Solution
ETT selected Burns & McDonnell to provide full engineer-procure‑construct (EPC) project delivery support, as well as permitting and commissioning, for the transmission line and the new Coulomb Substation.
Meeting the expedited timeline was the primary challenge. We were tasked with completing the Certificate of Convenience and Necessity (CCN) application filing, scoping design, procurement, permitting, acquisition support, construction and commissioning within a span of approximately 14 months.
Prior to kickoff, we conducted extensive site surveys to evaluate multiple potential routes, helping result in the selection of the optimal route in less than two months. Forward‑thinking routing and permitting processes helped optimize cost and schedule throughout the life of the project. During the CCN filing process, the station layout and orientation were changed to minimize project costs without affecting the schedule. Time saved during the design phase helped mitigate later construction delays due to extended periods of poor weather and hindered site access.
Our EPC approach stacked normally linear schedules and tasks, allowing multiple activities to progress simultaneously. Within these efficiency gains, the scoping time frame was reduced from up to nine months to less than three months, while detailed engineering was shortened from one year to less than four months in spite of multiple layout changes during the scoping phase.
The 345-kV transmission line was constructed using optical ground wire (OPGW) and built as a single circuit, providing cost savings to ETT. Only a 0.7-mile section west out of the Coulomb Substation was built as double-circuit-capable. We also cut in one circuit of the existing 84‑mile‑long Edith Clarke to Clear Crossing double‑circuit, 345-kV line into the substation. The greenfield substation was designed as a four‑bay ring bus station, expandable to a breaker-and‑a‑half scheme for the addition of future lines. The site grading was redesigned to optimize costs, and the station breaker foundation was utilized for bus support to facilitate future expansion.
We selected regional subcontractors to help with the construction phase. Using local subcontractors also helped expedite the acquisition and delivery of materials to the remote location in north-central Texas.
Although the COVID-19 pandemic complicated many construction projects across the country during the final months of this project, construction and testing of the transmission line and substation were able to continue without stoppage during the first wave of the pandemic in March and April 2020 because of proactive health and wellness safeguards already on-site.
