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Tight Timeline, Tolerances on Port Project

Date Posted : March 8, 2022

by Asphalt Pro Magazine staff in : News and Events
Source: Asphalt Pro Magazine

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The United States isn’t the only country experiencing supply chain issues. Our neighbor to the north is facing challenges of its own. “Shortages have been a topic of conversation across Canada,” said Denis Labelle, operations manager for All Roads Construction Ltd., Surrey, British Columbia. “A lot of goods at the port just aren’t moving because trucks aren’t available to offload it.”

If you want to get into Millimeter GPS or LPS, you need to have the proper team in place to do it

Labelle attributes a large amount of the backlog to the major flooding the Vancouver area experienced before Christmas. The 2021 Pacific Northwest Floods, particularly in southern British Columbia, resulted in severe disruption of the transportation corridor linking Canada's largest port, in Vancouver, to the rest of Canada.

"We had kilometers of highway under water and washed away, bridges collapsing as water undermined the piles," Labelle recalled. Stranded people were getting picked up by helicopters. There was a $30 limit on the purchase of gas. One of All Roads' recent projects in the city of Abbotsford saw nearly two weeks of work washed away.

Despite the hectic events, All Roads crews continued to do their part to shore up Canada's supply chain for the future.

All Roads is subcontracted by CXP, the design build team awarded this work, to perform all milling, grading, concrete work and asphalt paving on the Vancouver Fraser Port Authority's $400 million CAD project, which expands and improves its Centerm terminal.

Along with improving traffic flow in and around the port, the project first and foremost aims to increase capacity at the port to support Canada's growing trade demand for goods shipped in containers.

Construction began in 2019 and is expected to wrap by the end of 2022. "It's a very high profile project with a tight schedule," Labelle said.

In total, the project calls for 120,000 tons of asphalt to rehabilitate the terminal's existing pavement, expand the terminal by 15 percent, pave a new overpass on Centennial Road, and reconfigure Waterfront Road to create a continuous port road from Canada Place to Highway 1.

In 2021, All Roads was able to pave 30,000 tons; they hope to finish the remaining 90,000 tons by September of this year.

The project is tricky not only because of a particularly tight timeline, but also because the need for the port to keep as much space available as possible for shipping containers limits the amount of space in which All Roads' crews are able to work at any given time.

"Ports are busy with containers constantly coming in and out, so we only had certain small areas in which to work," Labelle said. "They won't give you another area until each area is complete, so they can move containers to that area."

The average area in which All Roads' crew is working is around 7,500 square meters (80,700 square feet). "That isn't a lot of space when you're putting in all kinds of concrete structures, milling 12 to 18 inches of existing asphalt at full depth, and paving," Labelle said.

Plus, they're working under very tight specifications, including a 5-millimeter (1/4-inch) tolerance for elevations and cross falls of less than 0.5 percent.

"The tolerances are very tight," Labelle said. "When you're stacking containers as high as they do, there's not a lot of room for grade without risking those containers falling over."

All Roads knew it would need top-notch technology to achieve that level of accuracy. That's why they decided to use their Millimeter GPS system from Topcon Positioning Systems, Livermore, California.

"The design is so tight that to do it without technology would be rolling the dice," Labelle said.

All Roads first invested in the Millimeter GPS two years ago when they had a 26,000-square-meter (280,000-square-foot) parking lot for CP Rail where Ford was parking vehicles after they came off the train.

"It had very tight grading with curved swales without a lot of fall," Labelle said. When he reached out to equipment dealer Brandt Tractor about renting a grader for the project, Brandt recommended using Millimeter GPS to achieve those tight tolerances.

"We demoed it and were floored with how well it worked and how much aggregate it saved us," Labelle said. "We were sold after that job."

However well Millimeter GPS had worked on previous projects, the tight areas in which All Roads was working proved problematic on the port project. "We had so many trucks and traffic in that small area that we were constantly breaking the connection between our Millimeter GPS and our paver," Labelle said. "That created some down time for us, because we were constantly having to reset it or move it."

