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Fdi H ME OW KLEINFELDER soil samples collected and the screening results using a qualitative soil-vapor reading instrument. Since field screening did not indicate the presence of volatile hydrocarbon compounds in B-1 and B-2, the bottom samples from each of those borings were submitted for analysis. Positive readings were observed from the bottom sample from B-3 and was selected for chemical analysis. The locations of the three borings with respect to z local benchmark are provided on Table 1. 3.3 MONITORING WELL INSTALLATION On March 6 and 7, 1990, three monitoring wells were installed in accordance with the sampling work plan dated May 1, 1989. Regional ground water elevation maps indicated that ground water flow direction was to the northeast. The monitoring wells were installed based on regional ground water flow directions such that MW-1 would be upgradient and MW-3 would be downgradient of the excavation. MW-2 was installed at a location perpendicular to the assumed flow direction to provide the necessary data for calculating the on-site gradient. Well construction details are shown in Table 1,and their locations are shown on Plate 3. Generally, clays and clay-rich silts were encountered to a depth of approximately 10 or 15 feet below land surface. Below 10 to 15 feet, the soil changed to fine grained sands and clayey sands. Water was encountered at a depth of approximately nine feet below land surface in MW-1 and MW-2. Ground water was encountered at a depth of approximately 14 feet below land surface in MW-3. Well logs are included in Appendix C. More specific protocol for installation of monitoring wells is presented in Appendix B. 3.4 MONITORING WELL DEVELOPMENT AND SAMPLING On March 13, 1990, the three monitoring wells were developed to set the sand pack. Development was performed using a Teflon bailer. Approximately 12 well volumes (36 gallons) were purged from each well during development. Well development protocol is described in Appendix B. Well development logs are shown in Appendix D. On March 16, 1990, the three monitoring wells were purged to o6taii a sarrip e o water- -- ---- representative of formation water. Approximately four to five well volumes of water were purged from the wells using a Teflon bailer prior to the collection of a sample. Purge logs are contained in Appendix D. Sampling protocol is described in Appendix B. F15.90.101 4 Copyright 1990 Kleinfelder, Inc. ',V.'