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13.8. CASING <br /> 13.8.1. Casing shall be ASTM, API and/or AWWA approved. Refer to the State <br /> of California Water Well Standards Bulletin 74-81 and 74-90. <br /> 13.8.2. Casing should be protected from damage due to sagging and bending, <br /> severe impacts and loads, direct sunlight or subjected to freezing <br /> temperatures and potentially harmful chemicals. <br /> 13.8.3. All well casing shall be assembled and placed with sufficient care to <br /> prevent damage to casing sections and joints. All casing joints above <br /> intervals of perforations or screen shall be watertight. Any perforations <br /> shall be below the depth specified in Section 13.12. The casing shall be <br /> equipped with centering guides or"centralizers", if installed in open <br /> borehole, to ensure the even radial thickness of the annular seal and <br /> filter pack. <br /> 13.8.4. Steel casing may be joined by welds, threads, or threaded couplings. <br /> Welding shall be accomplished in accordance with standards of the <br /> American Society or the most recent revision of the American Society of <br /> Mechanical Engineers Boiler Construction Code. Casing shall be <br /> equipped with a "drive shoe" at the lower end if it is driven into place. <br /> 13.8.5. A specifically designed adapter may be used to join plastic casing to <br /> metallic casing or screen. <br /> 13.8.6. Special considerations for monitoring well casings are: <br /> 13.8.6.1.Casing, couplings, centralizers, and other components of the <br /> well casing shall be free of pollutants and contaminants at the <br /> time of installation and non-reactive with water chemistry and <br /> contaminants. <br /> 13.8.6.2.The bottom of a monitoring well casing shall be plugged or <br /> capped to prevent sediment or rock from entering the well. <br /> 13.8.6.3. Depending upon the type of material and its fabrication, plastic <br /> casing shall be mechanically joined (threaded or otherwise <br /> coupled) in a manner that ensures its water tightness. Organic <br /> solvent cements or glues shall not be used for joining plastic <br /> casing where a monitoring well is to be used for certain <br /> sensitive water quality determinations. <br /> 13.8.6.4. Plastic casing or screen shall not be driven or otherwise <br /> subjected to significant impact forces during installation. <br /> 13.9. CONDUCTOR CASING <br /> 13.9.1. If temporary conductor casing is used to stabilize the borehole during <br /> drilling, it shall be removed during the placement of the filter pack and <br /> annular seal materials. <br /> 13.9.2. If a permanent conductor casing is to be installed or temporary <br /> conductor casing cannot be removed, the monitoring well borehole <br /> EHD 43-03 Page 22 of 27 WELL STANDARDS <br /> 10/9/07 <br />