About

About this site

Massachusetts requires the seller of any property with a septic system to determine and disclose whether that property is subject to a nitrogen upgrade requirement. Answering that question correctly means reading several government documents that do not reference each other. This site puts them in one place.

Why it exists

310 CMR 15.215(4) places two duties on an owner: to find out whether the property is in a designated Nitrogen Sensitive Area, and, before transferring title, to disclose to the buyer and the Board of Health whether an upgrade requirement applies.

What has to be disclosed is not whether the property is in a Nitrogen Sensitive Area. It is whether an upgrade requirement applies — and that depends on what the town filed for that particular watershed. MassDEP's address map answers the first question. It does not answer the second. The disclosure form does not mention the document that does.

So a seller is asked to reach a legal conclusion from a source that cannot produce it. That gap is what this site fills.

Where the information comes from

Everything here is read from primary sources: the regulation itself, MassDEP's watershed permit application table, MassDEP's NSA address lookup map, and MassDEP's own implementation guidance. Filings currently reflect the application table dated 11 June 2026. Watershed names as they appear on the map were transcribed by hand and are dated separately, because the two documents do not use the same names.

The sources page lists every document, what was taken from it, and what has and has not been verified.

How it is kept current

The application table changes as towns file. It is re-checked quarterly, and the filings and the date shown across the site are updated together. Every page that makes a claim about a town's position carries the date of the records behind it, so you can see how fresh it is rather than having to assume.

Where two government sources disagree, this site says so on the page rather than picking the tidier answer. Where something is inferred and not confirmed, it is labelled as inference.

What this site is not

It is not legal advice, and it is not affiliated with MassDEP, Barnstable County, or any town. It cannot tell you whether a specific address is in a Nitrogen Sensitive Area — only MassDEP's map and your Board of Health can settle that. The official text of 310 CMR 15.000 governs, and where this site and the regulation differ, the regulation is right and we want to hear about it.

Corrections, from anyone, go to hello@capecodsepticguide.com. More detail on how to reach us is on the contact page.