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F File No. 20-3941-01.E01 k'q'K L E t N FELDER January 22, 1997 A-4 GROUNDWATER MONITORING A-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: 1. The wells are opened and allowed to equilibrate with the atmosphere. 2. The water level probe is decontaminated in a trisodium phosphate wash, followed by a distilled water rinse, prior to use in each well. 3. 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 in PVC well casing. The water level measurements are converted to elevations using the surveyed casing elevations. A-4.2 Groundwater Sampling ! Groundwater samples are collected from the monitoring wells at the site. The sampling ' protocol for each well is as follows: i 1. Down-well equipment (pumps, bailers, etc.) is decontaminated by steam cleaning, or by scrubbing in a trisodium-phosphate wash followed by a distilled water rinse, prior to use in each well. Bailer cord is replaced prior to use in each well. f + 2. The depth-to-water is measured using a conductivity-based water-level meter. ' 3. The volume of water standing in the well is calculated by subtracting the depth-to- water measurement from the depth of the well and multiplying by the appropriate conversion factor (3.14 *radius 2). 4. Three to five well volumes of water are purged from each well using a submersible pump, bladder pump, or Teflon bailer. 5. Physical parameters (pH, electrical conductivity, and temperature) are monitored for stability during purging. The physical parameter measurements are recorded on purge- and-sample logs, along with the time and volume of water purged at each measurement. 6. Samples are collected with a disposable bailer or bladder pump into appropriately prepared bottles provided by the analytical laboratory. r 20-3941-O1.E011207PE026 Page A-5 01997. Kleinfelder, Inc.