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Geosyntec O consultants meter and recorded on a field data sheet with the date and time the measurements were taken. All the wells and piezometers will be gauged within a period of a few days. There were 13 stream gauges installed at RRI that were still in place at the time of the Navy 2002 RI report(Tetra Tech, 2002). The locations of the stream gauges are shown in Figure 26. Field staff will inspect these locations to determine if the stream gauges are still present in the drainage channels.The condition of stream gauges that are located will be recorded on field data sheets. If the stream gauges are in good condition, then the surface water depth will be recorded with the date and time the measurement was taken. The inspection and measurements at the stream gauges will be conducted concurrently with the water level monitoring event. 5.3 Selection of Monitoring Wells for Sampling Monitoring wells at RRI were selected to be sampled based on historical concentrations, the EVS®model,and the MAROS concentration trend analysis. Wells that were selected to be sampled generally meet one of the following criteria: • The most recent sample from the well had VOCs detected above MCLs; and/or • The well defines the lateral or vertical extent of VOCs in groundwater. The rationale for selecting each individual well at RRI for groundwater sampling is included in Table 7. Figures 21 to 25 show the wells selected for sampling in relation to the concentration trends, and Figure 26 provides an overview of all the wells at RRI that will be sampled. 5.4 Sampling and Analysis Samples from all wells that are sampled will be analyzed for VOCs by United States Environmental Protection Agency (EPA) Method 8260B. Additionally, wells that had concentrations of TPH as gasoline(TPHg)or diesel (TPHd)greater than 100 µg/L during the 2015 groundwater monitoring event and that define the extent of TPH in groundwater will be sampled for TPHg by EPA Method 8260B and TPHd by EPA Method 8015B (Table 7). Wells that had concentrations of mercury during the 2015 groundwater monitoring event greater than the DTSC tapwater screening level of 0.063 µg/L will be sampled for mercury by EPA Method 7470A. Wells that had concentrations of cobalt RRI Groundwater Monitoring Work Plan 23 1 June 2018