Data Modeling Is Key to Efficient Inflow and Infiltration Mitigation

Stop trying to replicate projects; customized method analysis is the way to go

Data Modeling Is Key to Efficient Inflow and Infiltration Mitigation

Classification of sewer renewal technologies defined by American Water Works Association and European Standards.

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Practically every municipality in the U.S. is experiencing problems with inflow and infiltration right now, but the similarities pretty much end there. Each town and city has its own specific issues — geological, topographical, hydraulic — making it difficult to standardize solutions.

So how could one possibly determine the most efficient type of rehab or replacement technology? The simple answer is you can’t, at least not without a sophisticated decision support system, which is exactly what a white paper by Mahmoud Halfawy and Samar Baker set out to address.

The paper, “GIS-Based Decision Support System for Evaluating Costs and Benefits of Sewer Renewal Technologies,” takes a comprehensive approach to efficiency assessment.

“Renewal technologies are advancing rapidly,” the paper states. “The use of trenchless methods has been steadily increasing around the world. New materials and construction methods are constantly introduced to the market, causing the process of evaluating these technologies and selecting the most appropriate solution to become a daunting task for municipal practitioners.”

Quantifying pipeline renewal

The first issue is to decide what factors affect the cost-effectiveness and practicality of sewer renewal, which is done by defining and categorizing all potential renewal options.

“Once renewal categories are determined, the renewal methods within each category are further evaluated in terms of their ‘applicability’ ... technology limitations and compatibility with the pipe physical characteristics, site characteristics, and other social or environmental criteria and user requirements,” according to the paper.

When assessing cost, the condition of the system must also be taken into account.

“The increase of renewal costs with the deterioration of sewer condition grades has been reported in several studies,” Their approach uses a point modifier system for different condition levels, on a scale of 5, with 1 being the least critical and condition 5 being pipe with impending failure — where a higher cost is assumed.

They suggest formalizing “compatibility rules,” such as what methods are only applicable for pressure pipes, or what applications sliplining can be used for. Some pipe characteristics require a specific rehabilitation method — all of these factors have to be quantified and associated with the relevant categories established previously.

Past approaches have been as simple as “a set of tables and forms with yes or no questions to evaluate the technical compatibility of the renewal methods with the project requirements.”

Halfawy and Baker’s recommendation is a software-based approach using object-based data modeling. Essentially, it attempts to break down every reasonable angle of pipeline renewal, on both existing factors in the aging infrastructure and potential factors of renewal options.


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