PURPOSE: This rule describes the minimum standards for a properly constructed closedloop heat pump well.

1. (1) Casing, when used, shall follow the minimum standards pursuant to 10 CSR 23- 3.030(1)(A) and be grouted full-length.

2. (2) Heat Pump Loop Material. In a closedloop heat pump well, the material used to make up the heat-exchange loop that is placed in the borehole or trench must be composed of high density polyethylene or polybutylene pipe and must be installed and grouted without delay upon completion of drilling each well.

   1. (A) High Density Polyethylene Pipe. This pipe must be manufactured in accordance with dimensional specifications of ASTM D- 2513 or ASTM F-714 and must have a minimum cell classification of PE345434C or PE355434C when tested under ASTM D- 3350 to be acceptable for use in closed-loop heat pump systems.

   2. (B) Polybutylene Pipe. This pipe must be manufactured in accordance with ASTM D- 2581. The pipe material must be—

      1. 1. Either Class B (general purpose and

dielectric, in colors) or Class C (weather resistant, black in color containing not less than two percent (2%) carbon black);

1. 2. Type II (density, ninety-one thou-

sandths to ninety-two thousandths (0.091– 0.092) grams per centimeter (g/cm));

1. 3. Grade 1 (flow rate twenty-five thou-

sandths to seventy-five thousandths (0.025– 0.075) gallons per ten (10) minutes (g/10 min)).

1. (C) Other pipe may be used upon advanced written approval by the department.

1. (3) Connecting Closed-Loop Pipe. Polyethylene and polybutylene pipe must be thermally fused according to the pipe manufacturer’s specifications and must not leak after assembly.

   1. (A) Other connection methods may be used upon advanced written approval by the department.

2. (4) Heat Transfer Fluid. The fluid used inside the closed-loop assembly must meet the following standards:

   1. (A) Heat transfer fluids must be composed of—

      1. 1. Inhibited glycol;
      2. 2. Methanol;
      3. 3. Water;
      4. 4. Ethanol; or
      5. 5. Other fluids may be used upon

advanced written approval by the department.

1. (B) The fluid as it is used in a diluted state in the closed-loop must have the following properties:

   1. 1. Be ninety percent (90%) biodegrad-

able;

1. 2. Demonstrate low corrosion to all

materials common to ground source heat pump systems;

1. 3. Be homogeneous, uniform in color,

free from lumps, skins, and foreign material that would be detrimental to fluid usage;

1. 4. Not have a flash point lower than

ninety degrees Celsius (90°C);

1. 5. Not have a five- (5-) day biological

oxygen demand (BOD) at ten degrees Celsius (10°C) that exceeds two-tenths (0.2) gram oxygen per gram nor be less than one-tenth (0.1) gram oxygen per gram;

1. 6. Have a toxicity that is less than the

lethal dose (LD) of fifty (50) oral-rats of five (5) grams per kilogram; and

1. 7. Show neither separation, or increase

in turbidity, from exposure to heat or cold; and

1. (C) While this rule attempts to define antifreeze fluids that will protect the environment, it is the responsibility of the permittee to take necessary precautions to ensure groundwater protection.

1. (5) Borehole Size. The hole size for heat pump wells that are grouted full-length with high solids bentonite slurry (see 10 CSR 23- 5.050(9)(A)) must be of sufficient size to allow placement of the pipe and placement of a tremie to emplace the high solids bentonite slurry grout. The slurry must be pumped via tremie to fill the hole and surround all pipes. There must be at least one-half inch (1/2") between the hole and all pipes. If full-length high solids bentonite slurry is not used, then the following hole sizes are required:

   1. (A) At least a six-inch (6") borehole when the loop pipe is one and one-quarter inch (1 1/4") or greater in diameter;
   2. (B) At least a five-inch (5") borehole when the loop pipe is less than one and one-quarter inch (1 1/4") in diameter.
2. (6) Borehole Depth. Closed-loop heat pump wells must not be deeper than five hundred feet (500'). Total depth of a new heat pump well in Drilling Area 12 (formerly Special Area 3) and Drilling Area 13 (formerly Special Area 4) shall be determined in advance of drilling by the department.

3. (7) Grouting Depth of Vertical Heat Pump Wells. Grouting the annulus of a heat pump well must be completed immediately after the well is drilled due to cave-in potential in the uncased hole.

