WORK PLANS FILE 1 - Laserfiche WebLink

Home Browse Search

Monitoring and Sampling Procedures WEST CLAY PROPERTIES 639 West Clay Street, Stockton, California STATIC WATER LEVEL MEASUREMENTS Before sampling and during groundwater monitoring, static water levels are measured using an electric water level indicator. Water level data is recorded to the nearest 0.01-foot from a reference point marked on the top of the PVC well casing. WELL PURGING Subsequent to measurement of depth to water and prior to sampling, each well is purged to ensure samples are representative of the formation, rather than standing water in the well casing. Wells are purged using a Waterra inertia pump and dedicated 5/8-inch plastic tubing or disposable polyethylene bailers. Wells are purged until a minimum of three casing-water volumes are removed from the well and/or the field-measured ground water parameters (pH, temperature, and conductivity) are stabilized. However, if a well is purged dry prior to evacuating three casing volumes, a sample is collected following 80 percent recovery of ground water within the well, or after a minimum of one hour, but within eight hours, of well purging activities. Field data and logs are provided in Appendix C. SAMPLE WITHDRAWAL Water samples are collected from each monitoring well using an inertia pump with dedicated plastic/Teflon tubing or disposable polyethylene bailers-, plastic tubing used with the inertia pump is either dedicated to each well point or changed at each sampling event, thereby minimizing cross contamination due to sampling devices. Samples are drawn and collected in such a manner that agitation and exposure of groundwater to the atmosphere is minimal. The current monitoring well sampling schedule is semi-annual for well with minimal contamination, annual for other wells lacking significant detection and quarterly for three dieep well on the eastern edge of the site. Some well sampling was suspended to the lack of historical detections. Advanced GeoEnvironmental, Inc.