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1. Steel used in the manufacture of casing for Section 17. Special Provisions for Driven Wells ("Well bored and dug wells should conform to the specifications for Points"). casing material described in Section 12. Minimum thickness of steel casing for bored and dug wells shall be: A. If the well is to be used as an individual domestic well, an oversize hole with a diameter at least Diameter U. S. Standard Gage Inches Mid etres or Plate Thickness 3 inches (75 millimetres) greater than the diameter of the pipe shall be constructed to a depth of 6 feet (1.8 meters) 18 450 8 gage 4.18 millimetres) and the annular space around the pipe shall be filled with g g neat cement, cement grout, or bentonite mud. 24 600 1/4 inch 6.35 millimetres) 30 750 1/4 inch (6.35 millimetres) B. The minimum wall thickness of steel drive pipe 36 900 1/4 inch (6.35 millimetres shall be not less than 0.140 inches (3.5 millimetres). 42 1050 1/4 inch 6.35 millimetres 48 1150 1/4 inch (6.35 millimetres C. Well points made of thermoplastic materials Corrugated steel pipe used as casing shall meet the should not be driven but jetted or washed into place. specifications (including the latest revision) of ASRM1/ A444, Section 18. Rehabilitation, Repair and Deepening of Wells. "Standard Specification for Steel Sheet, Zinc Coated (Galvanized) by the HOT-DIP Process for Culverts and Under- A. Rehabilitation is the treatment of a well by drains". The minimum thickness of sheet used shall be chemical or mechanical means (or both) to recover lost 0.109 inches (2.8 millimetres). production caused by incrustation or clogging of screens or the formation immediately adjacent to the well. The follow- 2. Concrete casing can consist of either ing methods used for rehabilitating a well when done with poured-in-place concrete or precast concrete pipe. Poured- care are acceptable: (1) introduction of chemicals designed in-place concrete should be sufficiently strong to withstand for this purpose, (2) surging by use of compressed air, the earth and water pressures imposed on it during, as well (3) backwashing or surging by alternately starting or as after, construction. It should be properly reinforced stopping the pump, (4) jetting with water, (5) sonic cleaning, with steel to furnish tensile strength and to resist cracking, (6) vibratory explosives, and (7) combinations of these. and it should be free from honeycombing or other defects Methods which produce an explosion (in addition to the use of likely to impair the ability of the concrete structure to vibratory explosives mentioned above) are also acceptable remain watertight. .Aggregate small enough to place without provided, however, the are used with eat care "bridging" should be used. Poured-in-place concrete shall be p y , rs particular- "bridging"A" ly where aquifers are separated by distinct barriers to the (6 sacks of cement per cubic yard or movement of ground water. 0.76 cubic metre) or Class B (5 sacks per cubic yard or 0.76 cubic metre). In those cases where chemicals or explosives have Precast concrete pipe is usually composed of been used, the well shall be pumped until all traces of them have been removed. concrete rings from 1 to 6 feet (0.3 to 1.8 metres) in diameter and approximately 3 to 8 feet (0.9 to 2.4 metres) B. In the repair of wells, material used for long. To serve satisfactorily as casing, these rings should casing shall meet the requirements of Section 12 "Casing" of be free of blemishes that would impair their strength or these provisions. In addition, the requirements of serviceability. Concrete pipe shall conform to the specifica- Section 11, Part A "Disinfection" and, when applicable, tions listed in Section 12, Part A,' item.4. Section 14 "Sealing-off Strata" shall be followed. E. Covers. All bored and dug wells shall be C. . Where wells are to be deepened, the requirements provided with a structurally sound, watertight, cover made of of Sections 11, 12, 13, 14, and 15 of these standards shall be concrete or steel. followed. 1 American Society for Testing and Materials. Section 19. Temporary Cover. Whenever there is an interruption in work on the well such as overnight shutdown, during inclement weather, or waiting periods required for the setting up of sealing materials, for tests, for installation of the pump, etc., the well opening shall be closed with a cover to prevent the introduction of undesirable material into the well and to insure the public safety. The cover shall be held in place or "weighted-down" in such a manner that it cannot be removed except with the aid of equipment or through the use of tools.