05-08-17 Utilities - Laserfiche WebLink

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Treatment Plant Expansion challenge is proving to be very difficult. The flaw with the current plan is there is no CSO storage tank at the wastewater treatment plant. However, our studies have revealed that the outfall closest to the treatment plant is the most significant in the system. The first finding was the sense to build a large CSO storage tank at the treatment plant because we are doing a really good job of getting a lot of flow to the treatment plant. Four (4) small tanks were listed as having very small capacities but it is still very expensive to build small tanks. Those tanks were at the point that through smart and green-infrastructure,they could be eliminated from the plan. The storage conduit is basically a tunnel. Costs in relation to that escalated dramatically. The essential thing to realize is the need to build these. The greatest flaw with the initial project was it was designed for four(4) overflows. Our data revealed the plan would come back with thirteen (13)total overflow CSOs, which would not meet our objectives even after spending all the money. That is the key takeaway. This Smarter Alternative for a Greener Environment (SAGE) Plan that we are presenting will only have nine (9) CSO basins that include green-infrastructure. The financial capability analysis gives a ratio of the old plan and the financial burden on the resident. The ratio of the old plan is a three point six nine (3.69). Greater than two (2) is denoted as `high' by the EPA. We are almost double that with the old plan, hence,the motivation is there for the SAGE Plan. Eric Horvath, Public Works Director with offices on the 13th floor of the County-City Building, stated, I think you've seen we've had tremendous success to date with the initial parts of this plan. We've come a long way from where we started by rethinking the current plan. We have a great team of folks who have put together a wonderful solution. I want to thank the Council for their patience. One (1) of the first things we did was put in one-hundred and fifty (150) sensors. We have the most censored sewer network in the entire world. This gives us critical data to come up with real results. We have over 15.8 million data points from the system that come in every year. That tells us, at any given time and any given day, exactly what level the sewer should be at. We have been monitoring the sewers every single day. This has helped us eliminate dry- weather overflows. It also provides operational optimization, essentially preventing back-ups. We knew which sewers to clean, fix and help. It also helped us look at the system as a whole and look at where the most capacity was. The sensors communicate with one another to figure out capacity and redirection of overflow. We also built the second throttle-line. The initial throttle- line would overflow to the river, so we built the second one with real-time control. There is a value and sensor on it to tell it when to open up when there is capacity. In certain cases we had CSO basins have durations of twenty (20) hours of overflow that, after we did this,became only two (2) hours. In the previous plan we were underestimating and overestimating overflow. Compared to the LTCP,the SAGE Plan improves the accuracy of estimation and gives a more precise recommendation for the number of CSO basins and their respective sizes. We need to know how much overflow there will be in order to create the perfect model. Using the data we had, we try to predict each drop of water and where it goes. We previously had only fifty (50) miles modeled but are now modeling one-hundred twenty (120) miles. We took three-hundred and sixty-four (364) nodes and we modeled two-thousand two—hundred(2200) nodes. We then took sub-catchments, which are the contribution areas of each of these nodes, and made them smaller so we could have a more accurate representation of where the flow was going and how and where it was getting into the sewer system. Mr. Horvath then referenced a chart in the presentation in regard to the existing 2013 model that showed flow-to-capacity ratios. 5