How Design and Construction of a Parallel Wet Weather Interceptor Meets Sustainable and Hydraulic Goals

Purpose: The purpose of this presentation is to walk the audience through the process of increasing the capacity of a wet weather collection system and how this affects the sustainability of the system. The presentation will present the concepts of sustainability as defined in the ASCE MOP 151 Sustainable Design of Pipelines. Benefits of Presentation: There are several benefits to the industry that this presentation will provide. This presentation will provide a real-world project where the San Antonio Water System had to work through the process of increasing the capacity of a major interceptor through the historic and congested downtown area. This presentation will describe the options available and the deciding factors used for the ultimate solution. When faced with the requirement to increase capacity of a centralized gravity wastewater collection system, utilities have numerous options that can span the full range of costs, schedule, impacts to resources, customers, the environment, and to the public. The recently issued ASCE MOP 151 Sustainable Design of Pipelines publication provides an abundance of ideas for engineers and utilities to consider when designing and constructing a pipeline project to increase its sustainability and minimize its adverse impacts. As the San Antonio Water System (SAWS) Broadway Corridor Interceptor Improvement Project was recently placed into service, this provides an opportunity to compare the project to the precepts presented in ASCE MOP 151. There are multiple solutions available for designing an interceptor to handle both dry flows and wet weather flows. These solutions include inline and offline storage, upsizing, pumping, and parallel pipes (typically with one being the relief sewer). Each of these have their own unique hydraulic properties and requirements and influence the final design. This presentation will review the hydraulic characteristic of each solution and how this can affect the ultimate sustainability of the project. The hydraulics of a gravity sanitary sewer are of utmost importance to ensuring the proper operation of the system and long-term longevity and unimpeded service to the public. However, it is imperative that proper hydraulics is not the only or even the top-ranked factor used in determining the final solution. Status of Completion: Completed, operational since 2020 Conclusion: Many projects use a matrix to help consider other influences that could steer the decision-makers toward one solution or another. This is exactly the approach that SAWS and the design team used in determining the final solution for the Broadway Corridor Interceptor. ASCE MOP 151 provides a well-documented and step-by-step guide for scoring those influences that affect the sustainability and resiliency of pipeline projects. As laid out in the MOP, the areas that should be considered include pipeline materials, owner best practices, planning and design best practices, construction, operations and maintenance, and life-cycle analysis. This presentation will evaluate each of these areas and how the Broadway Corridor project measures up against each of these sustainability goals. With the updated Broadway Corridor Interceptor operational since 2020, this presentation will provide the audience with a real-world example of how projects can be designed more sustainably by applying the principles of MOP 151 during the planning and design phase and how important it is to continue the application of those principles through construction and operation to benefit the owner and community.