02-04-19 Utilities - Laserfiche WebLink

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CITY OF SOUTH BEND OFFICE OF THE CLERK Referring to the presentation, Mr. Fahey stated, The black line represents what a model predicted would happen for a particular rain event, and the blue line is what actually happened. At the first (1St) peak of this storm, which would be around 4:10 a.m. or 4:15 a.m., you'll see that the black line predicted a certain amount of CSO, but the actual volume was a little bit less. Whereas,just past 6:00 p.m., what was actually predicted was less than what it actually was. You're designing and if you are consistently over or consistently under,you can account for that,and sometimes you have too much or too little capacity. There was confusion and there were inaccuracies in the model which meant that we shouldn't be investing $713 million based on a model that had inaccuracies in it. Another example, if you look at the red, those are the actual measurements. Very few cities actually have these, versus the model in the green. The green is higher, so the model is mostly more conservative. That gap between the green and the red is extra capacity we would have built, and dollars spent that we wouldn't have needed to spend. He continued, When you have something that you expect versus what you actually monitor, the relationship,if it is exactly the same it will be one(1)to one(1).The higher that number,the better. Two point two nine (2.29) is actually not that bad, which is maddening to have to say. It is considered acceptable in most communities.Now we're at point nine three(.93),which means that the relationship between what we know might happen versus what does happen is much more accurate. So, therefore, we design a more accurate model and have a Long-Term Control Plan based on that. The blue and dotted red lines pretty much mirror each other. The point here is that the hydraulic response system,which is an aspect of the combined sewer,allowed us to learn based on previous data what to expect in future events.We eliminated all of the assumptions and modeled it with greater accuracy. We could say this is how this pipe will react, or this is how much capacity it will or won't have so we know how much overflow to expect. It allowed us to design and build a better plan than we would have. He went on, In summary, on these smart sensors, time gave us knowledge. That knowledge allowed us to do the modeling using real data as opposed to the assumed data that we had. That real data was then used in a way that, you can imagine previously people would make all of those assumptions, then come up with a plan saying, what if we build a tank here and a tank there, how would it work? Someone would go and put it into a computer and look it up and say it was either good or not good. It was random, dependent on a human's idea of what might happen. What we were able to do, was gather all of the real data and have it sort itself out to show us what the best selection of the infrastructure would be. This way we can say if a square foot of tank costs this much, a square foot of green infrastructure costs this much, and these are the locations I want you to focus on, based on the data we've gathered. We know what capacity we need and based on the cost, we knew that we didn't need what we previously had thought. He continued, We were able to do that modeling, or optimization, and on top of that, for a number of reasons we had a green infrastructure. Green infrastructure benefits the community not just for the purpose of the water quality but socially as well. It is something people will see on the ground that will clean up and brighten up neighborhoods rather than a tank that isn't seen. It is a rain garden or a new footpath or a new roadway that is socially, economically, and environmentally beneficial. One(1) of our reasons for adding that is because we're dealing with the environmental regulators and we want to accurately be able to say that this plan is not only better in terms of water quality,but overall it is a greener plan. Our old Long-Term Control Plan does not have green infrastructure. We didn't add it just because it is nice, we wanted to make sure that everywhere it would be would be beneficial. EXCELLENCE ACCOUNTABILITY INNOVATION INCLUSION EMPOWERMENT 455 County-City Building 1227 W.Jefferson Bvld South Bend,Indiana 46601 p 574.235.9221 f574.235.9173 TTD 574.235.5567 www.southbendin.gov 6