Guidelines for Minimum Standards in Water Well Construction, Province of British Columbia — June 1982
Part 2 — Technical Information Appendices
APPENDIX 1: WELL PLUMBNESS AND ALIGNMENT
1. Introduction
Well plumbness and alignment are never 100% in any well. Where the outside diameter of the pumping equipment is considerably smaller than the diameter of the well, plumbness and alignment seldom are a problem in a shallow well.
However, well plumbness and alignment become critical on deep holes and/or where a vertical turbine pump is to be permanently installed in the well. A vertical turbine pump may operate satisfactorily when considerably inclined from the vertical; however, when well alignment is badly out and there is also evidence of kinks, bends or corkscrews in the well, the well should be rejected because of the severe wear that can take place on pump shaft, bearings, and discharge casings. Also the pump may become stuck in the hole!
2. Methods of Testing
Testing for plumbness and alignment tests are given in the AWWA standard for deep wells and also in EPA 570/9-75-001, the latter Is reproduced below:
"Alignment" shall be tested by lowering into the well to the depth of the lowest anticipated pump setting, a section of pipe 40 feet long or a dummy of the same length. The outer diameter of the pipe or dummy shall be not more than 1/2 inch smaller than the inside diameter of that part of the casing or hole being tested when the casing diameter is a nominal 10 inches or less. When the nominal diameter of the casing being tested is 12 inches or greater, the outer diameter of the test pipe or dummy shall not be more than I inch smaller than the inside diameter of that part of the casing or hole being tested. The dummy when lowered into the casing shall pass freely the entire depth of the well.
The test for plumbness shall be made with a plummet. Construct a tripod or frame "B" similar to that shown in Figure 1. The center of the pulley "C" should be exactly 10 feet above the top of the well. The pulley must be so located that the plumb line "A" will come off its outer edge exactly over the center "D" of the well casing.
Figure 1
Make the plumb ring or plunger "E" 1/4 inch smaller in diameter than the inside diameter of the well casing. It can be made from a piece of steel plate or a short piece of pipe. Whichever is used, it must be heavy enough to keep the plumb line taut. The hub of the ring must not be solid as the water must pass through it as it is lowered in the well. The hole "F" through which the plumb line "A" passes must be in the exact center of the ring. Knots or marks should be made every 10 feet on the plumb line, to indicate the depth the ring has been lowered in the well.
The well characteristics are determined by lowering the plumb ring 10 feet at a time and taking a reading at each location. If the plumb line passes exactly through the center line "D" at any location, the well is plumb at the depth the plumb ring is suspended. However, if the line "A" does not pass through "D," the well at that depth is out of plumb by an amount equal to distance "A" from "D" plus an equal distance for each 10 feet that the plumb ring "E" is below the floor level. For example, assume that "C" is exactly 10 feet above floor level and "D" is at floor level. If plumb line "A" is 1/16th of an inch from the center line of the well at "D" and the plumb ring "E" is 10 feet below the floor line, then the well is 1/8th of an inch out of plumb at the 10 foot level. If "A" is 1/16th inch from the center of the well at "D" when the plumb ring "E" is 50 feet below the floor level at "D" then the well is 1/16th plus 5/16th, or 3/8th of an inch out of plumb at the 50 foot level. This is simply the proportion of similar triangles, and expressed in that way, variation from plumb equals,
60 ft. 1 6 3
— X — inch = - inch = — inch
10 ft. 16 16 8
This reading at the various depths tested may be plotted on cross section paper and an accurate diagram of the well developed.
It is recommended that the readings and plottings that are described above should be made on two planes 90 degrees from each other so that the tendencies of the well to "corkscrew" or bow can be determined.
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