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' method of maintaining and advancing the boring will be made <br /> All drilling and sampling equipment will be cleaned before drilling each boring using a <br /> high-pressure, steam-cleaning apparatus The split-spoon sampler will be cleaned with <br /> phosphate-free soap and rinsed with water following each sample collection Sod cuttings <br /> generated during drilling operations will be placed on and covered with visqueen or in 55-galoon <br /> DOT drums on site until laboratory results are obtained and proper methods of disposal have <br /> been approved <br /> ' 3.0 SOIL SAMPLE SCREENING <br /> ' After the vapors in the soil samples are allowed to equilibrate with the air in the headspace of the <br /> plastic bags, the organic vapors within the headspace will be screened with a PID or flame <br /> ionization detector equipped with a 10 2 eV lamp calibrated to hexane The sample bag will be <br /> opened and the detector probe immediately placed within the headspace of the bag The highest <br /> observed reading will be recorded This number provides a relative comparison of the petroleum <br /> hydrocarbon concentration with the sod samples but is not quantitative The field readings will be <br /> recorded on the boring logs <br /> The soil samples will be selected for laboratory analysis on the basis of organic vapor screening <br /> results and field observations Selected sod samples will be submitted to a state certified <br /> ' laboratory for analysis of benzene, toluene, ethylbenzene, and total xylenes (BTEX) using EPA <br /> Method 8021 B, total petroleum hydrocarbons as gasoline (TPHg) concentrations using EPA <br /> ' Method 8015 Modified, and oxygenate compounds using EPA Method 82608 <br /> 4 0 WELL CONSTRUCTION <br /> 4 1 Monitoring Well Filter Pack and Slot Size Selection <br /> ' The filter pack material of each well will be selected to permit the development of a zone of <br /> higher hydraulic conductivity adjacent to the well screen, but not allow piping of the <br /> finer-grained formation materials into the well The slot size of the monitoring well screen will <br /> be selected such that it will retain a minimum of 95 percent of the filter pack material <br /> ' 4 2 Monitoring Well Development <br /> ' After the monitoring wells are installed, each well will be developed either prior to emplacement of <br /> the bentonite seal and cement grout, or after a period of 72 hours to allow the grout seals to cure <br />