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' method of maintaining and advancing the boring will be made. All drilling and sampling equipment will be cleaned before drilling each boring using a high-pressure, steam-cleaning apparatus. The split-spoon sampler will be cleaned with phosphate-free soap and rinsed with water following each sample collection. Soil cuttings ' generated during drilling operations will be placed on and covered with visqueen or in 55-galoon DOT drums on site until laboratory results are obtained and proper methods of disposal have been approved. 3.0 SOIL SAMPLE SCREENING ' After the vapors in the soil samples are allowed to equilibrate with the air in the headspace of the plastic bags, the organic vapors within the headspace will be screened with a PID or flame ' ionization detector equipped with a 10.2 eV lamp calibrated to hexane. The sample bag will be opened and the detector probe immediately placed within the headspace of the bag. The highest 1 observed reading will be recorded. This number provides a relative comparison of the petroleum hydrocarbon concentration with the soil samples but is not quantitative. The field readings will be recorded on the boring logs. The soil samples will be selected for laboratory analysis on the basis of organic vapor screening results and field observations. Selected soil samples will be submitted to a state certified ' laboratory for analysis of benzene, toluene, ethylbenzene, and total xylenes (BTEX) using EPA Method 802113, total petroleum hydrocarbons as gasoline (TPHg) concentrations using EPA ' Method 8015 Modified, and oxygenate compounds using EPA Method 8260B. 4.0 WELL CONSTRUCTION ' 41 Monitoring Well Filter Pack and Slot Size Selection The filter pack material of each well will be selected to permit the development of a zone of higher hydraulic conductivity adjacent to the well screen, but not allow piping of the finer-grained formation materials into the well. The slot size of the monitoring well screen will be selected such that it will retain a minimum of 95 percent of the filter pack material. ' 4.2 Monitoring Well Development After the monitoring wells are installed, each well will be developed either prior to emplacement of the bentonite seal and cement grout, or after a period of 72 hours to allow the grout seals to cure.