Kansas City Smart Sewer Program Savings Using Adaptive Management - A Case Study

Purpose and Benefits This paper demonstrates the benefits of an adaptive management approach (AMA) for Combined Sewer Overflow (CSO) or Separated Sewer Overflow (SSO) reduction programs. The audience will hear about the AMA for a CSO Reduction Consent Decree (CD) program, learn components necessary to support an AMA , and see a case study of the Kansas City, Missouri (KCMO) Smart Sewer Program (SSP). Introduction The US Environmental Protection Agency (EPA) and/or state agencies enforce CSO elimination and reduction through a CD, an agreement that defines steps and the timeline for the utility to manage the CSOs. A CD describes how an Overflow Control Program (OCP) would be implemented. Thus, an OCP needs to be defined before a CD . However, since the OCP is the first step in a CD, it is often based on limited information. The AMA provides a framework to develop a CSO reduction program that can limit the impact of information uncertainties on the program's success. Adaptive Management Approach The AMA is a decision-making process designed to manage information uncertainty through iterative system monitoring and structured decision-making. The AMA uses information about past system performance to optimize the next phase, as shown in Figure 1. With AMA, CD compliance can be achieved on schedule with reduced cost compared to the original OCP. The steps of the iterative phase of the AMA approach applied to CSO reduction are: (1)Plan - Use the available information to plan the next-phase CSO reduction solutions, (2)Design - Select the next-phase solutions and the pre- and post-construction monitoring plan, (3)Implement - Deploy CSO reduction solutions, (4)Monitor - Monitor CSO reduction effectiveness, (5)Analyze - Use the hydraulic model to evaluate the performance of implemented solutions, and (6)Optimize - systemwide CSO reduction using the latest information from implemented projects. A CSO reduction program must satisfy a set of criteria for AMA use. First, the program implementation must be phased to allow the AMA to change proposed solutions. Second, the program needs to monitor the performance of the implemented solutions, thus, collecting information for AMA decision-making. A predictive model is needed to evaluate the performance of the proposed solutions. And finally, the CD compliance must be based on the observed or model-predicted system performance. 2021 KC Water CD Modification 3 provides the framework for the use of AMA on the SSP. The CD Modification 3 changes will enable the City to revise, remove, or replace projects currently contained in the CD if the EPA approves City's request. A revised or alternative control measure must: (1)Reflect sound engineering practices; (2)Results in an equal or greater level of CSO control than the original Control Measure(s); and (3)Include a schedule for implementation that is no later than the original Date of Achievement of Full Operation for the original Control Measure. KCMO Smart Sewer Program Kansas City, Missouri (KCMO) is the largest city in Missouri, with over 500,000 residents. KC Water's SSP is a 30-year, multibillion-dollar effort to reduce the volume of CSO. KCMO developed an OCP in 2009 to capture 97% of the typical year systemwide CSO volume. SSP implemented 33 projects worth over $750M in the first program decade. In 2017, KCMO submitted a request for a modification of the CD. This modification was approved in 2021. Today, SSP has the flexibility to reevaluate OCP control measures as they come for implementation and optimize systemwide, cost-effective CSO reduction. The 37th & Norton green infrastructure (GI) project is an example of how the SSP uses AMA to improve CSO reduction outcomes by changing OCP-proposed control measures based on the information collected on previous projects. 37th & Norton Case Study 37th & Norton green infrastructure (37NGI) project is located upstream from Diversion Structure 152 (DS152). DS152 contributes flow to the Blue River Interceptor Sewer (BRIS) and Blue River WWTP. The original project was proposed to manage CSO at DS152. The original suite of CSO control measures, including this project, was selected based on the basin-wide control plan that assumed that BRIS could receive increased flows. Since, the KCMO has significantly improved hydraulic models. The updated systemwide model has shown limited capacity in BRIS. Modeling indicates that this project would not provide the predicted CSO reduction systemwide. Instead, the SSP used an AMA to search for a cost-effective alternative. A green infrastructure solution was identified to replace the relief sewer control measure with a significantly greater CSO reduction and a lower cost. The Original CSO Reduction Project The original control measure was to install approximately 3,400 linear feet of 48-inch pipe between the DS152 and BRIS. The project was predicted to reduce the typical year CSO by 18 MG, from 28 MG to 10 MG, assuming BRIS had the available capacity. The relief sewer increases the peak flow and volume in the BRIS, increasing the CSO. Upon reevaluating the original control measure with the updated model, it was determined that overflow reductions gained at DS152 were significantly reduced to less than 1 MG due to increased overflow along the BRIS. Due to the BRIS flow increases from the proposed relief sewer, KC Water decided to pursue alternatives using the CD provision for the AMA. Updated GI Project An alternate control measure was proposed to separate approximately 195 acres and provide GI. The discharge from the GI would be downstream of DS152. Simulations show a significant increase in annual systemwide CSO reduction at DS152 and along BRIS. The proposed alternate has a preliminary estimated construction cost of $17M, which is about twice the cost of the relief sewer. However, from a cost-effectiveness standpoint, the alternate control measure cost is much lower based on the cost per CSO gallon removed. The alternative project also provides social justice benefits that were not accounted for in the comparison. At the time of this proposal submittal, the EPA has approved the alternative control measure and the planning work will be completed next year. Conclusions KC Water has used the AMA to cost-effectively substitute the original 2009 OCP interceptor relief control measure with a GI project. While the cost of the green infrastructure project is about twice as much as the originally proposed project, the proposed cost-effectiveness, expressed as the cost per CSO gallon removed, is an order of the magnitude higher than that for the original project, one dollar per gallon of CSO removed compared to almost $9. Additionally, the proposed project in this area would directly contribute to protecting high-risk populations' public health and environment and is consistent with EPA's ongoing commitment to environmental justice.