Bring 1 gallon water and 1 teaspoon salt to a boil in a Dutch oven. Add beans to pan; cook 3 minutes or until crisp-tender. Drain and plunge beans into ice water; drain.
Combine remaining 1/2 teaspoon salt, vinegar, and next 4 ingredients (through pepper) in a large bowl, stirring well with a whisk. Slowly drizzle oil into vinegar mixture; stir well with a whisk. Add beans to vinegar mixture; toss to coat.