1.  Use allowed.  Notwithstanding any provision of law to the contrary, except as provided in Title 12, chapter 423‑A, for any area in which residential uses are allowed, including as a conditional use, a municipality shall allow structures with up to 2 dwelling units per lot if that lot does not contain an existing dwelling unit, except that a municipality shall allow up to 4 dwelling units per lot if that lot does not contain an existing dwelling unit and the lot is located in a designated growth area within a municipality consistent with section 4349‑A, subsection 1, paragraph A or B or if the lot is served by a public, special district or other centrally managed water system and a public, special district or other comparable sewer system in a municipality without a comprehensive plan.  

1-A.  Implementation date.  For purposes of this section, "implementation date" has the same meaning as in section 4364, subsection 1‑A.  

1-B.  (REALLOCATED FROM T. 30-A, §4364-A, sub-§1-A) Exception.  This section does not apply to a lot or portion of a lot that is within the watershed of a water source that is located in the City of Lewiston or the City of Auburn and that is used to provide drinking water by a water utility that has received a waiver from filtration pursuant to 40 Code of Federal Regulations, Sections 141.70 to 141.76, as determined by the Department of Health and Human Services.  

2.  Zoning requirements.  With respect to dwelling units allowed under this section, municipal zoning ordinances must comply with the following conditions.  

3.  General requirements.  A municipal ordinance may not establish dimensional requirements, including but not limited to setback requirements, for dwelling units allowed under this section that are greater than dimensional requirements, including but not limited to setback requirements, for single-family housing units, except that a municipal ordinance may establish requirements for a lot area per dwelling unit as long as the required lot area for subsequent units on a lot is not greater than the required lot area for the first unit.  

4.  Water and wastewater.  The owner of a housing structure must provide written verification to the municipality that the structure is connected to adequate water and wastewater services before the municipality may certify the structure for occupancy. Written verification under this subsection must include:  

5.  Municipal implementation.  In adopting an ordinance, a municipality may:  

6.  Shoreland zoning.  A housing structure must comply with shoreland zoning requirements established by the Department of Environmental Protection under Title 38, chapter 3 and municipal shoreland zoning ordinances.  

7.  Subdivision requirements.  This section may not be construed to exempt a subdivider from the requirements of subchapter 4.  

8.  Restrictive covenants.  This section may not be construed to interfere with, abrogate or annul the validity or enforceability of any valid and enforceable easement, covenant, deed restriction or other agreement or instrument between private parties that imposes greater restrictions than those provided in this section, as long as the agreement does not abrogate rights under the United States Constitution or the Constitution of Maine.  

9.  Rules.  The Department of Economic and Community Development may adopt rules to administer and enforce this section. The department shall consult with the Department of Agriculture, Conservation and Forestry in adopting rules pursuant to this subsection. Rules adopted pursuant to this section are routine technical rules as defined in Title 5, chapter 375, subchapter 2‑A.  

10.  Implementation.  A municipality is not required to implement the requirements of this section until the implementation date.