Placing layer upon layer
Following toe construction, the contractor placed an 8-in. revetment layer consisting of No. 2 stone with an average size of 2 to 3 in. Placement of geotextile fabric on this layer turned out to be one of the most difficult tasks on the project.
"We have some tricks," says Matheu. "We had the cloth pre-sewn by one of our subcontractors into panels that were 130-ft. long by 36-ft. wide. We found where the toe was for the structure and we put in 2-in. metal posts, then we would drag the filter cloth out."
The cloth was stretched out on shore, then two workers were sent into the water in wetsuits, even in the winter cold. "The guys in the water got out to where they could hold onto the poles and we had some other guys on the shore who stretched out the cloth," Matheu explains. "We used 3-in. rings and we zip-tied the rings to the filter cloth, then dropped the rings over the fence posts. Then, on land, we would pull that side tight."
Even with the fabric carefully deployed, more finesse was still required for the next 8-in. layer of 4- to 8-in. average-size gabion stone. "Instead of dumping the stone on it, you have to sink the cloth," Matheu notes. "That was labor intensive. Two guys would stand on the cloth and sink it. I would pass a bucket of rocks out there and they would hand throw small rocks until we got the cloth down. That's the trick to getting it down. If you just dump stuff on it, it tugs and pulls and it doesn't go where you want it. Doing it slowly gets it the most even and spread out."
After placing the third layer and checking the grade with the HiPer Lite+, Shoreline Design placed a 2-ft. layer of 400- to 1,200-lb. secondary armor stone. The final "primary armor" layer consisted
of stone weighing 800 to 2,500 lbs.
The GNSS really proved its worth near the end of the project, Matheu reports. "For the last 400 ft. of the project, the elevation of the toe changed. It actually came up 1 ft., which changes the width of the slope because you're 1 ft. lower in height," he says. The company that built the 3-D model for the project, Take Off Pros, Peoria, AZ, incorporated this elevation change into the model.
According to Matheu, grade checking the work without the GNSS would have required the use of stakes and a laser. "I would have had to have somebody in the water with a grade rod," he says. "At least one person who is a surveyor would have had to be out there.
"We would have used a laser level, but just due to limitations of my work force, I would probably have hired a surveyor to come out there," he continues. "The problem with this work is that you don't put in a layer and then call somebody and have someone show up. We probably would have put somebody on the payroll who was more skilled in surveying than any of us."
Ultimately, the use of the HiPer Lite+ GNSS saved time and cost, and made Shoreline Design significantly more productive compared with conventional surveying methods. As a result, the contractor was able to successfully complete the project ahead of the 180-day schedule.