Maine contractor gets impressive, all-weather GNSS performance in bridge replacement project.
Home to just over 500 Maine residents, the town of Beals is located on a small (5 square mile) island across from moderately-larger Jonesport. To access either town by car from the mainland, residents and visitors alike must cross the Jonesport-Beals Bridge, a half-mile span built in 1958. After more than six decades of service and constant exposure to the salt air of the Atlantic, the structure’s pier piles were recently identified as being deteriorating, prompting the bridge to be classified as “structurally deficient” and slated for replacement. Heading up construction of the new $22 million span, CPM Constructors had for years relied heavily upon their existing robotic total station and GNSS technology. Facing this project in an area traditionally hindered by foggy coastal weather, however, it chose to replace those older instruments with newer state-of-the-art technology. Doing so, has not only eliminated long periods spent waiting to gain a satellite fix, it has improved overall performance of the company’s survey-based operation.
Excellent Bridge Work
CPM Constructors is a general contractor which performs everything from marine construction to power station work to roadbuilding and more. However, the Freeport, Maine-based company has established itself as one of the state’s go-to sources for excellence in bridge construction, according to Ken Sienko, CPM’s survey manager.
“We probably have anywhere from seven to ten bridges going on at any given time,” he said. “That can include structures designed to carry vehicles, railroads, pedestrians, you name it. So we were definitely in our element when we got to Jonesport. Here, we are replacing an existing structure that has succumbed to the elements, with an updated design which will serve area residents and visitors for the next 60-70 years or so. When we secured the bid for the Jonesport project, we felt the time was right to upgrade our survey equipment and spoke to Stuart MacDonald at Maine Technical Source (MTS), the area Sokkia dealer. Because our two companies have worked together for quite a while, we trusted their expertise in these matters.”
The upshot to that discussion with MacDonald at MTS’s Yarmouth, Me., location was the purchase of a GCX3 GNSS receiver and an iX503 robotic total station—both from Sokkia. Sienko said that, while they set out to simply bring their capabilities more current, they quickly discovered the benefits went far beyond that.
Making a Connection
Work on the Jonesport-Beals Bridge began in September, 2017. In addition to the structural construction itself, CPM was also responsible for all the earthwork at the approaches, the abutments and all adjacent roadwork. Structural work started with driving of piles which, according to Taylor Light-Surek, CPM’s field engineer, immediately drew upon the strengths of their new GNSS solution.
“We used GPS heavily to help with setting the piles,” he said. “Working alongside Case Foundation, we first located the centerline of bearing for two H-piles welded to the deck of a barge and pushed the barge into location to set a temporary frame to drive the pile,” he said. “We then set a larger driving frame to hold the caissons onto the header of that initial driving frame. Then, while standing on the deck of the barge, I shot center line of bearing and center line of construction and used those points to guide the upper driving frame into place where it was welded and braced off.”
Simple as the procedure described above might seem, things were complicated by the weather which threatened to wreak havoc with their schedule.
“The weather here is very erratic—there was one month in which we had 20 separate days of dense fog with visibilities less than 1/8 mile,” he said. “Because most of the shots I’ve been taking out here are between 700 and 1500 feet, we obviously couldn’t use a robot in those conditions, so we turned to the GNSS solution and were pretty amazed at what it did for us. To be able to functionally use a base and rover in those conditions and have tight accuracies is pretty amazing, but that’s exactly what we got. In fact, I shot a number of points with the base and rover and then checked them the next day using the robot and it was within hundredths. That really convinced us that we hit on something good with the Sokkia gear.”
Though they have not had occasion to use it to date, CPM’s new system also offers Sokkia Fusion technology, which provides an ability to bring a true hybrid solution to the jobsite. Doing so has been shown to dramatically speed up field work; get rapid prism acquisition, even in dense areas; and easily jump between optical and GNSS measurements.
Lighten the Load
While Sienko might focus on the accuracies they are now able to achieve—and maybe even how well the newly-added solutions fit into their budget—Light-Surek recognized another benefit neither of them foresaw: the comfort factor.
“Our older equipment is so much heavier,” he said. “You don’t think it’s much of a big deal until you are out here for ten hours a day walking around with a rover. Walking back and forth doing centerlines, carrying a 10 to 15 lb. rod definitely wears on a person. By comparison, I can literally put everything I need now in a backpack. For the size and convenience factor alone it’s amazing. This system takes me about 10 minutes from the time I get a call that someone needs a shot to the time I’m there and working. In the past, that could have easily been twice as long, so there’s a time savings at work here with the new solution as well.”
It’s important to note that prior to the Jonesport project, Light-Surek’s familiarity with GNSS solutions was extremely limited. Though he’d worked a bit with Sienko using GPS on previous projects, the new bridge was, in a sense, a baptism by fire for him.
“It was a little difficult at first, but mostly because Ken also does GPS for all our other projects and couldn’t be out here that often,” he said. “However, the process came quickly to me and once I got the hang of it, I’ve pretty much done it all since then. In fact, if I was put in a situation where I had to hand someone else one of the Sokkia controllers, it would be much easier for that person to functionally use this instrument than anything else. If I was sick and someone had to stake something out, I could literally talk them through it—it’s very streamlined and intuitive.”
