Combine 6 cups water and farro in medium saucepan. Bring to boil. Reduce heat to medium. Cover partially; simmer until farro is tender, about 20 minutes (about 45 minutes for wheat berries).
Drain well.
Whisk oil and vinegar in large bowl. Season with salt.
Add farro; toss. Cool.
Meanwhile, cook favas in pot of boiling salted water for 3 minutes.
Add peas and cook until just tender, about 1 minute longer.
Drain. Cool in bowl of ice water.
Drain.
Add favas and peas to farro. (Can be made 4 hours ahead. Cover; chill.)
Add arugula and tomatoes to farro mixture. Toss to combine. Season generously with salt. Spoon salad onto platter.
Garnish with additional arugula.
*Farro is sold at some Italian markets; or order from Dean & DeLuca, 800-221-771
Wheat berries are sold at natural foods stores and some supermarkets.
**Available at Middle Eastern markets, some supermarkets and farmers' markets.