Water Well Standards


Section 12. Casing.

  1. Casing Material.Note 14 Requirements pertaining to well casing are to insure that the casing will perform the functions for which it is designed, i.e., to maintain the hole by preventing its walls from collapsing, to provide a channel for the conveyance of the water, and to provide a measure of protection for the quality of the water pumped.

    1. Well casing shall be strong and tough enough to resist the force imposed on it during installation and those forces which can normally be expected after installation.

    2. Steel is the material most frequently used for well casing, especially in drilled wells. The thickness of steel used for well casing shall be selected in accordance with good design practices applied with due consideration to conditions at the site of the well.Note 15 There are three principal classifications of steel materials used for water well casing, and all are acceptable for use so long as they meet the following conditions.

      1. Standard and line pipe. This material shall meet one of the following specifications, including the latest revision thereof:

        (1) API Std. 5L, "Specification for Line Pipe".

        (2) API Std. 5LX, "Specification for High-Test Line Pipe".

        (3) ASTM A53, "Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated Welded and Seamless".

        (4) ASTM A120, "Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated (Galvanized) Welded and Seamless, for Ordinary Uses".

        (5) ASTM A134, "Standard Specification for Electric-Fusion (Arc)-Welded Steel Pipe (sizes NPS 16 and over)".

        (6) ASTM A135, "Standard Specification for Electric-Resistance-Welded Steel Pipe".

        (7) ASTM A139, "Standard Specification for Electric-Fusion (Arc)-Welded Steel Pipe (sizes 4 inches and over)".

        (8) ASTM A211, "Standard Specification for Spiral-Welded Steel or Iron Pipe".

        (9) AWWA C200, "AWWA Standard for Steel Water Pipe 6 Inches and Larger".

      2. Structural Steel. This material shall meet one of the following specifications of the American Society for Testing and Materials, including the latest revision thereof:

        (1) ASTM A36, "Standard Specification for Structural Steel".

        (2) ASTM A242, "Standard Specification for High Strength Low Alloy Structural Steel".

        (3) ASTM A283, "Standard Specification for Low and Intermediate Tensile Strength Carbon Steel Plates of Structural Quality.

        (4) ASTM A441, "Tentative Specification for High-Strength Low Alloy Structural Manganese Vanadium Steel".

        (5) ASTM A570, "Standard Specification for Hot-Rolled Carbon Steel Sheet and Strip, Structural Quality".

      3. High strength carbon steel sheets referred by their manufacturers and fabricators as "well casing steel". At present, there are no standard specifications concerning this material. However, the major steel producers market products whose chemical and physical properties are quite similar. Each sheet of material shall contain mill markings which will identify the manufacturer and specify that the material is well casing steel which complies with the chemical and physical properties published by the manufacturer.

      4. Stainless steel casing shall meet the provisions of ASTM A409, "Standard Specification for Welded Large Diameter Austenitic Steel Pipe for Corrosive or High Temperature Service".

    3. Plastic. Two basic types of plastic are commonly used for plastic well casing: thermoplastics and thermosets. Thermoplastics soften with the application of heat and reharden when cooled. Thermoplastics can be reformed repeatedly using heat and sometimes can unexpectedly deform. Attention should be given to the effect of heat on thermoplastic casing from the setting and curing of cement. Additional discussion on sealing material and heat generation is in Section 9, Subsection D, 'Sealing Material'.

      Thermoplastics used for well casing include ABS (acrylonitrile butadiene styrene), PVC (polyvinyl chloride), and SR (styrene rubber). PVC is the most frequently used thermoplastic well casing in California. Styrene rubber is seldom used.

      Unlike thermoplastics, thermoset plastics cannot be reformed after heating. The molecules of thermoset plastic are 'set' during manufacturing by heat, chemical action, or a combination of both. The thermoset plastic most commonly used for well casing is fiberglass.

      1. Thermoplastics. Thermoplastic well casing shall meet the requirements of ASTM F480. Standard Specification for Thermoplastic Well Casing Pipe and Couplings Made in Standard Dimension Ratios (SDR), SCH 40 and SCH 80, including the latest revision thereof. (Note: A 'dimension ratio' is the ratio of pipe diameter to pipe wall thickness.)

        Pipe made in Schedule 40 and 80 wall thicknesses and pipe designated according to certain pressure classifications are listed in ASTM F480, as well as casing specials referencing the following ASTM specifications:

        (1) ABS Pipe. ASTM D1527, Standard Specification for Acrylonitrile- Butadiene-Styrene (ABS) Plastic Pipe, Schedules 40 and 80.

        (2) PVC Pipe. ASTM D1785, Standard Specification for (Poly Vinyl Chloride) (PVC) Plastic Pipe, Schedules 40, 80, and 120.

