Access Matting for Structure Replacement  – New Hampshire

April–June 2020

Riggs Distler’s environmental construction and matting teams provided civil services to improve access to an aging 115kV transmission line in New England in support of a project to replace 9 wooden structures with new hardened-steel poles. The project area paralleled Route 9 in the Town of Antrim, and the terrain presented significant challenges, including steep and side-sloping topography, wetlands, a boulder-riddled landscape with water bleeding out of the hillside, and archaeological sensitivity areas. Careful planning and coordination with the client and subcontractors was critical to working together and delivering the project safely and on schedule. Our work involved:

  • Building access roads and workpads
  • Installing erosion and sedimentation controls

Challenges Overcome

The transmission line traverses a difficult and rugged landscape full of boulders, steep hillsides, and wetlands. The area’s topography and ground surface conditions required our environmental matting team to lay mats up to eight layers high in places to create surfaces level enough for rubber-tired equipment to access the structures to be replaced.

Riggs Distler installed 3,700 tons of stone and processed gravel to create accesses and ensure stable worksites at three of the structures. One access point (for the replacement of the remaining six structures) required a nearly 1.5-mile-long continuous stretch of timber matting. Due to the nature of the terrain, the most cost-effective and timely way to build access roads was to install timber mats in both wetlands and uplands. Uplands had to be roughed in with an excavator, moving boulders and benching in a road prior to the installation of timber mats. This particular area required the installation of approximately 4,100 timber mats for access and workpads. Mats were transported with forwarder through the right-of-way from the stockpile to the excavator for installation; at the most remote worksite, it took 1.5 hours per round-trip to move the mats.

The project also required careful adherence to an outage schedule in order to complete the necessary work while ensuring minimal service disruption to the client’s customers. Riggs Distler coordinated closely with the client, line contractor, and drilling contractor in order to enhance workflow efficiency.

Results Delivered

Thanks to the joint efforts of Riggs Distler, the primary contractor, and the service provider, the project was completed on schedule. Careful planning, constant communication, and efficient execution allowed our crews to prepare each access and workpad ahead of the construction schedule, ensuring a safe work environment for the client and their contractors.