1. Heat olive oil in a 7-quart pot over medium heat. When hot, add the scallions and garlic, and saute until fragrant, about 5 minutes. Add tomatoes and chipotle in adobo, and cook for 3 minutes. Chop up 4 of the cilantro sprigs, add to the pot, and cook for another 2 to 3 minutes.
2. Stir in 1 1/2 tsp. salt, 1 1/2 tsp. pepper, and cumin. Add pork ribs and brown on all sides, 5 to 7 minutes. Stir in 10 cups water. Add rice, peas, and carrots, and stir again. Drop in the remaining cilantro sprig.
3. Cook, covered, over medium heat until water has been mostly absorbed and rice grains have opened, about 60 minutes. Turn off heat; leave covered for 10 minutes.
4. Taste broth and season with more salt, cumin, and black pepper if necessary.