For the first 15,000 tons of paving on the port project, All Roads made the Millimeter GPS system work. "We weren't aware of any technology that would help us," Labelle said. Then, they had another conversation with Brandt management, which recommended they use a Local Positioning System (LPS) robotic total station.

After trying out the system in the summer of 2021, All Roads purchased two stations for the port project.

A Closer Look at LPS

According to Topcon, the LPS setup uses a robotic total station to track an on-machine prism and uses radio communications to track the machine's real-time position. Millimeter GPS, on the other hand, uses land-based laser transmitters alongside global navigation satellite system (GNSS) technology.

The crux of the issue with the Millimeter GPS system on this project was that they couldn't raise the devices any higher while retaining accuracy.

"With the LPS system, you can elevate it as high as you'd like without sacrificing accuracy," Labelle said. If mounted at a greater height, he added, it's much less likely an object will break the connection between the station and the paver.

He had a tree stand-type platform fabricated to attach each LPS system 15 to 20 feet up the light poles around their working area at the port.

The LPS system also isn't affected by tall buildings or trees. "We've done projects with Millimeter GPS where we've hit a heavily wooded area and we lose signal so we have to put up a string line to finish the project," Labelle said. "The LPS system doesn't require that signal, so it makes it way more efficient."

"The only downside is you need an LPS system for every prism you have," Labelle said. For example, with two pavers on the port project, they needed three LPS systems.

Labelle also said the LPS system wouldn't be practical for big highway paving jobs because it only works 450 meters (1,476 feet) away from the robotic station. Furthermore, once you lose the lock on the prism you have to physically set it up again.

In that scenario, Labelle would still use Millimeter GPS, if needed. Although each Millimeter GPS transmitter has a range of around 200 meters, All Roads has five transmitters.

"We can set the others up ahead to make sure we have that consistency without having to stop," he said. "But for anything like a port or a parking lot or a municipal road that calls for high levels of accuracy, I would definitely go with LPS."

Another difference between Millimeter GPS and LPS is the setup. Labelle said the setup for the LPS system is less than half the time compared to Millimeter GPS because there's no need to add control points.

"That usually takes us a couple hours before starting a project," Labelle said. "With LPS, you set up on one control point on the site and then you're good to go."

However, he added, the setup process is similar enough to Millimeter GPS that it wasn't a big learning curve for All Roads' crew.

"If you want to get into Millimeter GPS or LPS, you need to have the proper team in place to do it," Labelle said. He recommends having someone who can design surface files, either a subcontractor or internally, as well as someone with surveying experience who can implement the design file into the equipment, ensure the technology is working as intended, and troubleshoot as needed. All Roads has had these resources in place ever since it began using SmoothRide two years ago.

SmoothRide scans the existing roadway, then creates a design based on the existing elevations, and tracks the paver's location within that area so it knows how thick to pave. However, Millimeter GPS and LPS are instead based on the design the client has provided, giving you a set elevation. "I take those elevations and input them into Millimeter GPS or LPS and those systems tell me where that elevation is," Labelle said.

"It all relies on the same Topcon software and equipment, which our guys are very familiar with, so they picked it up quite easily," Labelle said. However, he added, "If you buy the system and just throw it at the crew, they will fall on their face."

Return to Port

Labelle estimates that 30 percent of the asphalt on the port terminal is new construction; the remaining 70 percent is rehabilitation of existing paving. Throughout the duration of the project, All Roads will have milled 90,000 square meters (nearly 1 million square feet) of asphalt with its Wirtgen 210i milling machines.

After milling 12 to 18 inches, they work on the curbs and gutters. Then, they usually work on the access roads while other contractors perform the civil, electrical and crane installation. Although the length of time All Roads has in a given area depends on that particular area's scope of work, each area requires at least a few weeks, of which four to six days fall within All Roads' scope of work.

When it comes time to pave, All Roads hauls in asphalt from its plant in Vancouver, just 27 kilometers (17 miles) from the port.

According to All Roads President Rod Stephens, the port's mix designs called for both a 19 mm nominal Superpave mix for the lower asphalt courses as well as a 12.5 mm nominal surface course Superpave mix, both with design ESALs greater than 30 million.

