A. Groundwater samples shall be collected from each of the District’s three monitoring wells biannually each year, during January and July. Sample collections must be performed from all three wells on the same day. All samples must be refrigerated. B. Monitoring wells are of 2-inch PVC construction, 30 feet deep, with a 10-foot screened interval at the bottom. Groundwater elevation has historically been at approximately 20 feet below the top of the casing. C. Sample collection must follow the District Sampling and Analyses Plan. Specific requirements from this plan include: i. Appropriate decontamination procedures shall be followed for sampling equipment to prevent sample contamination and well cross-contamination. ii. Static water levels shall be measured prior to and following purging of the wells. Measurements will be taken using an electrical measuring device capable of measurements to 0.01 foot. iii. Wells shall be purged prior to sample collection using an appropriate bailer or pump. The water must be monitored for temperature, pH, and electrical conductivity during the purging of each well. The well must be purged until measured parameters have stabilized to within 10 percent (10%) of consecutive readings or not less than three (3) borehole volumes have been removed. Readings shall be reported to the District for use by the District’s geologists. iv. Samples shall be collected following recovery of the static water level to at least 70 percent of the initial static water level. Samples must be obtained using a pre-washed Teflon bailer with a bottom-emptying device. Sample collection forms must be used during sampling. v. Water samples must be collected in laboratory supplied sample containers that are consistent with the volume and preservative requirements. Water samples must be identified by well number/sample number, date, and time of collection. Chain of custody procedures, including usage of chain of custody forms, shall be used to document sample handling and transport. vi. One duplicate sample from one of the two downgradient monitoring wells (MW1 or MW3) and a field method blank sample shall be collected for analysis during each sample round.
