Vital Houston oil tanker routes shut amid spill cleanup

* Coast Guard says no timeline for reopening Houston Channel

* Exxon: Channel closure has not affected Baytown refinery

* Second barge collision on Houston Channel this month (Updates with notice to mariners on length of closure, birds affected)

By Terry Wade

TEXAS CITY, Texas, March 24 (Reuters) - The closure of major Texas shipping channels that deliver crude to more than a tenth of the nation's refining capacity was set to run into a third day and could continue through the week as crews were still working on Sunday night to clean up after an oil spill.

The Houston Ship Channel, which allows oil barges and cargo ships to sail from the Gulf Coast to refiners and terminals further inland, was shut on Saturday (Shenzhen: 002291.SZ - news) following a collision between a Kirby Inland Marine oil barge and a cargo ship, spilling some 4,000 barrels, or 168,000 gallons (636,000 liters), of residual fuel oil.

A warning to mariners issued by the U.S. Coast Guard on Sunday said portions of the Houston Ship Channel and its offshoots to Texas City and Galveston, Texas, along with a portion of the Gulf Intracoastal Waterway could be shut through Saturday March 29 or longer depending on the requirements of the cleanup. Kirby Inland Marine is operated by Kirby Corp.

There were signs of progress on Sunday. Coast Guard Capt. Brian Penoyer said cleanup crews have pumped all remaining fuel oil from the barge, which is partially sunken near the entrance to the channel. The barge has been refloated and moved to a different position near the site of the collision in the channel.

The channel will remain shut "until clean water is assured," Penoyer told reporters at a news conference in Texas City.

A local official said the channel was expected to be shut well into Monday. The official asked not to be identified as the information had not yet been made public.

The outage has yet to impact operations at Exxon Mobil (TLO: XOM-U.TI - news) Corp.'s 560,500 barrel-per-day (bpd) refinery in Baytown, Texas, the nation's second-largest, company spokesman Nicolas Scinta said.

Representatives for seven other refineries in Houston and Texas City, Texas, did not reply to requests for information about possible reductions in production.

As of Sunday evening, 40 ships were waiting to depart the port of Houston and 35 were waiting to enter. Another seven ships were waiting to leave Texas City; five were waiting to sail to that refining hub.

CRUISING TO PORT

Late on Sunday, Carnival Corp.'s cruise liner Carnival Magic docked at the port of Galveston with special permission from the Coast Guard. Carnival (LSE: CCL.L - news) 's ship Carnival (Berlin: CVC1.BE - news) Triumph will be allowed to dock on Monday morning.

Both Carnival Magic and Carnival Triumph are scheduled to depart Galveston on Monday.

A Kirby (Frankfurt: KIY.F - news) -operated barge carrying fuel oil collided with a ship carrying rice at nearly the same location on March 14. In that accident, the cargo ship was damaged, but no fuel oil was spilled.

The Ship Channel is a 55-foot (17-meter) deep pathway for barges and deep-draft ships cut into the floor of Galveston Bay, which averages 20 feet (6 meters) in depth.

The spill is far smaller than that by the Exxon Valdez tanker, which struck a reef in Prince William Sound, Alaska, in 1989. A total of 11 million gallons of heavy black crude oil were estimated to have been released by the Exxon Valdez.

In contrast, only one tank on the barge was ripped open by the collision with the cargo ship in the Houston Channel on Saturday, releasing an estimated 168,000 gallons.

Wildlife Response Services, a Texas-based wildlife rehabilitation service, is helping affected birds and marine life.

Fewer than 10 birds covered with oiled have been sighted and brought in for recovery, said the Coast Guard.

As of Sunday evening, 24 vessels are skimming from the waterway, the Coast Guard said. More that 69,000 feet of floating barriers have been deployed to contain the spill. Another 141,000 feet of barriers are on standby for use if needed. (Reporting by Terry Wade in Texas City, Erwin Seba in Houston, Kevin Murphy in Kansas City, Missouri, Alex Dobuzinskis in Los Angeles and Chris Michaud in New York (Frankfurt: HX6.F - news) ; Editing by Edith Honan, Cynthia Osterman, Bernard Orr, Jan Paschal and Muralikumar Anantharaman)