Sienko also had a particularly unique opportunity to benefit from the compact nature of the new GNSS solution when working to streamline placement of the structure’s pier caps.
“We are having a Virginia-based company called Coastal Precast Systems in Virginia do all the precast caps,” he said. “I recently flew down to their plant and, using long range Bluetooth, set up the base in their yard and recorded all the as-builts for the caps right there. By doing so, when we went to place them here in Jonesport, all the rebar coming up out of the columns lined up perfectly with the holes. It worked out really well, but was made even better by the fact that I didn’t have to lug several cases of bulky equipment to get those results. That small system packs a lot of power.”
Getting Their Fix
Though reduced to one lane with traffic signal metering (the second lane is being used for construction of the abutments, concrete pours, trucking of materials, etc.), the existing Jonesport-Beals Bridge is remaining operational while the new structure takes shape. The presence of the bridge, compounded by the on-again off-again weather issues, has allowed CPM to fully appreciate the strengths their new GNSS and robotic solutions bring to the job site.
“We used both our previous system and the new one out here at different times and there really is no comparison in terms of signal acquisition,” said Sienko. “Our older GPS receiver really struggles to keep a connection, particularly when we are close to the existing bridge—unfortunately, that’s where most of our work takes place. As a result, when using the older solution, we would have to stay a good 30 feet off from the bridge.”
Contrast that, he said, with the ability of the GCX3 to get a fix on the satellites while almost directly under the structure, and the differences become stark.”
“We were working at times between several barges and the bridge,” he said. “Even though I could probably only see 20-30% of the sky, we were still able to get—and hold—a fix on between 10 and 14 satellites. That was enough for me to keep my residuals within a half-inch and impressed the heck out of me.”
The Big Attraction
The Jonesport location, while picturesque, is in a fairly remote area—a good 3 ½ hours from Portland and roughly the same distance to CPM’s corporate offices in Freeport. To expedite the transfer of files, implement updates, and so on, Sienko’s crew is using Topcon MAGNET (Field and Enterprise) in conjunction with their Sokkia SHC500 and SHC5000 controllers. According to Light-Surek, the software solution has fit into their operation nicely.
“I started out using different software here and as far as functionality and ease of use and being able to switch tasks on the fly, MAGNET is far ahead of what that software had to offer,” he said. “There are a number of functions that have impressed me, but I really like the opportunity to create layers. I’ve probably taken at least a thousand shots on this site and having that many points in a relatively small area can make things look extremely crowded. So it’s really nice to be able to go into the new software, layer all those points, then turn individual layers on and off, letting us see only what we need to see.”
Sienko added that the MAGNET Enterprise function has also proven key for the transfer of information. “If our office was a 15 minute drive up the road it’d be no big deal—but it’s not,” he said. “So that function is invaluable for us; if Taylor needs a point, I can calculate it in the office, shoot it to him and it’s done. In the same way, at the end of the day, he simply uploads his data and I can review it in real-time in Freeport—it doesn’t get any easier than that.”
It’s About Time
By now it should be obvious that the key savings CPM is realizing—even when considering a unit’s superior ability to acquire a signal or pierce fog and allow work to proceed—are in time. Both Sienko and Light-Surek will attest that time spent waiting for technology to work is time wasted.
“The most obvious savings is in data acquisition,” said Sienko. “When we had work near the bridge with the old system, there were times when Taylor was spending very long periods waiting to get a fix. In fact, when I first brought the new GNSS receiver to him to do a side-by-side comparison, he told me he’d have a fix with that older unit in 20 minutes—I already had one. So for us, the time savings is really in how fast it can grab a signal—and that’s been substantial.”
Light-Surek concurs, adding that the advantages can be even more basic than that. “Our older system had a tendency to freeze up in cold weather and, being Maine, there’s no shortage of that,” he said. “Waiting for a unit to respond is a huge waste of time. But this past winter, we ran both the new receiver and the new robot in subzero temperatures without seeing any adverse effects on performance. That was great to see. In addition, I often have to do centerlines provided by the office, which can consist of roughly 25 to 30 points. With the Sokkia, I have a fix for each point in about three seconds. In the past, I’d have to wait a minute and a half for each point. While that might not seem like much, when you add it up, you’ve suddenly lost three quarters of an hour just waiting.”
Smoothing Out the Bumps
For CPM, the process of moving into the newer solutions was not without its speed bumps. However, according to Sienko, it was those challenges that helped them realize they’d made the right choice in both an equipment manufacturer and dealer.
“We decided early on that we wanted to boost satellite coverage by adding the Galileo Constellation package,” he said. “But we quickly realized that we had an issue getting the unit to see those satellites. So Pat Moran, the Sokkia regional manager, came out here and worked with us until things were resolved and we were getting the coverage we wanted. We are currently averaging about 22 satellites at all times. The new solutions have been key in helping us keep pace on this job and it’s great to have that level of support from both the manufacturer and the dealer to back it all up.”