Top oil executives faced a second day of grilling on Wednesday by U.S. lawmakers over a gushing well leak in the Gulf of Mexico as BP scrambled with its latest deep-sea effort to control the huge spill that threatens environmental disaster.

BP Plc, Transocean Ltd and Halliburton Co are all back in the hot seat in Washington for their roles in what could be the worst oil spill in U.S. history. In Tuesday's Senate hearings, company officials traded blame with none having a concrete solution or explanation for the disaster.

A desperate race is on to contain the catastrophe with BP preparing another potential subsea fix and troops -- in some areas accompanied by prisoners -- rushing to limit damage to the coast, where oil has started to reach shorelines.

An attempt to maneuver a top hat containment dome over the seabed leak -- the second such effort in days -- was under way on Wednesday. BP officials have said they cannot be certain it will succeed, given the difficulties of working almost a mile under the ocean surface.

Investors have driven the value of BP shares down more than $30 billion, far exceeding even the worst estimates of the spill's cost, reflecting uncertainty about how the calamity will play out, with an unprecedented and shifting situation.

BP shares were down slightly in midday trading on the London stock exchange.

With oil gushing unchecked from the sea floor at an estimated daily rate of least 5,000 barrels (210,000 gallons/795,000 liters), and the expanding slick oozing toward land, Wednesday was shaping up to be another rough one for the oil industry and its soiled reputation.

The U.S. House of Representatives hearing, which begins at 10 a.m. EDT (1400 GMT), and more panels in coming weeks could spawn legislation on offshore drilling, an issue that has been thrust onto President Barack Obama's crowded domestic agenda.

HARSH INQUISITION

If Tuesday's hearings are anything to go by, Wednesday's congressional grilling is likely to be harsh.

In two separate hearings on Tuesday, senators accused executives from the three companies of trying to shift the blame to each other and subjected them to tough questions about safety and how the well was sealed.

Senator Ron Wyden, a Democrat, at one point interrupted BP America's president, saying, The culture of this company has been one accident after another. BP had been trying to repair its image since a 2005 explosion at its Texas City refinery killed 15.

Some also questioned the response, noting BP seems to be trying various solutions to cap the gushing oil without any certainty of success.

We've seen the most catastrophic possibilities and it seems to me like they're flailing around going from one thing to another not really knowing what in fact is necessary to stop this, short of that relief well that will just take way too long, Democratic Senator Robert Menendez said on ABC's Good Morning America on Wednesday.

BP is now trying to cover the leak with a much smaller funnel than the 98-tonne dome it tried in vain to put in place over the weekend.

The so-called top hat dome has been lowered to the seabed floor and is being readied for deployment by the end of the week, BP spokesman Bryan Ferguson said on Wednesday.

He said BP also is trying to drill a relief well, which could take 80 more days. Within two weeks the company hopes to try to plug the leak by pumping materials like shredded tires and golf balls into the well at high pressure.

PROTESTS PLANNED

Protesters are becoming more active, with many in place at the Capitol Hill hearings. On Wednesday, an activist group called Seize BP plans protests at the company's offices and other sites across the United States to demand the government freeze the company's assets to ensure payment for the cleanup and compensation for those hurt by the spill.

Eleven workers were killed in the April 20 explosion that sank the rig. Fisheries and tourism, two of the Gulf's economic mainstays, and birds, sea turtles and other wildlife, are all threatened by the unfolding fiasco that could next month surpass the massive Exxon Valdez disaster in Alaska in 1989.

Cathy Norman of the Edward Wisner Donation, a land trust that owns the property that makes up the Port of Fourchon, the principal supply harbor for the Gulf's deepwater oil and gas industry, said the area's shoreline already is disappearing at an astronomical rate.

The land is holding on by its fingernails. If oil gets in there and the plants all die off, we're going to have just all water, she said.

BP spokesman Daren Beaudo, who took reporters on a boat tour, said oil had washed ashore at three locations: Dauphin Island, Alabama; the Chandeleur Islands off Louisiana; and the South Pass-Port Eads area on a remote stretch of Louisiana's mainland.

The National Oceanic and Atmospheric Administration forecast persistent southeast winds throughout the week, which have the potential to move new oil onshore.

FISHERMEN IN TROUBLE

Fishermen said news that oil had made land has increased their fears.

Everybody's scared because ... commercial fishing is our way of life in Lafitte, and if we ain't got that we ain't got nothing, said fisherman Lance Lacrose in Venice, Louisiana.

Louisiana Governor Bobby Jindal on Tuesday urged the National Guard to expand efforts to reinforce the state's storm-battered shoreline as a buffer against the slick.

Jindal's call for additional helicopter sand-bagging operations along stretches of beach, and crews to fill in other shoreline breaches with sand hauled in with dump trucks, came just as the state ran short of oil containment booms for newly menaced coastal areas west of the Mississippi River.

The Unified Command for spill response operations said the U.S. Air Force was flying in additional boom to Louisiana from Alaska. But Jindal said time was growing short.

Jindal also sought approval for plans to dredge sand from the Gulf floor to build artificial barrier islands in three zones off southeastern Louisiana.

(Additional reporting by David Alexander in Washington, Shaleem Thompson and Don Pessin in Venice, Louisiana, Verna Gates in Mobile, Alabama and Tom Bergin in London; Writing by Deborah Charles and Ed Stoddard; editing by Bill Trott )

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