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dog information will be utilized in the selection of this grain size. The gravel pack will be selected such that it will permit the development of a zone of higher hydraulic conductivity adjacent to the well } screen but will not allow piping of the finer-grained formation into the well bore. The slot size of +" the well screen will be selected such that it will retain a minimum of 90 percent of the gravel pack material. r.. 1 Monitorip Well D vel m nt If monitoring wells are installed, each monitoring well will be developed after construction with a w 1.75-inch-diameter manual pump until the water produced is relatively sediment free or until measurements of pH, specific conductance, and temperature stabilize. If the well is pumped dry a. during the development process, recharged rates will be recorded. No water or chemicals will be introduced into the monitoring wells during well development. All developed water will be placed in drums on site for later disposal. ' I& Ground Water Sampling A minimum of 24 hours following well development, and after water levels have been allowed to stabilize in the well, three to five wetted casing volumes of liquid will be removed from each well by bailing with a laboratory-cleaned teflon bailer. Measurements of pH, specific conductance, and temperature will be made at regular intervals during this procedure. Removal of Iiquid from each well will continue until the measurement pH,specific conductance, and temperature have stabilized. 6. A liquid sample will then be collected from each well with a laboratory-cleaned, dedicated teflon bailer. Each sample will be appropriately labeled and stored on ice from the time of collection through the time of delivery to the laboratory. Ground water samples will be transported to the laboratory and analyzed within the EPA-specified holding times for the requested analyses. 1.7 Petroleum Product If free petroleum product is present in a well, the thickness of the product layer will be measured 60 by collecting a sample in a transparent teflon bailer with a check valve at the bottom or by measurement using appropriate fluid-level sounding equipment. The sample will be transferred to an appropriate sample container and subsequently submitted for fuel fingerprint analysis at the laboratory. 2.0 ANALYTICAL PROCEDURES All soil samples submitted to the laboratory will be analyzed by EPA Method 8020 for benzene, toluene ethylbenzene, xylene, (BTEX) and by EPA Method 8015 for total purgeable petroleum hydrocarbons (TPPH). All ground water samples submitted to the laboratory will be analyzed by ' EPA Method 602 for BTEX and by EPA Method 8015 for TPPH. Total lead will be analyzed in soil L. and ground water samples by EPA Methods 6010. ONE W