GreenGov from the White House
Tutt Library has many government documents in print and microform. There are also a number of online publications in the Library Catalog. For a search of government documents in all formats, try this:
Advanced Search: sustainab* [keyword] with Limit by: Collection set to Government Documents
Locate materials by the SuDocs call number
— e.g., A 13.88/2:INT-92.
Note: This is different from Library of Congress classification, also used in the library.
Go to Advanced Search and select Collection, desired document type (U.S., Colorado, etc.)
Find more by checking the subjects page on the Government Documents Libguides and databases.
You can always ask a reference librarian for help too.