Sec.25-128-48a. Annular space

(a) Unless otherwise specified in section 19-13-B51f of the Regulations of Connecticut State Agencies, any annular space between the outside of the piping or casing and the natural materials penetrated by a well or geothermal bore hole shall be filled with suitable material to make this space as impervious to the movement of fluids and competent to support the piping or casing as are the natural materials surrounding the well or geothermal bore hole. The annular space for a geothermal bore hole shall be grouted in accordance with subsection (g) of this section. The driller may fill the annular space with the natural materials excavated during the drilling of a water supply well to meet the following requirements:

(1) The annular space shall be filled as completely as possible from the bottom of the casing to the land surface without any depressions, voids, holes or channels;

(2) The driller shall employ whatever techniques are effective for the existing conditions to achieve maximum density, strength and impermeability of the fill material; and

(3) The surface of the fill material shall be sloped away from the casing.

(b) In locations where potentially contaminating or corrosive fluids are encountered, or impermeable natural materials cannot be adequately placed and compacted to where geologic conditions or the isolation distance may not be adequate, the annular space shall be grouted for the full length of the casing, or the portion thereof below the frost line or pitless adaptor, so that no fluids may move in the zone needing to be grouted.

(c) A well driller shall only use the following grouts in the process of drilling wells or geothermal bore holes, or in the abandonment of wells or geothermal bore holes:

(1) Bentonite cement grout: A mixture of cement grout or sand cement grout with a minimum of ten (10) per cent bentonite added to reduce shrinkage.

(2) Bentonite clay grout: A mixture of mined, processed bentonite clay and potable water with not less than two (2) pounds of bentonite clay for every gallon of water.

(3) Cement grout: A mixture of portland cement, sand, and potable water. The mixture is commonly composed of one (1) bag of portland cement weighing ninety-four (94) pounds, an equal volume of dry sand, and five (5) to six (6) gallons of water.

(4) Concrete grout: A mixture of portland cement, sand, gravel and water.

(5) Natural grout: A mixture of water and natural materials excavated during drilling of a well. The materials shall be placed by whatever techniques are effective for the existing conditions to achieve maximum density, strength, and impermeability of the fill material.

(6) Neat cement grout: A mixture of not more than six (6) gallons of water to one (1) bag of portland cement weighing ninety-four (94) pounds.

(7) Sand cement grout: A mixture of not more than two (2) parts sand to one (1) part portland cement, and not more than six (6) gallons of water to each ninety-four (94) pound bag of portland cement.

(8) Sand clay grout: A mixture of bentonite clay and sand in equal proportions, and water.

(d) Notwithstanding subsection (c) of this section, a well driller shall use salt water resistant grout to seal the annular spaces in a water supply well when such water supply well is located within seventy-five (75) feet of a roadway where road salt is applied or in a coastal area in which the water supply well may be subject to brackish or salt water. Any additives to the grout other than silica sand and water shall meet NSF International/American National Standards Institute standard 60.

(e) All closed-loop geothermal bore holes, upon installation of loop piping, shall be grouted with one of the following grouting materials:

(1) Grout 111, as developed by Brookhaven National Laboratories for use with copper piping typically employed in a direct exchange geothermal system, or as directed per manufacturer recommendations;

(2) High grade bentonite or thermally enhanced bentonite compounds based upon the manufacturer’s recommendation; or

(3) Other grouting materials approved by the department in consultation with the Department of Public Health.

(f) Grouts shall be mixed and installed in accordance with the manufacturer’s specifications. Grouts may be used whether consolidated or unconsolidated formations are encountered. All closed-loop geothermal system bore holes shall be grouted within seven (7) days of the completion of drilling. After installation of piping, the bore hole shall be covered with a protective layer of grout at least one (1) foot thick and three (3) feet in diameter, centered over the bore hole. Detectable underground tape shall be installed above all bore hole locations.

(g) All closed-loop geothermal system bore holes shall be filled using the tremie method. The entire bore hole shall be filled with grout beginning at the bottom of the bore hole. The tremie employed shall be properly sized for the type of grout used, the ground conditions encountered, and the type of loop system installed. The minimum bore hole diameter shall be that specified by the manufacturer and subject to industry approved standards. Drilling mud and cuttings shall not be mixed into the bore hole.

(Effective May 21, 1993; Amended July 8, 2022)