With the 2005 highway bill nearing its Sept. 30 expiration date, the Senate Environment and Public Works Committee is preparing to pass a “clean— extension, just to carry the current programs over for 18 months.

But just in case an “unclean— bill becomes a viable option, Chairman Barbara Boxer (D-Calif.) is inviting her Democratic colleagues to offer earmarks they would like to attach to the bill.

In an e-mail to staff Tuesday, Boxers’ office noted, “We anticipate a clean extension,— but the chairman would “like to be prepared for all possibilities. With that in mind, Senator Boxer wants to know your boss’ top priority projects.—

The e-mail asks offices to submit their request letters — along with the required certification that the Senator has no financial interest in the project — by July 22.

Ranking member James Inhofe (R-Okla.) has not extended a similar invitation to Republican Senators, his spokesman said, because his biggest concern is getting the extension done quickly, and adding projects is likely to slow down the bill.

The House Transportation and Infrastructure Committee is moving ahead with a comprehensive reauthorization, and its members in June wrote to President Barack Obama complaining about the administration’s endorsement of a simple extension.