The Governing Framework

Maine regulates subsurface wastewater disposal under:

• 10-144 CMR Chapter 241 — Subsurface Wastewater Disposal Rules. The substantive Maine rule.
• Maine Center for Disease Control (CDC), Subsurface Wastewater Unit — state-level administrator. The Subsurface Wastewater Unit sits within Maine CDC (not Maine DEP, which some people assume).
• Licensed Site Evaluator (LSE) — a professional-license category specific to Maine onsite wastewater. LSEs perform site evaluations, soil profiles, and system designs. The LSE requirement is stricter than many states' "soil evaluator" or "designer" categories.
• Local plumbing inspectors (LPIs) — issue permits and perform field inspections under Maine CDC oversight. Every Maine municipality has an LPI or LPI coverage arrangement.

The September 2023 Amendment Package

Maine CDC adopted significant amendments to Chapter 241 effective September 23, 2023. Key changes include:

• Watertight riser requirement. New installations require watertight risers on septic tanks to prevent surface water intrusion and facilitate maintenance access without excavation.
• 40-year-fill rule replacing 1974 soil cutoff. Historically, Maine's rules distinguished "natural" vs "fill" soils based on 1974. The 2023 amendment replaced this antiquated cutoff with a 40-year-fill rule (fill placed more than 40 years ago is treated as natural soil for permit purposes). This significantly simplifies evaluation of older modified sites.
• Seasonal-to-year-round conversion requirements. Converting a seasonal cottage (summer-only) to year-round use now triggers specific system evaluation and potential upgrade requirements. Seasonal systems were historically designed for lower flow and are not automatically adequate for year-round service.
• Grinder pump capacity additions. Requirements for grinder-pump-served systems were clarified to match modern installation practices.

If your project was designed under pre-2023 rules and construction was delayed, verify with your LSE whether the design needs to be updated to comply with the current amendments.

Septic Tank Capacity

Maine Chapter 241 establishes tank capacity based on bedroom count and design flow. Typical residential sizing:

Your LSE will specify the exact capacity based on your site's design flow and Chapter 241 tables. Polyethylene tanks meeting IAPMO/NSF listings and Chapter 241 construction requirements are accepted.

Permit Process

1. Hire a Licensed Site Evaluator (LSE). The LSE is your design professional. Maine CDC maintains a list of licensed LSEs by region.
2. LSE performs site evaluation. Soil profile, percolation, site restrictions per Ch 241.
3. LSE prepares HHE-200 application. The formal permit application form including system design.
4. Submit to Local Plumbing Inspector (LPI). The LPI reviews and approves at the municipal level.
5. Licensed installer construction.
6. LPI inspection before cover.
7. Approval of completion. Formal sign-off from LPI.

Regional Considerations

• Southern Maine (York, Cumberland): Highest population density, mix of municipal sewer and dense-septic suburbia. Coastal parcels face saltwater-table concerns and erosion setbacks.
• Midcoast (Sagadahoc, Lincoln, Knox, Waldo): Extensive coastal cottage stock. Seasonal-to-year-round conversion requirements apply frequently.
• Down East (Hancock, Washington): Rural coastal. Long LSE lead times, short construction season (May–October). Plan well ahead.
• Western Mountains (Franklin, Oxford): Ski-country cottages and year-round rural. Rocky glacial soils, frost considerations.
• North Woods (Aroostook, Piscataquis, Somerset): Remote parcels, limited LSE coverage, logistical challenges. Shoulder-season siting often preferred.
• Central / Kennebec Valley: Agricultural and small-town. Standard systems typical.
• Lakes Region: Shoreland zoning layered on Chapter 241. Additional setbacks from lakes, stricter for phosphorus-sensitive watersheds.

Frequently Asked Questions

Can I design my own septic system in Maine?

No. Maine requires a Licensed Site Evaluator (LSE) to prepare the HHE-200 application. Homeowner-designed systems are not accepted. Budget for LSE services ($1,500-$4,000+ depending on site complexity).

How do I find an LSE?

Maine CDC maintains a directory of Licensed Site Evaluators. Contact LSEs in your region directly. In peak season expect 2-8 week lead times before site evaluation can begin. Book as early as possible.

What's the 40-year-fill rule?

Part of the September 2023 amendments. Fill soil (imported or placed soil over original grade) placed more than 40 years ago is treated as natural soil for permit evaluation purposes. This replaces the older 1974 cutoff and dramatically simplifies evaluation of mid-20th-century modified sites.

Is my seasonal cottage's septic system adequate for year-round use?

Usually not automatically. Seasonal systems were typically designed for lower peak flow and may have undersized tanks or absorption fields for year-round occupancy. The September 2023 amendments added specific requirements for seasonal-to-year-round conversion. Have your LSE evaluate before converting.

Are polyethylene tanks accepted in Maine?

Yes, when meeting IAPMO/NSF listings and Chapter 241 construction requirements. Major OEM rotomolded polyethylene tanks from Norwesco, Snyder, Ace Roto-Mold, and others are commonly approved. Your LSE will specify accepted models.

What about shoreland zoning?

