The Underground Scene

Jan. 28, 2019

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.

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.”

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.

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.” 

About the Author

David C. Richardson

David C. Richardson is a frequent contributor to Forester Media publications.

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