ARCHIVED REPORTS XR0008678 - Laserfiche WebLink

Home Browse Search

ATTACHMENT C FIELD AND LABORATORY PROCEDURES Depth to Groundwater/LPH Thickness Measurements Prior to purging each of the wells, the depth to groundwater and thickness of liquid phase hydrocarbons (LPH), if present, within each well casing is measured to the nearest 0.01 foot using either an electronic Solinst water level indicator or an electronic oil-water interface probe. Measurements are taken from a point of known elevation on the top of each well casing, as determined in accordance with previous surveys. Groundwater MonitoringWell Purging 9 g Wells not containing LPH are purged of approximately three casing volumes of water (or to dryness) using a submersible pump, centrifugal pump, gas displacement pump, or bailer. The equipment and purging method used for the current sampling event will be noted on field data sheets. During purging, temperature, pH, and electrical conductivity will be monitored in order to document that these parameters are stable prior to collecting samples. A minimum of three well volumes, measured as the annular space of the well casing below the groundwater surface, are removed from each well. However, in the case of very slow recharging wells, purging is deemed sufficient if the well contents are evacuated during purge operations. Unless recharge takes more than two hours, wells are sampled once the well is recharged to within 80 percent of pre-purge groundwater elevation. For very slow recharging wells (wells pumped dry during purging), samples may be collected after two hours of recharge. Groundwater Sample Acquisition and Handling Following purging operations, groundwater samples are collected from each of the wells, using pre-cleaned, single-sample polypropylene, disposable bailers. The groundwater sample is discharged from the bailer to the sample container through a bottom emptying flow control valve to minimize volatilization. Collected water samples are discharged directly into laboratory-provided, pre-cleaned, 40 milliliter(ml) glass vials and sealed with Teflon-lined septum, screw-on lids. Labels documenting sample number, well identification, collection date and time, type of sample and type of preservative are affixed to each sample. The samples'are then placed into an ice-filled cooler for delivery under chain-of-custody to a laboratory certified by the State of California Department of Health Services Environmental Laboratory Accreditation Program to perform the specified tests. Groundwater samples are analyzed for the presence of TPHg, BTEX, fuel oxygenates (MtBE, TAME, DIPE, EtBE, TBA, ethanol), and lead scavengers (1,2-DCA and EDB) using EPA Method 82606. Equipment that could potentially contact subsurface media and compromise the integrity of the samples is carefully decontaminated prior to sampling. Samplers, groundwater pumps, liners, and other equipment are decontaminated in an Alconox scrub solution, and double- rinsed in a clean tap water rinse followed by a final distilled water rinse. a