Short answer: Parts of downtown Lafayette and central Orinda can be within walking distance of their BART stations, but a simple radius is not enough. Hills, crossings, sidewalk continuity, lighting, and the route to a specific property determine whether the walk is practical.
Local Context
Walk the exact route in both directions. A comfortable downhill trip in the morning can be a different experience uphill after work. Also test the route after dark and consider mobility needs.
What to Verify
Start with the official Lafayette or Orinda station map. Then verify the public walking route and current construction conditions in person.
Related: Orinda versus Lafayette