La. Admin. Code tit. 56 § I-331

Current through Register Vol. 50, No. 8, August 20, 2024

Section I-331 - Well Development and Disinfection

A. Purpose and Methods of Development. The principal purposes of well development are as follows:

1. to remove silt, sand, drilling mud, and other materials that may retard the flow of water toward and into the well;

2. to correct any damages to, or clogging of, the water bearing formation that may have occurred during drilling; and

3. to stabilize the material around the screen so that the well will yield clear "sand free" water.

B. The following methods used in developing, redeveloping or conditioning a well are acceptable:

1. surging with a plunger or piston while jetting using air lift;

2. jetting with water, also known as crosswashing;

3. backwashing or surging by alternately starting and stopping the pump;

4. using chemicals designed for developing or redeveloping a well;

5. over-pumping.

C. The use of explosives is prohibited. Water used for well development shall be potable or chlorinated to prevent contamination of water-bearing formations.

D. Criteria for Development

1. A well should be developed at a yield of 1.5 times the proposed pumping rate and, if possible, it should continue until the observed specific capacity is the same, or nearly the same, as the theoretical specific capacity. Adequately developed wells should be "sand free" and should have fewer encrustation problems if the operating pumping rate is about two-thirds the developed rate, the entrance velocity is 0.1 foot per second or less, and the head differential across the face of the screen is at a minimum.

2. The acceptable amount of sand per unit volume should be between recommended ratios of 1 ounce of sand per 8,000 gallons of water (about 1 milligram per liter) and one ounce per 100 gallons of water (80 milligrams per liter), depending on the use of water. Because of the possibility of damage by sand to plumbing fixtures and industrial equipment and products, the tolerance for sand in water used for public supply, domestic and most industrial purposes is low and should not exceed 5 milligrams per liter. Many wells that are used for public water supply systems have an acceptable ratio of "no sand." The well owner should specify the acceptable limits of the "sand free" water with equal consideration given to the use of the water, the desired production rate, costs, and well development.

E. Development of Gravel-Packed Wells. The successful development of a gravel-packed well is dependent upon the grading of the gravel, the method of development, and thickness of the skin of the relatively impervious drilling mud filter cake which is "plastered" on the wall of the hole and is between the water-bearing formation, and the emplaced gravel. Because it concentrates energy in small areas, the jetting or cross washing method is usually the most effective in developing gravel-packed wells.

F. Chemicals Used in the Development Process

1. Glassy polyphosphate chemicals, if used strictly in accordance with the manufacturer's recommendation, will aid in the development or redevelopment process by reducing the gel-like properties of the drilling mud and by dispersing the clay particles that are on the sand grains.

2. The appropriate ratio of chemicals to water in the well is usually specified by the manufacturer. The mixture should be allowed to stand in the well for at least one hour, or the period of time recommended by the manufacturer of the chemical, before development starts. It should be noted that the polyphosphate should not be allowed to remain in the well for too long (several days). If the chemicals converted to the glassy orthophosphate state, any clay in suspension could be deposited, perhaps out of reach of any further removal, resulting in permanent reduction in yield.

3. Chemicals used in the development process shall either meet the standards of the American Water Works Association or be approved for use by the U.S. Environmental Protection Agency (EPA).

4. Disinfection of Wells. All new wells and existing wells in which repair work has been done shall be disinfected before being put into use, in accordance with Part XII of the State Sanitary Code (LAC 51:XII), if water is to be used for human drinking, cooking, washing or other potable purposes. Negative bacteriological analysis of water, performed by the Louisiana Department of Health and Hospitals, Office of Public Health (LDHH-OPH) or by a laboratory certified by the state health officer, shall be required for all public supply and domestic water wells.

La. Admin. Code tit. 56, § I-331

Promulgated by the Department of Transportation and Development, Office of Public Works, LR 1:249 (May 1975), amended LR 11:958 (October 1985), repromulgated by the Department of Transportation and Development, Office of Public Works, LR 31:942 (April 2005), amended by the Department of Natural Resources, Office of Conservation, LR 37:910 (March 2011), LR 37:3529 (December 2011).

AUTHORITY NOTE: Promulgated in accordance with R.S. 38:3091-R.S. 38:309.8.