A catastrophic oil spill was waiting to happen.

That's what one expert who has studied government data on the huge and growing number of Gulf of Mexico spills is saying.

"There have been thousands of spills from 1990 to 2009," said Walter Hang, head of Toxics Targeting, an Ithaca, N.Y., company that tracks and analyzes federal hazardous spill reports.

While many were small, the sheer number of incidents is mind-boggling, Hang said.

A provision in the federal energy bill passed by the House of Representatives last week could tack $260 onto the average Long Island water bill.

The add-on would pay for the cleanup of a carcinogenic gasoline additive, MTBE, that for decades has been leaking into the ground, posing a growing threat to the island's drinking-water supply.

Sen. Chuck Schumer (D-N.Y.) vowed yesterday to filibuster the bill in the Senate - unless the provision, which protects oil companies from having to foot the bill for the cleanup, is removed.