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CA ARNG Field Quality Assurance Project Plan 9.1.5 Groundwater Sample Collection Procedures 9.1.5.1 Prior to initiating groundwater sampling, a water level survey may be conducted to measure groundwater flow directions and horizontal gradients. Figure 9-1 (at the end of the section) is an example of a water level log. All measurements will be taken from the north side of the casing or as indicated (notched mark). Water levels in all wells and piezometers will be measured to the nearest 0.01 foot using an electronic water level sounder. All water levels will be measured within 72 hours to provide an accurate view of groundwater flow direction. These measurements will be used to produce potentio- metric surface maps for each horizon. The sounder will be decontaminated as discussed in Section 9.3. Monitoring Well Samples 9.1.5.2 Newly installed wells will be sampled no sooner than two days after well development. After that, wells will be sampled in the order of least expected contamination to highest expected contamina- tion whenever possible to minimize the potential for any cross contamination. Prior to beginning sampling activities, the waterproof, expanding well cap on the well casing will be removed and the well will be checked for organic vapors with an organic vapor analyzer (OVA) or photoionization detector (PID) meter at the well head. The water level and the depth of the well will be measured and the values obtained will be used to calculate the required purge. volume. 9.1.5.3 A minimum of three submerged well casing volumes will be removed during purging of the monitoring well using a submersible pump. Water quality measurements, including pH, specific conductivity (SC), temperature, and turbidity, will be performed periodically on samples of the discharge water. These measurements are collected at a minimum of five times (unless well purges dry) over an evenly spaced time interval of the required purge. Results will be noted on a purge log (Figure 9-2 at the end of the section). 9.1.5.4 Once the well is sufficiently purged and the measured parameters have stabilized, the well will be considered ready for sampling. Field parameters will be considered ready for sampling. Field parameters will be considered stabilized when less than 10% change in SC; less than 0.2 unit change in pH; and less than 1 °C change in temperature between consecutive measurements is recorded. If the water level in a well does not recharge to within 80% of the static water level within one hour, it will be considered impractical to purge the well of three well volumes and the well will be pumped dry once more and sampled as soon as 80% recharge has occurred. Portable Submersible Pump (Port -a -Reel System) 9.1.5.5 An electric submersible pump (2 -inch Grundfos® pump) or stainless steel bailer and/or a Teflon® bailer are used to purge water and collect samples at wells not equipped with dedicated systems. The pump is typically used to purge the groundwater while the Teflon® bailer is used for groundwater sample collection. A flow control valve attachment at the bottom of the bailer is used to transfer the sample to the sample containers. The equipment required to purge and collect groundwater samples are: • Submersible pump (2 -inch Grundfos® pump attached to a portable hose reel); • Water level, PID or OVA, pH, temperature, specific conductivity, and turbidity meters; • Electrical generator; • Wastewater container; field QAPP.DOC 9-4 May 2000