Georgia Transmission Corporation (GTC) works every day to keep pace with a per capita energy demand that is growing at a rate faster than the state’s population. Meeting this demand and ensuring reliable service requires maintenance of more than 3,000 miles of transmission lines and more than 650 substations, as well as new construction of up to 50 miles of new facilities a year. All told, GTC serves more than 4.1 million Georgians and 38 of the state’s 41 electric member cooperatives.

To assist with these vast efforts, GTC selected Merrick & Company for a five-year contract to provide on-site geographic information system (GIS) support, airborne mapping, and surveying services. To create a seamless workflow, Merrick located a team of professionals on-site in Tucker, GA, to support GTC’s enterprise GIS, which is critical to the utility’s daily operations.

Merrick’s Geomatics team maintains GTC’s Integrated Transmission System (ITS) facility data and supports all new construction projects with an innovative routing and siting methodology. Merrick also provides on-call surveying and airborne mapping support services related to GTC’s capital and maintenance projects in Georgia, which includes existing transmission and substation infrastructure assets.

Merrick has been involved in the power industry since 1955, from transmission and distribution to major infrastructure development. It's a commitment the firm made to the industry early on when Merrick’s professionals were designing the infrastructure for Vail, CO in the 1960s. Merrick has been involved in providing surveying, mapping, and engineering services for power infrastructure situated across the United States and Latin America.

Innovative Routing & Siting Methodology

The Electric Power Research Institute-GTC siting methodology begins with the creation of macro corridors using ArcGIS spatial analyst tools and suitability grids based on off-the-shelf land cover data. Using suitability grids that model three preferences for transmission line routing (parallel existing transmission lines, parallel roads, and cross country), the least cost path algorithm is run to generate macro corridors which model the top 5% of most suitable areas for a transmission line route. These macro corridors are used to define the project study area for aerial photography, data collection, and alternate corridor analysis. Alternate corridors are created using four suitability models: existing corridors, engineering concerns, natural environment, and built environment. The least cost path algorithm is then run to generate the alternate corridors using the data collected after macro corridors which model the top 3% of most suitable areas for a transmission line route. The last part of the siting methodology process is creating alternative routes and selecting the most preferred, based on a statistical analysis and expert judgment specific to each new transmission line project.