149.10 VERTICAL CLOSED LOOP SYSTEMS.

Vertical closed loop systems will only be allowed when it is shown that a horizontal loop system is not feasible due to lack of land area or to unique surface or subsurface geological conditions or unique topographical conditions as determined by the City Engineer.

149.11 GROUND WATER PROTECTION FOR VERTICAL CLOSED LOOP SYSTEMS.

1.   Vertical geothermal wells should be constructed with materials of such quality to ensure the integrity of the well during and after the construction process.

2.   The construction of a closed loop vertical system should follow the existing requirements of the City well drilling code. Where any conflicts between the well drilling code and this chapter exist with respect to geothermal wells, the requirements of this chapter shall prevail.

3.   If a water supply well is drilled into bedrock, the casing must extend at least ten (10) feet into the bedrock.

4.   Casings are not necessary for geothermal boreholes provided the borehole is filled with grout in a timely manner and the minimum separation distance from potential sources of pollution are met.

5.   Casings should be used during the installation of the borehole to protect the borehole from collapsing.

6.   Casings can be removed as the borehole is filled with grout.

7.   All boreholes shall be filled with grout within seven (7) days of installation.

8.   After the borehole is installed the casing should be capped until the grouting process begins.

9.   If a borehole is drilled so that it connects different aquifers, the construction must be such that the aquifers remain isolated from one another. The boreholes that become a connective apparatus to potential areas of pollution are prohibited.

10.   All boreholes must be terminated at least four (4) feet below the surface. Boreholes terminated in a structure should be terminated flush with the finished floor.

11.   All vertical loops of the system must be encased in grout to protect the pipes from damage as well as providing a heat transfer medium.

12.   Prior to completion of the geothermal loop, all pipes must be pressure tested to ensure no leaks are present. Any system found to leak must be replaced. Piping used must be 160 psi pressure rated high density polyethylene or polybrutylene. Piping must be pressure tested with air or potable water for fifteen (15) minutes at a pressure of 1.5 times the system operating pressure after installation in the borehole.

13.   All grout must have a maximum coefficient of permeability of 10-7 cm/s. Grout must form a good hydraulic seal with the pipes used for the geothermal loop so that water cannot flow along the pipe.

14.   The grout must be installed by filling the borehole from the bottom up using a minimum 1¼" tremie. The entire borehole must be filled with grout.

15.   Only grouts specifically formulated for geothermal applications shall be used. Grout shall not add chemicals to the aquifer.

16.   Boreholes must be protected from surface water intrusion and cross-aquifer mixing during construction. Boreholes must be grouted as soon as reasonably possible after the geoexchange piping system has been installed and pressure tested. Boreholes should not be left open for significant lengths of time after they are drilled. Steel casings shall be capped when not in use.

17.   Connection to piping must use socket fusion or butt fusion joining methods.

18.   Only food grade or U.S. PEA grade propylene glycol or calcium chloride may be used as heat transfer fluid. Any other materials or additives must be NSF approved for drinking water applications. A permanent sign must be attached to the heat pump specifying that only approved heat transfer fluids may be used.

19.   A flow measurement device must be installed on each system.

20.   Water make-up lines to the vertical heat exchanger must be protected with a back-flow prevention device.

149.12 VERTICAL LOOP SYSTEMS WITHIN 1,000 FOOT RADIUS OF A CITY WATER WELL.

1.   The well drilling contractor will drill one (1) bore to determine the bedrock elevation. This boring can be used for one (1) closed circuit vertical heat exchanger.

2.   The bottom of the remaining closed circuit vertical heat exchanger borings may be no lower than 30 feet above the top of the bedrock elevation.

149.13 CLOSED LOOP VERTICAL SYSTEMS BETWEEN 1,000 AND 2,000 FEET RADIUS OF A CITY WATER WELL.

In the event that a closed circuit vertical loop system is between 1,000 feet and 2,000 feet of a City water well, the following will apply:

1.   The bottom of the closed circuit vertical heat exchanger cannot be any lower in elevation than five (5) feet of elevation of the bottom of the water well casing.

2.   The closed circuit vertical heat exchanger may not, under any circumstances, be bored into bedrock.

149.14 CLOSED LOOP VERTICAL SYSTEMS OUTSIDE OF 2,000 FOOT RADIUS OF A CITY WATER WELL.

If a closed circuit vertical loop system is outside a 2,000 foot radius of a City water well, the following will apply:

1.   The bottom of the closed circuit vertical heat exchanger cannot be any lower in elevation than five (5) vertical feet of elevation of the bottom of the water well casing.

2.   The closed circuit vertical heat exchanger may not, under any circumstances, be bored into bedrock.

149.15 TESTING OF SYSTEM.

All geothermal systems must be pressure checked every ten (10) years at the owner's expense.

149.16 ABANDONMENT OF GEOTHERMAL SYSTEMS.

The procedure used for abandonment of geothermal systems must be the same as currently in the well drilling code. The heat transfer fluid must be removed by a displacement with grout. The top of the borehole must be uncovered and capped with grout.

149.17 REGULATION CONFLICT.

In the event any of the provisions of this chapter conflict with any State or Federal regulations, the State or Federal regulations will control.