user: Question: What is the surface for the Riverhead Raceway?
Columns: ['Track', 'City', 'State', 'Opened (closing date if defunct)', 'Surface', 'Length']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Altamont Motorsports Park', 'Tracy', 'California', '1966-2008', 'Asphalt', 'miles (km)']
SQL:

assistant: SELECT "Surface" FROM "Table" WHERE "Track" = 'Riverhead Raceway';