Project Information

Carroll Electric Cooperative is planning a new 69-kilovolt (kV) sub-transmission line to replace the existing transmission source serving the Grassy Knob Substation.

The proposed project would construct 12.25 miles of new 69 kV sub-transmission line between the Grassy Knob Substation and the Holiday Island Substation west of Eureka Springs. The purpose of the project is to maintain adequate transmission supply that can support long-term electric demand in the area and enable planned upgrades at the Grassy Knob Substation.

The project will enhance system reliability, address the capacity constraints associated with the existing 34.5 kV transmission source, and reduce CECC’s operational dependency on other power providers. 

This webpage will serve as the primary source of information for the Grassy Knob Sub-transmission Line Project and will be updated as planning and development stages continue.

Individuals who register below may receive periodic updates and other relevant project information as it becomes available.

The primary component of this project is the construction of a new 69-kV sub-transmission line connecting CECC’s Holiday Island transmission supply to the Grassy Knob Substation.

Along portions of the proposed route, CECC will also upgrade existing distribution lines to increase their capacity and support reliable electric service in the surrounding area.

In addition, equipment at the Grassy Knob Substation will be upgraded to increase both its operating voltage and overall capacity, allowing the facility to better serve current and future electric demand.

CECC does not own or operate any bulk transmission lines. Some residents may recall a bulk transmission line proposed in this area approximately 14 years ago. CECC’s current project is completely separate from that proposal and serves a different purpose.

The key differences are outlined below:

Bulk Transmission Lines

• Are part of the larger regional power grid and move electricity between utilities across a wide area.
• Operate at much higher voltages (typically 115 kV to 765 kV) to carry electricity over long distances.
• Use taller structures, sometimes up to 220 feet tall.
• Often use larger wires or multiple bundled wires to carry more electricity.

Sub-Transmission Line (This Project)

• Delivers electricity to local substations that serve CECC’s customers.
• Operates at 69,000 volts (69 kV).
• Typically uses shorter poles, generally ranging from 60 to 80 feet tall.

In simple terms, bulk transmission lines carry electricity across regions, while this sub-transmission line would deliver electricity directly to local communities.

CECC regularly evaluates its electric system to ensure it can continue providing safe and reliable service to members. As part of this process, the Cooperative develops both a long-term forecast (covering approximately 20–30 years) and a short-term construction work plan (covering approximately 4–6 years).

The need for this project was first identified in CECC’s 2016 Long-Term Forecast. By the 2022 Long-Term Forecast, continued growth and increasing system demands in the area further confirmed the need for additional infrastructure improvements. The project was formally incorporated into CECC’s 2023 Construction Work Plan.

These improvements are currently planned for completion in 2028. Based on projected growth trends, the project timeline is designed to ensure additional capacity is available before the existing system reaches its practical and operational limits.

Yes. While the primary purpose of the project is to increase transmission capacity, the upgrade is also expected to improve overall service reliability for residents located in the western part of Carroll County.

Today, the Grassy Knob Substation is supplied by a single 34.5-kilovolt (kV) transmission line. That line has served the area for many years, but it operates near the practical limits of what the existing infrastructure can support as electric demand continues to grow.

This configuration is actually an outlier within CECC's distribution system. Carroll Electric currently operates 48 substations, and Grassy Knob is the only substation supplied by a 34.5 kV transmission supply. All other substations are supplied by higher voltages (e.g., 69kV). 

The proposed project would replace the lower-capacity source with a new 69 kV transmission supply from the Cooperative’s Holiday Island Substation. By providing a modern, higher-capacity transmission connection, the Cooperative can better support future substation upgrades and maintain stable system operations as the area grows.

In addition, the project allows Carroll Electric to serve the Grassy Knob Substation directly from its own transmission facilities.

Overall, the upgrade helps ensure the electric system serving western Carroll County has the capacity, operational flexibility, and infrastructure needed to support reliable service in the years ahead.

CECC has taken several steps to minimize both the immediate and long-term impacts of this project on landowners and the surrounding community.

Because this project involves a 69-kilovolt sub-transmission line, CECC has more flexibility in route planning than is typically available with larger high-voltage transmission projects. This flexibility allows CECC to evaluate routing options that reduce impacts where possible.

One of the primary strategies is co-locating the new line with existing electric infrastructure. Where feasible, CECC intends to place sub-transmission and existing distribution lines on the same structure. Doing so can reduce the need to establish entirely new corridors — minimizing additional right-of-way impacts.

In addition, single-pole steel structures will be used where practical, which generally require less ground space and have a narrower visual profile than larger transmission structures.

CECC also recognizes the unique natural beauty and historic character of western Carroll County. The presence of environmentally sensitive areas, historic resources, topography, and existing land uses limits the number of practical routing options between Holiday Island and Grassy Knob. To guide route development, CECC uses objective geospatial mapping data to identify acceptable corridors.

CECC is currently working directly with landowners within the preliminary corridor to refine and finalize project routing.

Finally, CECC is planning with the long term in mind. By considering where future substations may be needed over the next 15–20 years, the line is being routed to accommodate future system needs and help avoid the need for additional sub-transmission lines in the area. 

No. 

Carroll Electric has no affiliation with the Nimbus Wind Farm or Scout Energy. 

Yes.

Your feedback is important to us. CECC is in the early stages of this project and welcomes input from all stakeholders. We encourage you to register as a stakeholder below and share any questions or concerns not addressed in the most recent version of this webpage.

Please note that we may not respond individually, but all comments and concerns will be reviewed and further assessed as it relates to this project.