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.- vim "_ �"`-' ,�;' ri: � -yam. ""� _ _.;,•� _ _ __ . _ wq A-2 The soil samples were selected for laboratory analysis on the basis of organic vapor screening results and field observations. Selected soil samples were submitted to a California-certified laboratory for analysis of concentration levels of BTEX and TPH as gasoline. 1.3 Monitoring Well Installation The monitoring well construction details are illustrated in Appendix D. Flush-threaded,Schedule 40 PVC blank casing,and Schedule 40 PVC well screen was used to construct the casing of the wells. The annular space above the well screen was sealed with bentonite pellets overlain by a cement grout containing bentonite powder. 1.4 Monitorin Well Devela meat and Ground Water.Sam lin After installation,the new monitoring wells were developed by bailing or pumping ground water from the well until the produced water was relatively free of silt. The development process was intended to insure representative eater sample quality. After the development water was purged from the well and the water level was sufficiently recharged,a liquid sample was collected from each well with a dedicated,disposable bailer. If product was present in the well casing after being purged,a water sample was not collected. Each sample was appropriately labeled and stored on ice from the time of collection through the time of delivery to the laboratory. The ground water samples were submitted to a California-certified laboratory and analyzed for BTEX and TPH concentrations. Ground water generated during the well development and sampling was stored on site in labeled 55-gallon drums for later collection and recycling by Ultramar. 1.5 Survey and Ground Water]Levels Following installation of the monitoring wells,the top of the well casing and the ground surface elevation near each well riser was surveyed. The vertical elevation of each well casing was surveyed relative to mean sea level to within 0.01 foot,allowing correlation of water levels between each well at the site. After the survey was complete,the depth to water was measured in each well to within 0.41 foot using an electronic water level indicator. 1.6 Sample Identification and Chain-of-Custody Sample identification and chain-of-custody procedures ensure sample integrity and document sample possession from the time of collection to its ultimate disposal. Each sample container submitted for analysis had a label affixed to identify the job number,sampler,date and time of sample collection, and a sample number unique to that sample. This information, in addition to a description of the sample, field measurements made, sampling methodology, names of on-site personnel, and any other pertinent field observations were recorded on the borehole log or in the field is aids: Ap samples were analyzed y a -. — State-certified laboratory.