62 Communities, 270 Square Miles--Local Sewer System Evaluation Studies Provide a Roadmap for the Northeast Ohio Regional Sewer District and Member Communities to Improve Sewer Systems

Introduction The Heights Hilltop Interceptor Local Sewer System Evaluation Study (HHI-LSSES) and Southwest Interceptor Local Sewer System Evaluation Study (SWI-LSSES) are two of four Northeast Ohio Regional Sewer District (NEORSD, District) Regional SSES projects implemented to support District initiatives to address water quality and quantity problems associated with sanitary sewer infrastructure. The problems adversely affecting human health and the environment include sanitary sewer overflows (SSOs), basement backups, illicit discharges and failing home sewage treatment systems (HSTSs, septic tanks). The studies focused on the local member community sewer systems upstream of the District interceptors. The HHI-LSSES project area covers 26,200 acres and 15 communities while the SWI-LSSES project area covers 51,600 acres and 14 communities. Two other LSSES projects are covering the remaining 31 District communities. The collection systems serving the District member communities range in age from new development to over 120 years. The LSSES projects were implemented at a planning level to use existing information and new field investigations, flow and rainfall monitoring, and sewer system hydrologic/hydraulic modeling to support District and member communities' understanding of system performance and regional water quality. The projects also developed and optimized feasible system improvement alternatives and prioritized potential solutions and costs to address the problems identified. Objectives - Review and understand existing information and ongoing problems. - Conduct targeted field investigations to confirm and/or discover existing problems. - Develop and calibrate hydrologic/hydraulic sanitary sewer system computer models for local collection systems tributary to District interceptors. - Correlate observed existing system performance and ongoing problems with the updated calibrated model. - Identify problem causes and cost-effective potential solutions using the calibrated model and a suite of analysis and costing tools integrated with the model. Consider how variation in rainfall may affect problems observed and the type, size, and cost of potential solutions. - Use ArcGIS Online (AGOL) to document and convey all key project information and results developed in near real time, including existing problem locations and areas, field investigations, condition assessment, feasible improvement alternatives considered and suggested potential improvements for community consideration. - Develop individual summary reports and supporting field investigation and condition assessment data files for each community to parallel the AGOL information. - Develop comprehensive summary reports and supporting information for each District interceptor LSSES project area to parallel the AGOL information. Status The HHI-LSSES project began in 2016 and was completed in 2020. The ongoing SWI-LSSES project began in 2018 and is scheduled for completion in Fall 2021. Fieldwork, modeling and alternatives analysis were completed in the spring of 2021. Methodology The LSSES projects completed four primary tasks: 1. Local system assessment strategy – Task 1 compiled and reviewed existing information from the District, local communities, and Cuyahoga County as the basis for project planning and development of the approach for system investigations and monitoring performed in Tasks 2 and 3. Community work plans were developed to share with the communities and confirm receipt of relevant existing information. Technical memoranda were developed to prioritize the study area for field investigations based on existing information and to define the field activities, standard operating procedures (SOPs), including the AGOL project platform set-up, and protocols for the investigations. 2. Local system inspection and condition assessment – Task 2 completed field investigations including manhole inspections, dyed water (dye) testing, sewer CCTV, smoke testing, and elevation surveys to identify and document sewer system connectivity, invert and overflow elevations, and condition and causes of reported and model-projected problems. The information developed was used to update District system documentation, including the AGOL geodatabase files, and to target and corroborate subsequent flow monitoring and sewer system model development and analysis. 3. Local Sewer System Evaluation – The local sewer system evaluation used information developed in Tasks 1 and 2, in conjunction with local sewer system flow and rainfall monitoring and modeling, to characterize existing system performance and identify significant problems to be considered for capital improvements or other corrective actions. Task 3 findings were provided to the local communities for review prior to development of potential solutions in Task 4. 4. Prioritized Capital Solutions and Maintenance and Policy Recommendations – Task 4 developed and analyzed alternatives to solve the identified problems and achieve the desired public health and water quality benefits. Feasible system improvement options, such as common trench sewer separation and rehabilitation, peak flow storage and private property I/I reduction, were analyzed to simulate potential solution alternatives for the local sewer systems. The alternatives were compared and optimized using planning level costs and non-cost criteria such as long-term system performance and serviceability, operation, and maintenance requirements, and potential effects at downstream District facilities to recommend potential solutions and suggested prioritization. Implementation considerations were developed to include coordination with the District's Member Community Infrastructure Program (MCIP) which provides technical and funding support to help communities implement improvements. Potential solutions, associated costs, and implementation considerations were documented in reports developed for each community. Findings The projects have largely corroborated community identified sanitary sewer problem areas and have identified other projected basement backup problem areas and SSOs based on monitored/modeled rainfalls. Other findings include high correlation of problems with aging common trench sewer systems (sanitary and storm sewers constructed in same trench). The alternatives analysis, summary reporting and AGOL system provide member communities with a prioritized roadmap of feasible, cost-effective solutions for their consideration and long-term implementation. The feasible solutions have been prioritized into three tiers to focus limited resources on the most critical water quality and system performance issues first (Tier 1), followed by longer term improvements (Tiers 2 and 3) to reduce risk of failure and improve system resilience. The approximate cost distribution across the three tiers is 10%, 60% and 30%, respectively. Significance The projects are helping the District and member communities understand the scope and important details of the local community sewer system problems, as well as potential system improvements, prioritization, and costs. This information helps the District plan and manage downstream conveyance and treatment facilities and helps communities plan for implementation of local system improvements that will support successful operation of the larger system. Parallel District stormwater master planning projects are providing findings and potential improvements for regional stormwater systems that are being considered in conjunction with the LSSES findings and potential solutions with the overall goal of integrating improvement projects where feasible to minimize cost and disruption and improve long-term resilience.