Portland-Milwaukie Light Rail Bridge Construction, June 2011 - TriMet

River Depth• 77.52’ vertical clearance for 150’ section of main span• 65’ vertical clearance for entire span 128 years of daily water heights evaluated to select vertical clearance (1879-2007) Since last dam installation on the Willamette, Columbia, and tributaries, highest riverelevation was 28.5’ during1996 flood – ordinary high water elevation is 14.7’ Excluding 1996 flood, the highest river elevations recorded range from 16’ to 20’between November and June. Riverbed roughly 53’ below mean water elevation (avg.) at East Tower, 22’ at West6