Realizing Real Rainfall Ramifications — Utilizing Peak Flow Recurrence to Improve Sanitary Sewer System Understanding

This paper illustrates through case studies of recently completed projects how both single event design storms and long-term continuous simulations can be applied for sanitary sewer master planning and rehabilitation effectiveness assessment, and provides proofs for why continuous simulation approaches better support long term planning and compliance with the pending SSO regulations. This paper also makes the case that it is more credible and defensible to utilize peak flow recurrence than rainfall recurrence as a basis for evaluating sanitary sewer system performance under wet-weather flow conditions. The current regulatory environment for SSO control appears headed toward risk-based approaches to managing collection systems. Cost-effective ways to incorporate risk-based concepts for managing peak wet weather flows are described in this paper and would be of interest to municipalities and utilities with sanitary sewer systems that are struggling with how to manage peak wet weather flows.