pmls, portland metro levee system
US Army Corps of Engineers
Portland District Website

New Start Feasibility Study of the Portland metropolitan area levee system

U.S. Army Corps of Engineers,
ATTN: Laura Hicks
P.O. Box 2946
Portland, OR 97208-2946



Portland Metro Levee System

PMLS feasibility study area along the Columbia River

New Start Feasibility Study

The Draft Integrated Feasibility Report and Environmental Assessment is posted below in the Related Documents and Resources section. *This document is large and may take a moment to fully load.*

The U.S. Army Corps of Engineers has initiated a Feasibility Study focusing on Flood Risk Management of the Portland Metro Levee System in partnership with the Columbia Corridor Drainage Districts (CCDD) Joint Contracting Authority. CCDD consists of four drainage districts: Peninsula Drainage District #1, Peninsula Drainage District #2, Multnomah County Drainage District and the Sandy Drainage Improvement Company. The study area includes 27 miles of levees along the lower Columbia River within the Portland Metropolitan Area, running from Sauvie Island to the Sandy River.

The levee system is experiencing significant signs of structural vulnerabilities during high water, including sloughing, boils, and seepage. The three-year federal feasibility study process will lead to a recommendation to Congress for federal investment in addressing the problem areas in the Portland metropolitan area levee and drainage system.

The study will focus on developing an integrated plan to address potential system failures, meeting current levee safety standards, and identifying potential impacts from future changes including system consolidation, changing water flow conditions and potential operational changes to the Columbia River System.

The Non-Federal Sponsor on the project is the Multnomah County Drainage District (MCDD), which has been granted decision authority to act on behalf of the four drainage districts. The feasibility study is authorized in Section 216 of the Flood Control Act of 1970.

Public involvement

The U.S. Army Corps of Engineers, in partnership with Levee Ready Columbia, has been hosting ongoing informational meetings on the Portland Metro Levee System feasibility study. The events are open to the public and provide updates on the feasibility study including refinement of alternatives, technical information and analysis conducted to date, and the next steps in the feasibility study process. Past public meetings occurred in August, October and December of 2019. The presentations shown at those meetings are posted below in the Related Documents and Resources section.


Bridgeton Road Map (2.3MB pdf)
Date: Tuesday, February 25, 2020
Time: 8 am
Meeting Location: Western end of Bridgeton Road at Blue Frogs Landing (Marina)
Video: Corps and MCDD discuss alignment options (Youtube)

East Columbia Neighborhood & Yacht Club Map (1.4MB pdf)
Date: Wednesday, March 4, 2020
Time: 8:30 am
Meeting Location: Portland Yacht Club

Heron Lakes Golf Course
Date: Wednesday, July 8, 2020
Time: 2:00 pm
Meeting Location: Virtual

Peninsula Terminal Co.
Date: Tuesday, May 19, 2020
Time: 12:30 pm
Meeting Location: Virtual

Riverside Golf Course
Date: Thursday, September 24, 2020
Time: 10:00 am pm
Meeting Location: Virtual

Public input is critical to the development of this feasibility plan. The Corps wants to hear the concerns and ideas of community members regarding the Columbia River corridor levee system and managed floodplain. The draft report is posted below in the Related Documents and Resources section.

Past public engagement: The Corps and MCDD held two scoping meetings in December 2018 to engage community members in discussing the study process, study milestones, and the development of preliminary alternative strategies for the reduction of flood risk in the Portland metropolitan area. Discussion also focused on modernization of the levees, flows and flood risk, geotechnical studies of the levees, and the economic risk and consequences posed by various flooding scenarios, as well as the effects on natural and cultural resources of alternatives considered.

In addition, The Corps and MCDD held informational public meetings in January 2020 in the Oregon cities of Fairview and Portland.

Our goals

  • Reduce flood damages, in particular critical infrastructure, in the Portland Metro Levee system over the period of analysis
  • Reduce threats to life safety from flooding and increase awareness of flood risk in the Portland Metro Levee system over the period of analysis
  • Increase resiliency of the flood management system over the planning period of analysis
  • Increase reliability of the flood management system over the planning period of analysis
  • To the extent practicable, provide opportunities for recreation, natural resources, and cultural resources
  • Improve operability of the flood management system and decrease flood response and recovery time

Understanding flood risk

Cross section of a river, a levee, and a building protected by the levee show the elements that make up flood risk: hazard, performance, exposure, vulnerability,

The primary goal of the feasibility study is to reduce the risk of flood damages to the Portland metropolitan area, thereby reducing threats to life and safety.

