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Standard Operating Procedure Page 2 of 6 SOP-011 Water Level Measurements in Monitoring Wells Revision No. 0 March 2020 4.0 Procedures Water level measurements are commonly taken in a monitoring well before, during, and following well development, and both before and after well purging and sampling. Water level measurements may also be taken where no development or purging is being conducted,strictly to monitor or generate water table or piezometric surfaces. When such measurements are made to monitor water table or piezometric surfaces, water levels in all wells at a given site should be measured within a 24-hour maximum period whenever possible. If the contaminant history is known for each of the wells, it is advisable to monitor water levels beginning with the least contaminated wells first and progressing to the most contaminated wells last. This is important when measuring wells for water table or potentiometric surface analysis. 4.1 Determining Water Level Measurement The standard procedure for determining depth to water in monitoring wells is described below. 4.2 Calibrate Calibrate all measuring devices according to the manufacturer's specifications. Measuring tapes should be checked a minimum of every six months against a surveyor's tape to determine if shrinking or stretching has occurred. 4.3 Decontaminate Before taking a water level measurement at each well, decontaminate the measuring device according to the procedures outlined in SOP-003 (Equipment Decontamination Procedures). During decontamination, all measuring tapes should be inspected for kinks, cracks, or tears and, if present, repaired or replaced with undamaged equipment. 4.4 Inspect Visually inspect the well to ensure that it is undamaged, properly labeled, and secured. Any damage or problems with the well head should be noted on the Field Activity Daily Log(FADL)in Attachment 1. Notify the site superintendent for repair or replacement of the equipment. Uncap the well and monitor the air space immediately above the open casing per the project-specific health and safety plan. Observe if any air is flowing into or out of the casing. In the event such conditions are observed, they should be noted on the Water Level Measurement Form (Attachment 2) as appropriate. Lower the electric sounder or equivalent(product probe or steel tape) into the well until the water surface is encountered. If air is observed to be entering or flowing out of the casing, the sounder should not be placed inside the well until the air flow stops and pressure equalizes. 4.5 Measure Measure the distance from the water surface to the permanent reference point. For aboveground "stickup" completions, the reference point is usually a groove cut into the north side of the casing. If no permanent reference point is available for an aboveground completion, measure from another Sharpe Army Depot