State of Maine Stormwater Program Overview - Chapter 500 Steering Committee Meeting 12/5/2023

Sep 17, 2026

Uploaded by Liam

State of Maine Stormwater Program overview presented for a Steering Committee meeting dated 12/5/2023, covering why stormwater is regulated and the foundational concepts in Chapter 500. The material explains key definitions such as stormwater, disturbed area, developed area, impervious and landscaped areas, and differentiates maintenance, redevelopment, and new development. It also outlines hydrologic concepts and flow-duration impacts (Ecosurplus and Ecodeficit), introduces typical stormwater pollutants affecting water quality, and summarizes major program structures and stakeholder engagement.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages41

Reading Time1 h 43 min

AccessFree to download

Why Do We Regulate Stormwater?

Key Definitions (Chapter 500)

Stormwater and Disturbed Area

Developed, Impervious, and Landscaped Area

Maintenance, Redevelopment, and New Development

Low Impact Development (LID) and Green Infrastructure

The Water Cycle & Budget

Pre-versus Post-development Hydrology

Flow Duration Curve (FDC)

Stormwater Pollutants & Water Quality

2023-2024 Stakeholder Engagement

DEP Structure and Program Roles

State vs. Federally Delegated Programs

BLR Stormwater Program Components

Chapter 500 Steering Committee Meeting 12/5/2023 State of Maine Stormwater Program Overview Kerem Gungor, P.E. Senior Environmental Engineer Stormwater Engineering Team Bureau of Land Resources MAINE DEPARTMENT OF ENVIRONMENTAL PROTECTION Protecting Maine’s Air, Land and Water Outline • Why Do We Regulate Stormwater? • Key Definitions (Chapter 500) • DEP Structure • DEP Stormwater Programs: State vs. Federally Delegated • BLR Stormwater Program – Background – Important Components: Technical Guidance, Transportation MOA, Municipal Capacity & Delegation – Licensing Workflow – Interoperation of MCGP & Chapter 500 Programs & New MCGP – Chapter 500 Program Permits & Historic Data – Chapter 500 – 502 Overview – Chapter 500 Standards – Post-construction Stormwater BMPs – Post Permitting Standard Conditions on Stormwater Maintenance • 2023-2024 Stakeholder Engagement: Goals, Scope, Organization and Schedule The Water Cycle & Budget Precipitation = Runoff + Evapotranspiration + Groundwater Recharge Runoff = Precipitation – Evapotranspiration– Groundwater Recharge Reference: USGS. The Water Cycle Diagram: Water Cycle Diagrams | U.S. Geological Survey ( [usgs.gov](usgs.gov)) Pre-versus Post-development Hydrology In-stream Flow Duration Curve (FDC): Unregulated Seasonal FDC: Undeveloped watershed FDC Regulated Seasonal FDC: Developed watershed FDC • Ecosurplus: Increased probability of high in-stream flows → flooding, negative impact on stream channel and aquatic biota • Ecodeficit: Increased probability of low in-stream flows → drought, negative impact on aquatic biota Reference: Holistic Watershed Management for Existing and Future Land Use Development Activities: Opportunities for Action for Local Decision Makers: Modeling and Development of Flow Duration Curves (FDC 1 and 2 Projects) | US EPA Stormwater Pollutants & Water Quality Suspended Solids Temperature Metals Chloride Hydrocarbons Pathogens Key Definitions • Stormwater: – the part of precipitation, including runoff from rain or melting ice and snow, that flows across the surface as sheet flow, shallow concentrated flow, or in drainageways. • Disturbed Area: - all land areas that are stripped, graded, grubbed, filled, bulldozed or excavated at any time during the site preparation or removal of vegetation for, or construction of, a project. "Disturbed area" does not include maintenance. A land area on which the cutting of trees, without grubbing, stump removal, disturbance or exposure of soil has taken place is not considered a "disturbed area". Disturbed Area Developed Area Key Definitions Impervious Landscaped Developed the total area of a parcel covered with a low-permeability material that is highly resistant to infiltration by water, such as asphalt, concrete, or rooftop, and areas such as gravel roads and unpaved parking areas that will be compacted through design or use to reduce their permeability […] an area of land that has been disturbed and re-planted or covered with one or more of the following: grass or other herbaceous plants, shrubs, trees, or mulch; but not including area that has reverted to a natural, vegetated condition. An area of grass is considered landscaped ifit is mowed more than twice per twelve month period. an impervious area, landscaped area, orunrevegetated area. Developed area includes all disturbed areas except an area that is returned to a condition that existed prior to the disturbance and is revegetated within one calendar year of being disturbed, provided the area is not mowed more than twice per year. Key Definitions New Development Non jurisdictional/ Exempt • Maintenance: – an activity undertaken to maintain operating condition, original line and grade, footprint, and original purpose of the project. Paving an impervious gravel surface at original line and grade is considered maintenance. Activities that alter e

FAQs

Why does Maine regulate stormwater?

The overview frames regulation around controlling stormwater impacts, including effects on water quality and hydrologic conditions after development. It links regulation to the underlying water cycle and downstream stream impacts discussed in the presentation.

What are the key definitions for Chapter 500 that affect stormwater compliance?

The materials define stormwater, disturbed area, developed area, impervious and landscaped areas. It also clarifies categories for maintenance, redevelopment, and new development to determine which activities trigger stormwater requirements.

How do pre- and post-development hydrology changes relate to flooding and drought risks?

The presentation uses flow-duration concepts, contrasting unregulated seasonal FDCs with regulated seasonal FDCs. It explains Ecosurplus as increased probability of high in-stream flows leading to flooding, and Ecodeficit as increased probability of low in-stream flows leading to drought.

Which pollutants are highlighted as stormwater water-quality concerns?

The overview lists suspended solids, temperature, metals, chloride, hydrocarbons, and pathogens as major stormwater pollutants associated with water-quality degradation.

Sep 17, 2026

Uploaded by Liam