Laserfiche WebLink
Public Works, Stockton - 2 - 30 November 2022 <br /> on Figure 8 of the Work Plan, but with the top of the sand pack no shallower than <br /> 5 feet bgs. <br /> 2. Condor proposes to use quantitative leak testing quality assurance measures, in <br /> accordance with the recommendations of the Advisory. Quantitative leak testing <br /> consists of placing a shroud over the sampling train and equipment, applying a <br /> leak detection compound such as helium under the shroud, and then quantifying <br /> the concentration under the should via real-time measurement equipment or by <br /> collection of under-shroud air samples. The concentration of helium under the <br /> shroud can then be compared to the concentration of helium in the sample to <br /> confirm sample validity. Per Advisory recommendations, if the concentration of <br /> the tracer compound in the sample is greater than or equal to five percent of the <br /> tracer compound concentration under the shroud, a leak has occurred, the <br /> sample is invalid, and sampling must be repeated utilizing corrective actions to <br /> remedy the leak. <br /> 3. By 24 February 2023, please install and sample the three soil gas wells, and <br /> submit a soil gas sampling report. In the report, please include an evaluation of <br /> soil gas data against Petroleum Vapor Intrusion criteria established in the Low- <br /> Threat UST Case Closure Policy (LTCP). Please also provide conclusions and <br /> recommendations based on this evaluation. <br /> 4. The soil gas well installation and sampling scope of work is summarized in the <br /> table below. This table incorporated both Condor proposals and Central Valley <br /> Water Board staff comments above. <br /> Sand Pack Sample Analysis <br /> Well Location Interval (Method) CA Measures <br /> (ft bgs) <br /> SVP-1 N side of TPHg, BTEX, MTBE, <br /> Maint. Bldg Naphthalene, Oxygen, 1. Shut-in test <br /> 2 <br /> SVP-2 S side of Solid >5 6 Helium . Quantitative <br /> SVP-3 Waste Office (TO-15, ASTM D 1946-90) leak testing <br /> QA= quality assurance; TPHg= total petroleum hydrocarbons as gasoline; BTEX= benzene, <br /> toluene, ethylbenzene, and total xylenes; MTBE= methyl tert butyl ether <br />