Water

The Underground Scene

Trenchless pipe rehab and repair

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Credit: iStock/RomoloTavani
The Visitors From Beyond the Graves
One would think a storm drain tunnel would be a lonely place to work, especially where it twists and turns beneath a legendary old cemetery, but a strange thing happened during a pipe rehab project. David O’Sullivan, president of PW Trenchless Construction, says his technicians were dumbfounded as they watched mysterious figures furtively approaching out of the darkness of the clay brick storm sewers. As they worked on a project to rehab storm drains underneath the Ross Bay Cemetery in Victoria, British Columbia (BC), Canada, they suddenly found themselves somewhat in the grip of terror. The rehab crew, not expecting to encounter a gaggle of zombies coming down the deteriorated pipe, decided to play it safe and scramble away in the opposite direction.

O’Sullivan offers a rational explanation for the incident. Reasoning that not everyone you meet by chance in a storm drain has the same thing in mind, he says there are quite a few devotees of the occult in the region. For reasons that might evade those beyond their immediate circle of associates, enthusiasts of the supernatural have been rumored to secretly enter and travel through the ancient tunnels beneath the graves at Ross Bay Cemetery. As they were not expecting to encounter a living soul under the gravestones, he says, the would-be spiritualists were pretty scared too when they came upon goggled and geared-up installation technicians peering back at them through the tunnel. Fortunately, everyone seems to have escaped unscathed. But hobbyists steeped in mysticism are not the only visitors to the Ross Bay graveyard; in fact, O’Sullivan says the site has become an important attraction in Victoria for more conventional tourists as well and is considered an asset to the community.

The cemetery is located a coastal strip of land once owned by Isabella Mainville Ross, who was of part Native American and part French ancestry and was the first woman to be registered as a landowner in the territory. The graves here date back to as early as 1873. Memorializing numerous historical figures ranging from frontiersmen to premiers to war heroes, the cemetery gradually expanded to encompass a 27-acre landscape crisscrossed by creeks and waterways.

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Climate Change in the Graveyard
Over time, to make space for new gravesites, these creeks were walled in and encased in clay brick, allowing the former creeks to serve as storm drainage channels. However, the brick-lined tubes had their shortcomings in keeping up with changing times, including sea level rise. As O’Sullivan explains, although the tunnels were hand-crafted back in the 1870s and 1880s, by 2005 the lower end “was just about even with water coming in at high tides.” In addition, a number of trees that had been planted along a waterfront road over the pipe had grown so large that their weight threatened to crush the tunnel. “The brick sewer line was never designed to support a tree growing on top of it,” he notes. He says cemetery management “looked at the overall sewer grade and said, “Oh, my goodness, we’ve got to do something with it, particularly down at the lower end.”

The trees were not the only issue. “Because the sewer line had been installed into an old creek bed, it wasn’t straight; it had 14 bends on it, of anywhere from 5 degrees to 45 degrees. It had four vertical drops anywhere from 600 millimeters to 900 millimeters. That tended to preclude the use of in situ cured-in-place liner, because they’re not exactly able to pull the liner through horizontal bends, and they’re certainly not able to pull it through vertical drops. So that left the city looking for some other solution to rehabilitate the pipeline.”

Obviously, excavation of the cemetery was out of the picture. The other option would have been to reroute piping to bypass graveyard entirely. However, O’Sullivan says, “There were established waterfront houses all around it, so that eliminated that option as well. That left them looking at some kind of trenchless rehabilitation methodology.”

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Photos: AP/M Permaform
The Mount Hood culvert after repair

Custom Standards
With input from O’Sullivan, the engineering firm AECOM specified Channeline as the most workable option. He explains the choice. At the time the original channels were constructed by hand, there was no need to build them to any defined, standard shape. What that means today, he says, is that “because the cross-section of the pipeline was a very flat V on the bottom and then a pipe arch on the roof, it represents a fairly custom cross-section area.” A product that will successfully fit the variously shaped channels would have to be custom made, which, O’Sullivan says, is not an option most companies offer: “They have an off-the-shelf product, which they will customize for you.” But Channeline is different, he notes. “They custom-fabricate the pipeline sections to the exact specifications provided.”

He adds, “When we send an order and say we need X number of meters of pipe, they actually make up a wooden mold for us and start making pipes for us on that mold. They retain those molds, whereas most other companies will have standard circular shapes or certain egg shapes that they make and they’ll adapt for you. The advantage is Channeline custom-makes the pipe for you rather than forcing a standard product into your shape.”

