Nov 24, 2014
By Matthew DeNafo, Senior Engineer
As ACUA Vice President of Wastewater Joe Pantalone discussed back in his September blog, it is a known fact that United States infrastructure is in dire need of attention.
As an engineer working in the wastewater utility industry, trying to find a balance between being cost effective, practical and designing something with the longest life span possible can be a constant struggle.
Sometimes you are working with an emergency situation where sewerage is backing up into streets and other times you are working in a preventative position in the comforts of an office. Either time you face several challenges from a design prospective.
ACUA currently maintains 20 pumping stations and approximately 60 miles of pipeline.
In many of our replacement cases the failing infrastructure has been in place for at least 30 to 40 years. Costs and capacity needs have increased, technology has changed, new utilities have been installed and customers have become dependent on the consistency of a reliable system.
In early spring, our Department of Engineering was faced with a challenge: fix a leaking force main carrying 13 million gallons per day of sewage, prevent it from future problems and keep service available all the while keeping a budget constraint in mind.
This force main was originally installed in the 1970s and rehabbed in place in the 1990s. In the early 1970’s Wellington Avenue was approximately 2 feet lower than it is today, there were no high pressure gas systems and the number of homes in the area were about half of what is there today. The most important difference is that the local system was tied into a local treatment plant and not the regional plant that the ACUA operates today. This is critical because in the 1970s there would be no loss of service when the force main was installed since the existing system was not tied in until it was complete. Fast-forward to present day, there is no alternative; the system is connected and cannot just be turned off or diverted to make a repair.
The repair consisted of approximately 650 feet of newly installed force main. The installation was a constant struggle between weaving through existing water, sewer and gas utilities, high groundwater levels impacted by tides, excavating depths up to 16 feet and controlling the typical flow of traffic during peak summer months. The repair ended up taking almost 6 months to complete and cost approximately $1.5 million dollars due to the complexity of the situation.
While this is just an example of a small section of piping in a minimally congested area, it gives a sense of the magnitude of challenges that engineers are faced with in the U.S. with the deteriorating infrastructure. The next time you drive down a street or take a shower think about what goes into keeping these systems maintained and how often you actually have to think about it.