ARCHIVED REPORTS_XR0002862 - Laserfiche WebLink

Home Browse Search

determine the depth and length of the screen interval. Measure the depth of the pump intake while lowering the pump into location. Record pump location in sampling log. . 2. Dedicated s, stem (tubing already installed)— Refer to the available monitoring well information and record the depth of the dedicated submersible pump or tubing (in the case of a peristaltic pump) hung in the well on the sampling log. 3. Measure the water level and record, leaving probe in the monitoring well at depth. 4. Connect the discharge line from the pump to a FTC. The discharge line from the cell must be directed to a container to contain the purge water. 5. Start pumping the well at a flow rate of less than 500 ml/minute). Check the water level. Maintain a steady flow rate while maintaining a drawdown of less than 0.33 feet. If drawdown is greater than 0.33 feet decrease the flow rate. 0.33 feet is a recommended goal to help guide with the flow rate adjustment, but is not mandatory. This goal may be difficult to achieve under some circumstances and may require adjustment based on site-specific conditions, and personal experience. 6. Measure the discharge rate of the pump with a graduated cylinder (I Liter) with a watch that has a second hand. Also, measure the water level and record both flow rate and water level on the sampling log. Continue purging while monitoring and recording water level, water-quality parameters, and pump rates every three to five minutes during purging. Pumping rates should be kept at a constant ' minimal flow rate to ensure minimal drawdown in the monitoring well. 7. During the purging, a minimum of one purging volume must be purged prior to recording the water quality parameters. Eliminate the formation of air bubbles in the tubing by rectifying leaks. Then monitor and record every three to five minutes. The stabilization criterion is based on three successive readings of the parameters; The following are the criteria which must be used: 1 Parameter Stabilization Criteria pH ± 0.1 pH units Temperature ± 3% Specific Conductance ± 3% in S/em Oxidation-Reduction Potential ± 10 millivolts (other guide says it's microvolts) ± 10%NTUs NTUs should not be increasing. Turbidity (when turbidity is greater than 10 NTUs) Dissolved Oxygen ± 0.3 ug/L ' 8. If a stabilized drawdown cannot be maintained at 0.33 ft. and the water level is approaching the top of the screened interval, reduce the flow rate or turn the pump off for 15 minutes and allow recovery. Under no circumstances should the well be pumped dry or pumped below the top of the screen. After 15 minutes begin pumping at a lower flow rate, if the drawdown approaches the well screen interval again turn off the pump and allow recovery. Attempt low flow purge again. Allow recovery and proceed with sampling. This infonnation must be noted in the groundwater-sampling log. 1 9. Reduce the pumping rate to 100 ml/minute for sampling in order to minimize disturbance of the water column. Do not go below 100 ml/minute as this may cause the pump to stall. The goal is to maintain minimum flow. Samples should be collected directly from the discharge port of the pump tubing prior 1 to passing through the FTC so that the samples are collected from the pump's discharge tubing. In other words, disconnect the tubing from the FTC intake and sample at that point, not after the FTC). The tubing should be absent of any air bubbles possibly caused by joint leaks between tubing sizes ( if ' varying sizes of tubing are used). All sample containers should be filled with minimal turbulence by allowing the groundwater to flow from the tubing gently down the inside of the container, forming a meniscus over the mouth of the vial to eliminate headspace prior to capping. An in-line filter must be used for filtered metal samples. 10. Non-Dedicated System—Remove submersible pump and tubing from well. Disconnect tubing and reinsert down well or stare in a baggie with Site and Well I.D. labeled. H.. Peristaltic pump—Disconnect tubing at pump and hang in well for subsequent sampling events. 12. Before locking the monitoring well, measure and record the total depth of the well. Measure a second time for confirmation. Measurements must be within 0.01 feet. 3