Section 144-232-6-600.0 - CLOSED LOOP WELLS600.1Scope: This Chapter governs the location and construction of closed-loop geoexchange wells.600.2Variances: Variances from the standards outlined in these Rules for geoexchange wells must be approved by the Commission in advance using the procedures and forms used for Specialty Wells.601.0SETBACK DISTANCES601.1 Setback distances: Setback distances for closed loop geo-exchange wells are as follows: Leach fields less than 2,000 gpd: 50 feet
Leach fields equal to/greater than 2,000 gpd: 100 feet
Septic tanks, lift stations & holding tanks: 30 feet
Private potable water supply well: 45 feet
Public potable water supply well with a withdrawal rate equal to or less than 10 gpm: 45 feet
Public potable water supply well with a withdrawal rate greater than 10 gpm but equal to or less than 25 gpm: 75 feet
Public potable water supply well with a withdrawal rate greater than 25 gpm but equal to or less than 50 gpm: 125 feet
Public potable water supply well with a withdrawal rate greater than 50 gpm: 200 feet
(Withdrawal rate is determined based on the nominal size of the actual well pump installed in the well) Property lines: 10 feet
602.0GROUT602.1Placement method: Thermally enhanced grout shall be placed by the tremie method with the tremie first installed to the bottom of the borehole. Grout shall then be placed by pressure pumping through the tremie and the tremie should be raised slowly as the material is introduced. The tremie pipe should be continuously submerged in the grout. All grout shall be emplaced to the maximum extent possible in a single continuous operation upward from the bottom of the borehole so the entire length of the borehole is filled with grout.602.2Coefficient of permeability: All thermally enhanced grout shall have a maximum coefficient of permeability of 10-7 cm/sec.602.3Grouting timeframe: All boreholes are recommended to be grouted within seven (7) days from the date they are drilled.602.4Loss of grout: When a significant loss of grout is observed to large open bedrock fractures, it is generally permissible to place clean crushed stone into the annulus from the bottom of the bedrock fracture to as much as 10 feet above the fracture before resuming with the placement of the thermally enhanced grout. When a driller chooses to place stone into the annulus in these situations, the driller shall record the location of the fracture and the specific interval in the borehole where stone is placed, instead of grout, on the driller's log.602.5Grouting near bedrock surface: The annulus of a closed-loop well must always be grouted from a depth ten feet below the top of bedrock to at least ten feet above the top of bedrock to prevent the migration of shallow ground water down the borehole to the bedrock aquifer. It is not permissible to place stone in this interval if large open fractures are present.602.6Salt water resistant grout: When grout extends through zones of saltwater with chloride concentrations equal to or greater than 500 mg/l, a salt water resistant grout shall be used.602.7Grout additives: Any grout additives, other than bentonite, silica sand and water shall meet the requirements of NSF/ANSI Standards 60 and 61.603.0HEAT TRANSFER FLUIDS603.1Water used: Any water used as a heat transfer fluid shall be from a potable water supply.603.2Propylene glycol: It is recommended that food grade propylene glycol be used as an antifreeze material and that it be used at 20% or more concentration to inhibit bacterial growth.604.0CLOSED-LOOP PIPING604.1Piping certification: Piping shall be as specified in the most recent edition of the International Ground Source Heat Pump Association (IGSHPA) Closed Loop/Geothermal Heat Pump Systems Design and Installation Standards, 2010 Edition, Copyright, 2010, referenced in these regulations as "IGSHPA standards".604.2High density polyethylene: All pipe and heat fused materials should be manufactured from virgin polyethylene extrusion compound material in accordance with IGSHPA standards. Pipe should be manufactured to outside diameters, wall thickness, and respective tolerances as specified in IGSHPA standards for Polyethylene (PE) Plastic Pipe (DR-PR) Based on Controlled Outside Diameter, IGSHPA standards for Polyethylene (PE) Plastic Pipe, Schedules 40 and 80, Based on Outside Diameter, or IGSHPA