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Ogden Environmental Services May 3, 1990 <br /> William S. Rickman Page 2 <br /> the well installation, developing the wells, sampling and analysis of the wells <br /> quarterly for the duration of the project and preparing quarterly groundwater <br /> reports for submittal to the Regional Water Quality Control Board. The proposed <br /> monitoring plan is described in detail as follows. <br /> Well Installation. Two downgradient and one upgradient monitoring wells <br /> will be completed at the locations shown on Plate 1. The borings/wells will be <br /> completed with a hollow stem auger drilling rig. Borings will be logged and soil <br /> samples will be collected by a trained field geologist. Soil samples will be <br /> collected from -the borings at 5-foot increments, beginning at 5 feet, by driving <br /> a California liner sampler. Samples will be retained in brass liners, sealed <br /> with Teflon tape, and placed on ice for transportation to a state-certified <br /> laboratory for chemical analysis. Soil samples collected in the unsaturated zone <br /> will be analyzed for benzene, toluene, ethylbenzene, and total xylenes (BTEX) by <br /> EPA method 8020 and total lead by EPA method 7420. <br /> After completing the borings, wells will be installed through the auger. <br /> The wells will be constructed of 2-inch-diameter PVC with threaded couplings. <br /> The wells will extend to a 25-foot depth, with the lower 20 feet consisting of <br /> 0.020-inch slotted well screen. A sand pack of Monterey No. 3 sand will be <br /> installed in the annulus between the borehole and the screened interval of each <br /> well. The sand pack will extend from the bottom of the borehole to a minimum of <br /> 1 foot above the screen. Bentonite pellets without additives will be used to <br /> form a seal at least 1 foot thick above the sand pack. The remainder of the <br /> borehole will be filled with concrete grout to provide a surface seal. Road- <br /> grade, locking monitoring well covers will be provided for each well. <br /> Well Survey. The elevations of the top of the wellhead covers will be <br /> surveyed. All subsequent groundwater levels will be converted to elevations to <br /> allow for a determination of groundwater flow direction. <br /> Well Development. The monitoring wells will be developed prior to ground- <br /> water sampling. A bailer and suction lift pump will be used to develop the <br /> wells. Use of the bailer is intended to create a surging action into and out of <br /> the well screen to remove fine-grained materials from the sand pack and maximize <br /> well yield. Pumping will allow for the removal of a sufficient volume of ground- <br /> water from the vicinity of the well so that any potable water used in construc- <br /> tion of the well will be removed prior to the collection of a representative <br /> groundwater sample. Well development water will be temporarily stored on-site in <br /> 55-gallon D.O.T. drums. This water will be either conveyed to the sump in the <br /> soil stockpile or will be used as dust suppression c:f soil within the stockpile. <br /> Groundwater Sampling. Groundwater samples will be collected quarterly for <br /> the duration of the project. Prior to sampling, water levels and total depth of <br /> wells will be determined. Stagnant water will be removed from the wells by <br /> purging a minimum of three casing volumes. To ins;;re collection of representa- <br /> tive samples, field measured pft, conductivity, and temperature will be allowed to <br /> stabilize prior to sample collection. <br /> C; McClelland consultants 1640A/B-2 <br />