Maine shoreland zoning applies additional setbacks and restrictions near lakes, rivers, and coastal shorelines. These layer on top of baseline Chapter 241 setbacks. Phosphorus-sensitive lake watersheds have particularly strict design requirements. Your LSE will know which rules apply to your parcel.

Source Citations

• Maine CDC Subsurface Wastewater Program
• 10-144 CMR Ch 241 Subsurface Wastewater Disposal Rules
• Maine CDC LSE Licensing Directory
• Maine CDC Subsurface Wastewater Documents
• HHE-200 Subsurface Wastewater Application Form

Agricultural Tank Regulations — Maine BPC & DACF

The Maine Department of Agriculture, Conservation and Forestry (DACF) and the Maine Board of Pesticides Control (BPC) share agricultural-tank oversight under the Maine Revised Statutes Annotated (MRSA) and the Code of Maine Rules (CMR):

• 01-001 CMR Ch. 20-22 — Maine Board of Pesticides Control rules; applicator licensing, restricted-use pesticide (RUP) recordkeeping, bulk storage, repackaging, dealer registration.
• 22 MRSA § 1471-A — Maine Pesticide Control Act (statutory authority).
• 01-001 CMR Ch. 33 — DACF Commercial Fertilizer Law rules: registration, tonnage reporting, labeling.
• 06-096 CMR Ch. 691 / 692 — ME DEP UST and AST rules covering any petroleum or hazardous-substance tank used at or adjacent to an ag operation above threshold.

Maine agriculture centers on potato production in Aroostook County (the northern third of the state, the largest potato-growing region east of Idaho), dairy in the Kennebec and Penobscot valleys, apple orchards across western Maine (Oxford, Franklin, Androscoggin counties), wild blueberry barrens in Washington and Hancock counties (producing ~10% of world wild blueberry supply), and maple syrup and forestry products statewide. Aroostook potato country drives the most demanding fertilizer-storage patterns in Maine: bulk liquid UAN, ATS, 10-34-0, and potato-protection fumigants (metam sodium, Vapam) all move through ag-retail and on-farm bulk storage during the spring and fall windows. Operators handling bulk agchemicals build secondary containment to 110% of the largest tank with impermeable liners, loading-pad spill capture, and ME DEP spill-response plans. The BPC Restricted-Use Pesticide permit and buffer requirements are among the more detailed in the Northeast, reflecting public concern about drift and surface-water exposure in the St. John and Aroostook river watersheds.

Oil & Gas Storage — Petroleum UST/AST Path

Maine has no commercial oil or gas production; there is no upstream operator framework. Petroleum is imported by pipeline from Portland (the Portland-Montreal Pipeline, legacy asset) and by marine tanker to Searsport (Sprague) and South Portland (Global, Citgo, Sprague terminals). Petroleum tank storage is governed by:

• 06-096 CMR Ch. 691 — ME DEP UST rules: design, installation, corrosion protection, spill/overfill, release detection, operator training, closure, financial responsibility.
• 06-096 CMR Ch. 692 — ME DEP AST rules: regulated aboveground petroleum and hazardous-substance tanks; a notably detailed state AST framework for New England.
• 38 MRSA Chapter 3 Sub-chapter 2-B — UST statutory authority.
• 38 MRSA § 568-A — Groundwater Oil Cleanup Fund (state fund reimbursing eligible corrective-action costs for petroleum releases).
• NFPA 30 / 30A — adopted through State Fire Marshal and local fire-code enforcement for flammable and combustible liquids.

Heating-oil tanks at 1- to 4-unit residential buildings follow partial Chapter 692 exemptions and NFPA 31; insurance-driven integrity programs are common. Offshore federal OCS leasing in the Gulf of Maine is administered by BOEM/BSEE outside state jurisdiction. The State Fire Marshal maintains AST registration and inspection coordination with ME DEP.

Septic System Sizing — 10-144 CMR Ch. 241 Maine Subsurface Wastewater Disposal Rules

The Maine Department of Health and Human Services (DHHS) regulates subsurface wastewater under 10-144 CMR Ch. 241 (Subsurface Wastewater Disposal Rules), with Licensed Site Evaluators (LSEs) performing the design and soil evaluation. Maine's residential design flow is among the highest in the country at 270 gpd per bedroom, reflecting conservative sizing on cold, wet, shallow-bedrock soils:

Maine soils run from shallow-bedrock granite across much of the western mountains and Downeast, sandy glacio-marine sediments along the coast (fast perc but salt-water intrusion concern), heavy glacial till across the central state, and Aroostook County's rich Caribou silt loam (excellent perc, but seasonal frost penetration to 6 feet). Frost depth drives deep burial, Styrofoam insulation blankets, and heat-trace on risers. Alternative and advanced systems are common: pressure-dosed dispersal, mound systems on shallow bedrock, peat biofilters, and recirculating sand filters. Every new system is designed by a Licensed Site Evaluator; the LSE program is one of Maine's distinctive regulatory features.

