The City of Naperville Puts the Plug in Inflow and Infiltration

Inflow and infiltration, or better known as I&I, has increasingly become the topic of conversation, articles, blogs and videos of late. Heavy rainfalls in the Midwest and Northeast United States — some being classified as high as 500-year and 1,000-year events — have strained the sanitary sewer collection and treatment facilities of many cities.

Basements flooded with sewer water, sewage treatment plants dumping partially or untreated wastewater into streams, rivers and lakes, EPA mandates and fines, rainwater and sewage spewing from manhole covers, beaches closed because of water contamination and other stories of this nature fill magazines, web content and television news stories. Burdened by these issues, many cities are now raising the water and sewer prices of their residents to provide the additional money necessary to make repairs and upgrades to their sewer systems that are 100 to 150 years old.

But other cities were fortunate enough to get a head start on addressing their sanitary sewer issues.
In 2006, the City of Naperville, Ill., decided that traditional manhole castings were no longer providing the performance they required. Unable to achieve a positive seal on the manhole cover, cast iron frames were allowing extraneous water and debris to flow directly into the sewer collection system through the top of the manhole. This was requiring greater quantities of sewer water to be processed, increasing the City’s treatment costs and the amount of pollution released into the atmosphere. At a rate of one kilowatt hour to convey and treat approximately 1,000 gals of water, the impact added up quickly.

The problem was only made worse by numerous annual freeze-thaw cycles and ground movement, which created more cracks in the concrete — thus, more entry points for inflow and more street repairs around their manhole openings.

In addition to overloading the collection system, their manhole covers presented other headaches, such as binding with the frame due to corrosion, traffic-related noise complaints because of covers no longer seated properly within the frames and ultimately the costly manhole rehabilitation.

When the City finally decided to research other options, Darin Severson, supervisor for the utility and repair division, suggested The Lifespan System, an integrated manhole system he had learned about during his tenure in public works. Severson’s boss, John Vose, described as someone who is open to new technology, agreed to install a few trial systems so the City could gauge how well they performed.

Unlike conventional manhole frames and covers, The Lifespan System from Hamilton Kent is specifically designed to eliminate inflow and infiltration at all critical points: the manhole structure to the adjustable risers, the risers to the frame and the frame to the cover.

Lifespan is made with ultra high-performance EPDM rubber to provide a watertight, naturally corrosion-proof and highly durable frame and cover system. As a flexible buffer, the system absorbs impact and retains the structural integrity of the underlying concrete structure, delivering a longer service life.

Suitable for new or refurbished installations, the manhole system is also safe, easy to install and ergonomically designed. Unlike 100 lb-plus cast iron frames, the frame weighs only 55 lbs and the adjustable risers weigh only 22 lbs each.

Naperville Sees Results

After installing a couple of Lifespan systems in rehabilitation applications, the City was pleased with the results.

“The most obvious benefit is the positive seal between all components of the system,” Severson says. “The cover is anchored down through the adjusting rings and into the concrete grade ring, so you know it’s not going anywhere. Nothing gets in there to cause the frame to [rise upward] and let water in.

“The other nice thing about Lifespan is that the 24-in. frame has the same diameter as the concrete grade rings we utilize. Unlike the old cast iron frames, it doesn’t hang over, so freeze-thaw cycles can’t lift up the side of the frame. The tapered adjustment riser rings also help in meeting the slope of a driveway or road surface for a natural fit.”

Another benefit the City recognized was the bolt-down, locking manhole cover that comes standard with the Lifespan System. By tightening the bolt heads on the topside of the cover with a 1-1/4-in. socket and wrench, the locking cams on the bottom of the cover swivel into designated slots on the inside of the frame. As the cams are drawn tight against the frame, the lid presses down firmly into the top of the frame, providing the positive seal the City desired.

As for the installation process, Severson says the crew can install a system in 90 minutes — and that includes digging around the structure and removing the old frame and cover. “There was a learning curve at the beginning, but now [the team] does it pretty quickly. The fact that the system is so light saves on manpower and equipment needs. The crew can just pull the units off the back of their truck with greatly reduced worry about injuries.”

Crews tend to appreciate anything that makes their job easier, which is why the team is also pleased with the butyl sealant that is applied between each layer of the system. It takes the guesswork out of the process, because workers know what the final grade will be when they are finished.

When asked how long it took to realize the benefits, Severson said that the installation benefits were clear as soon as the process was perfected. As for the performance features, he noticed them over time — after months of not receiving the usual calls. “We used to anticipate problems with our covers, especially in high-traffic areas. But I’ve got a Lifespan system in a major intersection and it’s been there for two or three years. There’s got to be an average of 2,000 to 3,000 cars that go over it every day and I haven’t had to go back to it once.”

Today, Naperville has between 20 and 30 Lifespan systems in the ground, with many more in inventory ready for the next manhole rehabilitation project.

Alan Siebenthaler is a marketing and territory manager for Hamilton Kent, based in Lexington, Ky.

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