user: Question: Which Year completed has a Dam type of Concrete gravity, and an Impounded body of water of Deep Creek Reservoir?
Columns: ['Dam constructed', 'Year completed', 'Impounded body of water', 'Reservoir capacity', 'Dam wall height', 'Dam type']
Types: ['text', 'real', 'text', 'text', 'text', 'text']
Sample row: ['Blowering Dam', 1968.0, 'Blowering Reservoir', 'ML ( × 10 ^6cuft)', 'm (ft)', 'Rockfill embankment']
SQL:

assistant: SELECT "Year completed" FROM "Table" WHERE "Dam type" = 'Concrete gravity' AND "Impounded body of water" = 'Deep Creek Reservoir';