Combined Sewer Overflows

Successfully protecting the public health and the environment means thoroughly understanding your collection system, the environment in which you operate, and the levels of risk you can accept. From these starting points, a strategy may be developed that preserves the health, safety, and quality of life for the community you serve.

The Conner Creek CSO Control Facility - the largest CSO facility in the state of Michigan - eliminates up to two billion gallons of untreated discharge to Conner Creek annually and was completed four months ahead

This sectional Computational Fluid Dynamics (CFD) view of the Conner Creek CSO Control Facility shows contour plots that illustrate the mixing effectiveness of a diffuser matrix. This three dimensional model analyzed chlorine contact time to optimize disinfection for this 8.6 bgd facility.

The Paerdegat Basin CSO facilities serve a tributary population of 500,000 and receive CSO from a drainage area of approximately 6,000 acres.

For Sanitation District No. 1 of Northern Kentucky, we developed a full system solution concept to address CSOs and SSOs to use as a bench mark for comparing the costs and benefits of using integrated gray, green and watershed controls to achieve water quality improvements more quickly and effectively.

Also for Sanitation District No. 1 of Northern Kentucky, we developed and implemented an innovative Continuous Sewer Assessment Program, based on the principles of Asset Management, that uses historical data to develop basin-wide priority scores for structural and service conditions.

Our 3D CAD designers can "build" facilities and systems early in the design process, facilitating earlier stakeholder input and avoiding unnecessary delays and conflicts.

Hazen and Sawyer led the development and calibration of a hydrologic and hydraulic collection system model (USEPA SWMM 5) for the Upper Monongahela planning basin and was responsible for conversion of a portion of the City of Pittsburgh’s existing InfoWorks CSTM model. The model ultimately includes over 32 miles of pipes, including all CSOs and SSOs.

Hazen and Sawyer designed the LEED Silver-eligible, 4-million gallon Manayunk CSO detention facility on Venice Island, a sensitive area requiring careful consideration of neighborhood impacts.

As part of the Solids/Floatables Control Plan adopted by the City of Camden, Gloucester City, and the Camden County Municipal Utilities Authority, we designed in-line netting technology to screen ½” solids and floatables from 16 outfalls in Camden City.

Hazen and Sawyer developed this tool to manage almost all aspects of a flow monitoring program. It offers fast, accurate and cost-effective data analysis and lends credibility to the data by demonstrating aggressive and timely QA/QC. We can quickly flag data quality problems using a variety of features such as scattergraph plots, meter flow balances, and hydrograph analysis.

Modeling systems and entire watersheds allows us to test design alternatives to most cost-effectively achieve desired outcomes and focus on projects with the greatest payback.

The construction of combined sewers has rapidly extended basic sanitation to countless communities over the past centuries, but combined sewer overflows pose ecological and human health risks that must be mitigated. Even the peak flows brought by relatively frequent storms can cause water quality deterioration and pervasive nuisance conditions such as unpleasant odors and unsightly shoreline deposits of floatable debris.

Climate change and population growth pose additional challenges – meaning potentially more and/or larger storms and certainly more sanitary sewage – so what can utilities do now to ensure that an acceptable level of service is maintained in the future?

Hazen and Sawyer is a leader in developing cost-effective solutions to the toughest CSO challenges, excelling in every facet of CSO planning and control:

  • Planning – The initial phase of most CSO projects involves identifying and quantifying CSO impacts, then developing the basic recommendation of a course of action. Hazen and Sawyer has extensive experience in hydraulic and hydrologic modeling and facility planning.
  • Design – Hazen and Sawyer has been designing CSO abatement facilities for decades, including some of the largest, most complex systems in the nation, but remains committed to identifying opportunities to maximize use of existing facilities and other cost-effective solutions.
  • Construction Management – Where Specs and Drawings turn into operating facilities, Hazen and Sawyer has a proven track record of representing the owner’s interests on site.
  • Program Management – Hazen and Sawyer has successfully helped municipalities track multi-faceted capital programs, often under consent decree.

Protecting public health and the environment is a growing challenge. A changing climate may bring more frequent and larger storms, a denser population means more sanitary sewage running through our sewers, and water quality regulations will only tighten. Hazen and Sawyer’s experience and real-world expertise can help you find the solutions to your CSO challenges.

For inquiries contact:
Peter Young