Maine Stormwater Best Management Practices ManualOn this page you will find:
The Maine DEP recognizes the importance of managing stormwater to preserve the State’s natural resources. This manual was developed to assist communities, watershed groups, individuals, engineers, and developers in understanding stormwater impacts and to select appropriate Best Management Practices (BMPs) to manage stormwater from development, in accordance with the Maine DEP’s Chapter 500 Stormwater Management Rules.
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The Stormwater BMP Manual has three volumes:
Volume I. Stormwater Management Manual This volume provides general information on the impacts of development, lists the DEP’s stormwater management objectives, and offers guidance to control stormwater runoff and associated pollutants.
Volume II. Phosphorus Control in Lake Watersheds: A Technical Guide to Evaluating New Development This volume outlines Maine’s phosphorus standards, which limit the amount of phosphorus that developments can add to a lake. It also outlines methods for reducing phosphorus loadings to meet the established standards. The following links provide additional information to Volume II of the Stormwater BMP Manual:
- Per Acre Phosphorus Allocations for Selected Maine Lakes
- Worksheets (excel files)
Volume III. BMP Technical Design Manual This volume provides technical information to assist in the selection and design of BMPs to control stormwater runoff and its impacts. Links to individual chapters from Volume III of the Stormwater BMP Manual follow:
- Chapter 1. Introduction
- Chapter 2. Stormwater Hydrology
- Chapter 3. Peak Flow Control / Detention Basins
- Chapter 4. Wet Ponds
- Chapter 5. Vegetated Buffers
- Chapter 6. Infiltration BMPs
- Chapter 7.0. Filtration BMP
- Chapter 7.1. Grassed Underdrained Soil Filter BMP
- Chapter 7.2. Underdrained Bioretention Cell BMP
- Chapter 7.3. Underdrained Subsurface Sand Filter BMP
- Chapter 7.4 Wetlands
- Chapter 7.5 Roof Dripline Filtration BMP
- Chapter 7.6 Vegetated Roof
- Chapter 7.7. Manmade Pervious Surfaces
- Chapter 8.0. Conveyance and Distribution Systems
- Chapter 8.1. Vegetated Swales
- Chapter 8.2. Flow Splitters and Bypass
- Chapter 8.3. Level Spreaders
- Chapter 8.4. Permeable Road Base (October 2010)
- Chapter 9.0 Separator BMPs
- Chapter 10. LID Design Practices and Techniques
- Chapter 11. Designing for Operation & Maintenance
- Appendix A. Hydrologic Data for Maine
For general questions on the Stormwater BMP Manual, contact: Jeff Dennis, (207) 215-6376. For specific technical or engineering/design questions, contact Ken Libbey (207) 299-4823 or Mark Stebbins (207) 592-4810
A system or practice designed for stormwater runoff treatment from a development has to meet all the stormwater requirements of Maine’s Stormwater Law, and the Chapter 500 Stormwater Management Rule to be considered equivalent to any of the suggested structures found in the BMP Manual. A proprietary system must be live-tested for a variety of storm lengths and intensities. The system must remove at least 60% total phosphorus, with at least similar removals metals (zinc and copper), and hydrocarbons; it must provide temperature reduction and channel protection storage detention either independently or in combination with another measure; and it must also be maintainable.
Filtration systems that store and treat a volume of water must be sized to store and treat 1.0 inch of runoff from the contributing impervious area and 0.4 inches of runoff from contributing landscaped areas. If channel protection storage and cooling are required, they must be provided independently, and the stored volume must be released slowly over a 24 to 48-hour period and cooled. Flow-through or hybrid systems that do not store the water quality volume prior to treatment must be sized so that they treat the entire volume of the 0.95-inch Type III 24-hour storm without bypass. Sizing of proposed systems that do not fit these two categories will be determined on a case-by-case basis with the goal of providing treatment for at least 90% of the annual runoff volume.
The DEP has reviewed the design and performance data from these following proprietary structures and can approve them as an alternative, or as an integral part of the treatment train for stormwater management. Each approval letter identifies the specific design for sizing, layout, installation and maintenance requirements that are necessary for the system to perform as approved. The approval date of a letter will supersede any older version of the same approval.
- ACO StormBrixx
- Bio Clean Kraken Filter
- Brentwood StormTank
- Modular Wetland System Linear
- Old Castle StormCapture
- StormTree System
Proper operation and maintenance of stormwater systems helps ensure that the BMP will continue to remove pollutants effectively over the long-term, decreasing the risk of re-suspending sediment, and therefore protecting water quality. Appendix B.3 of the DEP’s Chapter 500 Stormwater Rules requires that a certification be sent to the DEP every five years stating that the stormwater management system was inspected, maintained, and repaired (if needed). See Five-year Recertification for Long-term Maintenance of Stormwater Management Systems and Five-year Recertification FAQs for more detailed information.
The DEP maintains a list for persons interested in DEP Stormwater topics. Periodically, the DEP sends out updates on revisions to the stormwater law or rule, changes to the Stormwater BMP Manual, or other topics of interest. You are invited to sign up with the DEP stormwater engineering list serve to receive these updates.
If you have any questions on the list serve, please contact Mary York