The Mandatory Shoreland Zoning Act (38 MRSA § 435 et seq.) overlays coastal and freshwater shoreline corridors statewide; septic, tanks, and grading within the shoreland zone (typically 250 feet from great ponds, rivers, and coastal waters; 75 feet from streams) are subject to municipal shoreland permits consistent with state minimum standards. Coastal shoreland parcels face additional setbacks from coastal wetlands and erosion hazards.

Chemical Storage, Shoreland Zoning & Spill Reporting

Federal SPCC (40 CFR 112) applies at 1,320 gallons aggregate aboveground oil. Maine layers on:

• 38 MRSA § 543 — Maine Oil Discharge Prevention and Pollution Control statute; strict, joint-and-several, retroactive liability for petroleum discharges.
• 06-096 CMR Ch. 600 — Site Location of Development Act review for large facilities (industrial, commercial, subdivisions); siting-level review that pulls tank projects into ME DEP oversight at scale.
• Mandatory Shoreland Zoning (38 MRSA § 435 et seq.) — statewide minimum standards administered by municipalities; coastal and lakeshore setback regime that affects virtually every ag, residential, and commercial tank project near water.
• High-Yield Aquifer protection — mapped high-yield sand-and-gravel aquifers in the Presumpscot, Androscoggin, Kennebec, and other basins face tighter siting and containment expectations under local ordinance and DEP guidance.
• NFPA 30 / 30A — adopted through State Fire Marshal and local fire-code enforcement for flammable and combustible liquids.

Report federal-RQ releases to the National Response Center at 1-800-424-8802; report state releases to ME DEP Response Services at 1-800-482-0777 (24-hour).

Permit Pathways at a Glance

• Residential septic: Licensed Site Evaluator + municipal plumbing inspector under 10-144 CMR Ch. 241.
• Pesticide applicator license: Maine BPC under 01-001 CMR Ch. 20-22.
• Fertilizer registration: DACF under 01-001 CMR Ch. 33.
• Petroleum UST: ME DEP under 06-096 CMR Ch. 691.
• Petroleum/chemical AST: ME DEP under 06-096 CMR Ch. 692 + NFPA 30/30A.
• SPCC > 1,320 gal oil aggregate: Federal SPCC plan; ME DEP spill reporting.
• Shoreland zoning: Municipal permit under 38 MRSA § 435 et seq. state minimum standards.
• Site Location of Development: ME DEP under 06-096 CMR Ch. 600 (large commercial/industrial).

Current fees change; verify with ME DEP, BPC, DHHS, or State Fire Marshal before budgeting.

More Maine FAQs

What is a Licensed Site Evaluator and why does every septic project need one?

Under 22 MRSA § 42 and the Subsurface Wastewater Disposal Rules, Maine requires a Licensed Site Evaluator (LSE) to conduct soil evaluation, system design, and construction inspection for every new or replacement on-site wastewater system. The LSE program is distinctive to Maine and drives relatively consistent design quality across the state; LSEs are licensed by DHHS and carry design liability. Budget an LSE retainer early in any property-development timeline.

How does shoreland zoning affect my tank project?

Maine's Mandatory Shoreland Zoning Act sets minimum standards for any construction within 250 feet of great ponds, rivers, and coastal waters; 75 feet from streams; and within freshwater and coastal wetlands. Municipalities adopt conforming ordinances. Tanks, septic systems, and secondary containment within the shoreland zone require municipal shoreland permits, typically with setback and vegetation-protection conditions. Coastal shoreland parcels also face Erosion Hazard Area designations that may prohibit certain tank installations.

Why is Aroostook County fertilizer storage different?

Aroostook potato country handles bulk liquid fertilizer and fumigants at volumes uncommon elsewhere in Maine: on-farm bulk tanks of 6,000-20,000 gallons for UAN, ATS, and 10-34-0 plus specialty storage for potato-soil fumigants (metam sodium, Vapam). BPC buffer and drift rules are detailed; DEP spill-prevention expectations scale up accordingly. Aroostook's Caribou silt loam and proximity to the St. John and Aroostook rivers drive tight nutrient-management and containment discipline.

Does Maine have a state UST cleanup fund?

Yes — the Maine Ground Water Oil Clean-up Fund under 38 MRSA § 568-A reimburses eligible corrective-action costs for petroleum releases from registered, compliant tanks. Coverage caps and deductibles are set by ME DEP; unregistered or out-of-compliance tanks are generally ineligible, and documentation discipline matters.

Who regulates heating-oil tanks at a Maine home?

Residential heating-oil tanks at 1- to 4-unit dwellings follow partial Chapter 692 exemptions, NFPA 31 installation standards through local fire officials, and strict 38 MRSA § 543 oil-discharge liability on any release. State Fire Marshal plus local code enforcement handle inspection coordination. Insurance-driven tank-integrity programs (particularly for basement No. 2 heating-oil tanks) are standard.

How fast must I report an oil or chemical release in Maine?

Under 38 MRSA § 543 and Ch. 691/692 a petroleum or hazardous-substance release must be reported to ME DEP Response Services immediately; federal-RQ releases also go to NRC at 1-800-424-8802. The DEP 24-hour number is 1-800-482-0777. Delayed reporting compounds liability and can jeopardize state-fund eligibility. Maine liability is strict, joint-and-several, and retroactive.