100 days in, Gulf spill leaves ugly questions unanswered

The Gulf of Mexico oil disaster reached the 100-day mark Wednesday with hopes high that BP is finally on the verge of permanently sealing its ruptured Macondo well.

But years of legal wrangles and probes lie ahead even after the well is killed, and myriad questions remain about the long-term effects of the massive oil spill on wildlife, the environment and the livelihoods of Gulf residents.

BP aims to start the "static kill" on Sunday or Monday, pumping heavy drilling mud and cement down through the cap at the top of the well that has sealed it for the past two weeks.

Five days later a relief well should intercept the damaged well, allowing engineers to check the success of the "static kill" and cement in the area between the drill pipe and the well bore.

This so-called "bottom kill" should finally plug the reservoir once and for all, but it will not answer how the catastrophe was allowed to occur and who is responsible.

While the last surface patches of toxic crude biodegrade rapidly in the warm waters of the Gulf, the long-term impact of what is thought to be the biggest accidental oil spill ever may not be realized for decades.

As the focus shifts to the clean-up in the marshes and beaches of the Gulf coast, so it does to the US Justice Department investigation and state probes in Louisiana, Mississippi and Alabama.

The Washington Post reported Wednesday that a team has been established to examine whether the notoriously close ties between BP and federal regulators contributed to the April 20 disaster.

The "BP squad" will also probe rig operator Transocean and Halliburton, the oil services company which had finished cementing the well only 20 hours before the rig exploded, the Post reported.

If BP needs a reminder of the long legal road ahead as it tries to rebuild its reputation, one will be provided on Thursday as lawyers at a session in Boise, Idaho set the stage for a potential trial of the century.

The proceedings will examine whether complaints from around 200 plaintiffs can be consolidated and determine where the hearings should take place and under which judge.

They will also give trial lawyers a test run for the arguments they will make during what could be years-long legal proceedings against the oil behemoths.

BP announced Tuesday it would replace gaffe-prone British CEO Tony Hayward with Bob Dudley, an American, in a bid to repair its tattered US reputation.

It also posted a quarterly loss of 16.9 billion dollars and set aside 32.2 billion dollars to pay costs associated with the spill.

While BP has said it is the "responsible party" for the clean-up because it leased the Deepwater Horizon rig and owned the leaking Macondo well, it maintains it is not to blame for the disaster.

It has set up a 20 billion dollar fund to pay compensation to the battered fishing, oil, and tourism industries, and must pay civil damages for each of the up to 5.2 million barrels (218.4 million gallons) spilt.

But criminal proceedings are separate and BP, Transocean and Halliburton executives blamed each other in May when they were grilled by senators.

Regulators have been accused of taking bribes and failing to properly inspect the doomed rig, in particular the blowout preventer which should have contained the oil after the initial explosion that killed 11 workers.

Now that the well is finally on the verge of being sealed, US spill chief Thad Allen is planning a "transition" of his resources to focus on the shore clean-up and the claims process.

Sophisticated underwater operations involving fleets of robotic submarines at brain-crunching depths will make way for the less glamorous but equally complex work of Shoreline Clean-up Assessment Teams, SCATs for short.

They will sign off mile-by-mile on the 638 miles (1,027 kilometers) of Gulf Coast where oil has washed ashore.

The beaches should be relatively painless to mop up, but cleaning up the maze of marshes, where there is nothing to stand on and shallow-bottomed boats are needed to navigate the narrow channels, is a logistical nightmare.

An argument is already brewing over the long-term impact with some scientists warning the whole biological network in the Gulf of Mexico could be shifted by the disaster and others dismissing the effect as quite small.

"When you put somewhere between three million and 5.2 million barrels of oil into the Gulf of Mexico I don't think anybody can understate the impact and the gravity of that situation," Allen said Tuesday.