standards for Polyethylene (PE) Plastic Pipe (SDR-PR) Based on Outside Diameter. Fittings shall be manufactured to diameters, wall thickness, and respective tolerances as specified in IGSHPA standards for Butt Heat Fusion Polyethylene (PE) Plastic Fittings for Polyethylene (PE) Plastic Pipe and Tubing for butt-fusion fittings, IGSHPA standards for Socket-Type Polyethylene Fittings for Outside Diameter-Controlled Polyethylene Pipe and Tubing for socket-fusion fittings and IGSHPA standards for Electrofusion Type Polyethylene Fittings for Outside Diameter Controlled Polyethylene Pipe and Tubing for electro-fusion fittings. Table 604.1 Pressure ratings and applicable standards for high density polyethylene pipe:
| Nominal Diameter | Pressure Rating (psi) at 73.4[DEGREE]F | Applicable Standard |
| < 11/14 in. | 160 | IGSHPA standards |
| 11/14 - 3 in. | 110 | IGSHPA standards |
| > 3 in. | 100 | IGSHPA standards |
(1) If the pipe is used in a vertical bore application, it should be manufactured in accordance with IGSHPA standards with a minimum working pressure rating of 160 psi. Table 604.2: Pressure ratings of water filled pipe at 73.4[DEGREE]F for DR-PR PE 3408/3608 plastic pipe:
| Dimension Ratio | Pressure Rating (psi) |
| 9 | 200 |
| 11 | 160 |
| 13.5 | 128 |
| 15.5 | 110 |
| 17 | 100 |
Table 604.3: Pressure ratings of water filled pipe at 73.4[DEGREE]F for DR-PR PE 47102 plastic pipe:
| Dimension Ratio | Pressure Rating (psi) |
| 9 | 252 |
| 11 | 202 |
| 13.5 | 161 |
| 15.5 | 139 |
| 17 | 126 |
| 21 | 101 |
(2) Please note that as of the IGSHPA approval date (October 2007) of DR-PR PE 4710, there are a limited number of pipe manufacturers offering a geothermal pipe produced from DR-PR PE 4710 material. 604.3Material: The material should have a Hydrostatic Design Basis of 1600 psi at 73[DEGREE]F per IGSHPA standards and should be listed in PPI TR4 as either a PE 3408/3608 or PE 4710 piping formulation. The material should also be a high-density polyethylene compound having a minimum cell classification of PE345464C per IGSHPA standards for.604.4Markings: Sufficient information should be permanently marked on the length of the pipe as defined by appropriate IGSHPA pipe standard(s).604.5Cross-linked polyethylene tubing: Cross-linked polyethylene tubing should be manufactured by the high-pressure peroxide method (PEXa), and should conform to IGSHPA standards for Crosslinked Polyethylene (PEX) Tubing, and IGSHPA standards for Crosslinked Polyethylene (PEX) Plastic Hot- and Cold-Water Distribution Systems, or Crosslinked high-density polyethylene (PE-X) pipes-General quality requirements and testing. PEXa material should be high-density cross-linked polyethylene manufactured using the high-pressure peroxide method of cross-linking (minimum degree of 75% when cross-linking and tested in accordance with IGSHPA standards for Test Methods for Determination of Gel Contentand Swell Ratio of Crosslinked Ethylene Plastics, (Method B)). The tubing material designation code as defined in IGSHPA standards should be PEX 1006 or PEX 1008. Table 604.4: Pressure ratings of water filled tubing at 73.4[DEGREE]F (23[DEGREE]C) for DR-PR PEX 1006 or PEX 1008 plastic pipe:
| Dimension Ratio | Pressure Rating (psi) | Applicable Standard |
| 9 | 160 | IGSHPA standards |
604.6Polymer electro-fusion fitting material: All fittings used with PEXa tubing intended for geothermal applications should be polymer electro-fusion fittings or cold expansion compression-sleeve metal fittings. Polymer electro-fusion fittings should conform to IGSHPA standards for Plastics pipes and fittings. Crosslinked polyethylene (PE-X) pipe systems for the conveyance of gaseous fuels. Metric series. Specifications. Part 2: Fittings for heat-fusion jointing-First Edition. Polymer electro-fusion fittings for PEXa pipes of each dimensional specification should conform to IGSHPA standards. Polymer electron-fusion fitting should also be manufactured using materials in accordance to IGSHPA Standard 1C.2.2.604.7Metal cold compression sleeve fittings:Metal cold compression sleeve fittings should conform to IGSHPA standards for Cold-Expansion Fittings with Metal Compression-Sleeves for Cross-Linked Polyethylene (PEX) Pipe. Cold compression sleeve fittings should conform to IGSHPA standards, and have a minimum inside diameter of 82% of inside pipe diameter.
