Laserfiche WebLink
i <br /> I <br /> Well Purging and Development <br /> Before the sampling event, a bladder pump, pneumatic displacement pump, or <br /> Teflon® bailer will be used to purge standing water in the casing and gravel pack <br /> from the monitoring well Monitoring wells will be purged 24 to 48 hours after <br /> installation Each well is first sampled with a clear bailer to visually inspect for <br /> hydrocarbon layer or sheen If no petroleum hydrocarbon (product) layer or sheen <br /> is observed on the water, the well is developed by surging, pumpng or bailing <br /> Surging along the screened interval of the well is performed to draw sediment from <br /> the formation into the filter pack and the well and to set the sand pack The <br /> sediment laden water is purged from the 2-inch well at a rate less than 2 gallons <br /> per minute Development continues until the discharge runs relatively clear of <br /> fines After the wells are developed, the aquifer is allowed to equilibrate for at least <br /> 24 hours allowing for stabilization of pH, conductivity and temperature prior to <br /> sampling <br /> ' Following development, the well can then be purged and sampled In most <br /> monitoring wells, the amount of water purged before sampling will be greater than <br /> or equal to four casing volumes Some monitoring wells are expected to be <br /> evacuated to dryness after removing fewer than four casing volumes These low- <br /> yield monitoring wells will be allowed to recharge for up to 24 hours Samples will <br /> be taken as soon as the monitoring wells have recharged to a level sufficient for <br /> sample collection If insufficient water has recharged after 24 hours, the monitoring <br /> well will be recorded as dry for the sampling event <br /> ' Field measurements will be recorded in a waterproof field logbook Figure 4 shows <br /> an example of the Water Sample Field Data Sheet on which field data are <br /> recorded Field data sheets will be reviewed for completeness by the sampling <br /> ' coordinator after the sampling event is completed <br /> The pH, specific conductance, and temperature meter will be calibrated each day <br /> before field activities begin The calibration will be checked once each day to verify <br /> meter performance Field meter calibrations will be recorded on a Field Meter Log <br /> rWell Sampling <br /> ' A Teflon or disposable polyethylene bailer or bladder pump will be the only <br /> equipment acceptable for well sampling When samples for volatile organic <br /> analysis are being collected, the pump flow will be regulated at approximately 100 <br /> ' milliliters per minute to minimize pump effluent turbulence and aeration Glass <br /> bottles of at least 40-milliliters volume and fitted with Teflon-lined septa will be used <br /> in sampling for volatile organics These bottles will be filled completely to prevent <br /> air from remaining in the bottle A positive meniscus forms when the bottle is <br /> C -4 <br />