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4.3.9. If the minimum grout seal depth is not met, a grout seal will be required <br /> below the conductor casing into a clay layer or the required depth, <br /> whichever is greater, and between well casing and the borehole to the <br /> surface. <br /> 4.3.10. If more than one permanent conductor casing is utilized in the same <br /> borehole and they do not extend to the surface, the grout seal will be <br /> required below the deepest conductor casing into a clay layer or the <br /> required depth, whichever is greater, to the surface. <br /> 4.3.11. MINIMUM THICKNESS FOR STEEL WELL CASING: <br /> 6 Inch Diameter 10 Gauge 0.1406 US Standard <br /> 8 Inch Diameter 10 Gauge 0.1406 US Standard <br /> 10 Inch Diameter 10 Gauge 0.1406 US Standard <br /> 12 Inch Diameter 10 Gauge 0.1406 US Standard <br /> 14 Inch Diameter 10 Gauge 0.1406 US Standard <br /> 16 Inch Diameter 8 Gauge 0.1719 US Standard <br /> 18 Inch Diameter 8 Gauge 0.1719 US Standard <br /> 20 Inch Diameter '/4 0.2500 US Standard <br /> 4.3.12. For other types of approved well casing, see Bulletin 74-81 and 74-90, or <br /> as approved by the Director. <br /> 4.4 INSTALLATIONS OF CASING <br /> 4.4.1. Damage to the casing section and joints are to be avoided during <br /> installation. The joints must be structurally sound and watertight. <br /> 4.4.2. The casing shall extend a minimum of twelve (12) inches above the <br /> ground surface and a minimum of 1 inch above the concrete surface seal. <br /> 4.4.3. Casing shall be equipped with centering guides where applicable to <br /> ensure even thickness of the annular seal and/or gravel pack. <br /> 4.5. GRAVEL INSTALLATION <br /> 4.5.1. Gravel used in gravel packed wells shall be well-rounded particles <br /> containing no clay, silt, or organic matter, and to be installed at a rate that <br /> will prevent bridging. Other material may be used on approval of the <br /> Director. <br /> 4.5.2. Gravel used in gravel packed wells shall be chlorinated during the <br /> installation. <br /> 4.6. PERFORATIONS <br /> 4.6.1. The perforating of casing shall not deform the casing. The casing shall <br /> not be perforated within fifty (50) feet of the ground surface if the total <br /> depth of the well is greater than fifty (50)feet. The upper most perforation <br /> shall be below an impervious stratum in an aquifer of good quality water. <br /> 4.6.2. If a well with perforations fifty (50) feet deep or less from the ground <br /> surface is deepened, the perforations fifty (50) feet deep or less shall be <br /> EHD 43-03 Page 11 of 27 WELL STANDARDS <br /> 10/9/07 <br />