Most communities that manage combined sewer overflow (CSO) systems have made significant progress in adopting key provisions of the CSO control policy. However, according to the U.S. EPA, to date only about 33 percent of these communities have implemented all of the nine minimum controls, and even fewer have adopted long-term control plans. The EPA has estimated that current efforts have reduced CSO volumes and pollutant loads by approximately 12 percent since 1994. There is still much work to be done to improve water quality and meet regulations. Carollo Engineers can help. We specialize in water resources.

One of the biggest challenges in completing CSO programs is finding adequate funding. Estimates place the price tag on improving CSO infrastructure at as high as $1 trillion over the next 20 years. Although State Revolving Fund (SRF) loans have provided some help to address these needs, agencies are still in need of fund ing sources to close the gap. Carollo helps clients find alternate sources of funding.
Planning and design challenges presented by CSOs can vary significantly. CSOs contain a variety of pollutants, vary in volume and frequency, and result in a myriad of impacts on receiving waters. To compound matters, there is also a wide range of available control measures with a wide range of associated costs. Effective abatement strategies must consider site-specific conditions and match technology with economic issues and water quality impacts.
• Source control and reduction programs.
• Sewer system evaluations.
• Hydrologic and hydraulic modeling.
• Water quality monitoring and modeling.
• Collection system main te nance programs.
• Equalization and storage facility design.
• Collection system de sign and rehabilitation.
• Sewer separation programs.
• Wet weather treat ment facility design.
• Outfall and diffuser design.
• "Green solutions" such as best management practices (BMP) and low-impact development (LID) programs.

Along with CSO management, Carollo also offers extensive experience in sanitary sewer overflow (SSO) elimination programs. Carollo can help you develop a cost-effective and environmentally-sound wet weather control strategy that also protects public health. We will work with you to im plement the nine minimum controls, as well as to develop a cost-effective long-term control plan that is right for your system.
Our engineers have applied CSO management practices; designed wet weather treatment, transport and storage facilities; developed rehabilitation programs; and helped implement green solutions for a variety of clients.