The frail and elderly were put on buses Wednesday and authorities warned 1 million others to flee inland as Hurricane Ike steamed toward a swath of the Texas coast that includes the nation's largest concentration of refineries and chemical plants.
Drawing energy from warm Gulf of Mexico waters, the strengthening storm was expected to blow ashore early Saturday between Corpus Christi and Houston, with some forecasting it could become a fearsome Category 4, with winds of at least 131 mph.
Such a storm could cause a surge of 18 feet in Mata gorda Bay and 4-8 feet in Galveston Bay, emergency officials warned. The surge in Galveston Bay could push flooding into Houston, damaging areas that include the nation's biggest refinery and NASA's Johnson Space Center.
Four counties south and east of Houston announced mandatory or voluntary evacuations, and authorities began moving weak and chronically ill patients by bus to San Antonio, 190 miles from Houston. No immediate evacuations were ordered in Harris County, which includes Houston.
About 1 million people live in coastal counties between Corpus Christi and Galveston. Another 4 million live in the Houston area to the north.
The oil and gas industry watched the storm closely, fearing damage to the very heart of its operations.
Texas is home to 26 refineries that account for one-fourth of U.S. refining capacity, and most are clustered along the Gulf Coast in such places as Houston, Port Arthur and Corpus Christi. Exxon Mobil Corp.'s plant in Baytown, outside Houston, is the nation's largest refinery. Dow Chemical has a huge operation just north of Corpus Christi.
Refineries are built to withstand high winds, but flooding can disrupt operations and – as in Louisiana after Hurricane Gustav – power outages can shut down equipment. An extended shutdown could lead to higher gasoline prices.
No matter where Ike hits, its effects will likely be felt for hundreds of miles, said Mark Sloan, Harris County emergency management coordinator.
“It's a very large storm,” Sloan said. “The bands will be over 200 miles out from the center of storm.”