The Mount Hood culvert before repair

Starting in the Middle
The original bid documents designated entry points at both ends of the sewer line, but that plan presented complications. There were very busy two-lane roads at each end of the pipeline, meaning that excavation “would have caused a lot of traffic management issues on both ends. Additionally, on the upper side, there was a large water main that we would have to relocate,” explains O’Sullivan. As an alternative, PW Trenchless proposed entering the pipeline in the middle with a single excavation on a driveway that intersected that part of the graveyard.

Describing the dig, he says, “The driveway is about 12 feet wide, and at that point, it’s about 3.5 meters down to the top of the pipe. There are gravestones within a meter of the edge of that driveway, and of course, you cannot disturb those.”

“We went in initially and surveyed to mandrel the pipeline to come up with a design of the sections we needed. Based on entering from the center, we were able to determine the maximum length of the segments we could get through the pipe to where they needed to be.” Getting the Channeline pipe segments around the bends would be the major logistical challenge once inside the tunnel, “because you’re going around the bends, and every time you go around a bend you’ve got the three pitch points. You’ve got the inside of the curve and then you’ve got the two outside points as you go around the curve with a straight section, so you have to keep them short to go around those bends.”

With orders shipping from Channeline’s manufacturing base in Dubai, says O’Sullivan, “We went in and installed our entry pit and installed a special detail that they wanted there for a manhole to secure and support the existing brick sewer line.” It was important to eliminate the risk of failure of the original tunnel, “because once a brick sewer line starts to fail it then goes like a zipper, so we couldn’t allow that.” The four vertical drops in the sewer line had to be dismantled inside the pipeline and then converted into ramps rather than vertical drops. “Then we were able to start installing the pipe segments. We started in the middle and installed up and then installed down,” explains O’Sullivan.

“We started laying pipe backward, doing each 40- to 60-meter segment and then bulkheading it and grouting each segment before we proceeded on to the next segment and the ramps.” The straight segments were installed using bell-and-spigot-type joints with rubber gaskets joining the sections. The ramp sections didn’t allow the clearance for a gasket and were instead pushed together without a rubber gasket, to be sealed later with a caulking compound suitable for the Channeline pipe. Then grout was pushed in in stages, adding up to a total of eight grouting applications.

“And then, of course, you’ve got a key piece in the middle that you’ve got to put in,” he says.

“The original pipe was about 1.3 meters high and 1.6 meters wide. The Channeline product that we brought in was about 1.1 meters tall and 1.3 meters wide, so you had an annulus around it of about 100 millimeters. Each pipe had to be dropped in; we made a special bogie that went inside the pipe, and we had jacks that raised the top rail of the bogie and lifted the pipe up by the crown. As the pipe was lifted, the floor of the pipe came up, and we were able to push it along on the wheels of the bogie. When we got to our final position and lowered down the top rail, the pipe dropped down a little bit, and the bogie became smaller than the height of the pipe and was able to be pulled back out. Then we could push the pipe in. So each segment had to be pushed along by hand the whole way.”

In its entirety, the rehabilitation of the 250 meters of storm drain under the graveyard required close to 600 individual segments of Channeline piping. “We used a lighter-weight grout than straight sand and mortar. It also included a foaming agent. Because it was a standalone liner, having the foaming agent in it allowed the grout to travel much farther because its viscosity is much lower, so it can fill the void completely.”

The Happiest Graveyard in Town
O’Sullivan says graveyard management and city officials “were very happy” with the project. “They were contemplating major disruptions, and there was very little disruption.” While his crew was on the site, which has evolved into more of a tourist attraction than an active cemetery, “We had a lot of people coming up to us and thanking us for what was going on.”

It’s hard to think of anyone who would be unhappy, except perhaps the would-be denizens of the underworld who might well mourn the transfiguration of their rustic catacomb-like former haunts. But the good news is that with their custom-fabricated resin walls and freshly reinforced structural integrity, the storm drain tunnels under Ross Bay Cemetery will continue to perform their earthly functions, and the historic graveyard will live on.

