7.1.14 Drainage and Stormwater Management Facilities

Refer to discussion in Section 5.4.13 and the Pond Siting Report on file.

Water Quality Treatment: The alternative SMFs have been evaluated to provide treatment for the entire project limit in accordance with the following State standards based on the ERP Applicant's Handbook Volume I. For the impaired basins, BMP Trains was used to show a total of 80% nitrogen and 80% phosphorus removal for proposed project due to the impairment of waterbodies. A higher rate of nutrient removal of 95% on nitrogen and phosphorus will be evaluated for the Interim Improvements condition in the future phase to accommodate the encroachment of OFW's boundaries at the watershed downstream end.

Water Quantity: SWFWMD has water quantity criteria for open basins that must be satisfied.

• Southwest Florida Water Management District – The District's design storm event for construction activity is the 25-year/24-hour storm for open basins (40D-40, F.A.C.). It will be necessary to demonstrate that the post-development peak discharge from the design storm does not exceed the pre-development peak discharge for the same storm event for open basins.

7.1.15 Floodplain Analysis

The project’s drainage design is to provide floodplain compensation in compliance with FEMA, SWFWMD, and FDOT guidelines. No net encroachment shall occur as a result of the proposed activity.

All floodplain within the right-of-way is assumed to be completely impacted. This includes both existing right-of-way as well as areas where additional right-of-way has been proposed for roadway or use as stormwater management facilities.

The following floodplain information for the project area was reviewed:

• FEMA Flood Maps – The Flood Insurance Rate Map (FIRM) Community-Panel Number that includes the project area is 12081C0168F, 12081C0164F, 12081C0306F, 12081C0302F, effective August 28, 2008. Please refer to the project FEMA FIRMs included in Appendix A.
• City of Bradenton Watershed Study – The City of Bradenton Watershed model was used for floodplain evaluations and impacts for US 41, South of the DeSoto Bridge. Please refer to Appendix A.

The project traverses through two FEMA floodplains, including Zone AE on land and Zone VE over the Manatee River (North American Vertical Datum 88 (NAVD88)). The DeSoto Bridge is located over the Zone VE, but this should not impact the project. Roadway widening may impact the floodplain, and compensation will be accounted for in the pond design. Floodplain compensation

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