The annular space between the protective well casing and the wall of
the drilled hole or the surface casing shall be effectively sealed to protect
against contamination or pollution by surface and/or shallow subsurface waters.
This shall be accomplished in accordance with guidelines set forth below:
A. Depth of seal.
(1) Following is the minimum depth of seal below ground surface
for various uses of wells:
|
Type
|
Depth of Surface Seal
(feet)
|
---|
|
Local water supply wells
|
20
|
|
Domestic wells
|
6
|
(2) Exceptions are shallow wells where the water is at a
depth less than 20 feet. In this instance, the depth of seal may be reduced,
and special precautions shall be taken in locating the well with respect to
possible sources of contamination.
(3) The annular space shall be sealed to a minimum depth of 20 feet from the surface of the ground when the well is close to individual domestic wells or to sources of contamination or pollution described in §
480-8. Local conditions, such as the existence of shallow subsurface waters of undesirable quality, may warrant consideration of sealing the annular space around agricultural wells.
B. Sealing conditions. Following are requirements for sealing
the protective casing of a well:
(1) Wells that penetrate unconsolidated material.
(a) Driven wells or well construction by cable tool method. The temporary surface protective casings may function as the seal, provided that the length of casing corresponds to the depth of seal specified in Subsection
A of this section.
(b) Rotary, auger or jetted well construction. The annular space between the hole or surface or temporary casing and the protective casing shall be filled with sealing material to the depth specified in Subsection
A of this section.
(2) Wells that penetrate impervious formations. If a consolidated formation or an impervious unconsolidated formation is encountered within five feet of the specified depth of seal described in Subsection
A of this section, the seal should extend at least five feet into the impervious formation.
(3) Gravel-packed wells. The gravel pack of gravel-packed
wells shall terminate at the base of the protective seal.
(4) Wells penetrating consolidated rock. A hole of sufficient
diameter to accommodate protective casing must be constructed and the annular
space between the rock and casing sealed to depth specified in this section:
(a) Sealing material.
[1] The sealing material shall consist of neat cement, cement
grout, puddled clay or concrete. Organic polymer muds shall not be allowed.
The neat cement mixture shall be composed of one bag of Portland Cement (94
pounds) to five to seven gallons of clean water. Quick setting cement, retardants
to setting and other additives, including hydrated lime to make the mix more
fluid (up to 10% of the volume of the cement) and Bentonite (up to 5%) to
make the mix more fluid and to reduce shrinkage, may be used. Concrete used
shall be Class B (six sacks to the cubic yard) or Class B (five sacks to the
cubic yard).
[2] Clay in the form of a mud-laden fluid is similar to and
has the advantage of neat cement and cement grout. There is a disadvantage
in that clay may separate out of the fluid. A Bentonite-gelatenous mud is
recommended. Concrete is useful in sealing large diameter wells, particularly
where the width of annular ring is several inches or more. However, unless
care is exercised during placement, the coarse aggregate may become separated
from the cement.
(b) Thickness of seal. The thickness of the seal shall be
at least one inch, and not less than three times the size of the largest coarse
aggregate used in the sealing material.
(c) Placement of seal. The sealing material shall be installed
in one continuous operation from the bottom of the interval to be sealed to
the top.
(d) Sealing casing into bedrock. For all wells which terminate
in bedrock, a permanent casing shall extend from six inches above the ground
or floor of a pit into bedrock a minimum of 10 feet below the bedrock surface.
A well installed in an unconsolidated sand and gravel aquifer commonly
has a screen. Screen openings shall be properly sized, based on sieve analysis
of material at the screen depth. The well shall be properly developed to produce
sand-free water at the pumping rate of the permanent pump.
Where a well penetrates aquifers separated by confining layers and any
of the aquifers contain water that would be a contaminant, contaminated strata
shall be sealed to prevent entrance of the water into the well or its migration
to other aquifer(s).
A. The contaminated stratum shall be sealed by placing impermeable
material in the annular space between the protective casing and the contaminated
stratum. The seal shall extend into the upper and lower confining formations
for a sufficient vertical distance to prevent the vertical movement of water
from the producing formation. Sufficient sealing material shall be installed
to fill the annular space between the casing and the wall in the drilled hole
along the sealed interval and to fill the voids which might absorb sealing
material. Sealing material shall be placed from the bottom to the top of the
sealed interval.
B. Sealing material shall consist of neat cement, cement grout or other suitable impermeable material. See §
480-10B(4)(a).
All local water supply, domestic and industrial wells shall be disinfected
following construction, rehabilitation and well pump repair before the well
is placed in service. The well shall be pumped to waste until the water is
as clear as possible. Thereafter the well and pumping equipment shall be disinfected
with a solution containing at least 50 parts per million of chlorine. The
well shall remain in contact with chlorine solution a minimum of 24 hours
before the well is pumped to waste and chlorine flushed from the distribution
system. All water used in well drilling shall be disinfected.
A well shall be plumb to allow proper installation and pump operation.
Whenever there is an interruption in work on the well such as overnight
shutdown, inclement weather, waiting periods for the setting up of sealing
materials or concrete, tests, installation of the pump, etc., the well opening
shall be closed with a cover to ensure the public safety. During interruptions
of one week or more, a semipermanent cover shall be installed. For a well
cased with steel, a steel cover, tack-welded to the top of the casing, is
adequate.
Water used for cooling parts of engines, air compressors or other equipment
or water used for air conditioning shall not be returned to any part of a
potable water system or potable aquifer unless the water was obtained from
the same aquifer into which it is being discharged and the discharge water
is of equal or better mineralogical and bacteriological quality as the source.
All deepening or repair of wells shall meet all the requirements included
in these regulations and shall be done with a permit.
Installation of a water storage reservoir, but not an approved water
pressure tank, requires approval of and a permit from the Board of Health
or its agent.
An owner or occupant using a polluted water supply or a supply that
represents a health hazard shall be notified of the health hazard, in writing,
by the Board of Health or its agent (MGL C. 111, § 122A).
Permission may be granted by the Board of Health or its agent to use
springs, infiltration tile lines or other sources as a water supply or to
install water treatment facilities. Plans and specifications for such facilities,
together with operating procedures, shall be approved by the Board of Health.
A physical connection is not permitted between a water supply meeting the
requirements of these regulations and another water supply that does not meet
such requirements without prior approval of the Board of Health.