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i•W <br /> IA h1oniforing Well Gravel Pack and Slot Size Selection <br /> The size of the gravel pack that will be placed adjacent to the well screen will be determined by the <br /> project manager based on an estimation of the distribution of grain size in the formation which is <br /> likely to be encountered within the uppermost saturated zone at the site. Available geologic <br /> information will be utilized in the selection of this grain size. The gravel pack will be selected such <br /> that it will permit the development of a zone of higher hydraulic conductivity adjacent to the well <br /> screen but will not allow piping of the finer-grained formation into the well bore. The slot size of <br /> the well screen will be selected such that it will retain a minimum of 95%of the gravel pack materip.l. <br /> -- 1.5 Monitoring-Well_Dgelgpmgnt' <br /> If monitoring veils are installed, each monitoring well will be developed after construction with a <br /> 1.75-inch diameter manual pump until the water produced is relatively sediment free or until <br /> measurements of pH, specific conductance, and temperature stabilize. If the well is pumped dry <br /> during the development process, recharge rates will be recorded. No water or chemicals will be <br /> introduced into the monitoring wells during well development. All developed water will be placed <br /> w„ in drums on-site for later disposal. <br /> 1.6 Ground Water Sampling <br /> A minimum of 24 hours following well development, and after water levels have been allowed to <br /> stabilize in the well, three to five wetted casing volumes of liquid will be removed from each well <br /> by bailing with a laboratory-cleaned teflon bailer. Measurements of pH,specific conductance,and <br /> temperature will be made at regular intervals during this procedure. Removal of liquid from each <br /> well will continue until the measuremert pH,specific conductance,and temperature have stabilized. <br /> A liquid sample will then be collected from each well with a laboratory-cleaned, dedicated teflon <br /> bailer. Each sample will be appropriately Iabeled and stored on ice from the time of collection <br /> through the time of delivery to the laboratory. Ground water samples will be transported to the <br /> laboratory and analyzed within the EPA-specified holding times for the requested analyses. <br /> 1.7 Petroleum Pr duc <br /> If free petroleum product is present in a well, the thickness of the product layer will be measured <br /> by the"paste and tape"method. This method will consist of coating a water level indicator tape with <br /> a water-finding paste and measuring the thickness of the product Iayer as indicated by the color <br /> change of the paste. Position of the oil/water interface will be determined by subtracting the <br /> position of the interface as indicated by the color change from the depth indicated on the water level <br /> -- - — tl <br /> --------indicator-tape-adjacent-to the-top of the-AVC casing when the-measurement-is-made: -- <br /> If free product is present in a well, a free product sample will be collected in a laboratory cleaned, <br /> �: teflon bailer,transferred to the appropriate sample container and shipped to a California-certified <br />