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U.S. Army Corps of Engineers28 August 2019
PORTLAND METRO LEVEE SYSTEMFLOOD RISK MANAGEMENT FEASIBILITY STUDY
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2PURPOSE OF MEETING–Update on Corps’ planning process for the Portland Metro
Levee System Feasibility Study since the December open houses
–Explain next steps, including when the draft report is scheduled for release to the public for comment
STUDY AREA
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4STUDY AUTHORITY AND SPONSOR–Authority: Section 216 of the Flood Control Act of 1970
(33 U.S.C. § 549a)
–SMART Planning status: 3x3x3 compliantTitle IV, Division B of the Bipartisan Budget Act of 2018, Public Law 115-123, enacted February 9, 2018 authorizes the Government to conduct the study at full Federal expense.
–Non-Federal Sponsor: Columbia Corridor Drainage Districts
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<3 months <9 months ~ 12 months ~ 6 months~ 6 months
Alternative Evaluation& Analysis
Feasibility Analysis of Selected Plan
Washington-level Review
Alternatives Milestone9 Jan 2019
Tentatively SelectedPlan Milestone3 Oct 2019
Agency Decision Milestone3 Apr 2020
Chief’s Report Signed
3 Oct 2021
Draft Report Released for
Concurrent Review3 Dec 2019
District FinalReport Package
Transmittal2 Apr 2021
Scoping & Alt. Formulation
Draft Chief’s Report
Released
Section 1002 letter to NFS (<90 days after FCSA executed)
KEY MILESTONES IN A 3x3 STUDY
KeyDecision Milestone
Product Milestone
Includes Final Biological Opinion
<-------------------------- $800k --------------------------->
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CORPS FEASIBILITY STUDY PROCESS
ScopingAlternatives Formulation & Analysis
Feasibility-Level Design
Chief’s Report
Completed April 2020 – April 2021 April 2021 – Oct 2021
• Public input addressed• Data gathering• Environmental
coordination began
• Formulate, evaluate alternatives
• Draft Feasibility Report & Environmental Assessment released for public review, comment
• Agency endorsement for further design of recommended plan
• Further refine recommended plan; develop ~35% designs and cost estimate
• Final Feasibility Report & Environmental Assessment released
• Report to Congress to seek authorization for Construction
• Environmental compliance complete
Present
7WHAT IS FLOOD RISK?
Risk = Hazard + Performance + Exposure + Vulnerability + Consequences
Flood Risk (simplified) = Flood Probability x Flood Consequences
8FEDERAL INTERESTLevee System–All 4 drainage districts were authorized
and constructed in either or both the 1936 and 1950 Flood Control Acts.
–Additional work has occurred on the flood control system in all 4 drainage districts in subsequent years
SignificanceThe study area is a cornerstone to the regional, statewide, and national economy with over $16 billion in annual economic activity generated from businesses and over $7.3 billion in property values within the levee protection area.–Population At Risk estimated at approximately 60k–Thousands of businesses–12% of Multnomah County’s jobs–Drinking water supply to 966,600 customers–Natural gas pipeline that serves two states –2 airports:
• Portland International Airport (50k passengers/day, 18.4 M/year) • US Air National Guard Base
–3 Interstate highways: I-5, I-205, I-84–2 Transit and a Class I freight rail lines
9PROBLEMSConsequences of flood risk– Life Safety: large population at risk; difficult to evacuate– NED Economic Losses: critical infrastructure, structures, contents, vehicles,
hazardous materials inundation
Weaknesses in existing system– Overtopping of existing levees– Weak points (e.g. Railroad embankment)– Aging infrastructure– Pump stations lack of adequate pumps
10OBJECTIVES & CONSTRAINTSObjectives (within the PMLS, over the period of analysis)– Reduce flood damages, in particular to critical infrastructure– Reduce threats to life safety from flooding, and increase awareness of flood risk – Increase resiliency of the flood management system– Increase reliability of the flood management system – Improve operability of the flood management system – To the extent practicable, provide opportunities for recreation, natural resources,
and cultural resources.
Constraints– Cross-levees must stay in place – Railroad embankment will not be considered a levee in the same alignment.– Existing road infrastructure remains unchanged.
