Steve Lindsey of Jacobs Engineering Group has been working because the mid-1980s with the Metropolis of Memphis, Tennessee, to reconstruct deteriorated pipe, limit I/I and prolong the life of its sewer techniques. This typically consists of infrastructure rehabilitation, amongst different actions.
Operations lately hit a sour word when its Five Areas Venture ran into some notably difficult manholes on the Jack Carley Causeway line, which serves the President’s Island industrial space.
A 1,420-ft run with eight manholes — three brick-and-mortar, and five precast concrete — on a 15-in. VCP sewer primary of mid-20th century classic, required vital rehabilitation of buildings compromised by age and H2S fuel. One manhole required speedy consideration, for which Lindsey needed to oversee a completely new strategy to placing a coda on its remediation.
In a city with deep manholes, these weren’t the deepest, averaging 42 ft. However one particularly, a 50-ft brick construction, was rated as being in catastrophic failure status. Its mortar was largely non-existent, and its backside bench construction was badly deteriorated. However this one wasn’t just worn away, it was utterly missing, together with sufficient concrete to create a basketball-sized hole, from the invert up about four ft.
The cured-in-place pipe (CIPP) lining firm, Granite Inliner, which was rehabilitating the pipeline and manholes, felt the deteriorated manhole was a security concern, and stated their technicians wouldn’t re-enter the manhole till it was rehabilitated.
Right Place, Proper Time
Lindsey instantly contacted Troy Reed of CTR Coatings, a subcontractor on the challenge, since he was already accustomed to the undertaking, was on website, and had an established working relationship with Lindsey. Lindsey referred to as a meeting with Reed and Metropolis Environmental Administrator Scott Morgan, who informed Reed, “I want you to return take a look at this manhole, take videos and tell me what must be accomplished, so I can get it online.”
Granite’s technicians had been unable to move their jetter by means of the line on the backside of this 48-in. diameter manhole, inflicting them to find the missing bench. Except for the security challenge, they didn’t understand how they might get the water out of the manhole lengthy sufficient to put in their CIPP lining.
In the course of the assembly, it was decided that Reed would venture into the manhole to evaluate the precise severity of the difficulty, and return with suggestions for shifting ahead.
“Troy truly made an entry into the manhole and introduced back pictures and descriptions proving that we definitely did have a problem,” remembers Lindsey. “We decided to discover the potential of reconstructing the bench with a totally structural repair technique onto the bottom of the manhole. This is able to shore it up, restoring structural integrity so that CIPP crews might re-enter and lining might be completed.”
Unusually Troublesome Circumstances
Although it’s a uncommon undertaking that goes with no hitch, this manhole — the second-to-last on the run — proved uncommonly challenging. Apart from the severity of the structural deterioration and the depth of the manhole, it additionally was situated just 6 in. away from a loading dock at the Carolina Nationwide Transportation firm, an OTR trucking firm. Fortunately, it did afford simply sufficient room for CTR to set up its confined area entry gear.
The situation is firmly within the floodplain of the Mississippi River, solely about three,000 ft away. The soil there’s sandy and porous and — especially at 50 ft down — uncovered to hydraulic strain and a high groundwater table. Although the manhole was plugged and bypassed, it was persistently taking water from sustained excessive Mississippi River levels.
Demanding Software Necessities
This was an enormous drawback, as a result of the structural answer chosen, OBIC Armor 1000, uses a three-layer set up process that requires all lively leaks be stopped previous to software. It was chosen for both its structural enhancement and protecting properties, and its quick software and return-to-service. But to carry out properly, Reed says, “The No. 1 facet of doing any coating is prep, prep and prep. In case you don’t do this proper, there’s going to be a failure. I don’t care if it’s the perfect product out there. Seen it, completed it.”
On this manhole, CTR technicians used a three,500-psi strain washer to blast away debris and crumbling mortar. Then they put a person on a carry, safety harnessed on, and lowered him down inside. He pressure-washed it all by hand, then seemed for leaks. When he discovered them, he injected OBIC Hyper Seal grout to stop them. Then the tech came up and fed a 12-in. hose from a 200,000 BTU blower down inside, which took about 45 minutes to dry the manhole. This entire prep course of took all the first day of the installation. And that’s when the rain practice started.
“We had two or three events where there was some fairly arduous rain, which made it very troublesome,” recollects Lindsey. “There were groundwater inflows into the damaged manhole, a continuing drawback. The blokes spent a day or so chasing water around after which once we’d start, here would come another loopy rain, and we’d be right again the place we started. So, it took an extended time period. But Troy and his guys stored preventing the great battle.”
