Technology and Its Impact on Reducing Inflow and Infiltration

The United States has more than a million miles of collection systempipes designed to carry 50 trillion-plus gals of raw sewage daily. Partof this system is underperforming and posing a health risk tocommunities across the nation.

A large part of the problem is the aging infrastructure; some collection system pipes still in use are more than 100 years old. The U.S. Environmental Protection Agency (EPA) has estimated that water and sewer systems in the United States will require funding upward of $500 billion above current spending levels over the next 20 years to improve the aging infrastructure.

The federal government passed a decisive bill with the passage of the Clean Water Act in 1972. The CWA set the goal of eliminating all water pollution by 1985 and authorized expenditures exceeding $24 billion in grants. The availability of federal funding in the early years for improving existing wastewater collection systems and infrastructure brought inflow and infiltration (I&I) to the front burner of many municipalities but reduced the need to search for the most cost-effective solution.

In spite of substantial funding from the EPA’s Grants Program, initial efforts in the 1970s to reduce I&I in sanitary sewer systems were generally unsuccessful. Most I&I control programs were reduced to emergency programs. Further, the technology at the time limited the inspection and rehabilitation approach. In the 1970s, the inspections and designs were done without the aid of mini-computers, GPS or trenchless technologies. The results of performing I&I removal in one area often lead to I&I issues occurring in other areas of the system.

With reduced budgets and an aging infrastructure, collection system experts have been forced to do more with less. Over the past 40 years, the industry has seen the greatest advancement in technology and collection system engineering. These advances have increased efficiencies, reduced costs, produced cutting edge rehabilitation designs with longer life and have contributed to a cleaner and safer environment. This article will take a look at some of these advances.

Although the basic steps used to perform condition assessment of the sewer system has not changed since the 1970s, experience has led to many of the techniques involved in the assessment to be refined with the advancement in inspection technologies and being performed with a better understanding of the information and conditions necessary for the design engineers to develop a cost-effective solution.

Smoke testing, a technique used to identify I&I, was developed more than 50 years ago and to this day, remains the most cost-effective means to identify sources of surface water inflow. It has been established that the air blower used during the testing needs to have a high capacity to generate sufficient pressure to signal all faults in the line. With time, it was also determined that instead of using just a single blower; the use of a double blower can successfully identify three to five times as many defects.

Today, the advances and applications of flow monitoring have increased the reliability and accuracy of the data and provide the collection system engineer with a more thorough understanding of the system hydraulics. For instance, flow meters with cellular/wireless connectivity have real-time data and programming capabilities that is available on computers and smart phones. This advance in technology can reduce labor, increase safety, give field staff the ability to respond quickly to equipment failure and improve overall sample accuracy. The real-time data that is pushed through to the server can also be immediately integrated into GIS format and viewed by both engineer and agency project manager while monitoring is ongoing.

The advances in CCTV inspection over the last 40 years have been equally remarkable. Today’s digital technology provides clear detailed views and information of the pipeline. The high definition technology classifies pipe infrastructures as either satisfactory or in need of maintenance, repair/replacement with the capability to pan-and-tilt zoom camera to measure joint gap and cracks. Further, these high technology cameras offer built-in inclinometer, advanced multi-frequency sonar, 3D laser, H2S gas, temperature and XYZ position sensors.

There are many methods and technologies available to remove and reduce I&I. Modern techniques allow for the sewer lines to be inspected, cleaned, and even replaced or rehabilitated without traditional open-cut excavation. These trenchless technologies allow for rehabilitation and repair of sewers without the expense and interruption of conventional open-cut excavation. The range of applications and the boundaries of what can be achieved, to install and rehabilitate underground infrastructure using trenchless technology is continuously being extended.

Further, over the past decade major advances have been made in providing liners that offer higher standards of performance while being more economical and convenient to install. Using current technology, cities and towns are seeing a rehabilitation projects in the range of $30 to $40 per ft. In comparison, replacement projects can entail the unearthing and replacement of large sections of pipe at a per-ft cost of $50 to $75. Each year, projects are undertaken that push the boundaries of what can be achieved, as new types of equipment, materials and innovation grow.

The infrastructure industry has embraced the concept of asset management as a major new tool in managing the operations and costs associated with aging infrastructure. An Asset Management System captures and stores infrastructure asset data and provides analysis, reporting, and information throughout the enterprise. Asset documentation is one of the first steps in Capacity, Management, Operation and Maintenance (CMOM) and Governmental Accounting Standards Board Statement 34 (GASB 34) compliance.

Of course, most of this technology would not be possible without the advancement of microchips and microcomputers. Not long ago Ken Olson, president, chairman and founder of Digital Equipment Corp. in 1977, stated: “There is no reason for any individual to have a computer in his home.” Today, the computer is an essential tool for collection system engineers to perform field investigations, analyze flow rates, provide inflow/infiltration analysis, run accurate and complex collection system models and perform detailed designs.

The development of the tablet, handheld data loggers, cell phones, etc. has enabled project managers and field staff to deliver greater quality control and quality assurance with errors being caught and corrected by project managers in the office and from the prevention of common errors happening while in the field during a project.

Fixing I&I defects in collection systems with multiple I&I sources can be complicated. With the advancement in sewer line rehabilitation, removing the I&I is more affordable than in the past. Further, if you add in the potential costs of I&I to the environment and to the impact on a community’s growth and quality of life, I&I reduction is a high value, necessary investment.

The EPA estimates that if the nation’s infrastructure needs are not addressed in the next 10 years, 35 years of water quality gains will be lost. Even though removing I&I can be a net cost-saver, the work required to remove it from a sewer system isn’t cheap. Municipalities need to be strategic in designing their I&I remediation efforts and do whatever they can to minimize the cost impact of the program on ratepayers and taxpayers. Today’s technologies are playing a large part in closing this gap, and we can all expect the coming years to produce even greater technologies to address our infrastructure needs.

Paul Costa is vice president and business development manager at RJN and is based out of its Baltimore office.