Concerns About Environmental Assessment (EA) and Finding of No Significant Impact (FONSI) for Potomac Park Levee

June 11, 2020

To: Ethan A. Bean via email:

Re: Concerns about EA and FONSI for Potomac Park Levee project and still unaddressed Mall flooding threat

Dear Mr. Bean:

I am writing on behalf of the National Mall Coalition, a nonprofit citizens group based in Washington, DC, whose mission is to help ensure the vitality, beauty, and continued active role of the National Mall in the capital and in American life, to comment on the Draft Supplemental EA and FONSI for the Potomac Park Levee project.

The US Army Corps of Engineers (USACE) and the National Park Service (NPS) propose to add up to 4 feet of earth to the berm north of the Reflecting Pool, construct new earthen berms at 23rd St. and Constitution Avenue, and between the ramps of the Theodore Roosevelt Bridge, and remove 55 mature trees that threaten the levee’s integrity. Alternatives were considered for the 23rd St./Constitution intersection.

The FONSI, Table 1, states that of the project’s potential effects examined, from aesthetics to climate change, all but two are found to have “insignificant effects” or “resource unaffected by action.” The other two – historic properties and “other cultural resources” – are said to be “insignificant effects as a result of mitigation.”

In our view, both the EA and the FONSI have made these determinations prematurely, without the necessary close look at the effects of the project on the human environment – the visitor’s experience – of this part of the Mall, or serious consideration of alternatives to raising the height of the berm. It appears that the 2009 EA and FONSI, on which the current Draft Supplemental document is based, also did not fully consider the effects on the human environment or examine alternatives.

The Effectiveness of the Project as Planned

The National Mall Coalition understands the need to address the condition of the 1930s-era Potomac Park Levee, and its inadequacy to protect against Potomac River flooding into Downtown, particularly in light of the revised 2016 FEMA flood map showing the severe flooding threat. But we have concerns about the effectiveness of the solution, and about applying 1930s- era thinking to a 2020 flooding problem. The EA points out the inadequacy of the berm solution: it says that even with the new levee in place “the project would require additional temporary closure efforts on the levee crest, likely by sandbag, for the project to provide FRM with adequate freeboard for the authorized 700,000 cfs event.”

Even with the addition of four feet of earth, the levee would have to resort to sandbags – the very practice that was replaced by the post-and-panel closure at 17th Street after FEMA deauthorized sandbags there.

Even more alarming, recently updated FEMA flood maps show that even with the improved Potomac Park Levee in place, there would still be severe flooding to most of the same area of Constitution Avenue and Downtown due to another, unaddressed flooding problem: interior or stormwater flooding. The EA states, however, that this levee project “does not provide FRM for flooding that could occur from interior ponding resulting from precipitation accumulating in low areas of the city, or from sewer system failure. Project improvements evaluated in this EA do not cover means to remediate that risk.”

Interior flooding inundated the Federal Triangle and Mall area in 2006, and is predicted to increase in frequency and intensity in coming decades; the levee does not protect against interior flooding. Proceeding with this $14 million project, without having coordinated the project with an effective interior flooding solution, would leave our capital and Mall structures and national treasures still totally vulnerable to stormwater flooding. If a heavy rain event occurs that causes both Potomac River flooding and interior flooding, how will the levee system succeed in protecting our country’s vulnerable public buildings, museums, and public space? The FEMA map indicates it will not.

The EA does not examine alternatives to its 1930s berm solution – a solution the EA acknowledges is not fully adequate. Nor does it address the well-known fact that even with the enhanced levee in place, stormwater flooding remains a threat to this vulnerable low-lying part of the capital.

Unjustified Assumptions

Appendix E to the EA is an extract from a 2016 Interior Drainage Analysis and Risk & Uncertainty Analysis for Potomac Park Levee System. It is not clear why this appendix was included, since the levee is designed only to address riverine and tidal flooding, but be this as it may, Appendix E expresses some troubling assumptions.

  1. Appendix E, p. 21: “An underlying assumption is that the pipes have sufficient capacity to convey the flow collected by the catch basins” (on Constitution Avenue). But the 2006 flood occurred because the pipes could not hold the flow.
  2. Appendix E, p. 22: “A simplifying assumption made in this analysis is that the full pumping capacity of the Main and O Street pump stations is available to drain the Federal Triangle area.” This assumption may indeed be simplifying, but the 2006 flood demonstrated that the full pumping capacity of the Main and O Street pumping stations is insufficient to drain the Federal Triangle in the case of a 200-year flood.
  3. All four 4 scenarios discussed in Appendix E assume a 100-year flood. But the 2006 flood was a 200-year event. Surely those responsible for the 2016 Interior Drainage Analysis were aware of this reality. Yet they apparently tasked their consultant, Tetra-Tech, only with looking at a 100- year flood. Had the analysis modeled a 200-year flood event, we are confident that it would have shown the disastrous effects of interior flooding even with the levee fully completed.

