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analytical laboratory, along with the appropriate chain-of-custody documentation. Soil samples selected for chemical analysis will be determined from a head-space analysis using a hand-held photoionization detector (PID). The soil will be placed in a glass jar, sealed, and placed in a warm atmosphere. After approximately 15 minutes, which is generally sufficient for volatiles to escape from the soil, the PID probe will be inserted into the glass jar. The total volatile hydrocarbons present are detected by the PID and reported in parts per million (ppm). The PID will be calibrated to an isobutylene standard. Generally two soil samples from each soil boring will be submitted for chemical analysis. Soil samples selected for analysis typically represent the highest PID reading recorded for each soil boring and the sample just above first-encountered groundwater. Monitoring Well Installation Monitoring wells will be completed by installing 2- to 6- inch-diameter Schedule 40 polyvinyl chloride (PVC) casing. The 2-inch-diameter flush-threaded casing is generally used for wells dedicated for groundwater monitoring purposes. Larger diameter casings will be used for monitoring wells which will potentially be used for hydraulic testing and groundwater extraction. The screened sections of casing are factory machine slotted and will be installed approximately 5 feet above and 10 feet below first-encountered water level. The screened interval will allow for seasonal fluctuation in water level and for monitoring floating product. A filter pack of graded sand will be placed in the annular space between the PVC casing and the borehole wall. Sand will be added to the borehole through the hollow stem of the augers to provide a uniform filter pack around the casing and to stabilize the borehole. The sand pack will be placed to a maximum of 2 feet above the screens followed by a minimum 1 -foot seal consisting of bentonite pellets. Cement grout containing 5 percent bentonite or concrete will be placed above the bentonite seal to the ground surface. A concrete traffic-rated vault box will be installed over the monitoring well(s) . A watertight locking cap will be installed over the top of the well casing. Reference elevations for each monitoring well will be surveyed when more than two wells will be located on site. Monitoring well elevations will be surveyed by EMCON or a subcontractor to the nearest 0.01 foot relative to mean sea level (MSL) or a site datum. Exploratory boring logs and well construction details will be prepared for the final written report. Figures A- 1 and A-2 are examples of the Exploratory Boring Log and Well Details forms, respectively. SAC/pjOv011M1170530.4MM-94/pas:5 A-2 Rev. 0, 11 /30/94