Zone II & Nitrogen Sensitive Area FAQs

What is a Nitrogen Sensitive Area (NSA)?

Sites are designated “nitrogen sensitive areas” because they have logged so much nitrogen that they do not meet Massachusetts water quality standards.  The following areas have been determined by MA DEP to be particularly sensitive to the discharge of pollutants from on-site sewage disposal systems and, therefore, are designated NSAs:  

• Interim Wellhead Protection Areas and Department approved Zone IIs of public water supplies.
• Nitrogen sensitive embayments or other areas which are designated as nitrogen sensitive for purposes of 310 CMR 15.000 shall be mapped based on scientific evaluations of the affected water body and adopted through parallel public processes pursuant to both 310 CMR 15.000 and 314 CMR 4.00: Massachusetts Surface Water Quality Standards.

The necessity of providing increased treatment of pollutants and reduction in nutrients discharged from on-site sewage disposal systems, including nitrogen, nitrogen as nitrate, phosphorous and pathogens in these areas warrants the imposition of the loading restrictions set forth in 310 CMR 15.214.

What is a Zone II?

A Zone II is drinking water contribution area that has been determined by hydro-geologic modeling and approved by the MA DEP’s Drinking Water Program.  Properties located in a Zone II are restricted to one (1) bedroom for every 10,000 sq ft of land area.  Properties previously permitted by the Board of Health for bedrooms in excess of one per 10,000 sq ft are grandfathered in.  As an example, if your property is in a Zone II and your lot size is 20,000 sq ft, but the Board of Health previously approved an application and septic design plan for three (3) bedrooms, you may maintain those three bedrooms in perpetuity.

Properties serviced by a potable well are subject to the same bedroom/loading restrictions as properties located within a Zone II.