11INITIAL MEASURES1. Elevate structures2. Flood proof buildings3. Buy outs4. Relocation of residences/ businesses/
critical infrastructure5. Widen levees6. Early warning/flood evacuation
systems7. Increase levee heights (this includes
cross levees, mainstem, slough)8. Maximize/increase flood storage capacity
in the Willamette Basin Projects9. Bigger facility: buy real estate to expand
horizontal10.Add pump capacity11.Add gates12.Add ring levees13.Riprap14. Improve Flood Fight: access roads,
mobility of flood fighters, remove restrictions for equipment
15.Automate operations in the systems16. Improve permeability: paved parking lot
replaced with grid & grass17. Increase wetlands/retention ponds18.Complete Seismic retrofits19. Install Portable pumps similar to Brazil20.Add redundancy for pump system21. Install Submersible pump stations22. Improve/Increase Debris control23.Relocate MCDD Headquarters out of
floodplain (COOP plan)24.Reroute water/floodwater25.Construct levee next to railway/ highway
to act as drainage seep26.Aquatic invasive plants control/eradication27.Recreation trails on top of levees28.Operate tide gates to increase flow29. Improve/Increase seepage berms30.Build additional levees/floodwalls31.Remove existing levee (Pen 1)
32.Rehab or replace mechanical/structural features: gates, valves, pumps
33.Adjust/ensure levee slopes meet current standards
34.Relocate transportation corridors35.Utilize setback levees36.Education on flood risk37. Install/Improve Signs for evacuation38.Removal of Levee Vegetation39.Address existing erosion/control future
erosion on levees40.Reduce Area of Protection41.Establish "safe zones" for evacuation
Stem wall42.Add relief or overflow areas43.Zoning44.Secure floating homes
12RECONNECTING PEN 1Minimal flood risk benefits: If Pen 1 levees didn’t exist during February 1996 flood, decrease in flood levels would have been negligible. (0.02’)– Capacity– Conveyance
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FUTURE WITHOUT PROJECT CONDITION
Increase Levee Height Between Pen 2 and MCDD
14MEASURES RETAINEDStructural5. Improve levee performance7. Increase levee heights
10. Add pump capacity20. Add redundancy for pump system22. Improve/Increase Debris control30. Build additional levees/floodwalls32. Rehab or replace mechanical/
structural features: gates, valves, pumps
Non-Structural6. Early warning system/flood
evacuation system14. Improve Flood Fight15. Automate operations in the systems36. Education on flood risk37. Install/improve signs for evacuation41. Establish "safe zones" for
evacuation life/safety
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HOW CAN THE SYSTEM FAIL?
19PROBABILITY OF LEVEE FAILURE?
Probability of breach
0 1
Riv
er e
lev.
Less fragileMore reliable
More fragileLess reliable
20RAILROAD SEGMENT–Site of levee breach during 1948 flood–Unknown condition currently–Currently assuming no cooperation is
possible with railroad, though discussions continue
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MODEL RESULTS: FUTURE WITHOUT PROJECT
22INTERIOR DRAINAGE
Flooding caused from stormwater runoff that cannot be controlled by pump stations.
23INTERIOR DRAINAGE
Sandy Pump Station was swamped in February 1996 storm
24LEVEE BREACH SCENARIOS
DEPTH ARRIVAL TIME
25CONSIDERATION OF ENVIRONMENTAL & CULTURAL RESOURCES
Obtain early feedback from stakeholders• Open houses• Early coordination and pre-consultation with agencies and
federally recognized tribes
Evaluation of alternatives• Describe affected environment• Describe impacts of alternatives: avoid, minimize, mitigate• Evaluate environmental consequences
Agency & Public Review• Consultation with agencies and federally recognized tribes• Circulation of Draft Integrated Feasibility Report and
Environmental Assessment 3 December 2019
NEPA
Clean Water Act
Endangered Species Act
Fish and Wildlife Coordination Act
Migratory Bird Treaty Act & Eagle
Protection Act
National Historic Preservation Act
26LOCAL SPONSORSThe four individual drainage districts serve
as the local sponsors of federally-authorized levee system. Working closely with the US
Army Corps of Engineers on feasibility study. Also, members of Levee Ready Columbia
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20+ member coalition committed to: a) ensuring the levee system meets federal safety standards b) modernizing the infrastructure and the way it is managedc) making the most of opportunities to improve the environmental and
recreational value of the area
LEVEE READY COLUMBIA
DISCOVERY PHASE: 2013-2018
Levee Engineering Assessment
Flood Risk Assessment
Encroachment Evaluation Climate Change Study
Community Asset Inventory Economic Inventory Environmental
InventoryGovernance &
Revenue Analysis
CERTIFICATION NEEDS
PLANNING & IMPLEMENTATION PHASE2019 2020
Recertifying the levees
• Technical Advisory Committee Scoping Project Alternatives for minimum certification requirements + additional benefits
• LRC partners begin discussing responsibility and funding of certification projects + enhancements
• LRC partners review project alternatives and okay for public review.
• Community conversation about certification projects and added benefits
• Project partners consider feedback, make decisions about projects that can move forward.
Governance Reform
• Request of legislature to create new governance structure to take over management of levees
• New district’s initial board is appointed and oriented.
