(1) The applicant shall meet the following requirements relating to the design and construction of water supply systems:

(a) individual and shared wells must be constructed in accordance with ARM Title 36, chapter 21, subchapter 6, unless the requirements of this subchapter are more stringent;

(b) multiple-user water supply systems must be designed and constructed in accordance with Department Circular DEQ-3, and ARM Title 36, chapter 21, subchapter 6, unless the requirements of this subchapter are more stringent;

(i) multiple-user water supply systems with six or more connections, including connections outside of a proposed subdivision, must be designed by a professional engineer. If an existing system is expanded to serve six or more connections, the expansion must be designed by a professional engineer. The reviewing authority may require smaller systems that it determines to be complex (e.g., a water supply system with substantial pressure difference through the distribution system) to be designed by a professional engineer. Systems required by this rule, which must be designed by a professional engineer, are subject to the requirements of ARM 17.36.314;

(ii) if more than one multiple user water system is proposed for a subdivision, the systems must be tied together to ensure greater system reliability. The department may grant a waiver, pursuant to ARM 17.36.601, of this provision if the applicant demonstrates that interconnection of the systems is physically or economically impractical or would create an environmental or public health concern;

(c) the reviewing authority may require additional well construction and/or testing requirements not required in ARM Title 36, chapter 21, subchapter 6 or in department Circular DEQ-3, to ensure that wells within a particular subdivision will provide an adequate water supply.

(2) Public water supply systems are required to meet the requirements of Title 75, chapter 6, MCA, and rules promulgated thereunder.