Laserfiche WebLink
SAP/QAPP Addendum <br /> Lodi-125 N Stockton <br /> Final <br /> March 24,2025 <br /> 4.3.2 Historical Underground Storage Tank Soil Sampling <br /> Soil borings will be advanced to 15 feet bgs at four boring locations on the Site to collect soil samples (Figure <br /> 3).The soil boring locations will be north,east,south,and west 5-foot step-outs from the previous approximate <br /> former UST location as (Stantec,Inc. 2023).These will further delineate previously detected TPH exceedances <br /> in the former UST area and inform soil handling and disposal procedures during redevelopment. Subsurface <br /> soil samples will be collected at the following intervals: 5 to 8 feet bgs, 8 to 10 feet, 10 to 13 feet bgs. and 13 to <br /> 15 feet bgs. Soil samples will be analyzed for arsenic and lead (EPA Method 6010),and TPH (EPA Method <br /> 8015M [TPH-g,TPH-d,and TPH-mo]). <br /> 4.4 Soil Gas Sampling <br /> Soil gas samples will be collected to assess whether soil gas contamination from historical MGP activity and the <br /> Lodi dry cleaner groundwater plume is present on the Site. <br /> Twenty soil gas sampling locations will be finished as permanent soil gas wells for future soil gas sampling <br /> events (Figure 4). Soil gas samples will be collected at 5 feet bgs and 15 feet bgs. Soil gas samples collected at 5 <br /> feet bgs will have the screen interval from 4 to 5 feet bgs,and soil gas samples collected at 15 feet bgs will have <br /> a screen interval of 14 to 15 feet bgs. Soil gas sampling will not occur within 48 hours of installing the wells or <br /> within 24 hours after a precipitation event. Soil gas samples will be analyzed for VOCs (EPA Method TO-15) <br /> and helium (as a leak tracer gas) (ASTM D1946). <br /> 4.5 Ambient Air Sampling <br /> Indoor air samples will be collected to assess whether soil gas contamination from historical MGP activity and <br /> the Lodi dry cleaner groundwater plume is present on the Site. <br /> Five indoor air samples will be collected,one from each room in the unoccupied office building(Figure 4). <br /> Indoor air samples will be collected over an 8-hour period. One outdoor air sample will also be collected over <br /> an 8-hour period to determine background concentrations of AOCs.The outdoor air sample will be in a well- <br /> ventilated area (away from areas of exhaust) and placed at breathing height.The indoor and outdoor air samples <br /> will be analyzed for VOCs (EPA Method TO-15 SIM). <br /> 41 <br />