SITE INFORMATION AND CORRESPONDENCE_PRE 2019

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Stantec April 30, 2010 Page 5 of 6 Reference: First Quarter 2010 Site Status, Groundwater Monitoring and Remedial Summary Report-Stockton Terminals Technical Committee Facilities Appendix D-Analytical Program Description, Field Data Sheets, Groundwater Certified Laboratory Analytical Reports,and Chain-of- Custody Documentation Table D-3 First Quarter 2010 Number of Wells at or Number of Percent below the Wells with Maximum Decrease Number WQO Detections Concentration Average Median Maximum Detected from Detected of Wells and/or above the Detected in pg/L Concentration Concentration Historical Maximum Constituents Analyzed MRL WQO (Well ID) (Ng/L) (Ng/L) Concentration Historical Bold Concentrations below WQO or MRL (Well/Date) Concentration "C"Zone TPHg 14 9 5 4,200 588 <50 29,000 86 (TS/MW-1 C) (TS/MW-1 C/2002) TPHd 14 4 10 1,100 336 185 70,000 98 (OW-4C) (AR/MW-5C/2008) Benzene 14 6 8 1,500 194 2.7 13,000 88 TS/MW-1 C TS/MW-1 C/2002 MTBE 14 12 2 210(TS/MW-1 C) 18 <0.50 (AR/MW-5C/2008)600 65 TBA 11^ 6 5 570 500 (TS/MW-1 C) 67 9'8 (AR/MW-13C/2008) 90 DIPE 7^ 6 1 0.93 0.6 <0.50 1.1 15 (AR/MW-5C) (AR/MW-5C/2003) MBAS 11 6 5 AR/MW-013C 572 500 AR/MW-130C/2009 42 Definitions: MBAS=Methylene blue active substances =Requested by the RWQCB beginning in 2009 MRL=Method Reporting Limit TBA=Tertiary butyl alcohol ^ = In compliance with MRP pg/L=Micrograms per Liter TAME=Tertiary amyl methyl ether WQO=Water Quality Objective Median=the middle number in a sequence of numbers WQOs Unless otherwise noted,WQOs from AppendixA-Reports, Tri- TPHg(21 pg/L) DIPE(0.80 pg/L) Regional Board Staff Recommendations for Preliminary TPHd(100 pg/L) TBA(12 pg/L) Investigation and Evaluation of Underground Tank Sites, Benzene(1 pg/L) MBAS(500 pg/L,Secondary MCL) RWQCB,April 16,2004. MTBE(5 pg/L)