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} 6ETTLER - RYAN INC. ,0 A September 2, 2003 Mr Edward Ralston ConocoPhillips 76 Broadway Sacramento, CA 95818 RE: Fust Semi-Annual Status Report 2003 - Ozone Microsparge Remedial System 76 Branded (Former BP) Facility No. 11192 1403 Country Club Boulevard, Stockton, California At the request of ConocoPhillips, Gettler-Ryan Inc (GR), has prepared this report documenting the status of the uutial six months of operation of an ozone microsparge remedial system, installed at the location referenced above (Figure 1) to address petroleum hydrocarbon impacted groundwater The ozone system was placed into operation on December 20, 2002 A description of the installation and startup of the remedial system can be found in GR's report Groundwater Monitoring Well, CPT and Ozone Microsparge System Installation Report, dated May 9, 2003 The primary constituent of concern at this site is methyl tertiary butyl ether (MtBE), with Total Petroleum Hydrocarbons as gasoline (TPHg) and benzene as a minor concern Groundwater sampling began at the site in 1990 after the installation of groundwater monitoring wells MW-1 through MW4 Wells MW-5 through MW-7 were added in 1991, and wells MW-8 through MW-13 were added in 2001 through 2003 Monitoring well MW-2 was destroyed in approximately 1991 There are also two vapor extraction wells (VW-1 and VW-2) which were installed prior to 1992 The 12 existing monitoring wells are currently being sampled quarterly The quarterly sampling event poor to begin rung operation of the ozone sparge system was conducted on November 15, 2002, while the last quarterly sampling event documented in this report was performed on May 14, 2003 Historical sampling data tables for the quarterly sampling events which occurred from May 1990 through May 2003 are presented in Appendix A Ozone Micro Sparging—System Overview The C-Sparge'"' ozone microsparging system, manufactured by K-V Associates, was placed into operation on December 20, 2002 Ozone microsparging is a process where ozone in air is introduced into the groundwater at low flow rates (2-6 cubic feet per minute) through specially designed microporous plastic spargers to create "microbubbles " As these microbubbles nse within the column of water, the dissolved volatile organic compounds (VOCs) are rapidly oxidized The system is designed to cycle the ozone/oxygen infection between the 10-points (Figure 2) The schedule is currently set to cycle through each point 16 times per day, for between 5 and 15 minutes per point per cycle The schedule can be vaned as part of the system evaluation process 6747 Sierra Court , Suite J - Dublin , California 94568 ( 925 ) 551 - 7555