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S E C 0 R
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<br /> which involved the distribution of questionnaires to residences and businesses within the
<br /> study area None of the returned questionnaires indicated the presence of a water
<br /> supply well within the SRS study area (GRI, Monitoring Well Installation Report,
<br /> September 26, 2001)
<br /> Smith Canal is located approximately 1,300 feet south of the site, and the Calaveras
<br /> River is located approximately 3,500 feet north of the site Both of these surface water
<br /> bodies are channeled, flow generally to the southwest, and drain into the Stockton Deep
<br /> Water Channel (GRI, Groundwater Monitoring Well, CPT, and Ozone Mrcrosparge
<br /> System Installation Report, May 9, 2003)
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<br /> MONITORING AND SAMPLING — FIRST QUARTER 2005
<br /> The current monitoring well network consists of 12 wells (MW-1 and MW-3 through MW-
<br /> 13) that are sampled quarterly Groundwater samples were collected from each well on
<br /> February 25, 2005, and were submitted for analysis of total purgeable petroleum
<br /> hydrocarbons gasoline range organics (GRO), BTEX, fuel oxygenates (MtBE, TBA,
<br /> ternary amyl methyl ether [TAME], DIPE, ethyl tertiary butyl ether [EtBE], ethanol), 1,2-
<br /> DCA, and ethylene dibromide (EDB) by EPA Method 8260B Groundwater samples
<br /> from wells MW-3 were also analyzed for acetone by EPA Method 8260B Results are
<br /> discussed below and are summarized in TRC's Quarterly Monrtonng Report, January
<br /> through March 2005 dated April 4, 2005, which is included in Attachment 1
<br /> Groundwater monitoring and sampling activities at the site were performed in
<br /> conjunction with those performed concurrently at the nearby Shell Service Station, ;
<br /> located at 1267 Country Club Boulevard Groundwater samples collected from Shell
<br /> wells S-1 through S-6 by Blaine Tech Services were submitted for analysis of total
<br /> purgeable petroleum hydrocarbons (TPPH), BTEX, and 1,2-DCA by EPA Method
<br /> 8260B, and TPHd by EPA Method 8015M Split samples were also collected from wells
<br /> S-1 through S-6 by SECOR, and were submitted for analysis of GRO, BTEX, fuel
<br /> oxygenates (MtBE, TBA, TAME, DIPE, EtBE, ethanol), 1,2-DCA, and EDB by EPA
<br /> Method 8260B
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<br /> DISCUSSIONx
<br /> During the first quarter 2005, depth to groundwater ranged between 13 15 and 17 71
<br /> feet bgs, which was in range of historical levels Historical groundwater depths have
<br /> been reported between 11 40 feet and 32 14 feet bgs The direction of groundwater flow
<br /> was toward the northeast, which is also consistent with the groundwater flow direction y
<br /> reported over previous quarters (north and northeast)
<br /> Evaluation of dissolved concentrations through the first quarter 2005 indicates that the
<br /> highest concentrations of residual petroleum hydrocarbons continue to be detected off-
<br /> site in the vicinity of Shell well S-2 The highest concentrations of MtBE and TBA were
<br /> detected in the split samples from off-site wells S-5 and S-6, and on-site wells MW-7 and A
<br /> MW-11 GRO was reported at its highest concentration in well S-2 this quarter at 15,000
<br /> pgIL MtBE was reported at its highest concentration in well S-6 this quarter at 3,100
<br /> pg/L TBA was reported at its highest in well MW-7 this quarter at 43,000 pg1L �
<br /> Concentrations of TPPH, MtBE, and TBA have fluctuated within historical levels over the
<br /> IConocoPhi1hps\Retai1 Sites1111921QSSR1200511Q2005 QSSR and QRPS dor,
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