Lastly, the day after the newest drying, the rain held off and Reed was capable of go right down to the bottom of the manhole. He installed reinforcement that his foam-based structural materials might adhere to. Then he sprayed sufficient of the fabric used for the OBIC Armor system’s structural second layer to fill the void left by the lacking bench.
Afterward, a CTR tech, beginning at the prime of the manhole, was lowered slowly down whereas spraying the primary layer of the OBIC Armor 1000 System. This is the moisture barrier and goes on at 165 F, and absolutely sets in about 10 seconds.
Once the technician reached the bottom of the manhole, the spray gun was switched out for one that applies the second layer of the OBIC 1000 system, a closed-cell polyurethane foam. This is an uncommonly dense, structural material that goes on at about 135 F, and dries in about 20 seconds.
Apart from offering structural properties, the froth can also be injected to fill in bug holes, lacking mortar joints, giant cracks and another voids. It was applied on the best way up, as the tech was slowly lifted to the highest once more.
The third and ultimate layer is identical orange-hued polyurea as the primary, and acts as a corrosion barrier. Capable of stand up to up to a 30 % concentration of sulfuric acid, it passes the ASTM G210-13 Severe Wastewater Evaluation Check (SWAT). This layer is impermeable and non-reactive to most industrial compounds. It was applied in one other downward move by means of the manhole, after switching back to the first spray gun on the prime.
The whole dry time is about two minutes, in contrast to cement, whose remedy time could be as much as 28 days.
Finally, with the final layer completed, a Holiday spark check was carried out by a second tech. This can be a quality control verify, to ensure no spots have been missed or erratically coated.
All’s Nicely That Ends Properly
Lindsey is effusive concerning the outcomes. “Both the liner and the manhole turned out great. They appear wonderful on the post-remediation videos. It was a very troublesome undertaking, however that’s what we do. We’re recognized for not walking away typically, in all probability even once we should.” And he provides great credit to CTR as a associate within the effort.
“A number of people simply walk off, and say, ‘You’ll be able to’t do it.’ And that’s really one of the causes Troy and I have been capable of work collectively prior to now. There’s actually not an ‘I can’t do it’ thought course of in Troy’s mind.”
The opposite issue in the success of this undertaking, Lindsey believes, is within the new OBIC Armor 1000 answer. “It meets our bodily properties requirements, it meets our corrosion barrier requirements. And with this, I have amended many specs where I do enterprise or have that authority, to incorporate OBIC as an ‘or equal.’” He believes there’s a particular place for OBIC products in Memphis’s underground structure future.
“As a rule, in these older elements of city, Memphis has a excessive degree of hydrogen sulfide in its sewers, particularly as you get down towards the remedy plant. The hydrogen sulfide fee could be very high. It’s aggressive and just tears up the concrete, which is among the reasons clay was typically used in its inception, as a result of it’s impervious to that. But that doesn’t bode nicely for brick manholes and the mortar in between.”
Lindsey reflects on the success of this venture with the candor of somebody who’s been within the business long enough to know its realities. “I can plausibly make a case that pipeline rehab, when accomplished appropriately, is best than newly laid infrastructure, because the solution is usually monolithic. You don’t have joints, and it’s impervious to the issues that generally degrade sewers.”
He warns towards taking something as a right, nevertheless, when looking for trenchless remediation solutions. “Discover all of your prospects, and when you don’t know what they are, find somebody who does. They don’t train this in engineering faculty. There’s only one place to get this (information and experience), and that’s in the subject. Cruising the Web shouldn’t be a official various to real-world expertise. It’s in the area.”
That stated, he additionally cautions towards believing each claim that’s made about any answer till you see it for yourself. “This can be a specialized business that’s altering rapidly on a regular basis, and not all that glitters is gold.”
Writing good quality venture specs is a should, he says, but “one of the best spec is worthless in case you don’t have the information and can to make use of and enforce it and understand the place it got here from.”
The identical diligence is important when selecting contractors to work with, he believes. “I know what kind of individual it takes to deal with a tough challenge.” He leans lots on pals within the business to seek out good working partners, which is how he considers contractors. “Work together with your contractor, associate with him, group with him. Be firm, but be truthful. Foster an setting of cooperation as an alternative of an adversarial state of affairs, which I see so many occasions out in the subject.”
Finally, he says, for him selecting the best contractor associate and rehabilitation answer means being “someone who can walk between the raindrops and knows the distinction between the actual world, and the way it’s drawn up on paper. These are rare birds indeed, as a result of the only good undertaking is the one that’s never been built.”
Really, music to the ears of each engineer, within the Birthplace of Rock and Roll or anyplace else.
Mary Shafer, a technical writer and social media strategist for Artistic Raven.