345-kV Plant Tie Circuit

Location: Pasadena, Texas

Client: CenterPoint Energy

Completion Date: 2002

A design-build project consisting of a 345-kV plant tie circuit that connected the Deepwater Substation to the Calpine Channel Energy Center. The line is located at the Lyondell-Citgo Refinery in Houston and crossed over petrochemical process equipment and storage facilities. A double circuit line was designed using tubular steel structures that also included an ADSS communication line between the substations. Structures as high as 214 feet were required to maintain the 100-foot ground clearance requirement of the refinery. FAA applications were filed and required aircraft warning lights to be installed on one structure. Extensive coordination was required with the refinery, Calpine and Reliant/HL&P.

  • Specification/Bid Document Preparation
  • Stucture Conceptual Design
  • Equipment and Material Procurement
  • On-Site Construction Management
  • Construction Activity Sequencing
  • Evaluation and Awarding of All Construction Subcontractors
  • The majority of the interconnecting 345kV plant tie was built inside of the Lyondell-Citgo refinery. 
  • The constraints placed upon circuit routing and footprint size & locations were the main driving forces behind the development of the type and configuration of transmission line structures to be used for this project.
    • Self-supporting tubular steel poles were selected because of their relatively small foundation impact area and because of the limited erection and work space within the refinery. 
    • The largest steel pole was 214 feet in height and had a base diameter of 118 inches.
  • Due to the loading of this pole, an unconventionally large drilled shaft was required for the foundation that resulted in dimensions of 16 feet in diameter and 62 feet below grade. 
      • The design of foundation was accomplished with a special built continuous reinforcement cage that was placed in the shaft by three cranes. 
      • The reinforcement cages built for the three other foundations included custom built stiffener rings placed throughout the cage and mechanically connected to the longitudinal steel. 
      • This dramatically increased the ease in which these large cages could be lifted and placed within the drilled shafts. 


  • The combination of unique tubular steel poles and customized drilled shaft foundations provided a great solution to daunting restrictions.