(1) Aquifer. The Department may exempt an aquifer from being an underground source of drinking water if, after notice and an opportunity for a public hearing the Department determines, subject to the approval of the U. S. Environmental Protection Agency, that the aquifer:

1. (a) currently does not serve as a source of public drinking water; and,

2. (b) cannot now and will not in the future serve as a source of public drinking water because:

   1. 1. it is used to produce mineral, hydrocarbon or geothermal energy;
   2. 2. it is so contaminated that it would be economically or technologically impractical to render the water fit for human consumption; or
   3. 3. it contains more than 3000 mg/l Total Dissolved Solids and it is not reasonably expected to be used as a source of public drinking water.

(2) Registration. The following Class V injection wells are exempt from the registration requirements of 310 CMR 27.08:

1. (a) on-site subsurface sewage disposal systems used solely for the disposal of sanitary sewage and regulated under 310 CMR 15.000: The State Environmental Code, Title 5: Standard Requirements for the Siting, Construction, Inspection, Upgrade and Expansion of On-site Sewage Treatment and Disposal Systems and for the Transport and Disposal of Septage;
2. (b) Class V injection wells permitted under 314 CMR 5.00: Ground Water Discharge Permit Program; and

3. (c) Class V injection wells on properties that are only used for one single-family residential unit, and that are only used for one or more of the following types of discharges:

   1. 1. stormwater runoff;
   2. 2. water purification backwash;
   3. 3. wastewater from the recovery of geothermal energy for heating, or water used for cooling;
   4. 4. groundwater infiltration; and
   5. 5. swimming pool drainage.