The Historic Columbia River Highway east of Rowena Point may remain closed for two to three weeks due to the extensive rock slide that occurred there Sunday evening.  The Oregon Department of Transportation says the rockfall is about 200 feet long, scattered across the highway.  The rock fell from a wall next to the highway at about 7:30 p.m. on Sunday.  Some of the rocks are so large that ODOT will have to bring in special equipment to handle its removal.  ODOT spokesman Peter Murphy says the agency is bringing in geology specialists to examine the area for potential future rockfall and to insure that cleanup crews will be safe performing their duties, along with special rock scaling crews to deal with remaining hazards.  In the meantime, the historic highway remains closed to all vehicles, including bicycles, and hikers in the vicinity of the slide.