed. Decontaminate the sounder. 2. Tie a rope of appropriate size and material to the top of a disposable or stainless-steel bailer and the other end to an unmovable object. 3. Slowly lower the bailer into the water column to avoid disturbing sediment; stop lowering when the bailer is full. 4. Raise the bailer to the surface, keeping the removed rope on a clean surface such as plastic sheeting or in your hands. S. Contents of the bailer are dumped into a marked container such as a tank, drum, or bucket. The container has markings to track the volume of water purged from the well. Bail until at least three well volumes have been removed or the well has been dewatered. 6. Collect one set of water quality measurements from a fresh aliquot of sample after finished the well purging. Measurements are taken from a cup supplied with the multimeter. Note. Some project work plans specify water quality measurements after each well volume. Consult the PL or FTL for the project specifications. 7. Using the bailer tip or sample valve inserted at the check ball, empty contents into sample containers. If sampling for VOC/GRO, use a VOC tip to dispense the sample into the appropriate sample container(See Section 4.7 "Filling Sample Containers"). 8. If the well dewaters, collect samples after the well recharges to approximately 80 percent of its pre-purge volume. However, if its unlikely to achieve 80 percent recover, collect samples for the Page 9 of 14