Posted 11-27-2003 at 09:40:22
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I just did a seach on the net and found this pertaining to casing a well. Be sure you consult a well driller befor doing it. You do want to stop the flow of water between the different aquifers. Mark H.
36.21.645 PLASTIC CASING (1) All plastic casing shall be installed only in an oversized drill hole without driving. Wells cased with plastic shall have steel casing extending a minimum of 18 feet below the surface and 18 inches above the ground surface. Plastic casing to be used must be specifically designed for water well construction and bears NSF approval. Methods of installation shall be:
a. by installing a larger size steel casing on the outside of the plastic casing with a minimum of 4 feet of overlap (Figure 6A at the end of this sub-chapter); or
b. by attaching directly to the plastic casing a threaded plastic to steel coupling (Figure 6B).
(2) Thermoplastic well casing shall conform with American Society for Testing and Materials Specification F480-81 or latest revision as follows:
a. minimum standards dimension ratio shall be 26 for inner casing in bedrock applications;
b. minimum standards dimension ratio shall be 21 for unconsolidated formations greater than 125 feet;
c. minimum pipe stiffness shall be 224 foot-pounds/in2 [kiloneutron (meter . meter)] when tested according to section 5.4.1 of American Society for Testing and Materials Specification F480;
d. all casing 5 inches [12.7 centimeters] and larger shall be tested for impact resistance and shall meet or exceed IC-1 impact classification according to section 6.5 and table 6 of American Society for Testing and Materials Specification F480;
e. carry the seal of the national sanitation foundation.
(3) All casing shall have additional thickness and weight if standard thickness is not capable of withstanding forces to which it is subject.
(4) The well casing must be clearly marked by the manufacturer showing: nominal size, type plastic material, standard dimension ratio (SDR), ASTM designation, and national sanitation foundation seal of certified approval.
(5) The use of plastic well casing in connection with a pitless adaptor is not acceptable.
36.21.646 PLASTIC CASING JOINTS (1) All casing joints shall be watertight. Either "bell" type or coupling hubs or threaded couplings are approved. Hub couplings shall be of material meeting the specifications for plastic casings as stipulated in ARM 36.21.645. Solvent cemented joints shall be made in accordance with manufacturer's directions.
36.21.647 TOP TERMINAL HEIGHT (1) The casing head or pitless unit of any water well shall extend not less than 18 inches above the finished ground surface or pump house floor, and not less than 18 inches above the local surface runoff level. No casing shall be cut off below land surface except
during permanent abandonment of a well. The ground surface immediately surrounding the top of the well casing or pitless unit shall be graded so as to drain surface water away from the well. The casing of any water well shall extend not less than 18 inches above the established 100 year floodplain elevation or be capped with a watertight seal and vented above flood level
36.21.648 CASING OPENINGS (1) There shall be no opening in the casing wall between the top of the casing and the bottom of the required casing seal except for pitless adapters, screened vents (inverted u-construction), measurement access ports, and grout nipples installed in conformance with these standards.
a. All pitless adaptors must be installed according to manufacturers specifications.
(2) In no case shall holes be cut in the casing wall for the purpose of lifting or lowering casing into the well bore, unless such holes are properly welded closed and watertight prior to placement into the well bore.
36.21.649 CASING CENTRALIZERS (1) Well casing to be sealed into an oversize drill hole should be equipped with centering guides to ensure the proper centering of a casing. In all events, casings shall be centered in the sealed interval. Guides should be of steel, at least 1/4 inch in thickness, evenly spaced in groups of 3 or 4 in 20 foot intervals or less. (See Figure 1.)
36.21.650 CASING PERFORATIONS (1) Perforations above the lowest expected static water level shall not be permitted. Wells may be completed with perforations as follows:
a. in-place perforations with star, mills knife, similar type perforators, millslotted, sawed, or drilled;
b. perforated inner casing, either torch-cut, millslotted or punched. Such inner casing may be of steel, plastic or other suitable corrosion-resistant material, but if other than steel, a full evaluation of the structural stability of the inner casing must be made prior to its placement. They may be used in a natural development or gravel packed type of construction. Where appropriate, the top of the inner casing shall be fitted with suitable packers or sealing material and sealed to the well casing.
(2) Casing perforations that allow the well casing to act as a conduit for deleterious interflow between aquifers shall
not be permitted. (That is, interflow where waters of different heads, temperatures, or quality mix causing deleterious effects.)
(3) Perforations shall not be placed to allow cascading water within the well casing during static conditions.
(4) Perforations shall not be placed to allow upward art-esian flow from one aquifer to another.