The following article was a featured story in
ADSC’s Foundation Drilling Magazine July/August 2022 Issue.
The US power grid is under increasing pressure as it struggles to keep up with soaring electricity demands. Work is underway across the country to upgrade the aging infrastructure to increase reliability and alleviate overall pressure on the grid. Specialty contractor, Aldridge Electric, is a utility trade partner working to help solve this problem and provide reliable power across the country.
High in the Appalachian mountains, Aldridge crews worked to upgrade existing electrical infrastructure in southern West Virginia.
The Skin Fork Area Improvement project scope of work included drilled shafts, direct embeds, and grillage foundations for a 15-mile long transmission line rebuild that spanned across three different line segments and fed into a greenfield substation. The foundation types used for this project were determined by not only soil conditions but also based on accessibility and constructability. This would prove to be the largest challenge over the course of the project for all parties involved.
Grillage foundations were used in remote locations due to the terrain not being favorable for concrete accessibility. The backfill material for those sites saw a combination of stone (which was hauled in with the use of tracked dump trucks) and native soil (that was excavated from the foundation).
The project also included the replacement of aging equipment with new technology to provide overall strength to the power grid.
Planning
At Aldridge, all projects begin with an extensive pre-job planning process that brings together subject matter experts (SMEs) from across the organization, including the estimating and project teams and field leadership.
The project timeline required a unique approach to schedule sequencing since continuous work was not possible in all of the lattice tower locations. In addition, initial mobilization was delayed nearly two years due to land acquisition challenges the utility company had to work through. Ultimately, a number of different crews had to complete the work due to the on/off schedule - sometimes with a gap of months in between.
These issues were mitigated by continued coordinated planning efforts and constant communication among the team members to recognize and handle any foreseeable problems ahead of the work schedule. Weekly meetings and pre-construction site inspections with the general contractors, environmental representatives, and construction managers allowed us to understand everyone’s expectations and work out any issues prior to commencing on-site activities.
Safety
Drilled shaft foundation work is filled with many hazards. Everyone working on an Aldridge job site has a duty to themselves and to their fellow workers to be constantly aware of potentially hazardous conditions. Each project develops a site-specific safety plan. When hazardous conditions are noted, proper action must be taken to reduce or eliminate the hazard. Safety Absolutes are implemented consistently and uniformly for all of the following job site situations: fall protection, excavation safety, confined space, energized electrical hazard, and willful or repeated violations.
One of the greatest hazards of drilled shaft foundation work is the potential to fall into a drilled shaft opening. In an effort to address this, Aldridge has developed a 100% tie-off program for fall protection. The process consists of erecting a perimeter of yellow cones and chains around the drilled shaft opening. Entry into the perimeter area is only allowed by employees utilizing a personal fall arrest system for protection. This includes a self-retracting line connected to a tie-off block. Aldridge has even designed a trapezoid tie-off block that allows for more ease while moving around a site.
For the Skin Fork Area Improvement project, there were several variances for tie-off based on the constricted site conditions. Sites were so tight that the use of standard tie-off blocks was not always available. The project team quickly identified certain pieces of earth-moving equipment that could be used instead of traditional tie-offs. This dual usage of the equipment also helped to avoid clutter on-site.
To successfully and safely complete the work on this project it took coordination from all levels and between every company involved in the build. The communication and planning as one project team was crucial. While working in remote areas, cell service and even satellite service can be unpredictable. To ensure Aldridge could communicate effectively internally and with the customer, a combination of radios, satellite phones, different cell phone providers, cell boosters, and knowledge of the area where service would be effective was utilized.
While performing nearly 40,000 work hours, Aldridge did not experience any OSHA recordable injuries.
Terrain & Location
While Aldridge is no stranger to working in remote areas, the mountainside location of this project was one of our most extreme environments to date.
It is almost impossible to describe the steepness of the terrain at each of the lattice tower locations. Coupled with the extreme weather conditions, which brought about the possibility of landslides, it seemed nearly inconceivable to develop a site-specific work plan to navigate vehicles on the narrow access roads.
Working hand-in-hand with the local utility and general contractor, Aldridge was able to navigate this challenging terrain by mitigating landslides and using off-road equipment. With the use of dozer equipment, the project team was able to deliver the necessary materials and tools to the site. This included helping drill rigs reach their intended locations and, in some areas, the use of a long reach drill rig was necessary to work around big slopes.
Logistics
Drilling in the mountains often means perforating hard rock. Specialty equipment was used to penetrate the hard rock found on many of the sites as well as for the removal of overburden. The soil and rock on the project varied vastly as the line traversed valleys, hillsides, and ridges.
Due to the site conditions at various locations, a specialized long reach drill rig was used to reach some of the direct embed foundations. This approach was used because of the way the matting pads had to be built. In addition, the use of side by sides was utilized as a tracked people mover to get into sites where rubber tire pickups could not safely traverse.
There was no single approach to hole or excavation stability that could be applied across the board. The keys to success in tackling these logistical challenges were the extensive pre-planning, constant communication, and experience of the project team with these adverse conditions. The project team was made up of SMEs and an experienced crew, all of which brought years of experience with grillages, rock excavation, groundwork, wet hole drilling, rock drilling, and mountainous terrains.
This project also added a further challenge of working around active coal mining locations which required careful logistics coordination with the utility. The use of CB radios played a huge role in the communication with the active coal trucks to ensure their drivers were aware that large earth-moving equipment would be tracking down the same access roads. Due to the current economic climate, the coal industry is booming and crews saw a record number of trucks running on the haul roads in the final months of construction.
The sheer logistics of getting the crew to the site each day was a challenge. The yard was over an hour away from the job site location - with hundreds of feet of elevation changes and a combination of paved and gravel access roads. This created cascading effects on material and concrete deliveries that were further complicated by the lack of cell phone reception. Before the hour-long drive to reach the project site, crew leaders had to use two-way radio communication to coordinate deliveries at the bottom of the mountain. Due to these extensive haul times, meticulous coordination with the crews was needed for drilling in preparation for concrete pouring.
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In today’s connected world, it has become more important than ever to deliver safe, reliable, and resilient power across America. At Aldridge, we’re working hard every day to build and strengthen America’s infrastructure.