Orange County, California boasts more than 112 miles of coastal and bay beaches and 33,000 acres of parkland and open space for recreation use. Many of these areas benefit from direct ties or proximity to a water resource such as creek, bay, harbor, or beach. These resources are valued for a variety of reasons, and represent a major source of tourism dollars in costal towns. In recent years, the beaches have experienced an increased number of beach postings and closures, and many of the inland and coastal waters are listed as impaired water bodies on the 2002 303(d) list. The leading cause of these closures is the growing presence of bacteriological contamination due to sanitary sewer overflows (SSOs). SSOs represent an often large-scale, uncontrolled introduction of hazardous and harmful materials into the environment, and can cause significant ecological, surface water, ground water, and economic damage, as well as risks to human health. With growing concerns over bacteriological contamination and increasing regulatory and political pressure to improve water quality, the County of Orange (County), the flood control agency, and the Orange County Sanitary District (OCSD), the sewering agency, initiated a joint research project to better understand the dynamics of SSO travel, improve the SSO capture/mitigation process in the channel system, and streamline interagency coordination to better respond to and mitigate the impacts of SSOs. Working jointly, OCSD and the County have developed new tools to quickly respond to SSOs and identify flow characteristics, resource requirements, and physical constraints. This paper documents the project approach and methodologies that have been undertaken in developing and implementing the joint project. The primary objectives of the joint research project were to: �� Create broader awareness of SSO causes and measures to prevent them �� Improve the interagency coordination when responding to SSOs �� Understand the resource needs in responding to and mitigating SSO impacts �� Develop predictive tools for identifying impacts �� Establish methodology, resource requirements, and scope of work for in-channel SSO containment �� Protect the beneficial uses of local water bodies In order to achieve the project objectives, the County and OCSD, on behalf of the Orange County Flood Control District and the incorporated cities in Orange County, initiated a pilot project titled the Tustin Area Spill Control Demonstration Project (TASC). The first phase of the project completed the following tasks: �� Defined the project area selection criteria �� Identified the pilot project area �� Developed a series of GIS maps needed to characterize the project area �� Identified staging areas for set-up, containment and capture �� Performed velocity studies to understand the flow characteristics of SSOs for various types of channels �� Performed a field test to exercise interagency coordination and SSO capture procedures �� Documented lessons learned in order to identify the direction for the next phase The second phase was the implementation phase. After incorporating the lessons learned and resolving the deficiencies of the first phase, the second phase focused on the critical elements needed to successfully implement and expand the project area to cover all of Orange County. The key elements of the second phase included the following: �� Finalized interagency coordination and project management �� Defined standard procedures for SSO response, containment, capture, and cleanup �� Identified SSO response resource and equipment requirements �� Developed safety guidelines for in-channel work �� Solicited expert recommendations for improving the work procedures from environmental services contractors �� Expanded GIS maps to cover the entire OCSD service area �� Identified staging areas outside the initial project area �� Developed and issued a proposal to retain a local contractor for in-channel work This paper documents the proactive efforts the County and OCSD are making toward SSO response and cleaner environment. It summarizes the motives, methodologies, and lessons learned from the pilot project. The project set a milestone for in-channel SSO response and will serve as an important reference for others in developing their own guidelines for SSO response.