Just last month, the nation celebrated Infrastructure Week — a week dedicated to highlighting both the social and economic impacts of improving the under and above-ground infrastructure. The week has gained momentum and #InfrastructureMatters trended on Twitter.
In the sewer construction and rehabilitation sector, it is often the large-scale projects — long stretches of relining or microtunneling marvels — that garner the most praise and funding — winning awards and multi-page editorial spreads.
However, ask those involved in the manhole rehabilitation industry and they will tell you their sector is just as, if not more, important.
For many years, the entry points to the sewers have played second fiddle despite the fact that these bits of low hanging fruit hold the potential to being the doorway to reducing combined sewer overflows at a fraction of the price of the large-scale projects.
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“I think [system owners] focus a lot of their attention on the pipes and sometimes the manholes get forgotten. Even more important is that the top of the manhole is almost always totally forgotten,” says Alan Siebenthaler, marketing and territory manager, Hamilton Kent LLC. “Everything else gets done and then on the top is a regular manhole cover. They forget that last step. It’s like we say, ‘You’re putting a screen door on your submarine.’ You’ve sealed everything perfectly but then you left the door open.”
Both literally and figuratively, the manhole rehabilitation projects go deeper than that. Repairs include a variety of linings and coatings, cast iron and composite manhole covers and good old-fashioned cleaning programs to keep sewers functioning as intended.
“Manhole rehab is one of the most underutilized methods in the industry. Owners are spending millions of dollars on other system upgrades that offer zero sanitary sewer overflow (SSO) or inflow and infiltration (I/I) reduction like sewer treatment plant capacity upgrades.This is due to exceeding permit limits from excessive I/I,” says Eric Dupré, business director Blue Green Municipal Solutions. “The sewer plants, the lift stations and main trunk lines are not typically the critical key I/I contributors. It’s the brick and mortar manholes, deteriorated concrete adjustments rings, and vented or unsealed manhole covers. There’s no doubt that those other structures do need rehabs or upgrades but it does not offer near the SSO/I/I reduction impact nor the return on investment that you would get from manhole cover replacements or manhole rehab.”
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Blue Green Municipal Solutions holds an interesting place in the industry as the company owns the SewperCover composite manhole products, provides sewer condition assessment service and is a sister company to Southern Trenchless, a contracting firm.
“We’ve witnessed the problems first-hand and I have served on many different boards,” says Dupré. “I’ve sat at all sides of the table and I have seen the different perspectives of the owner, the designer and the rehab contractor.”
As with many aspects of the trenchless industry, the last decade has experienced growth in the manhole market as owners become more cognizant of the role manholes play in I/I, though it is nowhere near where it should be, according to Dupré. This, he says, is because some system owners focus more on the plant capacity out of duress as the facilities are at, or beyond, permitted capacity limits.
The owners default to upgrading sewer processing systems too quickly without doing a comprehensive feasibility study on the system’s I/I source point, which would dramatically reduce the plant’s I/I intake volumes and restore a large portion of lost capacity without paying for a plant expansion. Over the years when owners have invested in analyzing their I/I, the results have revealed that approximately 40 to 70 percent of the I/I was identified at the manhole, Dupré says.
“Using the scientific method with good factual system data to prove or disprove your assumptions makes all the logical sense to justify the source of the real problem when determining the solution needed,” Dupré says. “Once you determine your final conclusion, test it out on a small sample size scale and if successful results are proven then grow your sample as needed.”
This I/I is two-fold with a portion of the seepage — and the most easily accounted for — coming from the pick-and prevent holes. The other comes from deteriorated brick and mortar and precast manholes structures due to corrosion from sewer gases, namely hydrogen sulfide.
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According to Siebenthaler, a manhole with 2 in. of water sitting on top of it during a rain event is not uncommon and some have more. Hamilton Kent’s testing indicates that one manhole cover can let in approximately 1,000 gals per hour into the system. A system owner can take that figure, multiply it by the amount of similar manholes in similar locations and generate a total of the amount of unnecessary storm water flowing through treatment plants.
“You take those bad manholes and knock them out and a system owner can see a two-to three-year return on their investment. Big projects could take 10 to 15 years to see a similar return,” he says. “It’s about building awareness of what is right in front of you.”
Both Hamilton Kent, with its Lifespan System, and Sewper Cover offer composite locking manholes that eliminate infiltration at the cover, as well as resist corrosion — the scourge of manholes across the continent.
“Old cities have old sewer systems and old systems have not aged very well. Old brick and mortar manholes infiltrate groundwater. Most were built without concern for being water tight, in fact, drainage was a main part of their purpose,” says William “Bill” Shook, president and founder of AP/M Permaform. “While many of these older cities are on our East Coast, other areas suffer more from MIC (sewer gas) corrosion and even new manholes suffer from inflow in and around the manhole cover and grade rings. It seems that no area is exempt.”
