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Ms.Amber Ginorio,RWQCB January 30,2023 <br /> Addendum to Sampling and Analysis Plan <br /> 2478 Wilcox Road,Stockton,California <br /> Page 7 <br /> of approximately 75 feet bgs, at which point an additional grab groundwater sample will <br /> be collected. The actual grab groundwater sample target depths will be based on the depth <br /> at which groundwater is first encountered, as well as sediment type/properties and strata <br /> contacts encountered within the saturated zone. To prevent vertical migration, the boring <br /> will not be advanced through a potential confining horizon(e.g., clay interval greater than <br /> 5 feet thick). <br /> Once the target groundwater sample depths are achieved,the steel drive rods will be raised <br /> approximately one foot to expose the lower portion of the screened lead rod, permitting <br /> groundwater to enter and allowing a water sample to be collected. Depending on the rate <br /> of water entering the screened portion of the lead rod, a bailer may be used to surge the <br /> screen interval and purge additional water before sample collection. Collection of the <br /> water sample will utilize a 0.75-inch diameter Teflon tubing equipped with a check valve, <br /> which will enable groundwater to enter the tubing under head pressure, allowing <br /> accumulated water to be "lifted" through the tubing and collected into a laboratory <br /> provided sample container. <br /> Each sample will be labeled and placed in a re-sealable plastic bag, and stored in an ice- <br /> chilled cooler. All sampling equipment will be cleaned in an aqueous non-phosphate <br /> solution cleanser, rinsed with tap water, and rinsed a second time with deionized water to <br /> prevent cross-contamination between sample intervals. Once the two grab samples have <br /> been collected, neat cement will be tremied into the boring using the drive rods. After <br /> allowing for settlement of the neat cement,the upper two feet will be completed to ground <br /> surface with concrete to match the surrounding area. <br /> Task 2D: Groundwater Monitoring Well Installation(MW-1, MW-2, and MW-3) <br /> A licensed well driller will advance the well borings using a limited access direct-push drill <br /> rig, or equivalent, equipped with 8-inch diameter hollow stem augers, in the presence of a <br /> Stratus Geologist. The well borings will be initially advanced with 3.25-inch diameter <br /> hollow steel drive rods to approximately 10 feet below the depth at which groundwater is <br /> first encountered. Once the total depth is reached,the rods will be removed,and the borings <br /> will be overdrilled using 8-inch diameter hollow stem augers. The actual well boring <br /> depths will be based on the depth at which groundwater is first encountered, as well as <br /> sediment type/properties and strata contacts encountered within the saturated zone. To <br /> prevent vertical migration, the borings will not be advanced through a potential confining <br /> horizon(i.e., clay interval greater than 5 feet thick). <br /> Soil samples will be collected continuously from the total depth the air knife advances to <br /> the total depth of each boring, using acrylic tubes. The Stratus geologist will utilize the <br /> entire tube for lithologic inspection in accordance with the USCS and will screen the soils <br /> in the field for VOCs using a PID. The bottom-most 6-inch-long section of every five feet <br /> will be cut off and retained for possible chemical analysis. Additional samples may be <br /> T:\Stockton Propeller\Addendum to SAP\SM_Addendum to Sampling and Analysis Plan.docx STRATUS <br />