Sort beans, discarding any foreign material. Place beans in large Dutch oven. Add enough cold water to cover beans by 2 inches. Cover; bring to a boil over high heat. Boil 2 minutes. Remove from heat; let soak, covered, 1 hour. Drain. Add the 8 cups water. Simmer, partially covered, 1 hour. Cook bacon in large skillet until crisp. Add bacon and 2 tablespoons of the drippings to beans. Add tomatoes with juice to beans. Add onions, garlic, chilies, chili powder, dried oregano and cumin. Simmer, partially covered, 3 hours or until beans are very tender. At end of cooking, beans should have a little liquid. If beans become too dry, add more water. If beans have more liquid than you like, uncover and boil over medium heat, stirring more frequently as mixture thickens. Season with salt to taste. Garnish with fresh oregano if desired. Cut lime into wedges; pass at the table to squeeze over each serving.