CREATE TABLE table_51656 ("CERCLIS ID" TEXT, "Name" TEXT, "County" TEXT, "Proposed" TEXT, "Listed" TEXT, "Construction completed" TEXT, "Partially deleted" TEXT)

What construction completed is named nelson tunnel/commodore waste rock?
SELECT "Construction completed" FROM table_51656 WHERE "Name" = 'nelson tunnel/commodore waste rock'
SELECT "Construction completed" FROM "table_51656" WHERE "Name" = 'nelson tunnel/commodore waste rock'