Throughout the United States, an estimated 22 million manholes dot the infrastructure landscape. Of those, the U.S. EPA has determined about a quarter of them are suffering from serious decay and need immediate rehabilitation or replacement.
And those numbers continue to grow with each passing year — which makes for a steady and, in some areas, growing manhole rehabilitation market. Even during these days of a global pandemic, the maintenance of these critical pieces of infrastructure is required. In actuality, up until 25 to 30 years ago, a majority of the manholes went virtually untreated and unmaintained, allowing more than 100 years of neglect to take its toll.
Brick manholes, as well as stone manholes, have played a key role in the development of our wastewater collection systems. Manholes were constructed to provide an entry way to the underground network of sewer tunnels, requiring them to be safe collapse as workers made their way below to inspect, clean and repair sewer pipe. The brick or stone construction was a perfect design for this purpose, as the masonry material provided a strong and sturdy foundation.
And many of these manholes — some built 200 years ago — remain in use today. A majority of the early manholes were constructed with mortar and brick but stone, such as cobblestone, was also common. Because they were built from scratch, their designs, while most circular, were left to the hands of the masons. Some were square-shaped and some even triangular. Pre-cast concrete manholes entered the market in the late 1950s and 1960s, with cost for materials and labor the primary factors.
Generally speaking, these aging manholes have held up remarkably well but they are clearly showing their age with each passing year. Problem areas range from mortar joint cracking (from the constant pounding the joints take from the millions of cars and trucks that travel over a manhole each year), as well as leaks resulting in destructive inflow and infiltration. And, of course, corrosion. Their overall conditions depend on what area of the country they are in; many have suffered the effects of freeze/thaw cycles, poor construction methods, or just overuse due to regional expansion and suburban sprawl.
“Manholes in the United States are clearly showing their age. Many systems have not upgraded their manholes for decades and this is causing severe cracks and leaks throughout our manholes. These leads are then driving major infiltration issues for municipalities when rain events occur,” says Sealing Systems international sales manager Paul Wright.
OBIC LLC owner Dustin Schlachter sees the manhole rehab market as strong and healthy but appears to have flattened the last few years. “And now in 2020, with the concern over the pandemic and social unrest in the United States, it appears that concern over municipal revenue may cause this flattening to continue or even experience more downturn,” he says.
“The rehabilitation market for sectors in wastewater treatment and collection remain at the forefront for addressing preventative maintenance, structural repair, improved efficiencies, reduction of inflow and infiltration and improving water quality in the outgoing effluent water being discharged into creeks, rivers and our waterways,” says Sauereisen inside sales and market representative John Davis. “Billions of dollars are needed to restore, replace and upgrade existing facilities in both the treatment and collection side. The corrosion problems are magnified by the fact that, in general, available corrosion protection was not incorporated into the initial installation.
Joe Talley, Sewpercoat market manager at Imerys, notes that in areas in the United States such as the Southeast, manhole rehab is a relatively new area of infrastructure focus, with many municipalities not taking note of their condition until the 2000s. “In the Southeast, the water table is so high that the systems are continuously submerged and typically in sulfur-rich soil conditions,” Talley says. “The challenge with manhole rehab is determining the right solution.”
The solutions and material options for manhole rehab are plentiful. Spray-applied coatings and linings are very much the industry standard, whether for cementitious products or inert and organic-based materials. Options can include: cement, calcium aluminate cement, epoxy, polyurea, polyurethane and grouting.
“With an ever-crowding selection of products available in the marketplace, coatings suppliers are facing the challenge of differentiation,” Davis says. “Where one vendor touts physical strength, another promotes chemical resistance. Perhaps the bidder promoting ease of application and immediate cure might leverage application properties as a critical consideration. Each of these considerations offers some degree of merit, and the most important factor may ultimately depend upon unique project conditions.”
But experts caution owners and municipalities about relying on one product to fix all your manhole problems. “There is no ‘silver bullet’ when it comes to manhole rehabilitation and renewal,” says Cretex general manager Lee Haessig. “Each manhole often presents a variety of issues and owners and municipalities should determine what the problems are manhole by manhole and then select an appropriate technology to address each issue.”
He notes that many times, this process will involve using several different technologies to meet your manhole needs.
Schlachter concurs with Talley about zeroing on one technology to fix all your manhole issues. “This is not a one-size-fits-all industry and it takes different options to make the best decision,” he says.
“Understanding what options are out there and are time- and field-proven is only part of the battle. The installation of most products by a quality installation company is the key to the success of a manhole rehabilitation program. Without trained installers, most products will have a short lifecycle. The old saying still stands: Good work isn’t cheap and cheap work isn’t good.”
Experts say that customers — owners and municipalities — have gotten more and more knowledgeable over the years, upping their game when it comes asking questions, as well as better utilizing their limited and, in many cases, shrinking pool of funds to draw on for infrastructure rehab work. They are incorporating more inspections in their maintenance programs to take a more proactive approach to their systems. “Municipalities are getting smarter,” Wright says. “They realize in these days of limited funding that they need to very diligent about system inspections and evaluations. We see cities doing more CCTVing projects to inform where they should be putting their capital investments.”
Wright has this suggestion for cities going forward, “Focus on what will give you the biggest bang for your buck. It’s all about efficient spending first when selecting rehab methods.”
Trends are part of any marketplace; trenchless and manholes are no different. Trends can be regional or national or just showcase a shift in thinking when it comes to how a technology is used. For manholes, our panel sees a few taking place.
Talley notes a marked shift toward lining new construction manholes, particularly in Texas. “Some municipalities are well aware of their wastewater conditions and know that certain new development area will likely be highly corrosive and in need of rehabilitation in the near future,” he says. “With some forward thinking, these manholes can be identified for protection with a lining system during the initial installation. This provides for biogenic corrosion protection from Day 1 instead of a few years down the road when repair costs are likely higher and site access is more difficult and disruptive.”
Others point to the inclusion of “green” products and their use in the manhole market. “A ‘green’ product trend is emerging which improves lining performance in manholes and larger wastewater and storm water structures,” Davis explains. “One-part geopolymers, without the inclusion of Portland cement, are growing in popularity due to their high-strength, low porosity, chemical resistance and use of an industrial by-product, thus providing a ‘green’ solution.”
While Wright and others note that manhole rehab and repair work will continue to increase in the next decade, the COVID-19 global pandemic will ding the work in the short term, with even tighter budgets going forward as the virus wreaks havoc on the economy. Many see manholes becoming part of an overall rehab program, tying together the mainlines, laterals and manholes.
“We don’t have a crystal ball, but in my opinion, there will be an increase in manhole rehab and repair over the next 10 years,” Haessig notes. “I believe this is because many manholes that were installed new 40 or 50 years ago are reaching the end of their design life and will need to be rehabilitated, repaired or replaced.”
“We believe that the manhole rehab market is going to be the final frontier of infrastructure rehabilitation,” Schlachter says. “Many times, the main lines and laterals get the attention first and the manholes will get taken care of last. We see a trend in contractors along with manufacturers partnering with trusted products and installation companies to view the entire system as a package to be rehabilitated and not as separate items.”