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yS Status_ Report ARCO Facility No 6100 Tracy, Caltfortm . Page 2 total of 31 soil borings, ranging in depth from 26 to 115 feet bgs, were drilled, 20 of the borings were completed as vapor extraction wells Groundwater was not encountered during any of the investigations A water supply well was installed onsite in 1969 in the southwestern corner of the property and currently supplies water to the service station The well was constructed of 8-inch diameter casing to 540 feet bgs, screened from 396 to 416 and from 496 to 536 feet bgs, and gravel packed from 35 to 540 feet bgs (The IT Group, September 10, 1999) Reportedly a sanitary seal was not installed A water sample from this well was collected and analyzed to August 1999 All analyzed constituents were reported below laboratory detection limits Depth to water was recorded in the well at the time of sampling to be approximately 40 feet bgs In October 1998, Pinnacle Environmental Solutions, Inc submitted Hydrocarbon Mass Evaluation, presenting the estimated mass of TPHG and BTEX constituents An addendum to this report was prepared by the IT Group and submitted In September 1999 San Joaquin County PHS/EHD submitted a Case Closure Summary to the California Regional Water Quality Control Board (CRWQCB) on February 1, 2000 requesting "no further action" of environmental work at the site CRWQCB declined the request for no . further action (March 14, 2000) and required that a groundwater investigation be conducted at the site On June 5, 2000, Delta submitted a work plan for groundwater assessment The work plan was subsequently approved with comments by CRWQCB on June 9, 2000 Delta oversaw the installation of one groundwater monitoring well to a depth of 115 feet bgs using an air-rotary casing-hammer ng The boring was initially advanced to 200 feet in an effort to identify first encountered groundwater and to assess the vertical extent of residual hydrocarbons Groundwater was not encountered while drilling, though after the boring was completed, it was noted that water was entering the borehole at a very slow rate After allowing approximately 20 hours to elapse, at which time the water had stabilized at approximately 106 5 feet bgs, it was determined to construct a monitoring well in the boring On September 28, 2001, when the well was scheduled to be developed, the technician reported floating product present in the well Development was postponed and a free-phase product skimmer was installed in the well Results of laboratory analyses on soil samples collected from the boring indicate that petroleum hydrocarbons are predominantly present at depths between approximately 105 to 125 feet bgs The highest concentrations were detected at 111 feet bgs MTBE and other oxygenates were not detected in any of the soil samples analyzed (Delta, November 10, 2000) On January 10, 2001 a meeting was held with representatives of CRWQCB and San Joaquin County PHS/EHD to discuss the additional soli and groundwater investigation C\ARCO\61001Status Report16100 status-rpt 2Q01 doe