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

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• Known storm water drainage problems • Age of the individual sanitary sewers by reviewing the sequence of development in the area through plats and/or construction plans MONITORING DATA Under a separate contract with the City,ADS Environmental will coordinate, install,maintain and collect sewer flow and rainfall data for the investigation areas that is critical to calibrating and validating the sanitary sewer collection system models. Monitoring data will be collected by ADS Environmental for at least 90 consecutive days. CMT will have access to the data in near real-time via the FlowView Operations website maintained by ADS Environmental. CMT requires the monitoring data collected by ADS Environmental to meet the following requirements: • Flow meter data(at minimum level, velocity and flow rate) shall be recorded every 5 minutes continuously and be available for download in.xlsx or.csv type files. • Rainfall data shall be recorded every 5 minutes continuously and be available for download in .xlsx or.csv type files. • Both original and edited data shall be available for download. • Site installation notes and maintenance records shall be available for viewing. ALTERNATIVES ANALYSIS To effectively understand the existing collection system's condition, functionality and response to wet weather,the sewer system and monitoring data is needed to help build a collection system model representing the sanitary sewer system. The model will be developed using the Storm and Wastewater Management Model(SWMM)originally developed by USEPA and enhanced by XP Solutions. Actual collection system response can be replicated by calibrating the model using rainfall and flow data to reflect the conditions experienced during wet weather. Once the collection system model is calibrated and validated with an independent rainfall event, it can be used to establish the existing level of SSO protection within the sewer system(i.e.,at what design storm event are there no overflows). Alternatives to either reduce the I/I or provide relief to the sewer system can then be developed and evaluated using the collection system model. Reduced UI and/or additional conveyance capacity and storage modeled in the collection system for multiple wet weather events can be developed,refined and evaluated for efficacy,thus establishing an improved level of SSO protection. This flexibility allows the investigation to target needed improvements and make better informed and cost effective decisions when utilizing public funds. The ACO uses the word"eliminate"when discussing SSOs. The proposed Alternatives Analysis scope of services will investigate the elimination of SSOs and reducing sewer surcharging to an acceptable level. There are too many factors beyond the control of this investigation to eliminate surcharging in the system. To completely eliminate surcharging in the sewer system may be prohibitively expensive. The following headings and subsequent tasks outline the steps proposed to build a database of sewer system information and a collection system model that can be used to perform alternatives analysis to Last Revised:04/29/2015