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APR 20 '94 03:52PM OGDEN PROJECTS ENVIRONMENTAL DPT P.9'1© rim of the PVC well casing, but may vary depending on previous reference points. 4. The water level measurements will be converted to relative groundwater elevations with respect to mean sea level or a local benchmark by subtracting them from the surveyed casing elevations. The resulting groundwater elevations will be contoured to assess the direction of the groundwater gradient at the time of sampling. The information can then be used to assess which wells represent upgradient and which wells represent downgradient groundwater conditions. Groundwater Sam lin 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.) will be 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 will be replaced prior to use in each well_ 2. The depth to water will be measured using a conductivity-based water level meter. 3. The volume of water standing in the well will be calculated by subtracting the depth- to-water measurement from the depth of the well and multiplying the appropriate conversion factor (3.1.4 * radius'). 4. Three or more well volumes of water are purged from each well using a submersible pump, bladder pump or Teflon bailer, until physical parameters are reasonably stable. j. 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. 7. For all lead, TRPH, and TPH-diesel samples, in-line field filtration will be used to prevent the entrainment of air into the sample. Any samples to be analyzed for volatile constituents such as BTEX and TPH-gasoline, however, will not be in-line filtered. 8_ Samples will immediately be placed and sealed in labelled glass bottles, and stored on ice until delivery to the analytical laboratory. A custody seal will be placed on 4