user: Question: When was the site listed 03/31/1989 in Rockingham county proposed?
Columns: ['CERCLIS ID', 'Name', 'County', 'Proposed', 'Listed', 'Construction completed', 'Partially deleted']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['NHD980520217', 'Troy Mills Landfill', 'Cheshire', '04/30/2003', '09/29/2003', '09/30/2005', '–']
SQL:

assistant: SELECT "Proposed" FROM "Table" WHERE "Listed" = '03/31/1989' AND "County" = 'Rockingham';