Modeling Principles Sustained Through 25 Years of Application

In the world where engineering science developed from a record of tried and true solutions, computer modelling is a “new” discipline that lacks a long history of learning by doing. Sewer engineers often seeks reassurance that the investment in the computer modelling will indeed lead to improved solutions and more cost effective sewer engineering.This paper describes how early planning models, developed in mid-1970s, evolved through multiple computer operating systems, multiple software packages and multiple consultants into the “living” models now being applied to evaluate a wide range of infiltration/inflow reduction measures, relief sewers, storage expansion and real-time control improvements. The lessions learned by the many modellers during the development and evolution of the models are summarized into a set of modelling principles contributing to the contuined sustainability of the Milwaukee models and offered here as a base of experience for the developing practice of sewage conveyance system modelling.The key principles identified for fostering sustainable models are listed here and explained in detail in the paper. The principle include:Terminology should be clear and consistenceThe software and models must be well documentedThe assumption must be identified, tested and documentedModels and application should be share dataThe source data should be clearly referencedThe source data must be tested and verifiedData conversion protocol should be standardized and applied consistentlySystem data must be mainted in a manner that supports modelling needsThis paper summarize the Milwaukee Metropolitan Sewerage District(MMSD) modelling lessions learned and principles developed by the numerous modelers invloved from 1976 through the present. To the extent possible, the author have synthesized the lession into recommendation to guide future modellers towards sustainable models which will be usefull in evaluating, planning and maintaining sewer system performance.