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CA ARNG Field Quality Assurance Project Plan 6. If performing micropurge, wells are purged at a rate that is sufficient to minimize drawdown of the static water level within the well (estimated flow rate of 0.25 to 1.0 Ipm). The well is purged following the micropurge procedures. Submersible Pump Micropurge Procedures 9.1.5.10 The pumping rate for purging groundwater monitoring wells using the micropurge technique should range from 0.25 to 1.0 1pm. Minimal drawdown should occur during micropurging to avoid mixing of stagnant water within the well casing and the groundwater entering the well from the aquifer material. Drawdown should not exceed 0.5 feet during purging. Wells are purged using micropurge procedures until stabilization of pH (+/- 0.2 units), temperature (+/-1°C), and SC (+/-10%) occurs, usually after approximately two to six sampling system volumes have been purged from the well. Sampling system volumes are calculated as the volume of water standing in the discharge hose of the dedicated pump system Submersible Pump Macropurge Procedures 9.1.5.11 During purging, water parameter measurements, including pH, SC, temperature, and turbidity, are performed periodically on samples of the purge 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 are noted on -a groundwater sampling data sheet. 9.1.5.12 Once the minimum three well volumes have been purged and the measured parameters have stabilized, the well is considered ready for sampling. Groundwater parameters are considered stabilized when less than a 10% change in conductivity; less than 0.2 unit change in pH; and less than 1 °C change in temperature occurs between consecutive -measurements. if the water level in a well does not recharge to .within 80% of the static water level within one hour, the well will be. pumped dry once more and sampled as soon as 80% recharge has occurred. Submersible Pump Sample Collection Procedures 9.1.5.13 Groundwater samples are collected for all wells by carefully lowering a Teflon® bailer into the water column and allowing the bailer to fill with water. The bailer will be lowered below the depth at which the purge pump had been placed. A flow control valve at the bottom of the bailer is used to control sample flow into sample containers for samples collected for volatile analysis; other parameters are collected by carefully decanting the water into the sample containers. Sample containers for VOC analyses and other applicable parameters are pre -preserved. Volatile organic compound samples will be collected first, followed by semivolatile organic compounds (SVOCs), inorganics, and finally water quality samples. 9.1.5.14 All groundwater sample containers will be pre -chilled at 4°C prior to collection of samples to minimize volatilization and reduce any reactions with preservatives. All appropriate measures are taken to obtain representative water samples and avoid loss of volatiles in water samples by allowing a miniscus to form on the sample, and by "tapping" each filled container and checking for any air bubbles. Hand Bailing 9.1.5.15 Shallow wells with a small water column or wells that produce insufficient water to warrant the use of a pump are purged with a bailer. The equipment required for sampling these "low volume" wells includes: field QAPP.DOC 9-7 May 2000