AWWA ACE94257

New water regulations as a result of the Surface Water Treatment Rule, and new filter media cleaning methods have created need for filter underdrain systems which address installation and process issues for filter retrofit projects. Many older filters are being retrofit with deep bed mono-medias, dual-media, or tri-medias to address specific water treatment concerns and, thus, to meet new regulations. In addition, many of these retrofit projects are using air scour in combination with water backwash to increase cleaning efficiency. With these new processes, and deeper media bed designs have come problems associated with changes in head loss, and insufficient cell depth in older filter cells. Deeper media beds combined with increased bed expansion in air scour are using more cell depth, and imposing some limitations on design options. Additional issues associated with both retrofit and new filter projects are potential maldistribution of air and water, gravel bed upset, and inefficient distribution of simultaneous air and water through common exit orifices. EIMCO Product Managers and Engineers set out to design a filter underdrain system which would address needs of owners, consulting engineers, and contractors for such issues. This paper discusses the general development process for the EIMCO PolyKleen Underdrain.