The EA as Post-Hoc Rationalization

The minutes of telephone meetings between USACE and NPS representatives appended to the EA are interesting and rather troubling, in that they suggest why the agencies seem to be uninterested in considering alternatives. They convey the impression that the two agencies had decided what to do and prepared the EA to justify doing it, rather than preparing the EA as part of the planning process leading to a decision about what to do.

For example, a 2016 call opened with the USACE stating the purpose of the new EA is to be “used as the basis to obtain funds to complete the project.” In a call in 2017, NPS asked whether an EA was even required, since NPS had done one in 2009 on the 17th Street closure. These conversations do not suggest much interest on the part of either party in considering alternatives. They have decided what to do; the purpose of the EA is to support doing it. This is fundamentally inconsistent with the purposes of the NEPA.

Given the evident disinterest of the parties in considering alternatives, it is no surprise that on page 3-2 of the EA we learn that the “the only viable alternative identified was to improve the levee per the 1992 GDM.”

Cumulative Effects

The EA’s discussion of cumulative effects at Section 5.4 ignores the cumulative effects of flooding itself. DC has a cumulative flooding problem, but we seem able to consider only stopgap, jurisdiction-specific measures like the East Potomac Park levee project to address it. Put another way, what are the reasonably foreseeable future effects of considering only such measures?

Despite the rather grandiose title given this project – “Washington DC and Vicinity Flood Risk Management” (FRM) – the project actually involves only four local improvements to the DC levee system, designed to manage only riverine and tidal flooding of only 100- year magnitude – despite the fact that the next-most recent flood, in 2006, was calculated to be a 200-year event. The EA is explicit in saying that the “FRM project is designed to manage riverine and tidal flooding only,” and leaves it to local government to address interior flooding: “It will be incumbent upon Washington, D.C. to address remaining flooding threats to the downtown from heavy precipitation that could cause interior ponding and exceed sewer system pump capability” (Executive Summary, p. 6). By ignoring internal stormwater flooding and leaving it to DC to figure out, the EA avoids any real discussion of Cumulative Effects.

It would seem sensible, and consistent with best practice in cumulative effects analysis, to look comprehensively at the whole problem of flooding in DC and seek a comprehensive solution. The USACE has been a leader in the DC Silver Jackets team’s efforts to find such a solution; it is dismaying to see it so thoroughly ignored in this EA.

It is notable that, according to the Executive Summary (p. 6), the Corps has prepared two previous EAs on more or less the same project (1992, 1996), and NPS has produced another (in 2009, on the post-and-panel closure of 17th Street). Is it really cost-effective to keep producing EAs on versions of the same project? Would it not be wise to back up and seriously analyze more comprehensive solutions, and address their impacts in an Environmental Impact Statement (EIS)?

We urge the USACE and NPS to revisit the EA and FONSI. The EA should look at alternatives, including new flood mitigation approaches and technologies being developed in response to climate change and sea level rise in cities and regions around the country and the world. It should include in its evaluation of the project how the proposed levee solution coordinates with a (as yet unidentified) stormwater flooding solution to protect this historic and nationally significant core of the nation’s capital. We believe that a coordinated look at both riverine and interior flooding together, and a serious consideration of 21st century approaches and technologies, may reveal solutions that are more effective than the 1930s era berm solution now being proposed.

The rest of our comments focus on the project’s adverse effects on the National Mall and visitors, and on the consideration of alternatives.

Adverse Effects on the Unity of the Landscape

Raising the earthen berm between the Lincoln Memorial and the Washington Monument by as much as four feet will create a dramatic change to the historic landscape. The existing berm already creates a visual and physical separation between the Reflecting Pool and Constitution Gardens. But increasing its height will create a wall-like effect both visually and physically. Denuding the berm of trees and other greenery that help soften the effect of the berm today will further accentuate the wall-like effect separating the Lincoln Memorial precinct from Constitution Gardens.

The Coalition believes the berm should be identified as an adverse effect on the historic landscape. The seriousness of the adverse effect on this historic landscape is reason to look at alternatives to the proposed plan.

Adverse Effects on the Visitor’s Experience of the Mall

Section 4.3.2 on “landscape aesthetics and visual characteristics” offers only unsubstantiated declarative statements; nowhere in the EA can we find data or analysis to support the conclusion at section 5.3.8 “ that the project “would cause (only) minor and adverse, but temporary impacts to recreation and visitor use.” What studies were done or consultations carried out to develop a basis for this dismissive conclusion?

In our view, the proposed higher earthen berm denuded of trees cannot help but adversely affect the human experience of walking through and around that part of the Mall. We believe there should be added a category to Table 1 for “Human experience” to acknowledge that the Mall is a designed, unified experience for Mall visitors.

