According to the Edison Electric Institute, more than 200,000 miles of high voltage transmission lines span the U.S. as part of our nation’s comprehensive electric grid. Many of these power lines are aging and in need of upgrade. The increasing number of major weather events combined with the ever growing demand for energy to power more and more digital technology has created a need to prioritize expansion and update the grid for efficiency and resilience. KCI worked with the Tampa Electric Company (TECO) and multiple consultants and contractors to provide survey and subsurface utility services for a 37-mile circuit rebuild in Hillsborough and Polk counties in Florida.
The project focused on improving transmission out of the Polk Power Station, which had recently undergone a $660 million expansion to increase output by 460 megawatts. Next TECO focused on upgrading existing and adding additional transmission lines leading from the plant into the surrounding communities. KCI field crews supported the planning, design and construction efforts by providing design surveys, right-of-way mapping and monumentation, LiDAR control, legal descriptions, utility and wetland mapping, construction stakeout and as-builts along the entire corridor.
Our team utilized nearly every type of surveying methodology available, including Terrestrial LiDAR, GPS, conventional field techniques and SUE, to assist with planning, design and construction. Project challenges involved environmental concerns and the sheer volume of work to be completed on an aggressive schedule.
The Polk Transmission Project was the largest transmission line project TECO has undertaken in more than 50 years. When you are building or modifying on the order of two dozen circuits, you really need to be on your game, and KCI leveraged technology and their capacity to bring in additional crews to meet the needs of both our design and construction teams.
Rea Berryman, Senior Engineer, TECO
The transmission lines crossed waterways, highways, subdivisions and even a phosphate mine. Although the proposed route primarily followed existing alignments and right-of-way, new segments were erected in several locations. KCI’s work included locating existing poles in maintained easements, as well as detailing easements that ran through non-maintained areas. During the planning and design stages, survey crews established a complete network of horizontal and vertical control points every 500 to 1,000 feet for the entire length of the project. The alignment was then flown and the existing topography was mapped using LiDAR technologies and ground survey verification.
Minimization or possible elimination of impacts was a critical component to both the design and construction phases. KCI crews staked more than 25 miles of wetlands along the transmission corridor just prior to construction. Surveyors also staked buffers around eagle nests to enforce regulations that limit the proximity of vehicles to 600 feet and construction to 1,300 feet depending on the season.
TECO also sought to remove danger timber along the route. Gravity and electrical load causes transmission lines to sag between poles. These sagging lines can be blown into nearby tree branches creating a fire hazard. Our team identified and marked trees that could become potential hazards.
It was also critical that the proposed construction did not disturb existing surface water flow patterns along the entire length of the project. Crews surveyed existing grades before any disturbance. The pre-construction data was used in order to build the proposed gravel access roads to match previous site conditions. KCI surveyors then conducted as-built surveys following construction to confirm that grades had been restored to pre-existing conditions with no effects to stormwater flow. Crews also mapped two existing waterways that would need to be crossed by vehicles in order to access pole locations. Cable concrete roadways were designed and placed in the waterways in order to minimize the impact on the project area’s natural resources.
We used nearly every tool in our toolbox—LiDAR, GPS, robotic conventional, conventional leveling, SUE Level B, ground penetrating radar, SUE vacuum excavation Level A, and GIS data feature code collection.
Steven Burnett, PSMPractice Leader
Our subsurface utility engineering crews provided TECO with accurate locations of existing underground utilities, data that would determine the location of new power poles. Using vacuum trucks, technicians excavated holes to facilitate pole erection while avoiding potential utility conflicts.
In addition to the actual pole to pole alignment, the work also involved surveying adjacent properties, railroads, utility easements, and highway corridors, as well as miles of service roads with a gravel pad at various pole locations. Two substations were mapped via 3-D laser scanning to avoid having to enter these dangerous, high voltage environments. Once construction was complete, surveyors confirmed and documented the installations via as-builts and erected right-of-way monuments along the entire corridor.
Throughout the project, which began November 2012 and lasted four years in duration, KCI worked and built relationships with multiple design firms and contractors as the circuit rebuild moved through the planning, design and construction lifecycle. At its peak, as many as six survey crews from across the Southeast worked simultaneously to successfully upgrade and expand this 37-mile transmission line alignment within TECO’s aggressive schedule.