Current through Reg. 50, No. 187; September 24, 2024
Wells shall be grouted and sealed to protect the water
resource from degradation caused by movement of waters along the well annulus
either from the surface to the aquifer or between aquifers, and to prevent loss
of pressure in artesian aquifers. All wells shall be constructed and sealed
using a method which insures that an open or unnaturally permeable annular
space does not remain when a well is completed.
(1) All wells that are constructed in a
manner which creates an annular space between the casing and the naturally
occurring geologic formations will be grouted and sealed in accordance with the
methodologies listed in this section.
(2) Wells obtaining water from a formation
and having a casing less than four inches in outside diameter shall have a
nominal one inch thickness of grout sealing the annular space to ensure that an
open or unnaturally permeable annular space does not remain when the well is
completed.
(3) Wells having a
nominal casing size equal to or greater than four inches in outside diameter
and obtaining water from a formation shall have a nominal two inch thickness of
grout sealing the annular space for the entire length of casing.
(4) Wells obtaining water from a consolidated
formation and which are constructed using telescoping casings shall meet the
following conditions:
(a) The annular space
between the casings shall be sealed by grout, by packers or both as described
in subsection 40C-3.512(5),
F.A.C.
(b) The annular space
between each casing and the borehole shall be grouted in accordance with the
provision of subsections (1)-(3) above.
(c) For wells in which the largest external
nominal casing size is four inches or less and the annular space between the
internal casing and the borehole wall is less than one inch, the provisions of
subsections (1)-(3) above will not apply, provided that the clay formation
through which the internal casing passes is of such a caving nature so as to
naturally seal the annular space. If such caving nature is not present, the
provisions in subsections (1)-(3) above must be met. In all circumstances the
external casing must be grouted and sealed into a consolidated unit within the
intermediate confining unit.
(5) For wells constructed using a jetting
method and obtaining water from an unconsolidated formation of a naturally
caving nature in which the annular space is completely filled with formation
material, then only the upper three feet shall be grouted to provide protection
from contaminated surface water.
(6) Wells obtaining water from an
unconsolidated formation using a method other than jetting or driving a casing,
shall be grouted from the filter pack plug to the upper terminus with a grout
allowed in subsection
40C-3.517(8),
F.A.C.
(7) Cuttings shall not be
reintroduced into the annular space. Wells which breach confining units and
special monitor well installations will be grouted as outlined below.
(a) When confining units are breached and the
guidelines in subsection
40C-3.512(2),
F.A.C., are not met, the following practices will be acceptable:
1. Seating of a casing into the confining
unit and grouting as required, or
2. Placing of grout in the annular space to
meet subsection 40C-3.512(2),
F.A.C., requirements. When caving materials are present above and below the
confining unit, temporary casing or drilling fluids will be placed in the
borehole to maintain an opening to the confining unit.
In all circumstances, the annular space shall be maintained
by use of either drilling fluids or temporary surface casing until the
confining unit breach is plugged.
(b) Monitor wells required to comply with
Rule 62-761.640, F.A.C., which is
incorporated by reference in subsection
40C-3.036(5),
F.A.C., shall be grouted in the following manner:
1. The terminal box in traffic areas and well
casing shall be sealed to a depth of eighteen inches below land surface with
cement grout.
2. The well casing or
outside protective casing in high water table areas shall be grouted to a depth
of eighteen inches in a non-traffic area.
(8) Unless a variance has been granted by the
District, grouting and sealing of water wells shall be accomplished in the
following manner:
(a) The grout mixture shall
consist of either Portland Cement or a natural Bentonite slurry for wells and
boreholes meeting the requirements in subsection
40C-3.512(8),
F.A.C.
1. A mixture consisting of 5.5 to 6.0
gallons of water per sack of Portland Cement or a mixture of 6.5 gallons of
water per sack of Portland Cement with 3 to 5 pounds of Bentonite not to exceed
5% by weight will meet minimum requirements.
2. A mixture of 8-20-mesh granular Bentonite,
water, and an approved liquid polymer viscosifer or untreated 200-mesh
Bentonite and water is acceptable. In all circumstances, the manufacturer's
mixing instructions shall be followed.
(b) The minimum set time for grouting of
casing using either Portland Cement or Bentonite before drilling operations may
continue is 12 hours.
The minimum set time for grouting of casing using Portland
Cement and 2% calcium chloride by weight as an accelerator will vary with
depth. Set times are listed in Table 3 below. The addition of Bentonite as
specified in paragraph
40C-3.517(8)(a),
F.A.C., does not change the set times listed in Table 3.
TABLE 3 INITIAL SET TIMES FOR SPECIFIED DEPTH
RANGES
WHEN 2% CALCIUM CHLORIDE IS MIXED BY WEIGHT WITH
PORTLAND CEMENT
|
Depth
|
Set Time
|
|
(in feet)
|
(in hours)
|
|
0-200
|
4
|
|
201-400
|
3.5
|
|
401-600
|
3
|
|
601-800
|
2
|
|
801 & greater
|
1
|
(c)
Special application grout mixtures or depth of grout placement may require
adjustments in water per sack of cement, cement types, or additives. All
adjustments shall be approved by the District prior to use and will be based on
industry standards or recommendations.
(d) The casing shall be centered in the
borehole prior to grouting and sealing.
(e) In all cases grout will be introduced
into the annular space from bottom to top unless conditions in paragraph
40C-3.517(9)(e),
F.A.C., for abandonments are met. To assure that the grout will satisfactorily
seal the annular space, the contractor must employ one or a combination of the
following procedures:
1. The "Casing method"
by which a calculated volume of grout slightly greater than the volume of the
annular space of the entire length of casing is forced under pressure down the
inside of the casing, which is followed by a volume of water or mud necessary
to clear the grout from all but the last ten to fifteen feet of casing. This
should continue until a return of cement is observed in the annular space at
the upper terminus. If, after the set time has elapsed an open annular space
still exists the remaining void must be filled with grout.
