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`} I Texaco Environmental Services Standard Operating Procedures for Groundwater Monitoring and Sampling The following are routine procedures to be followed by personnel obtaining field information concerning petroleum product thickness and samples of groundwater during the monitoring and sampling of Texaco sites These procedures are designed to assure that • Information and samples are properly collected • Samples are identified, preserved and transported in a manner such that they are representative of field conditions • Monitoring and sampling results are reproducible Water Level Measurements Water level measurements are needed to document groundwater flow directions and calculate gradient By gauging the level of water in a groundwater monitoring well and comparing the complied data, calculations can be made that determine the direction the groundwater at the monitored well is flowing and the groundwater gradient between successive monitoring wells • An interface probe or electronic probe is generally used to gauge the level of water in a monitoring well When using either probe, it is slowly lowered into the well until the oscillating alarm indicating water is heard Raise the interface probe above the water level and lower it back into the water at least three times to verify that the true depth to water is measured The depth to water should always be measured from the same spot on the top of the well casing The designated "Top of Casing" mark should be at the North side of the casing Without moving the probe, read the numbers on the tape to determine the distance to water from the top of the well casing A chalked, steel add- tape may also be used to gauge the level of water in a monitoring well When using the steel tape, it is slowly lowered into the well until the chalked portion of the tape encounters water Read the numbers on the tape to determine the distance from the predetermined top of the well casing Raise the tape to the surface grade, re-chalk and lower it back into the water at least two times to verify that the true depth to water is measured Record the depth to water on the Well Gauging Form and Groundwater Sampling Form Petroleum Product Thickness Measurements If free phase petroleum hydrocarbons (product) are observed floating on the groundwater surface during the water level measurement, the thickness of the product will be measured in each appropriate well Groundwater samples will not be collected for chemical analysis from wells containing product (even a sheen) unless specifically requested by the Project Coordinator If the Protect Coordinator requests that wells containing product be sampled, only those wells with product thickness of less than 0 01 foot will be sampled Arrangements to bail, store, and dispose of product must be made separately When product is stored, according to Texaco policy, it will be double-contained and disposed of within 90 days of generation Product thicknesses will be measured using interface probes, and/or acrylic (clear plastic) bailers The procedures for obtaining level and thickness measurements using each instrument are Page 1 of 5 P 1GWMP\FORMSITEX-SOP DOC