Environmental Review for Floodplains
Executive Order 11988
In order to decide whether EO11988 applies to the project, it must first be determined whether or not the project lies within the 100-year floodplain, or for critical facilities, the 500-year floodplain as mapped by the Federal Emergency Management Agency (FEMA).
A detailed site plan that shows the floodplain boundary is necessary to make this determination. Check the floodplain elevations as listed in the Flood Insurance Study or Flood Insurance Rate Map (FIRM) and compare them to site topography. If the map shows the project to be out of the floodplain, the governing determinant should be project elevation related to the base flood elevation. If this review shows that the project is within the 100-year floodplain by elevation, then the community’s Floodplain Ordinance and Executive Order 11988 apply.
Executive Order 11988 and the State Executive Order require all projects that involve the expenditure of Federal or State funds to be reviewed in light of flooding potential and to be located outside a SFHA if possible. If, after close examination of practicable alternatives, certain aspects of the projects are required to be in the floodplain, flood hazard mitigation methods are to be employed to the greatest extent possible to avoid future flood losses and protect the natural and beneficial functions of the floodplain. This will help to ensure protection of the development, wise use of the floodplain, and responsible use of state or federal funds. Complying with the review and permitting standards in a community’s floodplain management regulations (based on the NFIP regulations), will meet some but not all of the E.O.’s requirements. Agencies that provide loans or grant funds for these types of projects have each adopted regulations to comply with E.O. 11988, which should be reviewed to make sure the project satisfies each agency’s procedures and criteria. For most agencies, they include some version of the 8-step decision making process that was developed as guidance by the Water Resources Council and further described in the Interagency Task Force publication titled, “Further Advice on Executive Order 11988, Floodplain Management”. Some of these steps include such things as public notification and input, identifying practicable actions, and incorporating mitigation activities.
A summary of the 8 step process includes:
- Determining whether the project is in or out of the floodplain
- Providing early opportunities for public review
- Identifying and evaluating alternatives to locating in the floodplain
- Identifying impacts of the proposed project such as impacting flood elevations or encouraging floodplain development
- Minimization or use, restoration and preservation of floodplain areas
- Re-evaluation of alternatives
- Publicizing findings and providing public information
Requirements for all development
A community’s local floodplain management ordinance should always be reviewed to ensure that the community has not adopted more restrictive standards.
Local FPM ordinances require that all development in areas of special flood hazard shall meet the following applicable standards (State Model Ordinance at Article VI.A.1.to 4.):
- be designed or modified and adequately anchored to prevent flotation (excluding piers and docks), collapse or lateral movement of the development resulting from hydrodynamic and hydrostatic loads, including the effects of buoyancy;
- use construction materials that are resistant to flood damage;
- use construction methods and practices that will minimize flood damage; and,
- use electrical, heating, ventilation, plumbing, and air conditioning equipment, and other service facilities that are designed and/or located so as to prevent water from entering or accumulating within the components during flooding conditions.
If the project does not involve new construction of a building or the proposed project (including all materials and labor) does not total more than 50% of the current value of the building, then to the extent possible, plans should include floodproofing, the use of flood resistant materials, and anchoring of project components. Elevation of utilities above the BFE is also recommended. Other considerations for work in a floodplain include the use of Best Management Practices for erosion control, timing construction for drier times of year, and storing equipment out of the floodplain or above the flood elevation.
Additionally, the local FPM ordinance requires that “all necessary permits have been obtained from those federal, state and local government agencies from which prior approval is required by federal or state law”, prior to the local FPM permit being issued.
New Construction or Substantial Improvement of a Building
If the project involves new construction and/or represents more than 50% of current value of a building only, then the local FPM ordinance will include the following minimum standards:
- The top of the floor of the lowest enclosed area must be located one foot above the BFE, and an Elevation Certificate must be completed as documentation. The EC is also used to determine flood insurance rating.
- To accomplish this, the project must either be either elevated on fill, continuous foundation walls with hydraulic openings (see the local FPO for standards), or on an open foundation system.
- For non residential structures, the building can be dry floodproofed and/or utilities can be elevated as an alternative to elevation of the lowest floor. The work must be designed by a Professional Engineer or Architect.
- If the project is located in Zone AO, provision must be made for adequate drainage around the structure. Also, buildings should have the lowest floor (including basement) elevated above the highest adjacent grade (a) at least one foot higher than the depth specified in feet on the community's Flood Insurance Rate Map or, (b) at least three feet if no depth number is specified.
