I-275 at Skyway Wave Attenuation, Manatee Co, FL

The Department has established the following project requirements: Design, permitting and construction of two breakwaters located approximately 200 feet offshore from the south Skyway fishing pier access road as depicted in the concept plans. The purpose of the breakwater is to provide both wave attenuation to prevent splashing and erosion of the recently repaired seawall and fishing pier access road and also allow for seagrass to grow behind the breakwater to satisfy future seagrass mitigation needs. The breakwater may consist of bank and shore rubble riprap or other wave attenuating products meeting the specifications below: Location #1 – Breakwater to be established at elevation minus 7.5 feet NAVD88 and rise to a minimum elevation of +3 feet NAVD 88 (10.5 feet tall) corresponding to the height of the existing seawall. The breakwater shall be a minimum of 1180 linear feet (LF) and provide a minimum of 3.0 acres of potential new seagrass growth bed area. Location #2 - Breakwater to be established at elevation minus 5.5 feet NAVD88 and rise to a minimum elevation of +3 feet NAVD 88 (8.5 feet tall). The breakwater shall be a minimum of 1512 LF and provide a minimum of 2.75 acres of potential new seagrass growth bed area. The proposed breakwater must demonstrate attenuation of at least 85% of the wave energy at the existing seawall for the 50-year return period event relative to both waves and storm surge at MHHW conditions with sea level rise (minimum of 0.29 meters over 100-year design life). Detail and specify how the breakwater will resist and avoid subsidence, settling, overtopping, and shifting to ensure uniformity along the horizon. Additionally, demonstrate how the proposed breakwater will minimize and prevent scour both along the seaward face and at the ends of breakwater.