Maine state law: rainwater harvesting and stormwater management

Unlike Colorado (CRS 37-96.5) where rain-barrel capture was historically limited, Maine has no statewide cap on the volume of rainwater a residential property owner may collect from rooftop runoff. Rain barrels, cisterns, dry wells, and rain gardens are unregulated by the Maine Revised Statutes for residential use and are actively promoted by Maine Department of Environmental Protection as Best Management Practices for stormwater reduction. Larger-scale stormwater management falls under 38 MRS § 420-D (Stormwater management): 'A person may not construct, or cause to be constructed, a project that includes one acre or more of disturbed area without prior approval from the department.' The statute explicitly exempts single-family residential construction: 'Impervious and disturbed areas associated with construction or expansion of a single-family, detached residence on a parcel do not require review pursuant to this section.' DEP review of larger projects targets phosphorus, nitrogen, and suspended-solids loading. Public-water-supply cross-connection control rules (Title 22) require harvested rainwater plumbing to be physically isolated from any potable water system. Potable use of harvested rainwater for human consumption requires public-water-system permitting under 22 MRS § 2601 et seq. if served to others.

No state penalty for residential rainwater capture. Construction of one acre or more without a stormwater permit: civil penalties up to $25,000 per day per violation under Title 38. Cross-connecting a rain-barrel system to potable plumbing is a state plumbing-code violation under 22 MRS § 2491 et seq.