The berm enlargement should be identified as an adverse effect on the visitor’s experience since it will significantly impede pedestrians who want to move between those two parts of the Mall. Visitors will experience Constitution Gardens as cut off from the rest of this western part of the Mall. The seriousness of the adverse effect on the visitor’s experience of the Mall is reason to look at alternatives to the proposed plan.

Impacts on Historic and Other Cultural Resources

In considering impacts on historic and cultural resources, at Sections 5.2.3, 5.3.3 and elsewhere, the EA and FONSI rely entirely on a “programmatic agreement” (PA) developed among the USACE, NPS, National Capital Planning Commission, the Commission of Fine Arts, the Advisory Council on Historic Preservation, and the Washington, D.C., Historic Preservation Office under Section 106 of the National Historic Preservation Act (NHPA). The PA, which builds on another PA developed in 2009, is appended to the EA.

In the view of the Coalition and its NHPA experts, the PA is deficient in at least two respects:

  1. It seems to have been developed with no public involvement at all, despite clear direction in the NHPA Section 106 regulations (36 CFR 800) that affected segments of the public be consulted. The PA is very much an interagency document, and it provides only for interaction among the signatory agencies going forward.
  2. It is virtually without substance; it only prescribes process, and the processes prescribed are largely those laid out in the Section 106 regulations, put off until later dates and distributed among segments of the project. Thus the “can” of considering impacts on the historic environment is “kicked down the road”, to be addressed after the decision is made to build the project. This is entirely inconsistent with the statutory requirement of NHPA Section 106 that effects on historic properties be taken into account prior to a federal decision.

By putting off consideration of impacts until after the government is committed to having such impacts, and by limiting that consideration to discussions among the signatory agencies, the PA gives only lip service to compliance with NHPA Section 106. In truth, impacts on historic and other cultural resources are not addressed in the PA, and hence are not addressed in the EA; accordingly, there is no basis for finding that impacts on this aspect of the environment will not be significant.

Consideration of Alternatives

The Coalition urges the USACE and NPS to supplement the inadequate EA with an analysis of alternatives as a means to improve or substitute for the current levee plan:

  • Evaluate alternatives to the proposed earthen berm solution, including the variety of modern strategies and approaches used by cities and countries in the US and around the world facing flooding dangers similar to those in the nation’s capital. What are the alternative solutions? Have they been proved effective? Could they work in DC?
  • Identify one or more stormwater solutions that can be employed in coordination with the proposed levee, or other alternative solution, in order to protect DC in the event of a flood that causes both riverine and stormwater flooding.
  • One example is the National Mall Coalition’s National Mall Underground, which has been studied by the USACE and found to be an effective solution for relieving stormwater flooding in the Mall and Federal Triangle area.
  • Examine how the riverine and stormwater solutions (levee? Underground?) would complement and supplement one another and prevent future flooding of the streets, buildings, museums, and so on in the event of future flooding.

The National Mall Underground as Back-Up during Potomac River Flooding

The Coalition believes that the EA for the Potomac Park Levee project cannot treat Potomac River flooding between the Lincoln Memorial and Washington Monument in isolation. It must acknowledge the interrelated flooding threats, especially riverine and stormwater flooding in the Federal Triangle and Mall area. And because the EA recognizes that raising the height of the earthen berm will not stop flooding and will require additional sandbags, the inadequacy of the levee solution must be seen as reason to continue to seek better solutions. We believe the National Mall Underground could play a role in helping with Potomac River flooding.

The Underground flood reservoir, bus parking, geothermal project is designed to take in floodwaters from the Federal Triangle and Mall areas during stormwater flood events. But it could be adapted to serve as a back-up for riverine flooding. Pipes could be laid under Constitution Avenue from the Underground to the 17th Street closure. Potomac River floodwaters flowing down 17th Street could be pumped to the Underground. This would be useful for collecting floodwater while the 17th Street post-and-panel closure is being put in place, which can take half a day. The Underground also could collect excess floodwaters that might overtop the raised earthen levee, thus obviating the need for sandbags during heavy flooding events.

As leaders of the DC Silver Jackets flood team, the USACE and NPS have tried but not succeeded in bringing DC and federal entities to agreement on a solution to the Federal Triangle and Mall area stormwater flooding threat. But without a solution to that flood threat, the levee cannot be seen as the answer to flooding on Constitution Avenue and Downtown. We urge the USACE and NPS to revise the EA to better evaluate the inadequacy of the levee plan, to acknowledge the seriousness of the adverse effects, and to consider alternatives that might better prevent Potomac River flooding as well as be coordinated with an effective solution to the stormwater flooding problem.


Judy Feldman signature



Judy Scott Feldman, PhD
Chair, National Mall Coalition