I want to preface this post by addressing a question I'm sure some will have: what qualifications do I have that allow me to question what the Sewer District says about dams?
The answer: I don't have any special expertise, but based on their public statements, NEORSD's expertise shockingly also appears to be lacking. All I do here is compare their statements to basic definitions and statements from people who actually are qualified, such as the Ohio Department of Natural Resources (ODNR), which is in charge of classifying and regulating dams. These comparisons reveal that the Sewer District has made multiple statements that are very misleading or even objectively false.
This is extremely important to the ongoing controversy around the Shaker dams. Think about it. Throughout this whole process - all the way back to NEORSD saying they were going to repair both the Horseshoe and Lower Lake dams and through everything that's happened since - it appears that our cities were relying on advice from people they looked to as experts, but who were actually giving them bad information. This includes advice about what new dams would look like and how much they'd cost.
This is a huge problem! Imagine if, years ago, the cities had consulted with independent experts who actually did understand these issues and were tasked with finding a plan that best fit the public interest. Who knows what the situation might look like now?
There are a few major issues here:
1. The possibility of redesigning the dams to a lower classification was inappropriately rejected.
2. The public has been misled into thinking the dams pose some grave danger.
3. Taking a broader perspective, whenever people question any aspects of NEORSD's plans or recommendations, we're told by some that we shouldn't question the experts. When we look more closely, the whole narrative of NEORSD being infallible experts falls apart.
Let's dive into all the details.
The Sewer District said the dams can't be reclassified. Fact check: false
Earlier this year, Cleveland Heights added a page about the Horseshoe project to the city website. The page is Sewer District PR, and I'm sure NEORSD produced most, if not all, of the content. With this update was a new FAQ.
In the FAQ, there was an answer to a question about dam classification that was so staggeringly inept that my jaw dropped.
First, let's go over how dams are classified. You can see the details on the ODNR website.
In brief, dams are rated from I (hightest) to IV (lowest) in three categories: height, storage volume, and potential downstream hazard. Whichever of the three is the highest determines the final classification. The Lower Lake and Horseshoe dams are both class I due to downstream hazard and would be class III by the other categories, so that's the important one to consider.
As ODNR explains:
Class I — probable loss of life
Class II — health hazard, flood water damage to homes, businesses, industrial structures (no loss of life envisioned), damage to state and interstate highways, loss of public utilities, railroads, downstream dams, only access to residential areas
Class III — damage to low value non-residential structures and local roads
Class IV — losses restricted mainly to the dam
The hazard levels are hazards that could potentially occur due to dam failure, based on modeling. (It might be dam failure during a huge storm; class I doesn't necessarily imply there would be any danger from a sunny day breach.)
A note on the term "high hazard dam": we often see the dams described as "high hazard," a scary-sounding term. But high hazard refers to the potential consequences of dam failure, not to whether the dam is likely to fail. An informative blog post from the Washington State Department of Ecology has a good explanation: Dam scary words for un-scary dam conditions
A high or significant classification does not imply that the dam is unsafe. It only reflects the consequences of a dam failure and is used to establish suitable minimum design levels for the safety of the dam. The safety of the dam is a separate issue from the downstream hazard.
Other class I or high hazard dams readers may be familiar with include the dam that NEORSD built and maintains in Lake View Cemetery and the dam at Hinckley Lake that the Metroparks recently rehabilitated. No one considers those dams threats to the community.
The Shaker dams are out of compliance and remedial action is needed. But people shouldn't panic: the Horseshoe dam was already breached after sinkholes were discovered, meaning there is no present emergency, and the Lower Lake dam has never been described by ODNR as at risk of imminent failure.
Importantly, the ODNR page about dam classification also states, "The Division has the right to reclassify any dam as a result of a change in circumstances not in existence at the time of the initial classification."
The Shaker dams are both small compared to most class I dams in the area, raising the question of whether the potential downstream hazard could be reduced without too dramatically changing the dams' sizes.
So, what was the staggeringly inept statement in the FAQ, and why was it so staggering?
There was a question about why the Horseshoe dam was class I. The answer stated, in part, "Because of the presence of dense population and properties downstream from Horseshoe Park, any dam in this location would be classified as a class I dam. Because the presence of population and properties downstream is unchanging, even if a new dam were built that were lower in height and storage volume, it would still be classified as a class I dam."
