Wells shall be grouted and sealed in accordance with subsection 62-532.500(3), F.A.C., (2-16-12), and this section, 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 artesian pressure in artesian aquifers. Subsection 62-532.500(3), F.A.C., (2-16-12) is incorporated by reference in subsection 40D-3.037(1), F.A.C.

1. (1) All wells that are constructed in a manner which creates an annular space between the casing and the naturally occurring geologic formations shall be grouted and sealed in accordance with the methodologies listed in subsection 62-532.500(3), F.A.C., and this section. The use of lead packers for this purpose is prohibited.

2. (2) Grouting and sealing of water wells shall be accomplished in the following manner using neat cement or bentonite grouts unless otherwise granted a variance by the District. The slurry grout mixture shall be introduced into the annulus space from bottom to top; the casing seat shall be clean allowing the casing to set at the total depth bored in a hole reasonably free of drill cuttings; the manufacturer’s mixing instructions shall be followed and any polymers added to bentonite slurry mixes must be approved by the District prior to use.

   1. (a) Grouting and Sealing Using Neat Cement Grout.

      1. Composition of neat cement grout shall consist of 5.2 to 5.5 gallons of water per cubic foot or 94-pound sack of Portland cement or a mixture of 6.0 gallons of water per sack of Portland cement with 3 to 7.5 pounds of Bentonite not to exceed eight percent by weight.

      2. The minimum set time for grouting of casing using neat cement grout before drilling operations may continue is twelve hours. The minimum set time for grouting of casing with Portland cement and two percent calcium chloride by weight as an accelerator will vary with depth and are listed in Table 1 below.

1. (b) Grouting and Sealing Using Bentonite Grouts.

   1. A Bentonite grout shall consist of a high solid sodium montmorillonite. The grout shall yield solids ranging from 20 to 30 percent, with a minimum density equal to or greater than 9.4 pounds per gallon, and a permeability of approximately 1 x 10-7 centimeters per second or less.

   2. Bentonite slurry grout used for sealing purposes is restricted to wells with an outside diameter of five inches or less in diameter nominal size. A formation packer or a five foot neat cement plug must be installed at the casing seat and an upper ten feet of neat cement is required to prevent deterioration of or damage to the bentonite seal.

   3. Bentonite grout used for abandonment purposes is not restricted by well size but cannot be used to abandon a dry well and cannot be placed any higher in the well than the height of the static water level. Any unsealed remainder above the height of the static water level must be filled with neat cement. At a minimum, an upper ten feet of neat cement is required to prevent deterioration of or damage to the bentonite seal.

   4. Only Bentonite grout approved by the National Sanitation Foundation is allowed on public supply wells or in any identified contamination areas. If artesian flow conditions occur, a neat cement plug shall be installed to stop the flow prior to the use of Bentonite grout. Use of Bentonite grout shall not be allowed in contaminated wells when the contaminants will prevent an adequate seal, or in wells with water quality concentrations exceeding 10,000 milligrams per liter total dissolved solids.

2. (3) For wells constructed by driving well casing, dry bentonite with an average mesh size between 4 and 20 U.S. standard sieve size or grain size between 5mm and .85mm must be added to the continuous casing string at land surface at the beginning and during construction of the well.

Rulemaking Authority 373.044, 373.113, 373.171, 373.309, 373.337 FS. Law Implemented 373.306, 373.308, 373.309 FS. History–New 7-1-90, Amended 9-30-91, 12-31-92, 12-12-11, 7-12-15.