Laserfiche WebLink
Appendix A Geosyntec Consultants <br /> Responses to Comments <br /> Investigation Work Plan-UST817B <br /> Rough and Ready Island,Port of Stockton <br /> Department of Toxic Substances Control Letter Dated November 13,2024 <br /> Comment <br /> No. Agency Comment: Geosyntec Response: <br /> Soil vapor samples should be tested for oxygen to assess the potential presence of a Work Plan Section 4.2.6.3 and Table 1 were revised to specify soil vapor samples will be analyzed for <br /> General bioattenuation zone in the subsurface.If oxygen levels are measured at greater than oxygen b ASTM International Method D-1946. Work Plan Sections 3 and 4.2.6.3 were revised to state <br /> Comment 1 four percent(4%),then a 1,000-fold bioattenuation of petroleum vapors can be that bioattenuation zone will be characterized through the collection of oxygen data. <br /> assumed for the bioattenuation zone. <br /> General Soil samples should also be collected at location 81713-12 to confirm Total Collection of soil samples at depths of 2,4,and 6 feet below ground surface from boring location 81713- <br /> Comment 2 Petroleum Hydrocarbon(TPH)concentrations are less than 100 miligrams per 12 has been added to the sampling plan.The work plan text,Figure 8 and Table 1 have been revised <br /> kilogram(mg/kg)in soil from at least two depths within the 5-foot zone. accordingly. <br /> To facilitate the interpretation of the data contained in Figure 4,please use separate <br /> Specific Separate figures depicting the estimated benzene concentration contours in groundwater(Figure 4)and <br /> Comment 1 figures to show the dissolved benzene concentration contours and the dissolved the estimated TPH-g concentration contours in groundwater(Figure 5)were added to the report. <br /> TPH as gasoline(TPH-g)concentration contours. <br /> A figure depicting the most recent MTBE concentrations from the groundwater monitoring wells has <br /> Specific Please include a figure depicting dissolved Methyl tert-butyl ether(MTBE) been added(Figure 6),however,contours were not generated as concentrations are generally non-detect <br /> Comment 2 concentration contours. or below the California Maximum Contaminant Level(MCL)of 13 micrograms per liter(Ng/L). <br /> Central Valley Regional Water Quality Control Board Letter Dated November 8,2024 <br /> Comment <br /> No. Agency Comment: Geosyntec Response: <br /> General Central Valley Water Board staff concur with the work scope presented in the Comment acknowledged. <br /> Comment 1 Work Plan.Please resubmit the Work Plan as a Final version. <br /> Page 1 of 1 <br />