Guidelines for Minimum Standards in Water Well Construction, Province of British Columbia — June 1982
PART 2 — TECHNICAL INFORMATION APPENDICES
APPENDIX 4: WELL DEVELOPMENT METHODS*
1. Pumping or Bailing Method
1.1 Continuous Overpumping
The continuous overpumping method of well development is accomplished by uninterrupted pumping at pumping rates up to 11/2 times the design capacity of the well.
1.2 Interrupted Overpumping
The interrupted overpumping method of well development is done with a pump capable of pumping at rates up to 2 times the design capacity. The pumping should be carried out in at least 5 steps. These steps should include pumping rates of 1/4, 1/2, 1, 11/2, and 2 times the well design capacity, with no check valve nor foot valve present. Pumping should be conducted in 5 minute cycles, and should continue a minimum of 2 hours or until such time as acceptable standards are attained.
1.3 Surging and Bailing (Utilizing Bailer)
The surging and bailing method of well development is accomplished by utilizing the bailer as a surging device. If fines have been drawn into the well and have settled on the bottom and accumulated to a depth where they block 10 percent or more of the total screen length, the well must be bailed or otherwise cleaned to the bottom before resumption of surging. On completion of development the well should be cleaned to the bottom.
1.4 Surging and Bailing (Utilizing Surge Block)
This development process is carried out by surging and bailing the well. Surging is done with a single or double solid (or valved) surge block. Surging starts at the bottom of the lowest screen in the well and proceeds upwards.
2. Mechanical Surging and Pumping Method
2.1 Surging and Pumping
In this development process surging is done by either a solid or valve surge block. The pumping is done through the surge block which incorporates a piece of the suction pipe in the fabrication of the block. Pumping is done simultaneously with the surging at rates up to 1/2 of the design capacity. Fines drawn into the well are pumped out periodically before such accumulation reaches 10 percent of the screen length. Upon completion of the development work the well should be cleaned to the bottom.
3. Hydraulic Jetting Method
3.1 Hydraulic Jetting
In the hydraulic jetting method well development is accomplished by simultaneous high-velocity, horizontal jetting and pumping. The outside diameter of the jetting tool should be one inch less in diameter than the screen inside diameter. The minimum exit velocity of the jetting fluid at the jet nozzle should be 150 ft./sec. The tool is rotated at a speed less than one rpm. The jetting tool is positioned at one level for not less than two minutes and then moved to the next level which should be no more than 6 inches vertically from the preceding jetting level. Jetting proceeds from the bottom of the screen to the top. Pumping from the well should be at a rate of 5 to 15 percent more than the rate at which water is introduced through the jetting tool. Water to be used for jetting should contain less than 1ppm suspended solids. A pump which can deliver a minimum 100 gpm at a minimum 100 psi is generally required.
4. Air Development Method
4.1 Single Pipe System Open to Atmosphere
In this method, development is done by the utilization of a single pipe air pumping system using the casing or the bore hole itself as the eductor line. The compressors, air lines, hoses, fittings, etc., are of adequate size to pump the well by the air lift principle at 11/2, to 2 times the design capacity of the well. Initially the well is pumped with air until it is developed to the point that the well yields clear, sand-free water. Air is then shut off and water allowed to return into the well until a static condition is reached. The valve is then reopened and air is introduced into the well until water is again brought to the surface by the air lift at which time the air valve is closed and the water allowed to drop back down the well and return to a static condition. This process of lifting and dropping of the column of water is repeated until the water in the well becomes turbid at which time the well is then continuously pumped with air until it again yields clear sand-free water. The above operation is repeated until the well no longer produces fine material when it is surged and backwashed as described above.
The bottom of the air line is placed at different levels in order to facilitate development of all intake areas and multiple water producing zones, and the process is repeated until all zones yield water free of turbidity when surged and backwashed.
4.2 Single Pipe System Closed to Atmosphere
For this method, a suitable valve is installed on the discharge line leading from the top of the casing, and an air fine is secured into a blowing "tee" or "ell" affixed to a valved air connection on the top of the casing. The valve is then closed on the discharge line, and an air hose is attached to the valved fitting and air is introduced into the well, forcing the column of water in the well down. Care must be exercised to prevent air from entering the water-bearing formation. This can be accomplished by the installation of a separate pipe, open to the atmosphere at the top, and installed in the well to a point ten feet above the water-bearing zone. When the water level in the well is forced down to the bottom of this air release pipe, the discharge valve is opened and the water is allowed to rise back to the static level. This procedure can be repeated and/or alternated with the "Single Pipe System Open to the Atmosphere" technique. A pressure gauge and relief valve can be installed at the top of the casing when this system is used.
4.3 Two Pipe System
The development process is carried out by the utilization of an air "introducing" pipe and an air and water eductor line. The compressors, air lines, hoses, fittings, etc., should be of adequate size to pump the well by the air lift method at 11/2, to 2 times the design capacity of the well. The well is initially developed as outlined in the above "Single Pipe System Closed to the Atmosphere," with the air line introducing air into the eductor line at a point above the bottom of the eductor line. When the well yields clear sand-free water, the air line can be lowered to a point below the bottom of the eductor line and air introduced until the water between the eductor pipe and the casing is raised to the surface. At this time the air line should be raised back up into the eductor fine causing the water to be pumped from the well through the eductor line. The procedure of alternating the relative positions of the air and eductor line is repeated until the water yielded by the well remains clear when the well is surged and backwashed by this technique.
*From EPA-570/9-75001
Back to Contents
| 
