(Multnomah Falls, OR)  --  The popular Larch Mountain Trail at Multnomah Falls will close September 20th for four to five weeks.  Officials say tension cracks have developed in the trail just past the Benson Bridge and need to be repaired.  The U.S. Forest Service says the problem didn't exist prior to the 2017 Eagle Creek Fire and were likely caused by more underground water flow and extreme temperature events.  The trail was built more than 100 years ago just after construction of the Benson Bridge in 1915.