Omaha's unique approach to updating their CSO Long Term Control Plan

Purpose: The purpose of this presentation is to provide an overview of the status of the City of Omaha's CSO program implementation and the development of their 2021 LTCP Update, providing information on the approaches and tools used to more efficiently comply with the EPA CSO Control Policy, thereby resulting in a reduction in the estimated cost of the LTCP. Background The City has recently completed and received approval from the Nebraska Department of Environment and Energy (NDEE) of its 2021 update to the original LTCP. In March 2021, the LTCP Update was submitted to NDEE, followed by approval on August 11, 2021. This latest LTCP Update includes changes to several of the previously planned CSO projects, which reduced the estimated total cost of the program. This reduction is in part the result of the City's 2018 modifications made to the Consent Order that provided until 2037 to complete implementation as well as clearly noted that the intent of the City's LTCP is to achieve 85% wet weather volume capture, providing a level of certainty. Current Program Status The presentation will discuss how the program has adapted. Implementation of the combined sewer overflow (CSO) controls in the 2009 LTCP started in the summer of 2009 and is continuing. The 2009 LTCP was updated in 2014, and more recently in 2021. The 2021 Update focuses solely on 85% volume capture to meet the EPA CSO Control Policy. This resulted in the 2021 Update approach being more cost effective and has been backed up by recent water quality modeling results. The 2014 LTCP Update included various types of controls including: - Targeted Sewer Separation - Underground Storage Tanks - Green Infrastructure - High-Rate Treatment Facilities - WRRF Plant and Conveyance Improvements - Deep Tunnel System The presentation will note that significant progress has been made in implementation of the LTCP with currently over 26 projects completed, 7 projects under design and 8 projects under construction. The City has spent approximately $775 million on the program through June 2021. This has resulted in modeled Wet Weather Volume Captures of: - 56% current wet weather volume capture in the Missouri River Watershed (71% capture after completion of projects that are currently underway) - 84% current wet weather volume capture in the Papillion Creek Watershed In addition, an approximate 50% reduction in the E. coli loading to the Missouri River from the CSOs has been accomplished through the completion of projects in the Missouri River Watershed. 2021 LTCP Update The presentation will detail how the modifications to the City's consent order in 2018provided the City with the regulatory certainty which resulted in the ability of the City to significantly reduce potential costs. The object of the evaluations performed were to comply with the EPA CSO Control Policy Presumption Approach, achieve ≥ 85% wet weather volume capture, meet water quality standards in the Missouri River, not preclude achievement in the Papillion Creek watershed, and document extensive evaluations to progress from current volume capture to 85% capture as required in the EPA CSO Control Policy. In addition, the presentation will describe the integration of the City's other significant infrastructure needs of the wastewater treatment facilities and collection system into the LTCP schedule in addition to incorporating the additional 10 years provided by Consent Order Amendment. The presentation will also describe the extensive Optimization Process that was undertaken to determine the appropriate controls to include the in the Updated LTCP. The process was based on a multistep process as noted in Figure 1. The evaluation was based on previous work, and involved a large effort using state of the art modeling tools such as Optimizer and InfoWorks ICM. In evaluation of the alternatives, one of the major elements was to choose an alternative that would not operate during river flooding but could help to reduce the effects of flooding. The outcome of the process is an alternative for the Missouri River watershed which replaces the originally planned Deep Tunnel System with other technologies including high-rate treatment, storage basin and active controls. In addition, the City performed evaluations which resulted in the demonstration that some planned projects were not necessary. Also, an innovation program to address infiltration and inflow in the combined system was developed which allows flexibility to the City to deal with issues that may remain after sewer separation. These will be described in the presentation. A description of the City's water quality modeling efforts will be presented. The City developed a water quality model based on the InfoWorks ICM water quality module. This model shows that the Missouri River will meet the water quality standard for E. coli in the Missouri River after implementation of the LTCP. The result of these efforts and other adaptive management measures has been a reduction in the potential costs of the Program from $2.4 billion to about $2 billion. Overall, the current estimated cost of the Program is actually less than what was originally predicted in 2009. Lessons Learned and Conclusion: The City of Omaha is committed to the implementation of the CSO LTCP. A tremendous amount of progress has been made, and many challenges have been successfully met. The presentation will explain how over the last couple of years, the City has performed evaluations and modified their LTCP in a manner that resulted in a reduction in the potential costs allowing the City to make necessary improvements to other infrastructure areas (wastewater treatment and collection system.)