CWR Value Proposition - Engineers

Finally...A Business Case for Investing More Money in the Collection System

• More assessment

• More flow monitoring

• More and improved standards for hydraulic modeling

• An opportunity to solve I/I problems at the source...without risking your clients money

• Provide your clients with an alternative that gives them guaranteed cost-effectiveness for Collection System spending

Excessive wet weather flows can have negative affects on the performance of a collection system and wastewater treatment plant (WWTP). Reducing these wet weather flows through an effective pipeline rehabilitation program can reduce the occurrences of sanitary sewer overflows (SSOs) and provide a more reliable system that has adequate capacity.
 
A rehabilitation program is typically developed in two phases. The initial phase of a rehabilitation program involves flow monitoring, I/I analysis, pipeline inspection, and rehabilitation recommendations. The flow monitoring data is used to estimate the quantity of I/I in each basin. After qualification, the basins are ranked so that the engineer can determine which basins are contributing the most significant I/I flows.
 
Once pipeline rehabilitation is complete, the second phase of the rehabilitation program assesses the effectiveness of the improvements. A post-rehabilitation flow monitoring effort provides the basis for quantifying how cost-effective the rehabilitation was.
 
If rehabilitation can be performed cost-effectively, it provides many benefits including:

• Regaining system capacity

• Improving asset value

• Extending the life of the collection system

• Deferring capital expenditures required to store and treat excess flows

• Reduce treatment costs

• Increasing groundwater levels

• Reducing/eliminating basement backups

• Reducing/eliminating SSOs

• Protecting the environment by meeting discharge permit regulations

Collection system rehabilitation can be an integral component of a Capital Improvement Program. I/I rehabilitation aids in the elimination of overflows with the collection system and directly reduces the amount of flow that must be conveyed, treated, or stored within a collection system or at a wastewater treatment plant. Rehabilitation of pipelines and manholes is a necessary task to keep a collection system operational over time.
 
The magnitude of I/I reduction for a given cost will dictate how cost-competitive rehabilitation is when compared against other methods. However, only through collection system renewal and I/I reduction can all the benefits outlined above be achieved.
 
Many municipal agencies want to know the most effective ways to remove I/I within their systems. The question for these agencies is, “How much do I need to remove, and where’s the best place to do it?” Before an agency commits to a pipeline or manhole rehabilitation project or some other kind of I/I removal strategy, it wants some assurance that the project will be cost-effective and money will be well spent.

“Many of us in the environmental engineering field have at one point undertaken a study or design for an I/I removal project and tried to make a sound estimate of the quantity of I/I that will be removed from the system as a result of the project. Typically, we rely on data collected during a Sanitary Sewer Evaluation Survey (SSES) project. Sometimes our removal estimates are reasonably accurate. Often times, however, we see the project through to completion of construction only to find they have missed their I/I reduction goal or target. With each project we may improve our estimating abilities, but the hoped-for reliability in the accuracy of our predictions still evades us at times.” (Lucas et al, “In Search of Valid I/I Removal Data: The Holy Grail of Sewer Rehab?”) (WERF: Predictive Methodologies for Determining Peak Flows after Sanitary Sewer Rehabilitation)