The Union Street Undercrossing in The Dalles will be closed to all traffic at times until further notice due to a combination of snow melt and rain elevating the Columbia River, causing it to overtop its banks in some locations and leading to water at the undercrossing to be deep enough to be hazardous to vehicles, bicyclists and pedestrians.  According to the Corps of Engineers, which operates the dams, the high water level of the Bonneville Pool is necessary for flood control due to recent rain and snow melt.  When necessary, Union Street northbound will be closed to through traffic at the railroad tracks, and will be completely closed north of the Hattenhauer access road.  Intermittent access to Lewis and Clark Festival Park will be open as river levels allow.  Approaching the undercrossing from the west side, West 1^st Street will be closed to through traffic at Terminal Way and will be completely closed beyond the employee access to the Oregon Cherry Growers Riverside facility.  Motorists, bicyclists and pedestrians are encouraged to use Webber Street as an alternate route to access West 1st Street and the west section of the Riverfront Trail during times the underpass is closed.  The closure may be periodic and sometimes sustained for several days during the spring water runoff times.