Project Overview
To support the interconnection of new wind generation resources, American Electric Power (AEP) selected Mortenson to engineer, procure, and construct the Bonilla Interconnect, a new 345kV substation near Rio Hondo, Texas. Following completion of the initial facility, AEP contracted Mortenson to deliver the West Raymond Expansion, enabling the connection of a second wind farm to the grid and expanding the capabilities of the energized switchyard.
Customer Impact
AEP required new transmission infrastructure to support the interconnection of a wind generation project near Rio Hondo, Texas. Mortenson delivered a new 345kV substation and associated transmission line modifications to support the initial interconnection while designing the facility to accommodate future expansion.
When expansion needs emerged, Mortenson completed additional work within the energized switchyard, coordinating closely with AEP to secure outages and integrate new equipment required for the second interconnection.
Key Takeaways
- Delivered a new 345kV greenfield substation near Rio Hondo, Texas.
- Supported the interconnection of two wind generation projects through a phased transmission infrastructure solution.
- Designed the original facility to accommodate future expansion requirements.
- Modified the North Edinburg-Rio Hondo transmission line as part of the interconnection scope.
- Completed additional expansion work within an energized switchyard environment. Managed construction through challenging groundwater and weather conditions while maintaining project progress.
- Delivery Method
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Engineer, Procure, Construct
- Additional Project Facts
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345kV Substation and Station Expansion
Completion Dates:
Bonilla Interconnect: January 2020
West Raymond Expansion: December 2020
Supporting AEP's Renewable Generation Interconnections
The Bonilla Interconnect included four breakers, 17 disconnect switches, 12 CCVTs, metering equipment, three ground switches, a control enclosure, and two A-frame dead-end structures. In addition to the substation scope, the project included modifications to the existing North Edinburg-Rio Hondo transmission line, including installation of two dead-end structures, one single-pole tangent structure, and OPGW modifications.
Delivering Through Challenging Site Conditions
Construction activities were affected by high groundwater levels and unusually wet site conditions.
On the day the contract was signed, the site experienced a 13-inch rain event that further increased water levels across the project site.
To maintain access and construction activities, the team elevated the access road by one foot, built temporary spur roads, and installed matting to support transmission line structure installation. The substation was also constructed on a ten-acre pad elevated five feet using imported fill.
To respond to changing weather conditions and maintain the aggressive project schedule, the project team coordinated both day and night shifts throughout construction.
Expanding Capacity Through Existing Infrastructure
In August 2020, AEP contracted Mortenson to complete the West Raymond Expansion to facilitate the connection of a second wind farm. The expansion included removing several piers from the original phase of construction, expanding the existing A-frame structures, and installing two new 345kV breakers, switches, and metering equipment.
Because the switchyard was already energized, Mortenson worked closely with AEP to coordinate required outages and safely complete the expansion. The West Raymond expansion was completed in December 2020.