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File No. 20-3978-01.W20 KLEINFELDER February 4, 1997 Monitoring wells are generally developed 24 to 48 hours after installation to allow the grout to set. Each well is first sampled with a clear disposable bailer to visually inspect for a hydrocarbon layer or sheen. If no product layer or sheen is observed on the water, the well is developed by surging, pumping or bailing. Surging along the screened interval of the well is performed to draw the sediment from the formation into the filter pack and the well, and to set the sand pack. Development continues until the discharge runs relatively clear of fines. Approximately 5 to 10 well volumes are generally removed from each monitoring well. Discharge water is stored in 55-gallon drums and left on site for later discharge or disposal by the client, depending on laboratory results. The drums are labeled with the date, well number, and a contact person and phone number. B-3.3 Equipment Decontamination To reduce the potential for cross-contamination between wells, developing equipment is washed in a trisodium phosphate or non-phosphate detergent solution and rinsed in distilled water or steam cleaned prior to use in the next monitoring well. B-3.4 Well Survey The locations of soil borings and monitoring wells, and the elevation of the top of the PVC casings are usually surveyed and tied into permanent markers, if readily available. Survey accuracy is 0.1 foot for the "x" and "y" coordinates and .01 foot for the "z" coordinate. The depth to static groundwater is measured from a set location at the top of the PVC casing (usually the north rim). The depth of water is then subtracted from the elevation of the top of the well casing to provide a groundwater elevation for each monitoring well location. B-4 GROUNDWATER MONITORING B-4.1 Water Level Measurements Water level measurements are made in the wells prior to purging and sampling the wells. Measurement protocol is as follows: I. The water level probe is decontaminated in a trisodium phosphate or non-phosphate detergent wash, followed by a distilled water rinse, prior to use in each well. 2. Water level measurements are made using a conductivity-based water-level meter. Depth-to-water is generally measured from a surveyed mark on the north rim of the PVC well casing. The water level measurements are converted to elevations using the surveyed casing elevations. B-4.2 Groundwater Sampling 10-73978-Ol.W20/207PE050 Page 6-5 01997, Kleinfelder, 1w.