ARCHIVED REPORTS_XR0005400 - Laserfiche WebLink

Home Browse Search

i r - ULTRAMAR FIELD PROCEDURES _ f { The following section describes procedures used by Ultramar field personnel In the performance of ground water sampling. r a Ground Water Level and Total Depth Determination I I A water level indicator is lowered down the well and a measurement of the depth to water from an established reference point on the casing is taken. The indicator probe is used to sound the bottom of the well andla measurement of the total depth of the well is taken. Both the water level and total depth measurements are taken # to the nearest 0.01-foot. f � Visual Analysis of Ground Water Prior tou in and ' P rg g sampling p g ground water monitoring wells, a water sample is collected from each well for. subjective analysis. The visual analysis involves gently lowering a clean, disposable, polyethylene bailer to approximately one-half the bailer length past the water table interface. The bailer is then retrieved, and the sample contained within the bailer is examined-for floating product or the appearance of a petroleum product sheen. .:If measurable free product is noted in the bailer, a water/product interface probe is used to determine the thickness of the free product to the nearest 0.01-foot. The thickness of free product is determined by subtracting the depth to product from the depth to water. Monitoring Well Purging and Samoling } i . Monitoring wells are purged by removing approximately four casing volumes of water from the well using a clean disposable bailer or electrical submersible purge pump. Purge volumes are calculated prior to purging. During 4 purging the temperature, pH, and electric conductivity are monitored. The well is sufficiently purged when:-the four casing volumes have been removed; the temperature, pH, and conductivity have stabilized to within 10% of the r initial readings; and the ground water being removed is relatively free of suspended solids. After purging, ground water levels are allowed to stabilize to within 80%of the initial water level reading. A water sample is then collected , from each well with a clean, disposable polyethylene bailer. If the well is bailed dry prior to removing the minimum volume of water, the ground water is allowed to recharge. If the well has recharged to within 80% of the initial i reading within two hours, the well will continue to be purged until the minimum volume of water has been removed. If the well has not recharged to at least 80% of the initial reading within two hours, the well is considered to contain I formational water and a ground water sample is collected. Ground water removed from the well is stored in 55- '• gallon drums at the site and labeled pending disposal. In wells where free product is detected, the wells will be bailed to remove the free product. An estimate of the i volume of product and water will be recorded. If the free product thickness is reduced to the point where a measurable thickness is no longer present in the well, a ground water sample will be collected. If free product persists throughout bailing, a final free product thickness measurement will be taken and a ground water sample will not be collected. Samples are stored in 40-milliliter vials so that air passage through the sample is minimized (to prevent volatilizing the sample). The vial is tilted and flied slow until an upward convex meniscus forms over the mouth of the vial. IY Pw The Teflon side of the septum (in cap)is then placed against the meniscus, and the cap is screwed on tightly. The sample is then inverted and the bottle is tapped lightly to check for air bubbles. If an air bubble is present in the k vial, the cap is removed and more sample is transferred from the bailer. The vial is then resealed and rechecked ) for air bubbles. The sample is then appropriately labeled and stored on ice from the time of collection through the time of delivery to the laboratory. A Chain-of-Custody form is completed to ensure sample integrity. Ground water samples are transported to a state-certified laboratory and analyzed within the EPA-specified holding times for the requested analyses. l Utb mar Field PioceGureaKWR-94 I e }