2020 Second Edition of AWWA M55 HDPE Pipe

The Second Edition of AWWA Manual M55 PE Pipe—Design and Installation is expected to be published in late 2020. In this edition, there are significant updates to the design and installation recommendations that users of HDPE water pipe should be aware of. For design, the new manual will include PE4710 compounds that have been added in the ANSI/AWWA C901 and C906 standards. Design updates also include higher E’ (modulus of soil reaction) values, use of composite E’ values, use of uniform soil classes, and terminology. For installation, M55 contains revised information on trench width, flowable fill, inspection and soil testing, and compaction requirements. These changes reflect the recent revisions to ASTM D2774 Standard Practice for Underground Installation of Thermoplastic Pressure Piping> The second edition of M55 encourages the use of basic installation and engineered installation. The basic installation is for HDPE pipe stiff enough to not need special bedding and embedment, for shallow burial with no live load, and for stable trench wall support. In this case, the HDPE pipe can be laid on the trench bottom and backfilled with soil from the excavation. This covers the majority of HDPE pressure pipe installations. For other conditions, the engineered installation means selecting an HDPE pipe and corresponding installation details to meet deflection and buckling requirements. In addition, the second edition of M55 has a new chapter describing trenchless technology and has new appendices on model specifications, seismic performance, marine applications, case studies, and PE4710 pipe data. This paper will focus on HDPE external load design and commensurate installations.