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Working to Restore Nature <br /> Subjective-Groundwater Observations <br /> The depth to groundwater in the monitoring wells is measured to the nearest 0 01-foot with <br /> an electronic water-level indicator Samples of groundwater are collected for subjective <br /> analysts from the air-fluid interface in each well by lowering approximately half the length <br /> of a clear Teflon bailer through the interface The bailer is retrieved and the water sample <br /> examined for free product, sheen, or other subjective evidence of hydrocarbons <br /> Groundwater Sampling <br /> Groundwater samples are collected after water in each well recovered to near its original <br /> level The groundwater samples are collected by lowering a clean Teflon bailer gently <br /> through the air-water interface to a depth approximately 3 feet below the groundwater <br /> surface The bailer is retrieved and the samples are transferred slowly to laboratory- <br /> cleaned, 40-milliliter glass vials or other appropriate containers as required by the <br /> laboratory The vials and bottles contain hydrochloric acid (or other appropriate <br /> preservative) and are filled so that no head space is left in the containers The field <br /> technician initiates a Chain of Custody Record and it accompanies the samples to the <br /> analytical laboratory <br /> Gradient and Direction of Groundwater Flow <br /> A licensed land surveyor produced a site map showing the location of the wells and other <br /> site features with listing of the horizontal and vertical references of the monitoring wells <br /> The elevation of the monitoring wells are referenced to within 0 01-foot of a nearby United <br /> States Geodetic Survey, County, or City bench mark The horizontal distances are measured <br /> to the nearest 0 1-foot The groundwater elevation in each monitoring well is calculated by <br /> subtracting the depth to water from the wellhead elevation The groundwater elevation <br /> information is used to evaluate the direction of groundwater flow, evaluate the groundwater <br /> gradient, and construct a groundwater gradient or potentiometric map <br /> 31009-10 <br />