Optimizing the Connection of a new 360 Mgd Headworks Facility to Live Incoming Sewer Trunk Lines and the Primary Treatment Process

The paper describes the approach which was taken by Orange County Sanitation District (OCSD) to tie-in a new 340 MGD headworks facility with multiple structures to existing incoming trunkline sewers ranging from 78-inches to 108-inches in size and also tying it to existing primary treatment processes, without compromising the plant operation and treatment. The paper describes the 20 step tie-in approach that was established to sequence the construction work which reduced the spill risks during these tie-ins and helped plan the shutdowns not only at the affected OCSD Plant No. 2 but also helped with coordination of flows with the sister OCSD Plant No. 1. The paper also describes the flow scenarios adopted to reduce spill risks and the techniques used to make the connections without stopping the flows.