        (3) Pressure-Rated PVC Pipe. ASTM D2241, Standard Specifications for Poly (Vinyl Chloride) (PVC) Pressure-Rated Pipe (SDR Series).

        Thermoplastic well casing that may be subject to signifiant impact stress during or after installation shall meet or exceed the requirements for impact resistance classification set forth in Section 6.5 of ASTM F480. Casing that may be subject to significant impact forces includes, but is not limited to; casing that is installed in large diameter, deep boreholes; and casing through which drilling tools pass following installation of the casing in a borehole.

      2. Thermoset Plastics. Thermoset casing material shall meet the following specifi-cations, as applicable, including the latest revisions thereof:

        (1) Filament Wound Resin Pipe. ASTM D2996, Standard Specification for Filament Wound Reinforced Thermosetting Resin Pipe.

        (2) Centrifugally Cast Resin Pipe. ASTM D2997, Standard Specification for Centrifugally Cast Reinforced Thermosetting Resin Pipe.

        (3) Reinforced Plastic Mortar Pressure Pipe. ASTM D3517, Standard Specification for Reinforced Plastic Mortar Pressure Pipe.

        (4) Glass Fiber Reinforced Resin Pressure Pipe. AWWANote 16 C950, AWWA Standards for Glass-Fiber-Reinforced Thermosetting-Resin Pressure Pipe.

      3. Drinking Water Supply. All plastic casing used for drinking water supply wells, including community supply well and individual domestic wells, shall meet the provisions of National Sanitation Foundation Standard No. 14, Plastic Piping Components and related Materials and any revision thereof. The casing shall be marked or labeled following requirements in NSF Standard No. 14. Standard No. 14 includes the requirements of ASTM F480.

      4. Storage, Handling, and Transportation. Plastic casing shall not be stored in direct sunlight or subjected to freezing temperatures for extended periods of time. Plastic casing shall be stored, handled, and transported in a manner that prevents excessive mechanical stress. Casing shall be protected from sagging and bending, severe impacts and loads, and potentially harmful chemicals.

      5. Large Diameter Wells. Because large diameter plastic casing has not been used extensively at depths exceeding 500 feet, special care shall be exercised with its use in deep wells.

    4. Concrete pipe used for casing should conform to the following specifications, including the latest revision thereof:

      (a) ASTM C14, "Standard Specifications for Concrete Sewer, Storm Drain, and Culvert Pipe".

      (b) ASTM C76, "Standard Specifications for Reinforced Concrete Sewer, Storm Drain, and Culvert Pipe".

      (c) AWWA C300, "AWWA Standard for Reinforced Concrete Pressure Pipe Steel Cylinder Type, for Water and Other Liquids".

      (d) AWWA C301, "AWWA Standard for Prestressed Concrete Pressure Pipe Steel, Cylinder Type, for Water and Other Liquids".

    5. Unacceptable Casing Materials. Galvanized sheet metal pipe such as 'downspout' tile pipe, or natural wood shall not be used as well casing.

    6. Other Materials. Materials in addition to those described above may be used as well casing, subject to enforcing agency approval.

  2. Casing Installation. All well casing shall be assembled and installed with sufficient care to prevent damage to casing sections and joints. All casing joints above intervals if perforations or screen shall be watertight. Any perforations shall be below the depths specified in Section 9, Subsection A, above.

    Casing shall be equipped with centering guides or 'centralizers' to ensure the even radial thickness of the annular seal and filter pack.

    1. Metal Casing. Metallic casing may be joined by welds, threads, or threaded couplings. Welding shall be accomplished in accordance with the standards of the American Welding Society or the most recent revision of the American Society of Mechanical Engineers Boiler Construction Code. Metallic casing shall be equipped with a 'drive shoe' at the lower end if it is driven into place.

    2. Plastic Casing. Plastic casing may be joined by solvent welding or mechanically joined by threads or other means, depending on the type of material and its fabrication. Solvent cement used for solvent welding shall meet specifications for the type of plastic casing used. Solvent cement shall be applied in accordance with solvent and casing manufacturer instructions. Particular attention shall be given to instructions pertaining to required setting time for joints to develop strength.

      The following specifications for solvent cements and joints for PVC casing shall be met, including the latest revisions thereof:

      1. ASTM D2564, Standard Specification for Solvent Cements for Poly (Vinyl Chloride) (PVC) Plastic Pipe and Fittings.

      2. ASTM D2855, Standard Practice for Making Solvent-Cemented Joints with Poly (Vinyl Chloride) (PVC) Pipe and Fittings.

      Plastic casing or screen shall not be subjected to excessive stress during installation and shall not be driven into place. Care shall be taken to ensure that plastic casing and joints are not subjected to excessive heat from cement-based sealing material.

      A specifically designed adapter shall be used to join plastic casing to metallic casing or screen.

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