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1 4 Monitoring Well Gravel Pack and Slot size selection <br /> The size of the gravel pack that will be placed adjacent to the <br /> well screen will be determined by the project manager, based on <br /> an estimation of the distribution of grain size in the formation <br /> which is likely to be encountered within the uppermost saturated <br /> zone at the site. Available geologic information will be utilized <br /> in the selection of the grain size. The gravel pack will be <br /> selected such that it will permit the development of a zone of <br /> higher hydraulic conductivity adjacent to the well screen but <br /> will not allow piping of the finer-grained formation into the <br /> well bore. The slot size of the well screen will be selected such <br /> that it will retain a minimum of 95% of the gravel pack material. <br /> 1.5 Monitoring Well Development <br /> Each monitoring well will be developed after construction by <br /> bailing until the water produced is relatively sediment-free or <br /> until measurements of pH, specific conductance, and temperature <br /> stabilize. If the well is pumped dry during the development <br /> process, recharge rates will be recorded. No water or chemicals <br /> will be introduced into the monitoring wells during well <br /> development. All developed water will be placed in drums on site <br /> for later disposal. <br /> 1. 6 Ground Water Sampling <br /> A minimum of 24 hours following well development, and after water <br /> levels have been allowed to stabilized in the well, three to five <br /> wetted casing volumes of liquid will be removed from each well by <br /> bailing with a laboratory-cleaned teflon bailer. Measurements of <br /> pH, specific conductance, and temperature will be made at regular <br /> intervals during this procedure. Removal of liquid from each well <br /> will continue until the measurement of pH, specific conductance, <br /> and temperature have stabilized. A liquid sample will then be <br /> collected from each well with a laboratory-cleaned, dedicated <br /> teflon bailer, Each sample will be appropriately labeled and <br /> stored on ice from the time of collection through the time of <br /> delivery to the laboratory. Ground water samples will be trans- <br /> ported to the laboratory and analyzed within the EPA-specified <br /> holding times for the requested analyses. <br /> 1.7 Petroleum Product <br /> If free petroleum product is present in a well, the thickness of <br /> the product layer will be measured by application of a water- <br /> finding paste to a water-level-indicator tape. A sample of the <br /> product will be collected with a laboratory-cleaned teflon bailer <br /> and transferred to an appropriate sample container and subse- <br /> quently submitted to a California-certified laboratory for fuel <br /> fingerprint analysis. <br />