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FDEP’s iNOI Web Application Up and Running

After years of development, FDEP’s new iNOI application is operational! The iNOI can be used for many purposes including completing, editing and submitting NOIs for: Generic Permits for Stormwater Discharge from Large and Small Construction Activities (CGP); Multi-Sector Generic Permits for Stormwater Discharge Associated with Industrial Activity (MSGP); and NPDES Stormwater Notices of Termination (NOT). Additionally, you can pay NPDES stormwater permit fees and track and search stormwater permits. View the iNOI application at:

Stormwater Policy

The following is an overview of the City’s Stormwater Management Policy. It will go into effect immediately.

Water Quality

For new undeveloped properties within the City and the City’s Community Redevelopment Area (CRA), the City will require that water quality is provided for projects involving the construction of greater than 4,000 square feet of impervious surfaces or semi-impervious surfaces subjected to vehicular traffic, or greater than 9,000 square feet total imperviousness. The water quality volume requirements will be similar to the South Florida Water Management District’s (SFWMD) Environmental Resource Permitting guidelines, which are located in Volume IV of the Permit Information Manual, and Chapter 40C-42 of the St. Johns River Water Management District’s Manual.

Water Quality for Wet Detention Systems – If the stormwater system is a wet detention pond, the greater of 1 inch run-off from the total project area, or 2.5 inches of run-off from the impervious area is required. The stormwater system will also be required to recover one half the required treatment volume within 24 to 30 hours. It should be important to note that no more than one half of the required volume should be released within the first 24 hours. If the stormwater system is being permitted through the South Florida Water Management District, then the District’s water quality and recovery requirements will govern.

Water Quality for Dry Retention Stormwater Systems will be required to recover 50 percent of the volume for Wet Detention Systems within three days.

Other systems, such as dry retention with underdrains and exfiltration systems are also accepted by the City. Underdrains are typically chosen because of their ability to drawdown the seasonal high water level to a point where the stormwater management system could effectively operate as a dry retention system. They should be sized to accommodate the drawdown of the seasonal high water level, and the required treatment volume. The water quality volume requirements will be the same requirement for a dry retention system. At least two feet of indigenous soil should be designed between the pond bottom and the underdrain trench. Side bank underdrains are not allowed.

Exfiltration systems are typically utilized in areas with deep groundwater tables and highly permeable soils. These stormwater systems are preferred when the project area is limited and there is no room for an above ground stormwater system. Two feet of separation between the trench bottom and the seasonal high water table will be required, unless the applicant demonstrates based on plans, test results, calculations, or other information that an alternative design is appropriate for the specific site conditions.

Underdrain and Exfiltration systems would be required to have a very detailed maintenance schedule. If they are not maintained appropriately through the life of the system, they may have an increased chance of failure. Adequate placement and spacing of inspection and clean out ports that extends to the surface for access and maintenance purposes are also required. We may also require the use of a secondary system, such as a retention swale with overflow weir, or some other form of Best Management Practices (BMPs) as a back up to the system.

Water Quality for Dry Detention Systems will be required to provide 75 percent of the required volume for a wet detention system. The requirements for the design of the bleed down device and recovery shall be the similar to the requirements for a wet pond.

From various excerpts, and studies, it has been observed that dry detention systems are favorable in removing particulate pollutants, but less favorable in removing dissolved pollutants. Therefore, the removal efficiency of a dry detention system is limited and its use should be restricted to sites that are less than five acres and the feasibility of using other BMPs, such as wet detention and dry retention systems are exhausted before utilizing dry detention systems. [Section 10.0; Applicants Handbook, Regulation of Stormwater Management Systems; Chapter 40C-42, F.AC.]

Design Storm

The design storm for any development within the City is the 10-year, 72-hour storm event. The volume of rainfall for this design storm is typically 7.6 inches. All development within the City should be designed to limit the post development peak rate of discharge to the pre-development peak rate for the 10-year, 72-hour storm event. Orange County’s 25-year, 24-hour rainfall (approximately 8.6 inches of rainfall) can also be substituted in lieu of the 10-year, 72-hour storm.

In an effort to accommodate smaller sites within the City, the City has decided to accept a smaller design storm, such as the 10-year, 24-hour storm (approximately 5.5 inches rainfall). If a proposed project is less than 10 acres, greater than 50 percent imperviousness, and qualifies for the South Florida Water Management District’s- No Notice General Permitting guidelines, Sections 40E-400.315 and 40E-400.316, Florida Administrative Code (F.A.C.), then the 10-year, 24-hour design rainfall amount can be utilized to demonstrate the post development peak rate of discharge does not exceed the pre-development peak rate. The rainfall amount for this design storm can be found on page C-6, Volume IV of the SFWMD’s Permit Information Manual, Surface Water Design Aids.

A variance to the City’s Land Development Code would also be required when designing for the 10-year, 24-hour storm.

An exemption from providing for water quantity and attenuation requirements may be applicable in some cases for small existing developments located within the CRA, and are not part of a larger development plan, which proposes a net increase of less than 10 percent total imperviousness. Please note that water quality requirements may be required.

Porous Pavement

Porous pavement is a special type of pavement that allows rain to pass through it, thereby reducing the run-off from a site and surrounding areas. In addition, porous pavement filters some pollutants from the run-off if maintained.

Porous pavement may substitute for conventional pavement on parking areas, areas with light traffic, and the shoulders of airport taxiways and runways, provided that the grades, sub soils, drainage characteristics, and groundwater conditions are suitable. Slopes should be flat or very gentle. Soils should have field-verified permeability rates of greater than 1.3 centimeters (0.5 inches) per hour, and there should be a 1.2 meter (4-foot) minimum clearance from the bottom of the system to bedrock or the water table [EPA Stormwater Technology Fact Sheet Porous Pavement, 1999].

For re-development within the CRA district in which parking lots are proposed to be constructed with a porous surface installed on a course sand bed with indigenous material as a subbase as required by the DRC and conditions for maintenance set, the City will consider allowing for some credit for the use of porous pavement by reducing the overall paved area by the material’s porosity. A weighted curve number or run coefficient can then be calculated based upon the effective area of the material and the credited area that is considered as existing soils.

Pervious concrete should be designed and maintained as per the City’s standards, which may require a secondary system, such as a retention swale or other BMP that will promote infiltration and reduce pollutant transport offsite. Maintenance and access ports extending to the surface are also required to be installed along with the installation of porous pavement. Porous pavements should be maintained a minimum of four times per year. The maintenance should include vacuum sweeping, high pressure hosing and proper disposal of removed material.

Master Stormwater Pond

The City is also proposing a master pond (or ponds) for the entire CRA District and other ideas to address stormwater issues City-wide. A task force will be established to determine how best to implement the goals the City has established. This process will start with a study being conducted, regulations being reviewed, possible mitigation locations identified, review by staff, review by the community, and review by the regional, state and federal agencies to ensure compliance and ultimately implementation of the overall system. This will allow The City to peruse its goals for the CRA District and the City expanding as proposed without having undue restrictions based on stormwater issues.

Please note the aforementioned guidelines are only an overview of the City’s Stormwater Design Policy. Please refer to the City’s Land Development Code for more detailed information/requirements. For questions or comments, please contact the City’s Public Works & Engineering Department at 407.518.2170.

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