08-20-18 Health and Public Saftey & Utilities

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CITY OF SOUTH BEND I OFFICE OF THE CLERK North Shore Triangle had sixty-four percent (64%), Riverside had fifty percent (50%) and Emerson had sixty percent (60%) disconnected. He went on,(referencing a slide in the presentation).Typically,the water flows from north to south to a thirty-six (36) diameter combined pipe, and there is also CSO thirty-three (33) and thirty-five (35) that provide relief along those areas. He pointed out the estimated flood boundary based on the 2018 flood, and the homes that experienced the 2018 flood. He referred to those that are actually in the one hundred (100) year flood plain (one percent (1%) annual chance flood area), where the river will pop out first whenever the water gets high. He stated, We created a profile looking along the river at this neighborhood, from the Grand Trunk Railroad Crossing to Twykenham. He pointed out the flood line from 2018 and the pipe that feeds that area. He explained,CSO thirty-three(3 3)and CSO thirty-five(3 5)relieve those sewers in those areas when flow gets too high and they were inundated by almost ten (10) feet of water for an extensive duration, possibly a couple of weeks. The river was up so high based on where the elevations are and the CSOs and the outlets, so water just couldn't get out. He continued, There were different levels of responses to how often basements flooded in the different areas. He explained while he pointed out results of the Emerson Avenue survey (referencing a slide in the presentation), It was found that the area has high groundwater that can fluctuate. A large percentage of the residents noted that their downspouts are disconnected, and this helps reduce the flow to the sanitary line sewer, and it also reduces the flow that could get back into their houses. He went on, In the Riverside(South of Bartlett) area,there is a CSO and it travels from southwest to the northeast, and there is a twelve (12) inch throttle pipe that carries flow back into another CSO. CSO ten (10) provides relief to that system. Mr. Metters showed a map of the flooding boundary based on the 2018 event. He explained, Based on the data,the flood boundary matched up with the homes that reported basement and surface flooding. There were several storm water outfalls that were under water for a long time, not allowing the water to get out into the river for an extended period of time. He then reviewed the survey results (referencing a slide in the presentation). He stated, Out of ten (10) responses, none noted that they had any backflow prevention devices installed. This was an area with high ground water. A large percentage of the basement flooding came from cracks in the floors. Most noted that the water was clear,but some noted that there appeared to have some sewage in it. Several residents noted that an earlier notification of some type with some information and instruction may have been helpful during the 2018 event. We compared this information to GIS data. We went out in the field to investigate some areas further. In Riverside, there is a combined area going to one (1) point with a twelve (12) inch throttle. During higher flow areas, it can't handle the amount of water. Some of these pipes are larger in diameter, so we may recommend that be looked at. He continued, Next is the North Shore Triangle area. This area is a separated storm sanitary system,and except for northeast of Hillcrest Road,there is a portion out there that is still combined. Flow travels from northeast to southwest into the eighty-four (84) combined pipe. Eventually it crosses Angela. CSO five (5) and twenty-five (25) give relief along these points. He referred to a map, pointing out the CSO points, storm water outfalls and the river crossing. He stated, The CSO outfall points have backflow devices on them to keep the water from coming back in as it rises. The storm pipes do not have those types of devices on them. Typically, most storm lines that discharge in rivers don't have those types of devices on them. Usually you like to have those EXCELLENCE I ACCOUNTABILITY I INNOVATION I INCLUSION EMPOWERMENT 455 County-City Building 227W Jefferson Bvld South Bend,Indiana 46601 p574.235.9221 f574.235.9173 TTD574.235.5567 www.southbendin.gov 5