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Geosyntec <br /> consultants <br /> 4.5.2 Groundwater Sampling <br /> Prior to groundwater sampling, the groundwater monitoring well will be purged using the low- <br /> flow sampling method. Field parameters, including pH, oxidation/reduction potential (ORP), <br /> dissolved oxygen (DO), specific conductance,temperature, and turbidity will be monitored in the <br /> field during purging. Groundwater samples will be collected after the field parameter values have <br /> stabilized for three consecutive readings per the following criteria: <br /> • ±0.1 units for pH; <br /> • ±10% for ORP; <br /> • ±10%for DO; <br /> • f3% for specific conductance; <br /> • ±10% for temperature; and <br /> • <br /> ±10% for turbidity (with reasonable efforts to reduce the turbidity to less than 100 <br /> Nephelometric Turbidity Units). <br /> Upon reaching stability of the parameters listed above as defined by the low-flow sampling <br /> protocol, groundwater samples will be collected in laboratory-prepared sample containers <br /> appropriate for the intended analyses. Groundwater samples will be submitted to a California- <br /> certified laboratory under standard chain-of-custody protocol. <br /> 4.6 Laboratory Analysis and Data Validation <br /> 4.6.1 Soil Samples <br /> Four soil samples will be analyzed at Cooper Testing for the following: <br /> • Total porosity by ASTM International D7263; <br /> • Moisture content by ASTM International D2216; <br /> • Volumetric water and air content; <br /> • Bulk density by ASTM International D7263b; and <br /> • Grain size by ASTM International D422. <br /> 4.6.2 Soil Vapor Samples <br /> Soil vapor samples will be submitted under standard chain-of-custody procedures to a State-of- <br /> California-certified analytical laboratory for analysis of VOCs by USEPA Method TO-15 and <br /> helium by ASTM International D-1946. Upon receipt of the analytical data from the laboratory, <br /> data validation will be performed. Data validation will include a data completeness check of each <br /> data package, a transcription check for sample results, and a thorough review of all laboratory <br /> reporting forms,particularly quality assurance/quality control samples. <br /> Work Plan for Vapor Intrusion Investigation 9 July 30,2021 <br />