BEST PUBLIC-WORKS PROJECT Bicentennial Park seawall This ten-million-dollar state-of-the-art bulwark is the first sign of real progress toward a future bayfront walkway for downtown Miami. The construction itself is notable for its quality. The seawall's steel casing is a high-grade, coated variety imported from Europe and known as sheet piling, which the contractor, Shoreline Foundation, Inc., is driving into the bay bottom for that sharp, squared-off, 90-degree-angle look. "It's the most impressive seawall you'll ever see. It's going to transform that whole area," says Robert Weinreb, the City of Miami's project director for Bicentennial Park. Portions of the existing barrier were 50 years old, which is about as long as it's been since a major public-works project in Miami was under budget and ahead of schedule like this one. (Funds are federal, state, and local.) The new seawall is the first in a series of improvements that are scheduled to include a sophisticated reworking of the long-neglected park and an expansive baywalk winding southward to the Miami River.