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2016 FHWA National Hydraulic Engineers Conference Portland, OR August 9-12, 2016

2016 FHWA National Hydraulic Engineers Conference Portland, OR August 9-12, 2016 Hydraulic Design Considerations of a Bridge Crossing a Levee Edward Foltyn, P.E., Sr. Hydraulic Engineer, ODOT Bridge Engineering Section David McDonald, P.E., Hydraulic Engineer, Region 1, Oregon DOT.

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2016 FHWA National Hydraulic Engineers Conference Portland, OR August 9-12, 2016

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  1. 2016 FHWA National Hydraulic Engineers Conference Portland, OR August 9-12, 2016 Hydraulic Design Considerations of a Bridge Crossing a Levee Edward Foltyn, P.E., Sr. Hydraulic Engineer, ODOT Bridge Engineering Section David McDonald, P.E., Hydraulic Engineer, Region 1, Oregon DOT

  2. Background • The existing bridge is a single-span through-truss. It is historic because of the welded truss • The existing bridge is functionally obsolete and is scour critical. Also, there is damage to some of the truss members from vehicular accidents. • The roadway has poor alignment for the agricultural and truck traffic to-and-from a quarry. • This bridge is at the downstream end of a USACE constructed levee system. • ODOT was asked to design and permit a bridge crossing for Umatilla County.

  3. Typical Bridge Hydraulic Considerations • Flooding Issues • No-Rise Certification • Balanced cut/fill below 100-yr flooding • Fish Passage Issues • Federal Aid Highway Program (FAHP) Programmatic with NOAA NMFS (anadromous species, OR - NMFS) • “…procedures and tools for implementing the Federal Highway Administration (FHWA) statewide programmatic Endangered Species Act (ESA) Section 7 consultation and Magnuson Stevens Act (MSA) consultation with the National Marine Fisheries Service (NMFS) and the U.S. Fish and Wildlife Service (USFWS). “

  4. Fish Passage (cont.) • Oregon Department of Fish & Wildlife • Local populations and In Water Work Window (IWWW) • Scour Issues • Long term aggradation/degradation • Both occur in this reach (degradation D/S of exiting bridge, aggradation near the proposed bridge). The abutments for the existing bridge are a choke point • Contraction Scour • Pier scour • No piers • Abutment Scour • Existing bridge is experiencing abutment scour, settlement has occurred

  5. Levee and Bridge Considerations • Could not find much clear-cut information about bridge construction within a levee (large multispan structures generally stay outside of levee) • Limited information about levee encroachment (mostly stay out) • FHWA could not provide any information • USACE “policies” were to stay away from the landside slope toe, but not written in stone

  6. Primary criteria for new design • Roadway alignment needs improvement for agricultural and trucks from quarry • Single span for fish passage, debris, and to eliminate pier scour issues • Had to meet USACE levee criteria • Low chord needs to be above the top of the levee • Any excavation/disturbance is supposed to be behind the landside slope toe

  7. Normal Design at a Levee

  8. Analysis and Design • We obtained a recent FEMA FIS HEC-RAS deck (2010 update of FIS; 100-yr flow 11,000 cfs, 500-yr flow 22,700 cfs) • Modified HEC-RAS data deck to incorporate USACE design flow of 18,600 cfs • The Modified data deck overtopped the levee at the location of the new bridge before the bridge was modeled.

  9. Analysis and Design (cont.) • Contacted USACE, Walla Walla District. They modified the deck • The new alignment for the roadway and bridge leads to a significantly longer span • Wanted to maintain a single span bridge to minimize fish passage, debris, and permitting issues

  10. Current Design at Levee

  11. Preliminary Design

  12. Conceptual Plan

  13. Current Status and Issues • This is a County owned structure and will remain so • Currently the project is delayed for R.W. issues • There are still issues with the existing bridge. It is historic, but the county wants it removed • The existing abutments are the downstream anchor for the levee system. When the existing bridge is removed, who is responsible for the maintenance and likely replacement of this portion of the levee? • USACE Review for Milton-Freewater Water District • Final plans due late winter/spring 2017

  14. Conclusions • When working near a levee, determine the “standards” early in the project • In our case, the levee standards were more strict than any other criteria that we normally use, this stream will never see the effect of a bridge unless the levee fails

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