This is completely incorrect. The classification depends on the potential threat to the dense population and properties, not just their presence. By the logic of this answer, a tiny dam that posed no real threat to anything downstream if it failed would still be class I if a bunch of people lived downstream.
I complained about this misinformation being presented to the public, and the answer was changed to something I think is probably still incorrect, but less blatantly so. Here's a marked-up screenshot of the original answer:
Let's contrast this with an answer provided by ODNR in the Shaker Heights Lower Lake FAQ:
There are generally 3 options a dam’s owner may choose to bring their dam into compliance with Ohio’s dam safety laws: (1) fully remediate the dam to meet all current dam safety standards for the dam’s current classification; (2) modify the dam to meet all current dam safety standards for a lower classification or to remove the dam from the Division’s jurisdiction; or (3) breach (remove) the dam.
So, NEORSD apparently thought a dam couldn't be reclassified after being modified. ODNR (the agency that classifies dams) disagrees.
I don't know how much modification would be necessary, but it clearly is possible, because ODNR said it is. The fact that NEORSD is currently doing a different project, in University Circle, to reduce flooding there could even help with this.
And this wasn't a stray misstatement by NEORSD. During the original fight over saving Horseshoe Lake, Friends of Horseshoe Lake hired a professional engineering firm (TRC) who created a plan for a smaller dam they hoped to get reclassified to class II. In their response to the proposal, NEORSD, apparently thinking they were rebutting this idea, asked if TRC had done this before, and they hadn't. NEORSD did not try to find out whether it was possible.
If only similar logic had been applied to the whole Horseshoe project. Has NEORSD ever previously been in charge of large-scale renovation of a historic park? No? Okay, they can't do it, then.
I want to really harp on how crazy it is to say, "Because of the presence of dense population and properties downstream from Horseshoe Park, any dam in this location would be classified as a class I dam."
According to the ODNR inspection report, the downstream hazards giving the Horseshoe dam a class I rating are the Lower Lake dam and University Circle (and nothing else). That is, it was determined that dam failure could potentially cause a cascade effect of the Lower Lake dam also failing, leading to flooding in Unversity Circle. No class I hazard upstream of Lower Lake was identified.
There are two other, smaller dams on Doan Brook that are also upstream of both the Lower Lake dam and University Circle! The Marshall Lake dam is a class IV and the Green Lake is a class II! Shortly before announcing that they wanted to get rid of Horseshoe Lake, NEORSD completed a project to restore the Green Lake dam!
How could they possibly think that any dam with those downstream features would necessarily be class I, when they'd just done a project on a class II dam with the exact same "dense population and properties downstream"??
Why is this so important? In addition to illuminating how NEORSD are not the infallible experts we've been told they are, it also has a potentially huge effect on the cities' decision-making.
The cities of Cleveland Heights, Shaker Heights, and Cleveland are ultimately responsible for the dams. NEORSD was giving recommendations to the cities that were based, in part, on cost estimates for new class I dams and on the aesthetics of NEORSD's designs for new class I dams. The cities' decision-making has been based on the assumption that NEORSD knew what they were talking about when it comes to dams. A reasonable assumption, one would think, but it appears that NEORSD did not know what they were talking about.
For example, NEORSD's plan for an updated class I Lower Lake dam would ruin the aesthetics of the site with 8-foot concrete walls by the lake. Part of their stated reasoning for recommending not restoring the dam was the plan "drastically changing the feel of the area due to the required concrete flood walls."
NEORSD never considered options for a somewhat smaller, class II dam. Apparently, they didn't realize this was an option.
I'll also mention that we shouldn't assume, without independent expert verification, that compliance with modern class I standards is impossible to achieve without these ugly concrete walls. Even if the dam isn't reclassified, we should be suspicious of this proposal. It could very well be what NEORSD thinks should be done if a new dam were built, not what would need to be done. If you've ever seen the dam NEORSD built in Lake View Cemetery, you know they have a history of building overly large concrete structures.
