Current through Register Vol. 50, No. 9, September 20, 2024
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.
AUTHORITY NOTE:
Promulgated in accordance with
R.S.
38:3091-R.S.
38:309.8.
