PORTLAND, Ore. - A megaload of oil refinery equipment approaching a million pounds and bound for the tar sands of western Canada is expected to begin moving through Eastern Oregon on Monday after a night's delay.

The megaload is the first of three that a Hillsboro company specializing in jumbo shipments is expected to haul through Oregon, Idaho and Montana on its way to Alberta.

The 901,000-pound load is for a water purification system described as vital to the oil extraction project.

It was supposed to leave the Port of Umatilla along the Columbia River on Sunday night, but "the equipment took longer than expected to load up," said Holly Zander, spokeswoman for Omega Morgan.

The megaload and transport vehicle are 380 feet long, 23 feet wide and 19 feet high, according to the state Department of Transportation.

The height precludes travel on Interstate 84, except for a short stretch near Pendleton where it will use on- and off-ramps to get around overpasses, the agency said.

Oregon rules allow the megaload to move only after dark, and for no more than 8 hours a night. Crews will block two-lane highways, and the transport must pull over every five to seven miles if traffic needs to get by. The transportation department said vehicles could expect delays of to 20 minutes.

The route planned through Eastern Oregon is about 315 miles. Much of it is on Highways 395 and 26 in some of the most sparsely populated areas of the state.

About 20 protesters gathered at the port north of Hermiston on Sunday night to decry the shipment to a project that environmentalists have criticized for adding to greenhouse gases and aggravating global warming, the East Oregonian newspaper reported.

The company hauled one load of the refinery equipment across U.S. Highway 12 earlier this year, but a federal judge stopped a second load from crossing tribal and environmentally sensitive lands.

Idaho Transportation Department engineers are studying the shipper's route through the state. Agency officials on Monday outlined more specifics of the map, starting from Homedale in the southwest corner where the load will enter he state.

From Homedale, the proposed route takes the load through Marsing and the desert south of the Snake River before connecting with I-84 near Glenns Ferry. The load then heads west on the interstate to Mountain Home and exiting at U.S. Highway 20 and through the central Idaho towns of Fairfield, Carey and Arco. The last leg of the Idaho route includes state. Highway 28 through Leadore and U.S. Highway 93 through Salmon.

The load leaves Idaho and enters southwestern Montana at Lost Trail Pass, with an elevation of more than 7,000 feet.