Prediction and quantification of Combined Sewer Outflows under extreme storm events: Flow dynamics and Reduction of Combined Sewer Outflows

EPA Grant Number: R835187
Title: Prediction and quantification of Combined Sewer Outflows under extreme storm events: Flow dynamics and Reduction of Combined Sewer Outflows
Investigators: Leon, Arturo
Institution: Oregon State University
EPA Project Officer: Packard, Benjamin H
Project Period: June 1, 2012 through May 31, 2017
Project Amount: $265,528
RFA: Extreme Event Impacts on Air Quality and Water Quality with a Changing Global Climate (2011) RFA Text |  Recipients Lists
Research Category: Global Climate Change , Earth Sciences - Environmental Science , Aquatic Ecology and Ecosystems , Aquatic Ecosystems , Air Quality and Air Toxics , Water Quality , Climate Change , Air , Water


Combined sewer overflows (CSOs) are a major water pollution source for more than 700 cities in the U.S. that have combined sewer systems (CSSs). CSOs occur in response to heavy rainfall and / or snowmelt events when the capacity of the storm-sewer system is exceeded or when the flow in the system is highly dynamic even when the system is not full. The overall goal of the proposed research is to develop a model for the accurate prediction and quantification of CSOs especially when the flow in a CSS is highly dynamic (e.g., under extreme flow events). The specific objectives are: (1) To develop a mathematical formulation for all possible cases of overflow discharges (e.g., CSOs) at vertical shafts and near-horizontal outlets under extreme flow events. (2) To implement the mathematical formulation of overflows into a state-of-the-art open source (free and open access) transient flow model that can be used in complex CSSs. (3) To validate the overflow discharge framework under highly dynamic flow conditions.


The following methodology will be used to conduct the proposed research.
  1. The mathematical formulation of overflows under unsteady flow conditions will be derived by combining the unsteady equations of conservation of mass and momentum ("x" and/or "y"), and by using the Riemann invariants or a shock-capturing based approach.
  2. The overflow framework will be implemented into the Illinois Transient Model (ITM). ITM, which was developed by the PI of this proposal, will be used for this implementation because it is a state-of-the-art open source model especially formulated for simulating the filling and emptying of CSSs under transient flow conditions. ITM was applied to complex CSSs of cities like Chicago and Dallas.
  3. A total of ninety laboratory tests for two experimental setups of complex pipe networks and three-dimensional flow numerical simulations will be used for the validation of the overflow framework under extreme events (highly dynamic flow conditions).

Expected Results:

The outcome of the proposed research will result in an open source model that can be used by Federal agencies, Municipalities and practitioners for predicting CSOs under extreme events. This framework will allow to assess the impacts of CSOs on the water quality of the receiving water bodies such as streams, rivers and lakes. Furthermore, this model will provide its users with the ability of modifying an existing combined sewer system within the model for assessing various proposed modifications and hence for retrofitting critical areas in the system. This will allow developing cost-effective strategies to reduce CSO events. The model will be used under present and climate change scenarios.

Publications and Presentations:

Publications have been submitted on this project: View all 17 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 4 journal articles for this project

Supplemental Keywords:

Effluent, Hydrology, Modeling, pollution prevention, risk, water;

Progress and Final Reports:

  • 2012 Progress Report
  • 2013 Progress Report
  • 2014 Progress Report
  • 2015 Progress Report
  • Final Report