American Transmission Company (ATC) needed to replace more than 100 K-frame structures with steel H-frame poles that supported a 345kV line. Much of the work was to take place on a 1.6-mile stretch of wetland, heavily protected by state DNR mandates and accessed only via private property. The wetland’s depth meant the utility could not use conventional timber mats which are normally employed in this situation. Given the deep and soggy soil conditions in the Bear Creek Marsh, crews would have had to stack the mats at least 10 deep to build a temporary road strong enough to support the heavy equipment. Even if the company had wanted to spend that much money on 20,000 mats, the weight of all those mats would have submerged the road — making work impossible and negatively impacting the marsh’s endangered wildlife.
Earthsafe & emtek™ devised another solution — an engineered floating mat system design called an “air bridge” that would support up to 190,000 pounds. Using cranes and loaders, crews set out mats singly, so no piece of construction equipment was ever on the wetland. The support mats were placed perpendicular to the main road decking, allowing the weight of the machinery to be dispersed across a large area. The road deck mats rest on those foundation mats, allowing the road deck to actually float on the wetland’s vegetative layer, providing virtually no adverse impact to the wetland ecosystem. What’s more, the RFID/GPS chips embedded in each mat allowed ATC to confidently inform regulatory officials that no materials had been left behind.
Build time: Three weeks
Access road length: 1 mile
Tractor trailer loads: 197 tractor trailer loads of material
Mats used: 3,000
Total road weight: 9.5 million pounds
Bridge downpressure: 3.5 psi