SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

Mr. Jeff Baker -4 - 17 February 2011 Stockton Terminals Technicoommittee ' aerobic degradation enzymes for TPHd, BTEX and TPHg are present in TS/MW-3DR, the well with the highest pollution levels. Anaerobic and MTBE degrading bacteria were non-detect and present at much lower levels, respectively, than the aerobic enzymes. The Annual Report did not include the DO, ORP, pH and conductivity data for the pilot study. These data were emailed to Central Valley Water Board staff at our request with a message stating that they would be included in future reports. The data show that DO is absent in the well with highest concentrations and present in very low concentration in other pilot study wells. The ORP data did not correlate directly with the DO concentration distribution and showed that the well with the lowest pollutant concentration (TS/MW-1D) had the lowest reduction potential. Oxygen injection commenced on 25 January 2011 in TS/MW-3DR and TS/MW-4D. Groundwater monitoring for the oxygen injection study will be conducted monthly during the first three months of the 1-year study and quarterly thereafter. The data will be presented in quarterly reports. A final report will be prepared following receipt of the final laboratory analytical results of the Bio Traps@, contaminant and redox parameter data.. Tesoro is also conducting a hydrogen peroxide injection (HPI) pilot study at the southwest property boundary shared with FTOC in the vicinity of TS-4R. Baseline groundwater monitoring was conducted in four wells described by Tesoro as upgradient well (TO/T-3), treatment zone wells (TS-4R, TS/M-2), and downgradient well (TS-5) for four-quarters to determine basetine values-for total chromium, hexavalent-chromium (Cr VI), vanadium, bromide, and bromate. The baseline values are used to monitor for the potential mobilization of Cr VI, bromate, and vanadium following injection of the hydrogen peroxide into wells TS/RW-1 and TS-RW-2. The baseline monitoring data were used to calculate a 95% upper confidence limit (UCL) compliance level for chromium, vanadium, and bromate. The compliance limits are listed at the top of Table 8. However, the Central Valley Water Board staff has not yet concurred with the STTC's suggested compliance level of 44 pg/L for Cr VI. The HPI pilot study began on 23 March 2010. Bimonthly monitoring for chromium, vanadium, and bromate (TS-5) was reduced to monthly in October 2010. In addition, monthly monitoring was initiated in TONT-3 in November 2010. The Annual Report shows that the metals mobilization compliance levels have not been exceeded in any of the four monitoring wells. Monthly monitoring to determine the effect of the HPI injections is performed for CDCs in treatment zone wells TS-4R and TS/M-2. The results listed in Tables 6 and 7 of the Annual Report show that between March and December 2010, COC concentrations have remained stable. Maximum concentrations of TPHg, TPHd, and benzene between October and December 2010 were 46,000 pg/L, 94,000 pg/L, and 11,000 pg/L, respectively. These concentrations are consistent with historical observations. Our comment is presented below. The absence of nitrate/nitrite and OZ electron acceptor data indicates that conditions at the TS/MW-1 D plume are strongly anaerobic. Under these conditions, biodegradation