Light at the End of the Tunnel
When someone poured gasoline down a drainpipe and set it on fire, SeaTac emergency responders needed to find answers fast. SeaTac, WA, stormwater manager Jon Kulju was willing and equipped to assist them. “They couldn’t see the fire because it was below ground. They called us and asked us to come out and use our camera system give them an idea of what was going on underground,” he says. “It turns out the polyethylene pipe was burning uncontrollably, and the backfill around the pipe was falling in on it. It was interesting to hear the firefighters strategize when they could see, versus when they couldn’t see. Their approach was totally different when it came to, ‘Now we know what’s going on; let’s do it this way.’”

When not called upon to battle underground infernos, SeaTac’s RapidView camera has proved its worth in such everyday storm drain maintenance tasks as tracking down lost soccer balls to relieve clogged pipelines and keeping tabs on where trash might be accumulating in the system. It plays a key role in the city’s five-year program to repair and upgrade stormwater infrastructure, giving the department the ability to remotely survey the condition of storm drain pipe and evaluate the need for repair.

Stormwater is SeaTac’s only municipally operated utility. As Kulju explains, “Stormwater is one of those utilities where you’re not producing something to create a product; you’re moving rain from one place to another. That’s the reason cities take over the MS4 through the NPDES permit. Each jurisdiction is responsible for its own stormwater.”

He adds, “We manage stormwater infrastructure through inspection, through construction projects, through repairs and replacement. We are working all the time to do improvements to how stormwater is conveyed and infiltrated with low impact strategies to improve water quality.”

SeaTac uses ITpipes inspection management software, a GIS database and asset management programs, to keep tabs on its stormwater system. With asset numbers assigned to each section of pipe, tables to store observations, and the RapidView IBAK camera to provide imaging, says Kulju, managers are able to inspect the pipe and visualize comparisons side by side to guide their decision making.

In deciding on a camera system, Kulju wanted a technology that was robust, with a good service record, and one that could be repaired and maintained in-house. Based on conversations with other jurisdictions, “The issue came down to ‘How often is it in the shop? How often is it broken down?’” According to Kulju, the RapidView IBAK system consistently received the best reviews. Additionally, with the comprehensive instructions provided by the manufacturer in both manuals and on video, many repairs can be made in the field, reducing disruptions during operations.

Attached by a cable reel and controlled by two joysticks—one for the tractor and the other for the camera head—the RapidView camera has a radio transmitter that allows the operator to track its position underground. The system makes it possible to precisely locate obstructions and hazards such as utility crossings. “We paint a spot and say ‘Here’s where we’re crossing a utility.’ We find two or three of those every year,” he says. “We don’t want to send our root cutter down and find out we’ve just cut a gas line.”

Avoiding That Sinking Feeling
“The City of Hot Springs is so old that a lot of pipes we find throughout the town, we didn’t know existed, because people would build their houses right on top of them,” says Danny Carder, stormwater manager for the city of Hot Springs, AR. He notes that sometimes the exact location of a pipe is not revealed until a problem crops up. In a recent case, a homeowner began to notice sinkholes developing on his property and called the city to try and figure out what was happening. “We found a 24-inch storm drain going underneath his house.” In this case, says Carder, “We knew the pipe was there; we just didn’t know the condition of it.”

He says, “We went out and camera-inspected the pipe and found the problems. Each joint of the six-foot sections was separating, and whatever water was flowing through there was sucking in the soil from his yard into the pipe until it created the sinkholes.”

Carder notes that the Hot Springs Stormwater Department generally restricts its maintenance and repair activities to infrastructure within the public right of way. In this case, the degraded pipeline was on private property—in fact, passing under the house itself—and thus was outside the scope of the department’s maintenance and repair programs. In Hot Springs, drainage issues are considered to be the responsibility of the homeowner. However, he says, the city has a stormwater utility fee fund that can assist if the household is suffering financial hardship and is unable to afford the necessary repairs. “We can help them out sometimes, and that’s what we did on this house.”

Carder says that prior to this particular project, the department had never before performed repairs using a trenchless pipe rehab system. “Usually, we dig up the pipes and repair them, but this one was special because it went underneath his house and his driveway and we just couldn’t do it any other way.”

A Better Home and Garden
To facilitate the repair, the Stormwater Department purchased 120 feet of A2 Liner Pipe in 10-foot sections from Contech. “The good thing about this pipe is it doesn’t have bells on it so it inserts smooth. It’s the actual width of the pipe. This one is flush, so you don’t have any part of the pipe taller than the other,” making for a streamlined approach within the confines of an existing pipe.

