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CITY OF LATHROP <br /> calculation of the amount of gravel packing material entering the borehole. The <br /> Contractor shall provide the City with a schematic drawing of the system of gravel <br /> placement he intends to employ prior to the installation of casing. <br /> 3. The tremie pipe shall be removed in approximately twenty-foot intervals when the <br /> gravel in the borehole reaches the tremie pipe. <br /> 4. The quantities of gravel placed in the annulus of each well shall not be less than the <br /> computed volume of the annulus. A quantity less than the computed value will be judged <br /> as an indication of voids, and corrective measures shall be taken by the Contractor. <br /> 5. If the volume of gravel installed in the annulus is less than the theoretical volume,the <br /> well may be rejected by the Engineer. <br /> 6. Gravel packing and bentonite seal placement shall continue uninterrupted until the <br /> gravel pack reaches the depth of the surface seal. <br /> 2.3.7 ANNULAR SEAL <br /> A. Scope--.This item shall consist of providing and installing a sand/cement grout annular seal in <br /> the annulus between the casing(s) and the well bore. <br /> B. Methods <br /> Installation of the annular seal shall conform to State Water Well Standards and the requirements <br /> of the well permitting agency. <br /> 1) The Contractor shall proceed with sealing operations after the Engineer verifies the <br /> depth of the top of the gravel in the well annulus. <br /> 2)The tremie pipe shall be installed no more than 5 feet above the placed gravel envelope <br /> before beginning seal placement.The bottom of the tremie pipe shall remain submerged <br /> in the sealing material maintaining a positive displacement throughout the sealing <br /> process until the grouting material has reached the ground surface. <br /> 3) The Contractor shall take measures to ensure that the weight of the cement column <br /> does not collapse the well casing during the sealing operation. <br /> 4) Well development shall not commence until a minimum of 24 hours after placement <br /> of the seal. <br /> 5)The annular seal shall have a minimum width of thickness of two (2) inches. <br /> LUHDORFF&SCALMANINI <br /> CONSULTING ENGINEERS 15 <br />