Structural Design of PP Stormwater Chambers Using Plastic Pipe Analysis

Plastic pipe has been used for many years in applications to control surface water runoff by detention, retention, and infiltration. Review of deficiencies with available pipe geometries resulted in creation of a new ‘pipe’ product, termed chambers. Stormwater chambers are arch-shaped, open bottom, polypropylene structures with unlined corrugated wall crosssection used in buried applications with cover between 450 mm (18 in.) to 2438 mm (8 ft). Chambers are manufactured by injection molding. This paper reports on chamber design in accordance with newly accepted thermoplastic profile pipe design theories incorporated into the American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor (LRFD) Bridge Design Specifications in 2001, analysis by accepted pipe-soil interaction finite-element analysis procedures, and in-ground testing by accepted pipe qualification testing procedures. The chamber described herein has span (including turned-out foot widths) of 1270 mm (50 in.) and rise of 762 mm (30 in.). This study compares the new thermoplastic pipe profile design methods with comprehensive in-ground testing. The American Society for Testing and Materials (ASTM) is balloting a new standard specification for polypropylene chambers based on the work described herein.