Maine Oil Tank Rules for Property Owners
Maine regulates buried heating oil tanks more tightly than the states around it, and most of the obligations attach to the tank rather than to whoever happens to own it now.
Registration of Every Underground Tank in Maine
Start here, because it is the fact that reframes everything else and almost nothing written about Maine oil tanks mentions it.
Chapter 691 requires that all underground oil storage tanks and facilities be registered regardless of use, size or type of petroleum product stored, and regardless of whether the tanks are in service or out of service. No exemption for houses. No gallon threshold.
That single sentence is why a buried Maine house tank has a registration number, why the closure notice asks for it, and why disconnecting a tank does not take it off the books. Owners arriving from a state that exempts small residential heating oil tanks tend to assume Maine does the same. It does not.
06-096 C.M.R. ch. 691 section 4(A). Read August 2026.
Chapter 691 and What It Covers
Chapter 691 is the Department’s rule for underground oil storage facilities, made under the underground tank statutes beginning at 38 M.R.S. section 561. Section 6 is the part written for heating oil burned on the premises, and it applies to all underground heating oil facilities used for consumption on site, with no size threshold attached.
The word underground does a lot of work. A tank standing in a cellar or outside on legs is an above ground tank and Chapter 691 does not reach it, which is covered on the basement tank page. You can read the rule yourself from the Department’s statutes and rules index.
Scope from ch. 691 sections 6(A)(1) and 6(A)(2). Read August 2026.
The Closure Sequence Maine Requires
Closure is a defined thing here rather than a description of finishing the job. It means the tank and its piping are properly removed or abandoned, the tank is emptied and cleaned of all liquids and accumulated sludge, what comes out is stored or disposed of correctly, and any discharge is cleaned up to the Commissioner’s satisfaction.
Around that sit three dates. A tank out of service twelve months must be removed within sixty days. Written notice must reach the Commissioner and the local fire department at least ten business days before closure. And where a tank is abandoned in place, a notice goes on the property deed within thirty days of completion, with a copy of the executed notice from the registry going back to the Commissioner.
Between three and twelve months out of service, a tank is “temporarily out of service” and the owner has to:
- Keep any corrosion protection system running
- Keep leak detection running, unless the tank is emptied to no more than an inch of residue
- Leave the vent lines open and working
- Cap and secure every other line, pump, man-way and fitting
- Report and investigate any evidence of a leak
Closure components from ch. 691 section 11(A)(1); dates from 11(D)(1), 11(F)(1) and 11(F)(3); temporary out of service duties from 11(B)(1). Read August 2026.
What the Maine Rules Do Not Require
Two things are widely assumed and neither is in the rule.
A site assessment at closure. Appendix P assessments are required for most facility closures, but on-site consumptive use heating oil facilities are exempt, and the rule adds a note making it explicit: assessments are required for heavy oil tanks but not for number two, kerosene and other heating oils stored and consumed on the same premises. Only oils heated during storage count as heavy oil.
A certified installer on a house tank removal. The requirement for direct on-site supervision by a Maine Certified Underground Oil Storage Tank Installer applies to tanks that have contained a Class 1 liquid, which the Department’s note reads as gasoline and possibly other products such as aviation fuel. Heating oil is not a Class 1 liquid.
Neither absence is a license to be careless. The exemption is from producing a document, not from the consequences of what is in the ground, and the Department can require an after-the-fact assessment on a previously closed facility if it decides a release poses a threat.
Site assessment exemption from ch. 691 section 11(A)(1)(d) and its note; installer requirement from 11(D)(3) and 38 M.R.S. section 566-A(5); after-the-fact assessment from 11(D)(7). Read August 2026.
Reporting a Discharge in Maine
The statutory duty is immediate. On a leak, spill or other prohibited discharge, the owner or other responsible party has to contain it and begin removing it to the Commissioner’s satisfaction.
The practical number the Department publishes is two hours: report within two hours of discovering a spill and the responsible party is exempt from fines. That is a short window on a Saturday, and it is the reason we look at an open excavation before anyone starts backfilling it.
What follows a discharge, including the deductible and the written agreement condition, is on the grants and clean-up fund page.
Containment duty from ch. 691 section 12(A)(1) and 38 M.R.S. section 568; two hour guidance from Maine DEP’s aboveground tank FAQ. Read August 2026.
Where Maine Differs From the States Around It
Guidance written for New England as a block gets Maine wrong in three specific ways, and all three matter to what you are told to do.
- Registration. Maine registers every underground tank regardless of size. Neighboring regimes commonly exempt small residential heating oil tanks outright.
- Site assessment. Massachusetts attaches an assessment to a removal by regulation. Maine exempts on-site heating oil facilities from it.
- The deed. Abandonment in place in Maine is recorded against the title. That is a permanent consequence with no equivalent in a simple removal.
The one thing Maine does not do is use the word decommissioning. That is Oregon’s vocabulary, and a great deal of what a search for “Portland oil tank” returns is written for Portland, Oregon, under a completely different program. Maine says removal, abandonment and closure.
Questions About the Maine Tank Rules
- Does Maine require me to remove an underground oil tank?
- Once it has been out of service for twelve months, yes: it has to be removed within sixty days unless the Commissioner has approved a longer out of service period in writing beforehand. A tank that is genuinely still in use is not caught by that.
- Is my house oil tank really registered with the state?
- If it is underground it is required to be. The rule registers all underground oil storage tanks and facilities regardless of use, size or type of product, and regardless of whether they are in service. There is no residential exemption and no gallon threshold, which is not how New Hampshire, Massachusetts or Suffolk County New York handle the same tank.
- Do I need a licensed contractor to remove a heating oil tank in Maine?
- Not under the certified installer rule, which is tied to tanks that have contained a Class 1 liquid. The Department's own note explains that as gasoline and similar fuels, and heating oil is not one. Work on the burner and the oil line side is licensed separately through the Maine Fuel Board.
- How quickly does a spill have to be reported in Maine?
- The Department's guidance is that reporting within two hours leaves the responsible party exempt from fines. The underlying duty is immediate: contain the discharge and begin removing it to the Commissioner's satisfaction.
- What is a wellhead protection zone in Maine?
- The area within 300 feet of a private well, or for a public well the greater of 1,000 feet or the mapped source water protection area. It matters at closure because it constrains where a replacement tank can go and it weighs against any application to leave a tank in the ground.
Check How the Maine Rules Land on Your Property
Tell us whether the tank is buried or indoors and roughly when it last ran. Those two answers decide which of the duties above are live.