2. The "Tremie method" in which a grout pipe
is lowered into the annular space to slightly above the bottom casing and grout
pumped through the pipe. As the pumping begins the tremie is gradually raised,
keeping the discharge end of the pipe submerged in the grout, until the grout
has been brought to the upper terminus. This procedure may be done in one
continuous operation or in stages. If, after the set time has elapsed, an open
annular space still exists the remaining void is to be filled with
grout.
3. The "Packer method" in
which a grout pipe is attached to a drillable packer and positioned at the
bottom inside the casing. The casing is then suspended above the bottom of the
borehole, and the grout is forced upward into the annular space either by pumps
or pneumatic pressure. Once the grout has reached land surface, the grout pipe
is disconnected. After the set time has elapsed, the operation is continued by
drilling out the packer and continuing into the next formation.
4. The "Halliburton method" in which the
grout is forced through the casing, preceded and followed by a "spacer" or
"piston." A calculated volume of grout is used to seal the annular space. A
measured amount of water equal to the volume of the entire length of casing is
used to force the second "spacer" to the end of the casing. After the set time
has elapsed the construction may continue by drilling out the
"spacers."
(f) In those
cases where, during grouting operations, circulation of the grout is lost so
that the annular space being grouted cannot be filled in one continuous
operation, a tremie pipe shall be installed in the annular space to a point
immediately above the zone of lost circulation. The annulus shall be bridged at
that point by sand and other suitable material introduced through the pipe
until a level is reached at which grouting can be
continued.
(9)
Abandonment procedures for water wells shall be undertaken in the following
manner:
(a) Portland Cement or natural
Bentonite slurry mixed as required in paragraph
40C-3.517(8)(a),
F.A.C., shall be pressure injected either from bottom to top by the methods
listed in paragraph 40C-3.517(8)(e),
F.A.C., or from top to bottom at the well head if the conditions in paragraph
40C-3.517(9)(e),
F.A.C., are met.
(b) Use of clean
aggregate to bridge cavernous or lost circulation zones may be allowed if
measurements indicate loss of grout and the borehole or screened portion does
not connect two or more producing units. Grouting of confining units is
required to segregate producing units of significantly differing water quality
as set forth in subsection
40C-3.512(2),
F.A.C.
(c) Proper sealing of the
casing seat must be accomplished by injecting grout where appropriate from a
point twenty feet below the seat to the upper terminus of the well. This depth
will be the minimum allowable in order to abandon a water well no matter what
cavity development is encountered below the casing seat unless the open hole is
less than twenty feet deep. In that case, the entire open hole will be
grouted.
(d) An abandonment plan
may be approved prior to the commencement of grouting if geophysical logs are
provided. The minimum logs required are caliper and natural gamma. Other logs
may be required or recommended based on individual well problems. The
contractor must notify the District at least 24 hours prior to commencement of
a District approved abandonment plan so that a District representative may be
on site to monitor the abandonment procedure.
(e) Abandonment by pressure injection of
Portland Cement or Bentonite from top to bottom at the well head will be
acceptable to the District if one of the following criteria is met:
1. Access to the site near the well head is
difficult as determined by District staff and will cause the contractor
excessive economic hardship;
2.
Overhead safety such as power lines or trees is of concern to the contractor or
District staff; or
3. Surface
stability is of concern around the well site due to collapse or cavity
development.
(10) Obstructions must be cleared in all
wells prior to grouting unless an alternate plan is approved by the District.
If a reasonable attempt cannot be made to clear the entire length of casing and
borehole or screen an alternative plan may be considered. A contractor must
supply the following minimum information to the District prior to abandonment:
well diameter, total depth, casing depth, and grout volume required. A District
representative may be on site to monitor the clearing of obstructions or to
observe the grouting. The contractor must notify the District at least 24 hours
prior to commencement of the abandonment.
(11) Wells constructed by methods which
require driven well casing are exempt from grouting and sealing guidelines set
forth in previous sections, provided that the following conditions are met:
(a) Casing is driven from land surface to its
final depth in a borehole smaller in diameter than the nominal outside diameter
of the casing used, or is driven from land surface to its final depth ahead of
the drill bit; and
(b) A drive shoe
in consolidated materials, or coupling in unconsolidated materials, is used;
and
(c) All annular space created
while the casing is being driven shall be sealed by adding dry Bentonite with
an average mesh size between 4 and 20 standard sieve size to the casing string
at land surface and allowing that material to be carried down the borehole as
the casing is driven. In all circumstances, dry Bentonite shall be added at the
full rate required to maintain an envelope of grout around the casing; and,
(d) Wells required to comply with
Rules 62-555.310,
62-555.312,
64E-8.002, or
64E-8.003, F.A.C., which are
incorporated by reference in subsections
40C-3.036(3)
-(4) and (6)-(7), respectively, shall have the bottom five feet underreamed
using either a commercially manufactured underreamer bit or an underreamer bit
constructed by a contractor and approved by the District in the following
manner: An underreamed borehole will be tested using a downhole caliper tool to
determine if the required two inch annular space has been achieved;
and,
(e) All other requirements are
met.
Rulemaking Authority
373.044,
373.113,
373.171 FS. Law Implemented
373.306,
373.308,
373.309
FS.
New 10-14-84, Amended 4-23-85, 12-5-85, Formerly 40C-3.517,
40C-3.0517, Amended 9-17-89, 7-27-16.
