2012 FDOT Mitigation Plan - Southwest Florida Water Management ...

REGIONAL MITIGATION PLAN
BACKGROUND INFORMATION
Mitigation Project Name: Ft. DeSoto Park – Ecosystem Restoration Project Number: SW 70
County: Pinellas
Location: Section 8, 9, T33S, R16E
IMPACT INFORMATION
(Proposed Construction Date)
1 -FM: 2569031, SR 682 (Bayway Bridge), SR 679 to W. Toll Plaza ERP #: 4423532.000 COE #: no permit required
2-FM: 2570831, SR 699 (Gulf Blvd.)–192 nd Ave. to Walsingham/Ulmerton (2011) ERP #: 44025373.000 COE #: 200307110
(NW 14)
3-FM: 4107552, SR 679 (Pinellas Bay Struct. E) @ Inter. Waterway (Undeter.) ERP #: 47023803.000 COE #: 200204286
(NW-PW)
Drainage Basin: Upper Coastal Water Body: Intercoastal Waterway SWIM water body? N
MITIGATION ENVIRONMENTAL INFORMATION
Mitigation Type: Enhancement
Mitigation Area: 16 acres
SWIM project? Y Aquatic Plant Control project? N Exotic Plant Control Project? N Mitigation Bank? N
Drainage Basin(s): Upper Coastal Water Body(s): Mullet Key Bayou SWIM water body? Y
Project Description
A. Overall project goal: The Ft. DeSoto Park Aquatic Habitat Management Area includes islands that were
physically connected to Mullet Key in the 1960’s by the construction of filled causeway roads (Figures A, B,
photos). Since no bridges or culverts were installed, these causeways blocked historic tidal circulation patterns
throughout the interior bay area (Mullet Key Bayou) along the north side of Mullet Key, resulting in severe stress
and mortality of seagrass habitat. With construction of a 40-foot bridge span through the Pinellas Bayway
causeway, flow patterns will be restored to the inner bays and enhance the health and survivorship of adjacent
seagrass beds. Based on previous studies, the minimal area of seagrass enhancement area associated with the
bridge is 230 acres (Figure B), with secondary enhancement of the adjacent mangrove habitat along the
causeway and additional seagrass beds further from the structure. Prior to the bridge construction in 2004, due to
the substantial ecological benefits, the project was supported by multiple agencies for over 15 years but could not
be implemented due to insufficient funds. The ecological value of this project has been recognized with Pinellas
County receiving regional, state, and national awards for engineering and environmental excellence.
B. Brief description of pre-construction condition: Prior to construction, tidal flow patterns filled the inner
bays, with slow and often stagnant hydrologic circulation. This recirculation problem resulted in elevated water
temperatures in the summer, decrease in dissolved oxygen, water quality degradation, and associated seagrass
mortality.
C. Brief description of constructed conditions: With assistance from eight agency funding sources, Pinellas
County constructed the bridge span in the location of historically open water break between two islands (Figures
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