With EPA estimates at more than 20 million manholes in the United States, the bulk of which were installed prior to the 1960s, it’s no wonder these professionals see the room for growth in the industry. The problem, however, boils down to funding and a lack of education.
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“The need [for manhole rehabilitation] outstrips the financial resources committed by cities. The unfortunate paradox is that controlling I/I pays for itself in a very short time,” says Shook. “Unfortunately, many cities cannot make the much more cost-effective commitment to invest in the necessary repairs so these cities are doomed to overpaying for their deteriorating sewer systems.”
The first step in addressing the manholes involves a proper condition assessment. This area is lacking in the manhole rehabilitation sector Dupré says. Too often, he sees owners paying for expensive CCTV programs to look at the condition of pipes with only a cursory glance at manholes, pointing out its characteristics, such as water marks, gaping holes or corrosion, but never discussing why.
“If you have good data that pinpoints the root of the problem, you can set up a proper program,” he says. “Everything you need to support the suggested repair should be included in the report.”
In addition to the characteristics, the reports, Dupré says, should include GPS coordinates for all manholes, digital photos of the entire manhole structure and down the pipe in all directions, pH levels and any defects. Armed with that information, owners can then precisely tailor a rehab program to get the most out of limited funds.
“Pinpointing allows an owner to attack the problem areas and in some instances save money and tackle more manhole projects,” Dupré says. “For instance, cities can take pH levels of manholes to monitor corrosion on the concrete and metal products. A more corrosive area gets epoxy and a less corrosive area can get by with a cementitious application, which could easily double the amount of manholes rehabbed for the same budget dollars.”
Also helping address uniformity and quality reporting are organizations like NASSCO with its Manhole Committee and its Manhole Assessment Certification Program (MACP). NASSCO developed MACP — now in version 7.0.1 — to standardize the coding of manhole defects.
“NASSCO’s Manhole Committee plays an important role in the industry for several reasons. First, while NASSCO is a contractor organization our committee members are made up of municipal employees, manufacturers, suppliers, professional engineers and contractors. This allows for diversity in viewpoints,” says Bob O’Connor chair of the committee and president of Municipal & Contractor Sealing Products Inc.
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“Next this fairly new committee (4 years old), was formed because there was a perceived need that the marketplace needed a better understanding of the advantages and disadvantages of the wide array of available products and services for manhole rehabilitation.”
O’Connor, who has been in the industry for 20 years, has personally witnessed the shift in understanding of the importance of manhole rehabilitation and the improved offerings from manufacturers.
One of those shifts is on the assessment side. As inspections have improved, so too has the quality of work. A decade ago, O’Connor says that owners had no idea what to expect from the inspection and they would often rely on a manufacturer or the contractor doing the work for advice.
“There was a lot of trial and error that went on 20 years ago,” he says. “Now municipalities are more sophisticated. They ask if a method has been used before or if there is a demo available. They also ask for, and actually follow up with, references. It is a more mature way of looking at manhole rehabilitation.”
Shook, who is also active in the NASSCO Manhole Committee, adds that the industry is committed at all levels to raise the standards for engineering, manufacturing and application of manhole rehabilitation methods. Organizations like NASSCO, NASTT, WEF and ASCE are established resources for advancing the industry.
“Certainly production techniques and materials have improved greatly at precast concrete facilities. In addition, in areas where cities expect to have exposure to excessive amounts of corrosion, they are specifying additives, liners or coatings to better protect the manholes from deteriorating faster than their design life,” Siebenthaler says. “As for existing manholes, I think cities are doing the best that they can to identify problems and repair them. However, they are not able to find all of them, and some are not able to keep up. Overall, I would say the state of the manholes throughout North America is better than it was 10 years ago.”
Though the reasons may vary, one thing is certain and that is I/I at the manhole affects every system owner in North America. As funding shrinks, owners need to be more cognizant of where they will get the most bang for their buck. This includes harnessing new technologies, ditching a one-size-fits-all rehabilitation approach and education.
“Folks managing old failing systems inherit failing assets, debt and a lot of bad things from the previous managers who retired. They now have to face hard truths that their budgets don’t match their current capital improvement needs,” Dupré says. “If we don’t harness technology transfer, common sense designs with economics in mind, and better decision-making from upper level decision makers, we will continue to see our infrastructure decline and deteriorate exponentially faster than we can keep up with it, until it ultimately fails.”
Mike Kezdi is associate editor of Trenchless Technology.