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No e x t e n d e d a b s t r a c t wa s s u b mi t t e d i n s u p p o r t o f t h e t e c h n i c a l p r o g r a m p r e s e n t a t i o n d e s c r i b e d i n t h e a b s t r a c t .

The Balch Consolidation Conduit (BCC) was operational at the end of 2011 to meet the City of Portland's, Bureau of Environmental Services (BES), Amended Stipulation and Final Order (ASFO) from the Oregon Department of Environmental Quality. The ASFO outlined staged reductions in the combined sewer overflows (CSO) to the City's waterways. The BCC consolidation pipelines were constructed to convey CSO flows from NW Portland to the larger Westside CSO (WSCSO) Tunnel. The City's CSO Tunnel System contains two large tunnels and numerous large diameter connecting consolidation pipelines. Evidence of transients and air entrapment issues in the CSO collection pipelines initiated a study of the CSO Tunnel System consolidated pipelines. The study results focused and recommended areas for improvements to protect the system from surge forces and air releases. This paper will discuss the field reports, larger system study findings, and resulting projects.