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• City of Stocldon TL 394-0074-01 <br /> May 4, 1994 Page 11 <br /> around the wellhead. Monitoring wells will be locked to restrict access to unauthorized <br /> personnel. <br /> Monitoring well construction details will be recorded on the field well construction form. <br /> Construction information will be transferred to Monitoring Well construction schematics for <br /> presentation in final reports. <br /> A-3 Groundwater Monitoring Well Development. When possible, <br /> initial well development will be performed during installation of the sand pack. A minimum <br /> of 48 hours following installation, groundwater monitoring wells will be developed in order <br /> to remove sediment that may accumulate in the well during installation, and to settle the <br /> filter pack. Groundwater monitoring well development will be performed using a <br /> combination of bailing, pumping, and surging. <br /> The development of each groundwater monitoring well will continue until a minimum of five <br /> well casing volumes of water have been removed, and the displaced water is relatively clear, <br /> free of sediment, and the values of pH, temperature, and specific electrical conductance <br /> (EC) have stabilized. Well development data will be recorded on the Sampling/Well <br /> Development Log (Attachment A). <br /> Purged water will be containerized in Department of Transportation-approved drums, and <br /> stored on site in an area inaccessible to the general public. The purged water is typically <br /> characterized either by sampling it, or on the basis of the groundwater sample analytical <br /> results. Twining can recommend an appropriate method for disposition of the purged water. <br /> Disposal will be the responsibility of the client. <br /> A-4 Measuring Depths to Water and Calculating Groundwater EIevations. Monitoring <br /> well locations and top-of-casing elevations will be surveyed by a California-licensed land <br /> surveyor. Surveyed data will be referenced to a local benchmark, an assumed local datum, <br /> or a United States Geological Survey benchmark. The surveyed data will be accurate to± <br /> 0.01 feet. <br /> Depth to groundwater will be measured relative to a surveyed point on the north edge of <br /> the well casing rim. The water depths will be measured using an electronic water sensing <br /> meter with a precision accuracy of ± 0.01 feet. The depth to water in each well at a site <br /> will be measured in a single day. Measurements will be recorded on the daily field log. <br /> If floating hydrocarbons are suspected,a bottom-filling clear bailer or hydrocarbon detecting <br /> paste bailer may be used to record floating hydrocarbon thickness. The bailer will be <br /> lowered to a point just below the liquid level, retrieved, and observed for floating <br /> hydrocarbon. <br />