With senators in a standoff over annual spending bills, the chamber is expected as soon as Wednesday to take up a bipartisan, $9 billion measure that would authorize spending on the nation’s water infrastructure. The bill includes $280 million to address the crisis over contaminated drinking water in Flint, Mich., as well as funding to combat the pollution runoff that has fed the vast bloom of algae in the waterways of southeastern Florida.

The water bill, introduced by Senators Barbara Boxer, Democrat of California, and James M. Inhofe, Republican of Oklahoma, is a rare sign of agreement between one of the most liberal and one of the most conservative members of Congress. It has wide bipartisan support, and staff members expect it to receive more than 80 votes.

However, the prospects for combining the bill with a more modest $5 billion House measure, which contains none of the Flint provisions, remain uncertain.

The Water Resources Development Act, which comes around every two years, does not appropriate new taxpayer dollars for spending. Rather, it targets and maps out projects to be addressed when lawmakers appropriate money in the future. A big part of the bill — roughly $5 billion — is intended for the upkeep of ports, dams, locks, levies and canals managed by the Army Corps of Engineers.