Title
The Nuts and Bolts of Manufactured Treatment Systems: An In-depth Look at Critical Design Variables
Publication Date
4-8-2008
Abstract
The use of manufactured stormwater treatment systems to mitigate the adverse impacts of urban runoff has become commonplace. Not surprisingly, as the demand for manufactured treatment systems has grown the number of available options has followed suit. The typical stormwater professional could make deciphering the various performance claims, sizing methodologies and other supposed benefits marketed with each device a full time job, but most have little time for such endeavors. The majority of state and local agencies have not established sizing criteria for manufactured treatment systems, so agencies often rely on the manufacturers' sizing recommendations. However, manufacturers' sizing methods tend to be unique to each device, making it virtually impossible to directly compare competing technologies to one another. Unfortunately, limited knowledge of critical sizing assumptions on the part of engineers and reviewers as well as fierce competition among vendors is resulting in the installation of undersized and poorly sited systems. Establishing uniform sizing criteria creates a level playing field from which to compare manufactured systems to one another and to other types of treatment systems, and ensures that devices are sized to meet applicable standards. This paper explores the fundamental unit processes that govern the performance of manufactured devices and the sizing variables often manipulated by vendors to make their units seem superior or more financially attractive to the end user. Examples of common sizing methodologies and associated assumptions are presented in a manner that allows the reader to make informed decisions regarding device selection and sizing. Standardized sizing methodologies that are already in use by a number of state and local agencies are also discussed.