Apparently the cities are doing an independent review of NEORSD's determination that Lower Lake doesn't provide a flood control benefit. If that comes back as saying that it does, and NEORSD goes back to saying they'll do the dam restoration, the cities should not blindly go forward with the concrete monstrosity NEORSD proposed.
Whatever comes of that independent review, the cities need independent experts to propose plans that would balance compliance with cost savings and with preserving site aesthetics. NEORSD cost estimates have skyrocketed multiple times, but who knows how much the project might cost for a smaller dam without massive concrete walls? For all we know, that project might cost significantly less than NEORSD's stream restoration.
When Friends of Lower Lake, a volunteer group that has done commendable work removing invasive plants around Lower Lake, surprisingly came out in favor of removing Lower Lake, they said, "We found NEORSD’s Plan A, maintaining the Lower Lake with a gravity dam, no parking, and eight-foot-high floodwalls on pedestrian pathways along North and South Park Boulevards, unpalatable."
I find this logic interesting. They (very understandably!) don't like the Sewer District's plan for restoring the dam. Because they think one plan the Sewer District made is bad, they support letting the Sewer District do a different plan, despite not having seen any details about the different plan.
I feel like if someone makes a plan you don't like, the next step should be to get an alternate plan from someone else.
NEORSD is misinterpreting a flood model to incorrectly say dam failure could cause catastrophic flooding
On September 14, the week before the EPA hearing about the controversial Horseshoe plan, Crain's Cleveland Business posted an article that is one of the most misleading pieces of journalism I've seen in a long time. (I emailed the author to explain how misleading the article was and ask for it to be corrected, but never heard back.) The article, although it does include a few quotes from plan opponents, mainly functions as Sewer District PR. It paints a frightening picture: the dam failing "could cause massive flooding" and put University Circle "under eight to 20 feet of water."
There's one big problem: the idea that the dam failing could cause this level of catastrophic flooding just isn't true.
To be clear, there is a legitimate public safety issue to address, but this story ludicrously exaggerates the hazards of potential dam failure in a way that only causes unnecessary fear among the public.
Last year, after NEORSD announced the recommendation to remove Lower Lake, CWRU physics professor Ben Monreal (who has relevant experience with subjects like environmental fluid mechanics and civil engineering) made a nice series of five presentations covering issues about Lower Lake and its dam. In the fourth, he dove into the details of the flood modeling, done by AECOM, that's attached to the dam's Emergency Action Plan. This is the same modeling NEORSD is describing in the "eight to 20 feet of water" scenario (I know this because I've seen a presentation of theirs with the same flood maps). It's the best modeling that currently exists for potential consequences of the Shaker dams failing.
If you want a really interesting and detailed explanation, I highly recommend Ben's presentation. I'll summarize.
Three flood models are used:
1. A model of the dam failing from a sunny day breach. In this scenario, there is no flooding in University Circle. The watershed downstream of the dam has enough capacity to handle the lake draining.
2. A model of the dam failing in a storm with 5" of rain. In this scenario, there is a flood in University Circle, but nothing approaching the catastrophic levels described above. Ben's interpretation is that it seems to be on the borderline of a flood with the potential to cause loss of life. Of course, for dam classification purposes, it makes sense to err on the side of caution.
3. A model of the dam failing in a worst-case scenario storm with 24" of rain in under 24 hours. Yes, this is an extraordinarily unlikely event, but ODNR does require this modeling. This would be a similar event to the devastation Hurricane Helene wreaked in parts of North Carolina. With climate change, it's not completely impossible this could happen someday.
This is the flooding model NEORSD is describing when they talk about University Circle being underwater. What Ben explains, and what NEORSD apparently missed, is that in this model, the water released by the dam failing is a very small fraction of the massive surge of water flowing into University Circle from the storm. Essentially the same level of catastrophic flooding would occur from this storm without dam failure, or if the dams had been removed.
Here I made an explanatory image using key slides from Ben's presentation:
So, yes, there would be catastrophic flooding if we were hit by a storm with 24" of rain. Shocking, I know. This does not mean that dam failure would be the cause of University Circle being "under eight to 20 feet of water."
(By the way, if you happen to look at the Crain's article, do be aware that even in this megastorm scenario the image at the top of the article is not based in reality. The image depicts 20 feet of water at the Euclid/Mayfield intersection, but the flood would be going down MLK, which isn't surrounded by ground-level buildings. This appears to be the fault of the author's article, and isn't important to the points I'm making, but I wanted to mention it in case anyone might be further misled!)