"The Superpave system recommends a one grade high temperature bitumen binder bump for slow moving traffic and a two grade high temperature bump for standing traffic," Stephens said. Typically, he added, container terminal traffic is considered slow moving, whereas areas such as security booths and truck gates would be considered as having standing traffic. "The base climate bitumen binder grade typically used for the connecting city streets in the Vancouver area is a PG64-22."

All Roads needed multiple mix designs utilizing three different binders for this project, PG64-22, PG70-22 and PG76-22. Not only does this create storage management challenges, Stephens said, but tanker truck delivery became a challenge too.

"The PG70-22 and PG76-22 had to come from refineries in Edmonton, Alberta," Stephens said. "Winter weather logistics creates a huge risk in transporting the material between October and March."

To mitigate this risk, while remaining ready to pave in appropriate weather windows, All Roads suggested the use of aramid fiber reinforcement for certain portions of the pavement structure on the project as an equivalent for these polymer modified asphalt binders. After extensive testing was completed to demonstrate that a single dose of 65 grams per ton of aramid fiber reinforcement provides an equivalent asphalt mix to using PG70-22 and a double dose of 130 grams per ton is an equal alternative to using PG76-22 polymer modified binder, the design team accepted this solution.

To ensure the accuracy and transparency of the fiber use, All Roads purchased a fully automatic doser from Surface Tech called a Sentinel. The Sentinel has a hopper system which controls the dosing of the fibers and an Allen Bradley PLC (programmable logic controller) system that interfaces with the variable speeds of the asphalt plant.

"For transparency in our quality control documentation, when the shift is over a detailed printable report is produced showing the total fiber dosed with start and stop times," Stephens said.

Another challenge All Roads had to overcome on the project was meeting such design criteria in such limited space with only one access point in and out of the area.

"It makes grading and paving very difficult when you consider where the designed high points and low points end up in that specific area," Labelle said. "The port gave us an area to work in, and the design is not considered during this process, which challenges how you are able to build the specific area."

Ultimately, All Roads placed three lifts of asphalt—90 mm (3.5 inches), 75 mm (3 inches), then 50 mm (2 inches) for a total of 215 mm (8.5 inches)—as well as the 150-mm (6-inch) gravel subbase. All Roads must submit build elevations after every section they pave, including gravel, base lift, intermediate and top lift.

"Tight tolerances from the bottom up on this project ensures we'll have a smooth surface and meet those elevations," Labelle said. "And the accuracy gets tighter as you go up, from 10 mm on the gravel aggregate to 5 mm on top lift."

Thankfully, the LPS robotic total station has made meeting tolerances easier on every level.

"I'm super happy with how the process has gone so far," Labelle said. "In my opinion, this is one step away from automating our pavers."

All Roads is the first paving company in Canada, and among the first in North America, to use LPS robotic stations on an asphalt paving job, according to Labelle. The company's interest in using the latest technologies has long set them apart. They've previously pioneered the use of a notched wedge joint in British Columbia and were the first in Canada to use Topcon's SmoothRide technology, he added.

They've also garnered interest as a pioneer in Millimeter GPS.

"People from all over the U.S. and Canada are calling us to ask about it," Labelle said. They recently did a milling project for Lafarge at the Vancouver Airport. "Even though they have their own milling crews, they brought us in because of our use of Millimeter GPS. Then word got around that we were doing airports and we were brought in to mill an air strip in Moose Jaw, Saskatchewan."

Labelle believes the use of Millimeter GPS and LPS will become increasingly popular on asphalt jobs in the coming years.

"I can't predict the future, but I think Ministries of Transportation across Canada will probably start putting incentives out there to use this technology in the next few years," Labelle said. "In five to seven years, I think some will start specifying it on certain projects with tight tolerances. Once the ministries of transportation, especially in Ontario, hop on the bandwagon, the rest will fall into place and begin specifying it."

"All Roads has decided we want to lead that trend," Labelle said. "When it does come, we will be ahead of the curve."


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