Residents of New Orleans had a terrifying sense of déjà vu this past September when Tropical Storm Lee stalled offshore, dumping more than 14 inches of rain on many parts of the city. While concerns were high about a repeat of the catastrophic events surrounding Hurricane Katrina six years ago, the city averted disaster, largely because of changes that have been made to its protective infrastructure.
One major effort to do so carried the burdensome name “The Lake Pontchartrain and Vicinity Hurricane Protection Project, Chalmette Loop Levee, Hwy 46 to River,” mercifully shortened to LPV 148.02. The project addressed one of the main causes of flooding from Katrina--failure of the city’s levee system--by constructing an 8.2-mile-long concrete T-wall on top of an existing earthen levee. Spearheaded by Baton Rouge-based Cajun Industries, working with the U.S. Army Corps of Engineers (USACE), the project was something of a logistical nightmare, with difficult access, a massive workforce and, most importantly, a tight timeframe. Fortunately, the survey facet of the job set the stage for a successful outcome.
The full scope of USACE’s Hurricane and Storm Damage Risk Reduction System, Lake Pontchartrain and Vicinity, is massive, entailing work on more than 350 miles of the area’s levees, floodwalls, gates and pumps, bringing them up to standards that will withstand a 100-year event. LPV 148.02 is just one part of that overall effort, but, at its peak, involved more than 1,400 workers, as many as 100 heavy-duty cranes and scores of additional equipment.
Laying out the entire project and seeing it through to completion was tasked to Brian Hargraves, PLS, the project’s survey manager, and his crew. “This was an amazing project from so many different perspectives,” he says. “For one, while it may not have been the largest job we’ve ever done, it was one of the most demanding. To both enhance stability of the earthen levee and to give it an additional level of protective capability, the top of the existing levee was cut down to a height of 17 feet and, on the top of that we constructed 15-foot T-walls, bringing the overall height of the structure to a 32-foot elevation. We started construction of the T-wall in October of last year and had to be done by June 1--essentially eight months for an 8-mile wall. That’s pretty aggressive.”
To make a project of that scope more manageable, Hargraves says they divided the 8.2 mile job into five different management areas, then broke each of those down into four different work areas. That relegated one surveyor for every two work areas with two assistant surveyors helping out and watching over two work areas each.
He adds that breaking it down into sections also helped their ability to communicate between each other and head off potential problems, which is invaluable on a project of that size. “In all, we had 16 surveyors and as many as 40-plus rod men; often a total crew of about 60 tackling the surveying effort for this job,” he says. “Even given a team of that size, however, we couldn’t have done what we did without bringing an awful lot of technology to bear--and we definitely did that.”
Looking at the project in advance, Hargraves says they realized the challenges that lay ahead and understood that an alternative surveying approach would be needed to help deal with them. “In its most basic sense, we needed to keep crew size down, given the number of workers that we knew would be onsite,” he says. “Doing things in a traditional manner would mean one man behind the instrument, one rod man and a party chief supervising their work. If we instead went with a robotic total station, I knew we could immediately eliminate one man from that equation and make crew size a bit more manageable. We were also looking at the tight timeline; putting the right equipment to work could help us deal with that as well.”
With that game plan in mind, Hargraves approached Chet Johnson, salesman for the Metairie office of Haag and Trammel, the regional Topcon and Sokkia dealer. Working through them, Cajun USA leased a dozen Sokkia SRX-3 robotic total stations, a Sokkia RSX base station and another dozen mixed 2700 ISX and GRX1 GPS rovers, also from Sokkia. “Both because of the way the contract for this job was structured and the fact that we are working for the government, leasing just made the most sense for us,” he says. “And Haag & Trammel seemed fine with that. When we told them the volume of equipment we needed, however, it just about floored them. But they came though with what we needed and were extremely supportive of us throughout the project. As our point of contact, Chet was excellent--helping us through the startup period, even coming out to set up the base station for us. They were outstanding.”
Hargraves says that using GPS and the robots paid huge dividends. While they still had a sizeable crew onsite, he says they would have easily needed double that without the Sokkia gear. “Having the robot set up and running itself with a party chief right there manning the rod to verify things, was a huge time saver,” he says. “And the GPS played a huge role, allowing us to set out a good baseline, check in to the initial points we were given and so on.”
Though the people on his crew were great surveyors, Hargraves says that many were not familiar with the newer technology. So the fact that the interfaces were identical on both types of equipment--the robotic total station and the GPS--meant once a surveyor knew how to use one, he also knew how to run the other. “However, I made it a point to stress that even though they were relying on the technology, they had to be a conscientious surveyor and not let the equipment run them--that’s when mistakes happen. All in all, though, it all couldn’t have worked out better.”
While Hargraves and his team were continually providing surveying support to the project, construction was going on around them at a feverish pace. That activity only added to the overall difficulty of getting things done. “The jobsite was just incredible to see; we had just about every major 200-ton crane in the southeast working on this job,” Hargraves says. “We had crews installing more than 18,000 14-inch steel H-piles, many of which were 162 feet long. And we had crews pouring more than 150,000 cubic yards of concrete for the wall itself. To set initial grades and provide grading support throughout the project to both the piling and the concrete crews, we purchased about 40 Topcon RLH3C laser levels from Haag and Trammel and literally had them all over the site. We wanted everyone to have the ability to grade-check when needed, so those units helped keep things on track.”
Because the project involved work on a levee, it stands to reason that access would be a huge issue--but LPV 148.02 took that to new levels. Hargraves says at most times, there were more than 1,000 men and hundreds of pieces of equipment working on the structure--with only two ways into and out of the job: one on the west side and one on the east. Add a pump house located 1.5 miles in from the east side, making pass-through travel impossible, and the level of difficulty rises exponentially.
“It was a challenge, to say the least,” he says. “There was more than one time when I was in Management Area 2 and I was needed in Area 1. That meant I would have to drive 6.5 miles out to the west side of the job, drive a loop of about 15 miles to get around to the east side of the job, and then come in to Area 1. It was frustrating at times, but we dealt with it.”
With the project behind them, Hargraves says they are able to say with conviction that forgoing standard surveying techniques in favor of newer technology allowed them to take a difficult, challenging situation and not just deal with it, but learn and benefit from it.
“There were a number of things that we did to help keep things moving along,” he says. “For me, one of the key points was that we didn’t really have an instrument man position out there. Because of the approach we took with the robotic total stations, the surveyor was behind the rod at all times which allowed him to see that the layout he was doing was correct. Contrast that to him getting behind the gun, directing a rod man around, laying something out from 300 feet away, walking up, seeing there was a mistake, then having to go back and shoot it again. Here, they got it right the first time, every time. It’s really hard to quantify, but I think saying we cut surveying time by 25 percent would not be a stretch. People from the Corps of Engineers have referred to this project as the ‘8-Mile Miracle.’ I’d like to think our entire survey team played a nice role on making that miracle happen.”
Aided by a literal arsenal of Sokkia GPS and robotic total stations, as well as other optical equipment, Cajun prevailed in its effort, completing the job just ahead of schedule.
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