604.8Markings: Product standard information should be marked on PEXa tubing and fittings as defined by the appropriate product standard specifications.604.9Joining: Joining should be as specified in International Ground Source Heat Pump Association (IGSHPA) Closed Loop/Geothermal Heat Pump Systems Design and Installation Standards. The most current edition of standards should be utilized and followed. All pipe joining should be performed by certified installers and follow manufacturers' recommended fusion procedures.604.10Polyethylene pipe: Polyethylene fusion transition fittings with threads should be used to join with copper. Polyethylene fusion transition fittings with threads or barbs should not be used to join to high strength hose. Barbed fittings utilizing mechanical clamps are not permitted to be connected directly to polyethylene pipe, with the exception of stab-type fittings. All mechanical connections must be accessible in case of emergency or maintenance. The only acceptable methods for joining buried polyethylene pipe systems are a heat fusion process or stab-type fittings. If using stab-type fittings, quality control should be assessed to ensure a leak-free union between pipe ends which are stronger than the pipe itself. If heat fusing, butt, socket, sidewall or electro-fusion processes are acceptable when performed in accordance with the pipe manufacturer's procedures.604.11Cross-linked polyethylene tubing: PEXa tubing should not be butt-fused or socket-fused to fittings. Polymer electro-fusion fittings may be used with PEXa tubing when installed in accordance with the manufacturer's published procedures. Cold-expansion compression sleeve fittings may also be used for all PEXa connections when installed according to the manufacturer's published procedures and is permitted to be direct buried with manufacturer-approved corrosion covering. New joining technologies may be developed which meet all IGSHPA standards for closed loop piping.604.12Centralized placement: Due to the flexible nature of the piping material, geology, and borehole geometry, centralized placement of pipe in the borehole may or may not be practical. In general, pipe centralized placement is not necessary for closed loop boreholes.604.13Placement to the bottom of the borehole: Due to the specific gravity of the loop piping, it may be necessary to artificially weight the pipe loop to allow placement to the bottom of the borehole. External weights shall be attached to the pipe in a manner that does not damage the pipe. Only potable water may be placed inside the pipe to add weight to the pipe loop. Using steel pipe for the tremie can assist in the placement to the bottom.
The loop assembly shall extend to the bottom of the borehole. If an obstruction is encountered in the borehole, preventing the installation of the loop to the borehole bottom, the loop and the obstruction must be removed or provisions made for the sealing of the borehole below the obstruction and the designer needs to be notified so adjustments can be made to the design of the system.
604.14Header backfilling: Because the contractor is motivated to produce a leak-free system, backfilling procedures for horizontal header trenches will include prevention of any sharp-edged rocks from coming into contact with the piping by removal of the rocks before backfilling. Sand bedding (native or foreign) is recommended for headers.604.15Pressure and flow testing: The entire system should be filled with water and tested to the system pressure recommended by manufacturer specifictions for that loop with no observed leaks prior to backfilling the loop field connection trenches. Flow and pressure loss testing should be performed and the actual flow rates and pressure drops should be compared to the calculated design values. If actual flow rate or pressure drop values differ from calculated design values by more than 10%, the problem should be identified and corrected. At the contractor's option, in addition to the final test, it may be desirable to test subcircuits of the loop field. Pressure in the pipe is greater at the bottom of the borehole than at the top due to the hydrostatic head. Caution should be exercised if hydrostatically testing vertical loops in boreholes of depths greater than 200 feet that have not been grouted or filled so as not to exceed the pressure rating of the pipe material. The pressure in the pipes being tested can vary with changes in temperature or from normal expansion of the pipe after being first pressurized. Approved pressure test procedures cannot guarantee that proper fusion/joining techniques or procedures were followed. Additional tests may be required by the overseeing engineer.604.16Temporary conditions: Any vertical closed loop piping that is completed prior to being placed in service, or is left uncompleted due to a recess or delay in construction, shall