40C-3.517. Grouting and Sealing

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. History–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.