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KLEINEELDER may vary at this site with time, however, past data have consistently suggested a similar groundwater gradient direction. Chart 1 shows the groundwater elevations recorded over time at the site. 4.2 QUARTERLY GROUNDWATER SAMPLING On August 29, 30 and 31, 2005, Kleinfelder sampled 13 monitoring wells and piezometer. The wells included MW-DIS-1, MW-DIS-2, MW-DIS-9, MW-DIS-11s, MW- DIS-11d, MW-DIS-12, MW-DIS-13, MW-DIS-14s, MW-DIS-14d, MW-DIS-15, NP1-70, NP1-80, and NP1-90. The wells were purged and sampled as described in Appendix A, Section A-4.2. The water purged from the wells was contained and labeled and left on site within the fenced Disco Area. After collection, the groundwater samples were labeled, logged on a chain-of-custody, and immediately stored in an iced cooler. The samples were transported under chain- of-custody control by courier to Sequoia Analytical Laboratories (Sequoia) of Sacramento, California for chemical analysis. Sequoia is certified by the California Department of Health Services to perform the requested analyses. The groundwater samples were analyzed for the following: • Total Petroleum Hydrocarbons-gasoline (TPH-g) by DHS LUFT; Benzene, Toluene, Ethylbenzene, Xylene (BTEX) by EPA Method 8015M18021 B; • 1,2 DCA by EPA Method 8260B; EDB by EPA Method 82608; TBA by EPA Method 826013; and Oxygenates, MTBE, DIPS, ETBE, TAME by EPA Method 82608 (MW-DIS-15 only). The samples were analyzed on a regular laboratory turnaround schedule, requiring approximately 10 working days for receipt of analytical data. 4.3 SOIL GAS SAMPLING The soil vapor extraction system originally installed by CH2M Hill was replaced by Kleinfelder during 2003 with an air sparging (AS)/high vacuum soil vapor extraction (SVE)lozone injection system. The ASISVE system consists of a network of two air sparging wells (shallow/deep) and a vapor extraction well positioned at five distinct locations, totaling 15 wells. The ozone injection system consists of a horizontally directional drilled (HDD) conduit for ozone/air transmitted to a system of wells triple- nested at three different depths below groundwater, at five separate locations, equaling fifteen wells. Active remediation began in May 2003 in the source area (actual Disco site) by means of ASISVE utilizing a thermal/catalytic oxidizer unit. Continual operation of the thermal oxidizer began in June 2003. In July 2003, the ASISVE unit was converted from a thermal oxidizer to catalytic oxidizer thereby optimizing the efficiency 12280.MONIST05R14241CD:ly Page 8 of 14 ©2005, Kleinfelder, Inc. November 15,2005