Heat oil in a large pot over medium heat. Sauté onion, garlic, and bay leaf until onion is translucent.
Add water, split peas, barley, and salt. Stir, bring to a boil, then reduce heat and simmer for 2 hours, stirring occasionally.
Add potatoes, carrots, celery, parsley, basil, thyme, and pepper. Simmer another 1 hour, until peas and vegetables are tender.
Adjust thickness with more water if desired. Taste and season before serving.
