R2017-26 Agreement with Crawford, Murphy & Tilly for Lost Bridge Inflow & Infiltration Reduction

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8. A prioritization of the alternatives and a schedule for implementation of the alternative chosen, with the final completion date of the chosen alternatives no later than December 31, 2018 9. Analysis of the cost effectiveness of the chosen alternatives, including a basic comparison of the preliminary planning level construction cost opinion to the alternatives analysis cost opinion. SEWER SYSTEM DATA Sewer surcharging(water levels higher than the top of pipe)and basement back-ups are typically associated with UI entering the sanitary sewer system and consuming any available capacity. I/I is usually generated from wet weather events. Inflow refers to storm water that flows into sewer systems through direct connections such as roof and foundation drains, storm drain connections, open pick manhole covers and uncapped cleanouts. Often times these sources are considered illegal connections. From flow monitoring hydrographs(a plot of flow versus time), inflow is usually seen as a sharp increase in flow rate. Infiltration can be groundwater that seeps into the sewer system through faulty pipe joints,poorly constructed service connections, cracks as a result of root intrusion and leaking manholes. Infiltration is not limited to the public sewer mains and manholes; it can also enter through defective sewer laterals(pipe from the house to the sewer main), as well as defective storm sewer. Also from flow monitoring, infiltration is usually seen as additional baseline flow and extended receding limbs of hydrographs. Root intrusion and pipe collapse can also cause surcharging and basement back-ups,but the problems encountered in the investigation basins are believed to be attributable to 1/1 and/or hydraulic restrictions. There are several tools available to locate,identify and quantify the severity of I/L flow and rainfall monitoring,televised inspection, manhole inspections, smoke testing, and dyed water flooding. Volumes of data can be obtained by utilizing the aforementioned techniques. The challenge is to determine the best way to organize and categorize the data collected so that it is most useful. The following pieces of information should be collected from the investigation basins and provided in the city's existing geographic information system(GIS) so that it can be viewed spatially to assist with analyzing data: • All pipe sizes,materials,rim elevations and invert elevations of sanitary sewer(City and SDD)not already entered • Sanitary sewer maintenance history, including repairs,cleaning and root treatment • Pump/lift station operation and flow data • CCTV data • Storm sewer networks not already entered • Ground contours • Planimetric data: impervious area outlines (e.g.,buildings, streets, sidewalks, etc.) • Water distribution network and watermain break records • Records of pumping of sanitary sewers in response to wet weather events • Basement back-up records with addresses • Investigation basin address database • Overhead sewer conversion participants • Residences with basements and basement elevations • Previous smoke testing results Last Revised:04/29/2015