   1. (A) Vertical heat pump wells require the annular space between the loop material, borehole, and/or casing to be grouted full length using materials in 10 CSR 23- 5.050(8).
   2. (B) Vertical heat pump wells drilled two hundred feet (200') or less that are not grouted full-length must follow the hole size requirements stated in section (5) and nonslurry bentonite plugs must be placed in the borehole. A plug (first plug) must be placed forty feet (40') above the total depth of the borehole. This plug must be composed of bentonite chips or pellets utilizing at least one
4. (1) bag of bentonite resulting in at least a five foot (5') plug. Every forty feet (40') of borehole that exists above the first plug must have a plug set as described in this section. A near surface plug, consisting of bentonite granules or powder, must be set from a point ten feet (10') below the bottom of the trench that connects the closed-loop to the heat pump machine to the base of the trench. All bentonite plugs must be hydrated immediately with six to eight (6–8) gallons of potable water for each bag of bentonite after emplacement if they are in the unsaturated zone. All clean fill material placed between the bentonite plugs must be chlorinated. Clean fill is defined as sand, local drill cuttings, pea gravel, varied sized agricultural lime, or clean aggregate free from contamination. Contractors utilizing this type of grouting method must notify the department at least forty-eight (48) hours prior to beginning any construction on the system. The department will maintain a list of current notification methods (includes, but is not limited to, telephone, fax, email, voice mail, and the department’s online notification system) and contact information available online or upon request. Notification information must include: owner name, owner address, GPS location, date work is to begin, primary contractor name, primary contractor permit number, drilling contractor name, and drilling contractor permit number.

5. (8) Approved Grout Materials. The following four (4) grout types are permitted for use in heat pump wells:

   1. (A) Bentonite Slurry. High solids sodium bentonite slurry must be at least twenty percent to thirty percent (20%–30%) by weight solids to be used as grout. Thickened drilling mud or thinner bentonite slurry is strictly prohibited. When bentonite slurry is used, it must be applied in one (1) continual motion, through a tremie lowered to the grouting point;
   2. (B) Nonslurry Bentonite. Only chipped or pelletized bentonite may be used when sealing the annulus of a well that is below the water level in the saturated zone. All nonslurry sodium bentonite varieties may be used in the unsaturated zone if the hole is dry and no bridging occurs. The dry bentonite must be hydrated after emplacement;
   3. (C) Thermal Grout Slurry. Grout containing at least seven and one-half percent (7.5%) by weight bentonite solids and no more than sixty-five percent (65%) by weight silica solids may be used as grout. Specialized pumps are required to pump thermal grout slurry through a tremie lowered to within twenty feet (20') of the base of the borehole; and
   4. (D) Other Grout. Other types of grout may be used if advanced written approval is obtained by the department.
6. (9) Wells that Encounter Karst Conditions. When a borehole encounters caves or larger fractures, chlorinated clean fill, such as gravel or sand, may be used to fill these intervals. Small fractures are effectively sealed by using chipped, hydrated bentonite. If the borehole cannot be grouted as specified, it must be plugged.
7. (10) Jetted Heat Pump Wells. Closed-loop heat pump wells that are jetted in Drilling Area 5 (see Figure 5) must have a minimum top grout plug of ten feet (10').
8. (11) Heat Pump Wells in Drilling Area 12 (formerly Special Area 3) may be constructed provided advanced written approval is obtained from the department pursuant to 10 CSR 23-3.090(12).
9. (12) Heat Pump Wells in Drilling Area 13 (formerly Special Area 4) may be constructed provided advanced written approval is obtained from the department pursuant to 10 CSR 23-3.090(13).

AUTHORITY: sections 256.606 and 256.626, RSMo 2016.* Emergency rule filed Nov. 16, 1993, effective Dec. 11, 1993, expired April 9, 1994. Original rule filed Aug. 17, 1993, effective March 10, 1994. Amended: Filed July 13, 1994, effective Jan. 29, 1995. Amended: Filed Nov. 1, 1995, effective June 30, 1996. Amended: Filed Dec. 16, 2002, effective June 30, 2003. Emergency amendment filed March 21, 2005, effective April 1, 2005, expired Sept. 27, 2005. Amended: Filed Sept. 27, 2005, effective April 30, 2006. Amended: Filed Jan. 4, 2007, effective Aug. 30, 2007. Amended: Filed May 17, 2013, effective Dec. 30, 2013. Amended: Filed June 27, 2018, effective Feb. 28, 2019.

*Original authority: 256.606, RSMo 1991 and 256.626, RSMo 1985, amended 1991.