Maine state law: Stormwater Management — 38 MRS § 420-D / DEP Chapter 500

Per 38 MRS § 420-D (Storm water 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 applicant must apply for a Maine DEP stormwater permit and may not begin construction until approval is received; vegetative-only treatment projects are decided in 45 days and structural-treatment projects in 90 days. Failure of DEP to act within the period results in deemed approval. The Maine DEP implements § 420-D through 06-096 CMR Chapter 500 (Stormwater Management Rules), which sets quality and quantity standards for runoff (general standard, basic standard, and a flooding standard). 06-096 CMR Chapter 502 layers additional protection for projects in direct watersheds of Lakes Most at Risk from New Development and Urban Impaired Streams. 06-096 CMR Chapter 501 administers stormwater compensation fees and mitigation credit for projects unable to meet on-site standards. Section 420-D exempts single-family residential construction, normal farming operations, forest management, snowmobile/ATV trail maintenance, and Maine DOT/Turnpike Authority projects; municipalities with DEP-approved local stormwater ordinances meeting or exceeding state standards may be granted delegated permitting. Phosphorus-export limits apply within great pond watersheds. Construction-phase erosion and sediment control is layered on through 38 MRS § 420-C (see Erosion Control entry).

Each day of a violation is a separate offense under 38 MRS § 420-D. Maine DEP enforces through administrative consent agreements, civil penalties up to $25,000 per day under 38 MRS § 349, stop-work orders, and remediation orders. Knowing violations can trigger criminal liability. Local code-enforcement officers in municipalities with delegated authority may also issue notices of violation.