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1 <br /> ARCADIS 2009/2010 Annual <br /> Monitoring Report <br /> ' Union Pacific Railroad <br /> Company <br /> Former Maintenance Facility <br /> ' 6.2 Free-Product Observations and Measurements Tracy,California <br /> Measureable free-phase product was observed at least once in eight wells (MW-06A, <br /> MW-08A, MW-11A, PZ-01, PZ-02,TW-01, TW-02,and TW-04) during the 2009/2010 <br /> reporting period.The product thicknesses in these wells ranged from approximately <br /> ' 0.84 inches in PZ-02 to 23.64 inches in MW-06A. In addition, the potential presence of <br /> hydrocarbons was assessed at selected wells by visually inspecting bailed <br /> groundwater.Table 3 presents a summary of product measurements and the <br /> estimated product thicknesses. Figure 7 presents the product thickness measurements <br /> recorded since May 2001.The slight increase of product thickness shown in Figure 7 is <br /> likely due to the high amount of rain that occurred during the previous few months. <br /> 6.3 TEPH Analytical Results <br /> ' The TEPH-d and TEPH-d SG concentrations in groundwater samples collected since <br /> February 2001 are presented in Table 4. ARCADIS understands the Central Valley <br /> RWQCB does not accept the use of the silica gel cleanup method for delineating <br /> ' TEPH-d plumes;therefore,the TEPH-d SG data are presented herein for comparison <br /> only and have not been used to delineate the dissolved TEPH-d plume.TEPH-d <br /> concentrations in A-Zone groundwater samples collected during the March 2010 <br /> monitoring event are shown on Figure 8. <br /> 6.3.1 A-Zone <br /> Groundwater samples were scheduled to be collected from seven wells during the <br /> ' November 2009 monitoring event(Table 1). MW-2B,which is not normally part of the <br /> November 2009 monitoring event, was sampled because it was not sampled during <br /> the March 2009 annual monitoring event.Well TW-04 was not sampled during the <br /> ' November 2009 event because free product was present. <br /> TEPH-d was detected in four of the six wells sampled during November 2009(Table 4) <br /> ' at concentrations above the 100 micrograms per liter(µg/L) Cleanup and Abatement <br /> Order(CAO) No. 92-707 cleanup level. In comparison,the corresponding TEPH-d SG <br /> concentrations were below the cleanup level. <br /> ' Twenty three wells were scheduled to be sampled during the March 2010 monitoring <br /> event(Table 1); however, groundwater samples were collected from only 19 of the 23 <br /> ' wells. Free product was encountered in four of the wells (MW-06A, MW-08A, MW-11A, <br /> TW-04), precluding groundwater sampling.The March 2010 TEPH-d and TEPH-d SG <br /> P:NAG5GI5 Dma�P,gecl%M4+e,11nlon Pedfc gBII1�ACTW <br /> �TryYeMDelvaedeTGW MonAonn9'p1001 Ta Ye Mruel GW 20®a71PFIW12JG}2010Frvuel <br /> ' n m Page:40 <br />