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k' ■ KLEINFELDER 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 SOIL AND GROUNDWATER INVESTIGATION 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%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. 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 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. 2. The depth to groundwater is measured using a conductivity-based water-level meter. 3. The volume of water in gallons standing in the well is calculated by subtracting the depth to groundwater measurement from the depth of the well and multiplying by the appropriate conversion factor(0.16 for 2-inch wells, and 0.65 for 4-inch wells). 27125.E01 /ST03R657 Page A-6 Copyright 2003,Kleinfelder,Inc. May 23,2003