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

1. (1) Casing Material. If permanent casing is needed in a heat pump well, it must meet standards set out in 10 CSR 23-3.030 for steel and 10 CSR 23-3.070 for plastic and must 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 ground or into a body of water must be composed of high density polyethylene or polybutylene pipe and must be installed and grouted without delay upon completion of drilling of 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 (.0091–.0092) grams per centimeter (g/cm));

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

sandths to seventy-five thousandths (.0025–.0075) gallons per ten (10) minutes (g/10 min)).

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.

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

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

      1. 1. Pure glycerine solution—glycerine

must be ninety-six and one-half percent (96.5%) United States pharmacopoeia grade;

1. 2. Food grade propylene glycol;
2. 3. Dipotassium phosphate;
3. 4. Sodium chloride;
4. 5. Potassium acetate;
5. 6. Methanol;
6. 7. Water;
7. 8. Ethanol; or
8. 9. Other fluids may be used if approval

by the division is received in advance;

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. Not have a toxicity that is less than

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

1. 7. Show neither separation from expo-

sure to heat or cold, nor show an increase in turbidity; and

1. (C) While this rule attempts to define antifreeze fluids that will protect the environment, it is the responsibility of the permittee to become familiar with safe and proper use of these fluids and to take necessary precautions to ensure groundwater protection.

1. (5) Hole 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. The slurry must fill the hole and surround all pipes. There must be at least onehalf 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) Hole Depth. Closed-loop heat pump wells must not be deeper than two hundred feet (200'). A variance must be obtained in advance, from the division, to drill a heat pump well deeper than two hundred feet (200'). A heat pump well drilled in Area C (see 10 CSR 23-3.100(3)) that is less than two hundred feet (200') deep and cuts the Northview Formation must have a thirty-foot (30') grout plug set starting at ten feet (10') below the bottom of the Northview Formation. A map will be provided by the division showing the depth the grout plug must start. Follow the grouting requirement set out in 10 CSR 23-5.050(8) for grouting the interval above the Northview Formation.
3. (7) Heat Pump System Design. The heat pump system that utilizes wells must be designed so that the grout used to seal the wells does not dehydrate because of excessive heat caused by an improperly designed heat pump system.
4. (8) Grouting Depth of Vertical Heat Pump Wells. Grouting the annulus of a heat pump well is very important and must be completed immediately after the well is drilled due to cave-in potential in the uncased hole. Fulllength grout is recommended and may be required (see section (5)) to prevent surface contamination from entering the drinking water aquifer through the borehole. The grout required for heat pump wells greater than two hundred feet (200') in depth must be determined by the division in advance. A variance form will be issued setting the grouting requirements. If the heat pump borehole is not grouted full-length, hole size requirements stated in section (5) must be followed and nonslurry bentonite plugs must be placed into the borehole. A plug (first plug) must be placed about forty feet (40') above the total depth of the borehole. This plug must be composed of bentonite chips or pellets utilizing at least one (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 after emplacement if they are in the unsaturated zone. All clean fill material placed between the bentonite plugs must be chlorinated.

5. (9) 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. Specialized pumps are required to pump a high solids bentonite slurry. When bentonite slurry is used, it must be applied in one (1) continual motion, through a tremie lowered to the grouting point. It is recommended that full-length grout be used in all vertical closed-loop heat pump wells. The tremie pipe may be removed while the borehole is filled or removed afterward;
   2. (B) Nonslurry Bentonite. Chipped or pelletized bentonite varieties that are designed to fall through standing water may only be used when sealing the annulus of a well that is below the water level in the saturated zone. Complete hydration is difficult to achieve when using dry nonslurry bentonite in the unsaturated 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. The effective use of nonslurry bentonite as a sealing agent depends on the efficient hydration of the product;
   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. The grout slurry mixture must exhibit a thermal conductivity greater than 0.85 Btu/hr. ft. degree F and permeability not more than 1 × 10-7 cm/s. Specialized pumps are required and the slurry mixture must be installed full-length through a tremie lowered to an initial grouting point within twenty feet (20') of the base of the borehole; and
   4. (D) Other Grout. Other types of grout may be used if approval is granted in advance by the division.
6. (10) Wells That Encounter Karst Conditions. When a borehole encounters caves or large fractures, grouting may become difficult. Small fractures are effectively sealed by using chipped bentonite. Clean fill (gravel, sand, and the like) may be used to fill these intervals. If the borehole cannot be grouted as specified, it must be plugged and a new location chosen. The heat pump loop can be redesigned for shorter boreholes not encountering these conditions.
7. (11) Jetted Heat Pump Wells. Closed-loop heat pump wells that are jetted in Area 5 (see Figure 5) must not be deeper that seventy-five feet (75') and at least the upper ten feet (10') of borehole must be grouted.

AUTHORITY: sections 256.606 and 256.626, RSMo 2000.* 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. *Original authority: 256.606, RSMo 1991 and 256.626, RSMo 1985, amended 1991.