Receiving water quality and effluent dilution requirements in the US are requiring extension ofrnWWTP discharge points away from shorelines, and disposal through deeper and/or longerrndiffusers. This chapter describes regulatory conditions that are forcing many wastewaterrntreatment plants to repair or upgrade their outfalls, and the design and construction methodsrnbeing used to meet the new requirements, including a description of one of the deepest andrnlongest HDPE outfalls in the world.rnAllowable construction methods are becoming more stringent. While some agencies arernrequiring improvements to outfall systems, other state and federal permitting agencies arernseverely limiting the methods of construction within jurisdictional waters, and the allowablernseasons when construction can occur. Recent case studies from the USA Pacific Northwest willrnbe used to illustrate emerging trenchless methods of construction through nearshore zones,rnand innovative construction materials and techniques that minimize impacts duringrnconstruction.
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