- For projects located in Zone A, A1-30 or AE and within the floodway limits, an engineer’s certificate is needed to prove that the project will cause either no rise or no more than a one foot rise in BFE. The owner may need to establish the BFE if it is not provided on the FIRM. See Floodway standards
Coastal Zones V1-30 or VE
- Buildings must be elevated on posts, piles, piers or columns.
- No solid foundation walls are allowed below the BFE.
- The lowest horizontal member must be one foot above the BFE, and an Elevation Certificate must be completed.
- Construction must be in accordance with the Coastal Construction Manual and certified by a Professional Engineer.
- On FIRMs where no regulatory floodway has been determined, in Maine, the default floodway is considered to be half the width of the floodplain on each side of the river/stream/brook until such time it is actually calculated by a Professional Engineer.
- For projects located in Zone A, A1-30 or AE (with no regulatory floodway designated on the FIRM or separate Floodway Map), an engineer’s certification is necessary to demonstrate that the project will not cause any more than a one foot rise in BFE. The owner may need to establish the BFE if it is not provided on the FIRM.
- For projects located in the regulatory (mapped) floodway, the applicant must demonstrate, with an engineer’s certification, that the project will not cause any rise in the BFE.
Water Supply, Sewerage and Subsurface Disposal Projects
For water supply or sewerage projects, in addition to the above standards for buildings, the Local Floodplain Ordinance language that says “All new and replacement water supply systems and sanitary sewage systems shall be designed and located to minimize or eliminate infiltration of floodwaters into the system and discharges from the system into floodwaters”. The inherent design of water and sewer lines should meet this standard. However, in certain floodplain environments, including floodways, it is important that the lines be specifically engineered, constructed, and placed with consideration given to the flooding forces anticipated at the specific site, particularly lateral and buoyancy forces.
If any lines involve a water crossing, an engineering study would need to be completed to determine whether the project meets the floodway standards and that the floodplain limits are not affected. If the pipe needs protection against scour or ice, it may need additional protection such as riprap that could also affect flood levels. This may require a hydraulic model of the river reach showing existing and proposed conditions, particularly in relation to flood elevations. Backup model information from the existing Flood Insurance Study may be available in the archives of the State Planning Office Floodplain Management Program, or through FEMA’s Region I office in Boston.
Boat Landings, Marinas, Piers
It is the recommendation of the Maine Floodplain Management Program that the following conditions be met for this project:
- Floats comprising the docking facility shall comply with all applicable local, state, and federal regulations, and should be engineered by a registered professional engineer. There should be an action plan for removing floating docks in the event of severe weather and a storage location secured during such events as well as during the off-season, which is outside the floodplain.
- Flood damage resistant materials are to be used in areas below the base flood elevation (BFE).
- Methods of design and construction for should be developed by an engineer to withstand the anticipated wind, water and wave forces of a base flood event at the site, particularly for coastal velocity areas zoned as V1-30 or VE zones.
- Any electrical utilities serving these facilities should be protected against infiltration of flood water and the main panel and access to it should be located outside the floodplain, allowing for safe access and shut off of power during flooding events.
- Any fill that may be proposed to be added should be placed such that it will not raise the BFE. It should also be protected against erosion and scour and placed so that it will not cause additional scour or erosion from flood waters.
- Floodway encroachment standards apply for all projects located in the floodway.
Stream Crossings, Bridges
For any project involving a stream crossing, if work will occur below the BFE, the work must be done by a Professional Engineer and must meet the floodway standards.
Altered or Relocated Watercourse
All development associated with altered or relocated portions of a watercourse shall be constructed and maintained in such a manner so that no reduction occurs in the flood carrying capacity of the watercourse.
Roadways or Railroads
As with all projects, roadways and railroads should be located above the BFE if possible. If a new or reconstructed transportation corridor is located below the BFE, provision should be made for emergency access via other routes, and for emergency closure of the facility. Design and construction should be done to avoid scour and erosion due to flood waters.
Remember: Always check with the local code enforcement officer to be sure a community has not adopted regulations that are more restrictive than state standards.
If you need additional assistance with your project, please submit your request to the Maine Floodplain Management Program.
Maine Floodplain Management Program
Department of Agriculture, Conservation & Forestry
93 SHS, 17 Elkins Lane
Augusta, Maine 04333-0093
or submit via e-mail to firstname.lastname@example.org