The contractor opened up an area about 4 feet wide and about 12 feet long to expose the concrete pipe at some distance from the house. “Once they exposed that concrete pipe, they got down there and cut it with a concrete saw and removed the top half to open a channel for the plastic pipe to slip into,” explains Carder. “We inserted that plastic pipe and pushed it 120 feet underneath his house, and we came out at the manhole on the other side of the property.

“The pipe was pretty light. We could almost shove it through, but once you got up to about three or four sections of it, you had to use the backhoe to push it along, but it slid pretty easily with that. We used grout flowable fill on both ends. Then we sealed it up.”

He adds, “It worked great; it was easy to maneuver and it was a quick process. It was done in a day and a half. The homeowner was happy his sinkhole went away, and he was able to get his yard back in shape.”

A River Runs Through It in Both Directions
Jim Atchison, president of SunCoast Environmental NW Inc., says his company has the capacity to provide a variety of solutions for pipe rehabilitation. “We do coatings—epoxy, cementitious, and cured-in-place linings for manholes—and we sell pipe. And we do culvert lining using AP/M Permaform products,” he says.

“A lot depends on the city. We’ll have cities that will require using a cured-in-place liner and some require using a cementitious liner; some require an epoxy sprayed-on liner. We also have some that request a cementitious liner underlayment with epoxy sprayed over that. We try to educate the city on what products should go in, and they talk to the engineers and get their advice and go from there.”

He says the Oregon Department of Transportation had been monitoring the ongoing the deterioration of a culvert flowing along a roadside on the slopes below Mount Hood. The culvert was 6 feet in diameter by 500 feet long and paralleled the highway between Hood River and Mount Hood. It was adjacent to a creek that bisected the road in multiple locations as it snaked its way down the slope, with the creek making a horseshoe and coming back 500 feet below to cross the road again. The culvert’s job, explains Atchison, was to capture any overflow of the creek generated by heavy rains. “If you had a lot of water coming in, you’d have a flood and wash out that bend, so they put that culvert in there so any overflow would have a way out. It was a safety factor because it would probably wash out the road as well if you had a serious flood.”

Atchison describes the pipe as galvanized metal originally selected to retard rust; nevertheless, he estimates it had been deteriorating for 20 years or more under the influence of sediment-laden stormwater. “When you have rocks and sand, it peels off that galvanized coating until you get down to bare metal. It’s kind of like sand-blasting material. Over time it has so much sand and rock hitting it that it just starts to rust and then give way completely.”

Walking the tunnel to inspect the damage, Atchison noted “huge gaping holes. In the channel, a lot of it was rotted out.” Behind the corrugated pipeline, he says, “there had been a lot of infiltration” and that moisture was carrying away the soil surrounding the pipe, a problem that couldn’t be seen from the outside. “If it had collapsed, and if you had raging water coming down, you would have had that whole area flooded out.”

He says, “The Department of Transportation had identified the site years before and believed it would eventually be an issue. They just decided they wanted it repaired. It’s cheaper to fix something that is not completely broken than it is to fix it when something fails.”

Caution: Wet Cement
“One thing when you’re spraying cement—the area has to be dry because water will want to wash it off,” cautions Atchison. And there was water coming in from all angles. “One of the problems that we ran into was the infiltration coming from the stream up above and the mountain on the side of us.”

To resolve that issue, technicians injected a chemical grout mixed in a foam. “Once it hits, it reacts with water and it will expand and stop the leaking.”

The next major challenge was logistical. Six hundred feet is a long stretch to rehab, especially in a 6-foot-diameter pipeline. “The concern is whether your hoses and your pumping equipment can go so far. You can shoot from one end then go to the other and shoot from that side. But it’s a lot of extra work to go from one end to the other.” To resolve the dilemma, says Atchison, “about halfway in there was a storm drain that opened up to the pipeline. So we had our equipment on top of that, and we ran our hoses down below. We went to one side and then went to the other side, so we didn’t have to move our equipment. It worked out pretty well for us.”

Atchison says the lifespan of cementitious lining can run about 50 years, but even with that relative durability, he notes, it has other advantages. “With the cement, if there’s a problem you can go in there and fix just that one little area. For example, if the channel was wearing out you could go in and just fix the channel; you wouldn’t have to do a complete rehab on the whole pipe.” Additionally, by smoothing out the corrugation on the interior of the pipe, a cementitious liner reduces turbulence and wear on the walls and allows the water to flow more easily.

