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KLEINFELDER ' A-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. A-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. 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. Prior to obtaining water level measurements, the monitoring wells would be opened and allowed to equilibrate for a period of approximately 1/2 hour. 2. 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. t3. 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. 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: 1. Down-well equipment (pumps, bailers, etc.) is decontaminated by steam cleaning, or by scrubbing in a trisodium-phosphate or non-phosphate detergent wash followed by a distilled water rinse, prior to use in each well. Bailer cord is replaced prior to use in each well. ' 20-3978-03.MN7/ST08R117 February 1,2008 ©2008 Kleinfelder Page A-5