be equipped with a watertight cap.605.0CASING IN CLOSED-LOOP WELLS605.1Temporary Casing: Temporary casing shall be installed through the overburden and into bedrock.605.2Temporary casing removal: Temporary casing shall remain in place until the closed loop is installed and the borehole completely grouted to the ground surface.605.3Final grouting: After the removal of the temporary casing, the grout shall be topped off back to ground level.606.0DECOMMISSIONING606.1Grouting an abandoned closed-loop geoexchange well: Any vertical closed-loop geoexchange borehole that is to be permanently abandoned shall be completely flushed and filled with a suitable grouting material.606.2Loop fluids: Loop fluids that contain antifreeze or other additives shall be captured and disposed of according to local, state and federal requirements.606.3Decommissioning documentation: All information relative to the decommissioning procedures of the abandoned vertical loop piping shall be prepared and assembled, with a copy supplied to the owner of the land and a copy retained by the licensed closed-loop driller who performed the decommissioning.607.0DRILLER'S LOGS & SITE PLANS607.1NGWA standards: For closed-loop wells, follow the NGWA recommended practices listed as follows: 607.1.1Minimum driller's log requirements: During the drilling of the test borehole or the first vertical loop borehole, the contractor shall prepare and keep a complete log setting forth the following:1. The geographic location sufficient to permit later location and identification relative to other boreholes or wells in the area;2. The reference point for all depth measurements;3. The depth at which each change of formation occurs;4. The identification of the material of which each stratum is composed, such as: c Sand and gravel: Indicate whether gravel is loose, tight, angular or smooth; color;d Cemented formation: Indicate whether grains (if present) have natural cementing material between them; e.g., silica, calcite, etc.;e Hard rock: Indicate whether sedimentary bedrock or igneous (granite-like, basalt-like, etc.).;5. Total depth of completed vertical closed loop borehole;6. Depth or location of any lost drilling fluids, drilling materials, or tools;7. The nominal borehole diameter(s) of the vertical closed loop borehole;8. The nominal diameter, depth, and length of any casing;9. Type of grout material used;11. Grout additives used;12. Borehole grouted from a depth of ___ feet to ___ feet;14. Groundwater depth (groundwater elevation); and15. Thermal conductivity of the grout. 607.1.2Distribution of driller's log: Within 10 days of the completion, the contractor shall submit a copy of the completed driller's log to the project owner/designated agent or their designated representative and keep a copy for his/her file.607.1.3Driller's logs and reports: Every vertical borehole should have a basic log as described in Section 607.1.1. The test borehole or the first production borehole should be used to log the essential lithology information. However, the driller should watch for noticeable changes in underground lithology during production drilling, and if observed, a subsequent next production borehole should also be logged. In some cases, a qualified geologist may be necessary to adequately characterize a site. See the Manual of Water Well Construction Practices (Smith, 1998) for details of performing the driller's log and report.607.1.4Loop field identification -site plan:The drilling contractor shall provide the owner/designated agent with "as-built" drawings of the installation. Such drawings shall show sufficient detail to locate the boreholes, show the finished borehole depth, and actual borehole heat exchanger lengths.
608.0MODIFIED CONCENTRIC CLOSED-LOOP WELL608.1Modified concentric well: A closed loop geothermal heat exchange well that utilizes two concentric pipes, consisting of smaller diameter pipe inside larger diameter pipe, to circulate the heat exchange solution through the borehole in a sealed and pressurized loop.608.2Casing installation: Casing shall be permanently installed and sealed into bedrock using the criteria required for drinking water wells in Chapter 4.608.3Casing seal: A proper water tight seal is required at the top of the casing.608.4Piping standards: All piping shall comply with IGSHPA standards for closed-loop wells. (IGSHPA standards currently approve the use of HDPE and PEXa pipe.)609.0Additional design requirements609.1Additional design requirements: Before drilling any closed-loop well to be utilized as a heat source for any structure other than a single family, residential, detached home and associated structures (for example, garages and other outbuildings), the driller shall first obtain a design for that specific well provided by either a Professional Engineer (PE) or a Certified Geothermal Designer (CGD).10-144 C.M.R. ch. 232, § 6-600.0