Credit: iStock/Creative-Touch

When the Cement Hits the Fan
“We mix our cement and put it through the pump. We have hoses that go down to the spincaster. Then we have our compressor that we use to spin-cast the cement. We have a setup right in the middle like a sled, and we have a spincaster that, when the cement hits it, it’s like a fan powered by the air compressor. It sprays it on the wall.” With the spincaster slowly pulled by a winch proceeding down the center of the tunnel, he explains, “as you coat the interior you’re getting an even coat through the whole process.”

To fine-tune the process, he says, “We have somebody on the sled watching, and he can say, ‘You’re going a little too fast, or too slow, or that’s just right—keep it there.’

“When it’s finished you take measurements,” he adds. “You want to be over the corrugation of the metal by an inch to two inches, depending on what the spec is. When we’re spraying, we’re measuring from the top ridge, not from the bottom ridge. If the spec is one inch over corrugation, then we’ll spray it and measure it from the highest point.”

Atchison likes that the cementitious liner sets up fast in case any repair work needs to be done before the crew leaves the job site. “You could go in hours later and walk on the channel, do some measurements, and then come out. If you need another coat, you let that set up and then you can do it the next day.”

He notes, “Putting on the cement is pretty uniform.” What is not uniform is how damp the environment in the culvert might be before the installation of the liner. “When looking at the job, you have to determine what kind of bypass you need and what kind of infiltration you will be dealing with. Those are the two things, as the contractor, that you have to seriously look at because that’s the stuff that will cost you money and time.”

Pointing out that this was his first job using AP/M Permaform, Atchison says, “This is the product we will use. Oregon has put the name of our product in their spec. It’s the only product that we would use for culverts.”

Ahead of the Curve
Derek Zahler, executive officer and owner of Colorado Pipeline Rehabilitation, says that Castle Rock, CO, an upscale suburb of Denver, had been exploring options to stay ahead of the curve on utility rehabilitation and replacement.

The city had a deteriorating 24-inch corrugated metal storm pipe it was considering for rehab. The pipe cut across Frontage Road, a major service road. Zahler says the city could ill afford to shut down a main thoroughfare right next to Interstate 25. “Therefore trenching and replacing would mean a lot of headaches beyond the cost factor.”

Proposing to rehab the 60-foot stretch of pipe under using a spin-cast epoxy coating, Zahler pointed out that it would be “a pretty significant semi-structural solution.” He says, “Spin-casting has a lot of benefits. If we put this in, one, it will stop the degradation of the pipe, and two, it will enhance the structure of it.”

Although he notes polyurethane lining processes have been around 25 or 30 years, epoxies have been around since the 1950s. That struck a chord with the city; officials liked the long track record of epoxies in pipe rehab applications. “We introduced the Raven 405 product” from Raven Lining Systems, he says. “Compared with concrete and other things, they were blown away and said, ‘Let’s see it go in.’”

Although epoxies have been around a long time, Zahler nevertheless admits, “They are not the easiest thing to work with. They have a slower cure time and they off-gas, but the process is what makes it easy. Our process is automated. We basically pull a hose through the pipe, and at the end of the hose, there’s a rotating spin head, which is where the two-part resins mix. The machine reeling that hose is calibrated, and it sprays the inside of the pipe. We’re more of a mechanical applicator; we set up the machine, hit go, and the machine mixes and applies the resin.”

He adds, “What we’re dealing with is all in the setup and the testing. Does the resin have the right viscosity? What is the cure time or gel time, and then what kind of outcome are we looking for? That allows us to decide which resin is most appropriate for the pipe.”

A Light Footprint
According to Zahler, the spin-casting process his firm employs “probably has the lowest footprint of any rehab process. We have three vehicles, the largest one being our spin-casting rig—a little bit smaller than a garbage truck—and then we have two support vehicles. It is also very quiet. Our customers like that. We could be lining and rehabbing a pipe and no one’s the wiser.” It’s also faster, he says. “No one can line a pipe as fast as we can, given certain preparations. It only takes us a couple of hours. And versus cement and mortar linings, the resin is a lot stronger, so you get a better product that lasts longer and doesn’t fail.”

Zahler says he looks forward to using Raven 405 again on future projects in Colorado. He believes epoxies are “tried and true for storm and sewer,” and although he concedes “epoxies take a little more surface prep than others,” he says, “the cost of materials for epoxy are very reasonable. Raven as a domestic producer is also very close, so that makes it easy. We’ll definitely use it.” SW_bug_web

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