Flood risk is made up of a variety of factors, beyond exclusively the condition of the levees themselves. These factors include: the hazard, system performance, exposure, vulnerability, and consequences.

The essential questions in determining flood risk are:

  • What possible loading events could occur?
  • How well will the levee system perform when the event occurs?
  • What are the consequences if the levee does not perform as expected? What loss of life could occur?

In even simpler terms, flood risk is the probability of a flood multiplied by the consequences of that flood.

Clarification of concerns we have heard

Q: I’m concerned that my property value has been been impacted by the PMLS feasibility study and will be impacted more in the future. What are you doing about this issue?
A: We are actively engaging community members to listen to their concerns. In the Spring of 2020, we walked the proposed floodwall alignments with some communities to capture site-based concerns, questions. . We have not made a decision on the final alignment of any floodwall evaluated in the draft integrated Feasibility Report and Environmental Assessment (FR/EA), nor have we confirmed our decision to construct a floodwall at this point. We had to layout conceptual floodwall alignments to evenly evaluate the cost and benefits of the different alternatives in the draft EA/FR.

The earliest construction would occur is 2025, pending approval and funding. We will spend the next year refining the recommended plan prior releasing the final FR/EA and final agency decision. We would then spend another 2-3 years further refining the design during Pre-construction Engineering and Design (PED). Thus, the final alignment of the floodwall will continue to evolve as the study and design of the plan progresses.

Q: If a 3-foot floodwall is built, would pilings need to be raised so floating homes stay attached during a flood? Aren’t floating home pilings required to be at least as high as the top of levee?
A: The proposed floodwall does not trigger any actions for floating homeowners under City of Portland code Section 28.06.040.D.1, which requires pilings be two feet above FEMA’s 100-year flood elevation, not the top of the levee.

For example, in the Bridgeton area, the FEMA 100-year flood is approximately 32 feet in the North American Vertical Datum of 1988 (NAVD88), therefore, the minimum piling height is approximately 34 feet NAVD88.

Even during an extreme flood larger than the FEMA 100-year event, the construction of the floodwall would have minimal effect on floating homes. An analysis of a 1000-year flood event, which has a 0.1% chance of occurring, as shown in Section 7.5 of Appendix A of the Draft Feasibility Report, was simulated with and without the floodwall. With the floodwall, water levels on the Columbia River were only about an inch higher. The floodwall has very little impact to water levels because the interior area is a relatively small volume compared to the volume of water in the Columbia River during an extreme flood. When the interior area fills with floodwaters, it produces very little change to water levels on the Columbia River.

While it may be prudent to extend the height of the pilings beyond minimum requirements to reduce risk, it is not required beyond two feet above the FEMA 100-year flood water level.

Q: The Tentatively Selected Plan does not adequately account for costs of cleaning up sites contaminated with hazardous wastes. This would be an additional burden on taxpayers.
A: Ideally, we could avoid areas contaminated by hazardous waste, but this isn’t always possible, especially in an urban environment. If we can’t avoid using a site that is contaminated, the non-federal sponsor is responsible for resolving the contamination issue in a manner that meets Environmental Protection Agency (EPA) and Oregon State Department of Environmental Quality (DEQ) standards. However, this does not mean that the non-federal sponsor must bear all the costs of cleanup activities, which are usually borne by the Potentially Responsible Party (PRP) responsible for creating the contamination. The non-federal sponsor may be able to recover clean-up costs or compel the PRP (or responsible third parties), to clean-up the site prior to the acquisition of the land. Before the final feasibility report is released, the local non-federal sponsor must commit either to accepting responsibility for the required response, or initiating procedures requiring the responsible parties to respond.

The draft feasibility report identified 25 potential sites with contamination concerns, but further investigation since the draft report was released shows three potential sites remain. It is anticipated that the number of sites with concerns will continue to decrease.

For the sites that cannot be avoided, an approximate preliminary cost estimate for Hazardous, Toxic, And Radioactive Waste (HTRW) response actions will be included in the final feasibility report. This estimate will be refined with more detail during Preconstruction Engineering and Design (PED).

Learn more about Hazardous, Toxic, And Radioactive Waste (HTRW) policies in Engineer Regulation 1165-2-132

Q: Is the Army Corps of Engineers complying with local and state regulations?
A: Compliance with state and local requirements is not a requirement for federal projects. However, state and local agencies are encouraged to provide their feedback to inform the Corps on the project’s conformance with state and local requirements. In addition, Federal projects require environmental coordination, evaluation and compliance with the appropriate federal agencies or state agencies administering federal laws (Water Quality Certification).