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Table Of Contents (Cont'd) <br />e.g~ <br />Section 9. Sealing the Upper Annular Space 13 <br />A Minimum Depth of Annular Surface Seal 14 <br />1. Shallow ground water. 14 <br />2. Encroachment on known or potential sources of pollution or contamination. 14 <br />3. Areasoffreezing 14 <br />4. Vaults 14 <br />B. Sealing Conditions. 15 <br />1. Wells drilled in unconsolidated, caving material. 15 <br />2. Wells drilled in unconsolidated material with significant clay layers. 16 <br />3. Wells drilled in soft consolidated formations (extensive clays, <br />sandstones,etc.) 16 <br />8. Wells that penetrate zones containing poor-quality water, pollutants, <br />or contaminants. 17 <br />D. Sealing Material. 17 <br />1. Water 17 <br />2. Cement 17 <br />a. NeatCement 18 <br />b. Sand Cement. 18 <br />c. Concrete 19 <br />d. Mixing 19 <br />3. Bentonite 19 <br />E. Radial Thickness of Seal. 20 <br />F. Placement of Seal 20 <br />1. Obstructions 20 <br />2. Centralizers 20 <br />3. Foundation and Transition Seals. 21 <br />4. Timing and Method of Placement 21 <br />5. Ground Water Flow 22 <br />6. Verification 22 <br />7. Pressure 22 <br />Section 10. SurfaceConstmctionFeatures 22 <br />A Openings 22 <br />5. Bases 22 <br />B. Well Pits or Vaults 23 <br />F. BackflowPrevention 24 <br />Section 12. Casing 24 <br />A Casing Material. 24 <br />3. Plastic 24 <br />a. Thermoplastics 24 <br />(1) ABS Pipe. 24 <br />(2) PVC Pipe. 24 <br />(3) Pressure-RatedPVCPipe 24 <br />b. Thermoset Plastics. 25 <br />(1) Filament Wound Resin Pipe 25 <br />(2) CentrifugallyCastResinPipe 25 <br />(3) Reinforced Plastic Mortar Pressure Pipe. 25 <br />VIII