When I first shared Ben's content in Facebook discussions about the dam, I was told that we should listen to the experts (that is, NEORSD), and since Ben's research wasn't related to these issues (even though he does have relevant professional experience), he wasn't qualified to question NEORSD's conclusions.
Admittedly, I myself have no experience interpreting flood models, but Ben's explanation was easy to follow and made a lot of sense. I emailed ODNR to ask if Ben was interpreting the model correctly. To my great amusement given the response from Facebook commenters, the ODNR official told me he'd watched some of Ben's earlier presentations, and Ben seemed to have a good understanding of the situation. And he told me that yes, Ben's reading of the model is accurate.
Full disclosure, I also learned from ODNR about some deficiencies in the existing flood modeling. The cities have been told that an updated flood model would be required with a remediated dam. The deficiencies, though, are in the details. They wouldn't change the broad conclusion that dam failure wouldn't cause the catastrophic flooding NEORSD is describing, simply because the lakes don't store nearly enough water for this to be true. All the other water flowing into University Circle in a 24" storm would dwarf the water from the lakes. Deficiencies or not, this model is the best currently available, and NEORSD is grossly misrepresenting it.
So, there you have it. Another example of NEORSD saying something about dams that just isn't true, also confirmed by ODNR. In the previous example, their lack of knowledge led to inappropriate limiting of options considered for preserving the lakes. In this example, their lack of knowledge has led to a great deal of unnecessary fear in the community.
"I understand where they’re coming from, but people’s lives are at stake," Cleveland councilman Kevin Conwell is quoted in the Crain's article as saying about pushback to the NEORSD plans.
It's frankly infuriating.
The worst part? I know for a fact that NEORSD has talked to Ben about his presentations, because they mentioned it when they talked to me about my blog earlier this year. His presentations cover both the fact that dam failure isn't the cause of the catastrophic flooding in the 24" storm model and the fact that dams can be modified and reclassified, with some ideas for how to potentially do that!
Everyone makes mistakes. Even experts. The important thing is not being right about everything all the time, because no one is. It's whether you're able to update your beliefs based on new information. If someone takes the time to carefully examine an analysis and point out something you overlooked, ignoring that and continuing to repeat your debunked conclusions is the opposite of what a real expert should do.
In arguments about the Shaker Lakes, NEORSD supporters often like to say that we have to listen to the experts and we shouldn't question the plans. This is a bad argument for several reasons, not least of which is that NEORSD has no expertise whatsoever in important subjects such as what features of a park make it most attractive to humans. But here we have a topic, dams, on which the Sewer District by all rights should be experts - and yet they've made multiple major claims that are just completely wrong.
I knew almost nothing about dams before I started researching issues around the lakes last year, and yet these errors are so basic that it's easy even for me to understand them. There are many other technical issues about the projects that I don't understand, and therefore haven't written about. How can we trust that NEORSD is working from a good understanding of all those other issues when they don't understand basic dam classification definitions or how to interpret a flood model? How can we feel confident about their projections for the effects of so dramatically and destructively overhauling a historic landscape?
Remember, there have been many other inaccurate pieces of information communicated to the public by NEORSD, as I've documented. This has led to plans being pushed forward after a public engagement process in which the public had no idea what was really going to happen. At this point, it's hard to rely on anything NEORSD says as being true without independent verification.
This whole situation is so sad. The cities should have started from a place of figuring out what the community wanted and then working with community members and experts in various relevant fields to figure out how to make it happen, or the best approximation. Who knows, if they'd done that, we might already be at work on preserving our parks with perhaps modestly smaller lakes that would still keep the feel of the historic landscapes intact. Instead, the cities got bad advice from the Sewer District and dragged us into a mess that continues to get uglier, and thanks to rampant inflation, whatever happens will just end up costing more and more.
I implore someone, anyone, in a position of authority - with the cities, with NEORSD, with both - to stand up and say we screwed up, we accept responsibility, and we're going to start the hard work of making things right. The longer it takes for that to happen, the more damage to our community will be done.
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