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<br />2.3.1 1 SEAWALLS <br /> <br />The BPAT observed widespread failure of seawalls and bulkheads along the Gulf of Mexico <br />shoreline (see Figure 2-15). Damage figures from the State of Florida revealed that over 3 miles of <br />seawalls and hulkheads were destroyed by Hurricane Opal, including 1.3 miles of concrete walls, <br />1.0 mile of concrete block walls, and 0.8 mile of timber walls (FDEP 1995). Failed walls <br />contributed to damage of buildings, pools, and other structures, due to loss of backfill and <br />generation of debris. <br /> <br />Many walls appeared 10 have failed because wing walls or return walls were flanked by <br />erosion and scour. Many seawall returns flanked by crosion and scour were no more than 20 to 30 <br />feet long, although some longer returns (50 feet to 75 feet) were also flanked. <br /> <br />Seawalls were usually destroyed when backfill was washed li'OID behind the walls because of <br />overtopping, insufficient wall embedment, or return wall flanking. Habitable structures founded <br />on slabs or shallow foundations, swimming pools, and other structures that relied on seawalls to <br />retain supporting soil, were frequently undermined and destroyed when seawalls tailed. <br /> <br />The BPAT noted that retaining ,valls constructed of concrete blocks were particularly <br />,"lnerable to damage by Hurricane Opal. Walls most likely to have survived were observed to have: <br /> <br />. reinforced concrete slab or sheetpile construction <br /> <br />. sutIicient ,vall height or backfill protection to prevent significant overtopping and loss of <br />backfill <br /> <br /> <br />FigU7~ 2-15 Fractured seawall, damaged by storm forces. Note the erosion of the bank behind the wall. <br /> <br />2-12 SITE OBSERVATIONS <br />