Emergency CSO Repair - CSO 018 and Backwater Gate Emergency Repair - Selge Construction, Inc.

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INTER-OFFICE MEMORANDUM DEPARTMENT OF PUBLIC WORKS DIVISION OF ENGINEERING TO: Linda M. Martin, Clerk Board of Public Works FROM:Sue Ellen Doudrick, PE SUBJECT:CSO 018 & Backwater Gate Emergency Repairs Project No. 120-017 DATE: March 30, 2020 Emergency repairswereperformed on the backwaterTideflex valve (backwater valve/duckbill) immediately downstream of CSO 018 and onthe weir within CSO 018 itself. CSO 018is located south of Lincoln Way Eastbetween the railroad tracksandBowman Creek. CSO 018 consists of two structures, the CSO itself and the downstream structure. The downstream structure contains a duck bill ( and prevents St. Joseph River water from flowing into the CSO 018 structure. On Monday 1/6/2020, Water Works team discoveredtheduckbill became dislodgedat the top of the plate and river waters flowedinto the CSO 018 structure (upstream). This condition damaged the woodenweir wall separating the There are 4 woodenplanks making up the weir. From what we can see, two of the planks have become dislodged from the concrete walls, and another plank is lifting upward. To prevent the planks from further damage, allowing CSO waters to flow directly to the River, and clogging the 2paired. These two elements are werebeyond what our in-house teams are trained and equipped to do. On Tuesday 1/7,the project was approved asan emergency repair. The first contractor contacted (Selge Construction)was available to meet onsite immediately on 1/7to inspect the conditions.Contractor mobilized to site 1/7. Description of work: Due to the forecastedrainfor the end of the week, it was critical to first repair the duckbillto reduce river water from further damaging the weirdueto increased backwater flow from the increased river water elevations. To get us thru the weekendrains, a fiberglasssheetwas installed at thedownstream face of the weir to protect the wooden planks from further damage. Sewer Department provided sandbags used to block flow coming from the river.Reducing water levels in the structureto perform work was critical. We wanted to avoiddetwateringas this wouldgreatly impact cost on the project. The duckbill repairincluded installing a cable attached to the top of the downstream structure and connecting the cable to the duckbill to lift it up in place in order toinstall new bolts to connect the duckbill to the plate. During work, we discovered the duckbill would not close all the way, which would continue to allow water to infiltrate the CSO 018,but therepairhelped reduce water coming in. S:\\Public Works\\Projects\\Projects by Year\\2020 Projects\\120-017 CSO 018 & Backwater Gate Emergency Repairs\\1-Admin\\1-BPW Documents\\Memo to BPW -CSO 018 Backwater Gate Emergecy Repair.doc