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4.3 GROUNDWATER Identified concentrations of constituents in groundwater showed few detections above laboratory reporting limits. The following is a discussion of the impacts in groundwater. Select analytical groundwater data is shown in Figure 13, and tabulated groundwater analytical data is presented in Tables 23 through 26. Laboratory analytical data is presented in Appendix L4. 4.3.1 Polycyclic Aromatic Hydrocarbons A total of nine groundwater samples, including a grab groundwater sample from Boring E3-2 (E3-2GW), were analyzed for PAHs in groundwater using EPA Method 8310. There were a total of three PAH detections above laboratory reporting limits in groundwater samples collected. Acenaphthene was detected in the grab groundwater sample (E3-2GW) at a concentration of 2.5 ug/L. All other PAH analytes in the grab groundwater sample were non- detect. In the samples collected from Well TW-5 during the RI [Samples TW-5 and TW-51) (duplicate)], naphthalene was detected at concentrations of 5.8 to 6.0 ug/L. In the follow-up samples collected during the SSI from TW-5 [Samples TW-5 and Dup-1 (duplicate)], there were no detections of PAHs. No other PAHs were detected in any of the nine groundwater samples. PAH analytical data for groundwater is presented in Table 23. 4.3.2 Total Petroleum Hydrocarbons A total of nine groundwater samples, including a grab groundwater sample from Boring E3-2, were analyzed for TPH using EPA Method 8015M. There were no detections of TPH in grab groundwater sample E3-2GW. There were two detections of TPH-d, two detections of TPH-g, and no detections of TPH-mo in the samples collected from monitoring well TW-5 during the RI and/or SSI. TW-5 had detections of TPH-g and TPH-d: 290 ug/L and 350 ug/L, respectively. TW-51) (duplicate) had detections of TPH-g and TPH-d: 250 ug/L and 340 ug/L, respectively. There were no detections of TPH in the follow-up groundwater samples collected during the SSI. As such, these detections are considered sporadic and non-reproducible. TPH analytical data for groundwater is presented in Table 24. 4.3.3 Title 22 Metals A total of six samples were analyzed for Title 22 Metals in groundwater using EPA Method 601013/7000. Of the 17 metals analyzed, there were only six metals detected above laboratory reporting limits: barium, chromium, molybdenum, nickel, vanadium, and zinc. Barium was detected in all six of the samples analyzed, the highest concentration of which was identified in TW-4 (0.11400 mg/L). Chromium was detected in one half of the samples analyzed at concentrations ranging from 0.00587 to 0.00825 mg/L. Molybdenum was detected only in samples from well TW-5 a concentrations of 0.00699 mg/L (Sample TW-5) and 0.00900 mg/L (Sample TW-51)). Nickel was detected in four of six samples at concentrations ranging from 0.00542 to 0.00877 mg/L. Similar to barium, vanadium and zinc were detected in all six samples. Concentrations of vanadium ranged from 0.00814 to 0.01490 mg/L and zinc concentrations ranged from 0.0305 to 0.0491 mg/L. Title 22 Metals analytical data for groundwater is presented in Table 25. PARSONS 36 FINAL RI REPORT-FORMER TRACY MGP APRIL 2010