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• (r- ETTLER - RYAN INC. MONITORING WELL AND SPARGE POINT INSTALLATION REPORT at Former Unocal Service Station No 0187 437 East Miner Avenue Stockton, California Report No 240042 11-1 INTRODUCTION This report presents the results of a subsurface investigation performed by Gettler-Ryan Inc (GR) at the above referenced site The work was performed at the request of Union Oil Company of California (Unocal) to further delineate the extent of dissolved petroleum hydrocarbons in groundwater downgradient of the subject site, and to expand the existing ozone microspargmg remedial system The scope of work performed included obtaining the required well installation permits from San Joaquin County Public Health Services Environmental Health Division (SJCPHS-EHD) and encroachment permits from the City of Stockton, updating the site safety plan, installing one groundwater monitoring well, installing eight ozone microsparge wells and supporting equipment, collecting soil samples from the monitoring well boring for description and possible chemical analysis, developing and sampling the monitoring well, analyzing selected soil and groundwater samples, surveying the newly installed wells, and preparing a report presenting the findings of the investigation This work was requested by the SJCPHS-EHD in a letter dated October 10, 2001 Work performed was proposed in GR's Work Plan For Additional Subsurface Assessment And Remedial Action (report 4240042 11, dated November 27, 2001), and approved by SJCPHS-EHD in a letter dated December 5,2001 SITE DESCRIPTION The subject site is a vacant lot located on the northwest corner of East Miner Avenue and California Street in the city of Stockton, California (Figure 1) The site is situated in an urban area of retail shops and hotels Topography in the site vicinity is flat lying, at an elevation of approximately 15 feet above mean sea level (MSL) Surface water in the vicinity of the site includes McLeod Lake and the Stockton Deep Water Channel, located approximately one-half mile to the west The site was an operating Unocal service station from 1922 until 1992 Most recently the station consisted of a three-bay station building, three product dispenser islands, and two gasoline and one waste oil underground storage tanks (USTs) in a common excavation All station facilities have been removed and the site is currently an unpaved vacant lot • 6747 Sierra Court , Suite J Dublin , California 94568 ( 925 ) 551 - 7555