(Recasts first paragraph, adds details of vessel restrictions schedule of movement)
By Erwin Seba
HOUSTON, March 26 (Reuters) - Restrictions at the busiest U.S. energy port on Tuesday continued to affect nearby refineries and slow efforts to end a shipping bottleneck after a massive petrochemical fire and spill near Houston halted vessel traffic for several days.
The U.S. Coast Guard reopened a portion of the Houston Ship Channel to shallow-water vessels during daytime hours to help clear a backlog of nearly 60 vessels waiting to enter and leave a portion of the waterway that connects the Port of Houston to the U.S. Gulf of Mexico.
Gasoline and chemicals from giant tanks damaged by a fire at Mitsui & Co's Intercontinental Terminals Co (ITC) unit in Deer Park poured in the channel last week. No one was injured but emergency workers were still removing the fuels, limiting traffic on a five-mile stretch of the waterway.
A total of 56 ships were waiting to cross the 53-mile (85-km) waterway to the busiest U.S. oil port, the Coast Guard said. Thirty-four ships were waiting to enter and 22 ships to exit.
Four refineries could be affected by the limited traffic: Royal Dutch Shell Plc's Deer Park plant, LyondellBasell Industries NV's Houston facility, Valero Energy Corp's Houston plant and Petrobras' Pasadena Refining System facility.
Lyondell on Monday cut production by 14 percent of the 263,776 barrel-per-day capacity at its Houston refinery and Shell reduced production at its 275,000-bpd joint-venture Deer Park refinery by an unknown amount, people familiar with the matter said.
Houston Pilots, whose members guide vessels in and out of the port, said nine ships, all with drafts - the vertical distance between the waterline and the bottom of the hull - shallower than 34 feet (10 m), are scheduled to transit the area near ITC on Tuesday. The ships carry liquid petroleum gas, cement and general cargo, said port agent JJ Plunkett.
On Monday, officials allowed two or three vessels to leave the area during daytime hours, he said. The vessels were approved after being checked for contamination from the fuel.
The decontamination area can only accept ships with a draft that is less than 34 feet, he said, preventing larger vessels from entering or leaving the upper ship channel.
Traffic was halted Friday on a five-mile stretch of the 50-mile-long ship channel due to the chemicals leak.
Ships may only move through the area near ITC at the rate of one per hour during daylight hours. Barges may only move through the spill area at rate of one per half-hour during daylight hours, the Coast Guard said.
Container terminals and Exxon Mobil Corp's 560,500-bpd Baytown refinery were not affected by the traffic limitations. Those areas account for about 10 percent of the daily traffic handled by Houston Pilots.
Refineries in Texas City were also not affected by the spill, which occurred on Friday when a dam at the ITC facility failed. (Reporting by Erwin Seba; Editing by Bernadette Baum and Jeffrey Benkoe)
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