CFRP System Repairs Riveted Steel Penstock

CFRP System Repairs Riveted Steel Penstock

CFRP System Repairs Riveted Steel Penstock

  • FRP installation at 3 separate locations of 48-104” penstock
  • Trenchless repair method delivered in-place, fully structural upgrade to critical pipeline segments
  • Preplanning and teamwork led to mitigation of emergent challenges, and successful project completion
  • Location
    Los Angeles
    Project Team
    • Owner:
      Los Angeles Department of Water & Power (LADWP)
    • General Contractor:
      Barnard Construction Company
    • Engineer of Record:
      Golder & Associates
    • Specialty Contractor:
    • Product Supplier:

Working with Los Angeles Department of Water & Power (LADWP) and Barnard Construction Co., STRUCTURAL implemented a trenchless repair of targeted segments of 48” to 104” diameter riveted steel penstock.  The overall project, a 2019 ENR Best-of-the-Best awardee, included replacement and rehabilitation of 9,420 lineal feet of critical pipeline connecting the Haiwee Power Plant to a water source in Central California.

STRUCTURAL was called upon to provide design, materials, installation and QA/QC of STRUCTURAL TECHNOLOGIES’ V-WrapTM carbon fiber system for 206 total lineal feet at challenging pipeline locations including under roadways, at bifurcations and in areas of diameter transitions.  The project scope included:

  • Area 1: 14 LF of 104” diameter penstock
  • Area 2: 23 LF of 102” diameter penstock
     8 LF of 98” diameter penstock
  • Area 3: 27 LF of 90” diameter penstock
    99 LF of 70” diameter penstock
    29 LF of 52” diameter penstock
    6 LF of 48” diameter penstock

Using trained and certified applicators, STRUCTURAL provided turnkey installation of the V-WrapTM system.  This included rigorous safety and quality control programs which were managed throughout the construction process.  There were several challenges which had to be overcome as well, including:

  • Remote job site location and inclement weather during the installation;
  • Active leaks at closed valve locations led to the need for continuous dewatering operation (which STRUCTURAL provides);
  • Field changes related to working in conjunction with the larger pipe replacement scope including deflections and deformities in the pipe not accounted for in project plan, necessitating additional shoring and some pipe rerounding and smoothing;
  • Special procedures for carbon fiber installation in riveted piping.

Working with the project team, STRUCTURAL was able to successfully manage these complexities – the project was completed safely, on budget and within the allotted schedule.

The Haiwee Project is a powerful example of how combining technologies, such as replacement along with segments of existing pipeline upgrade, can often deliver the best value for the Owner.  This large-scale pipeline replacement project scope was streamlined by utilizing the V-WrapTM trenchless repair system.  V-WrapTM is a precision repair method and can be designed and installed segmentally, or in extended pipe runs, to deliver fully structural long-term upgrade of difficult-to-access pipelines.


Following completion of the project, the Haiwee penstock got its first seismic tests during the Ridgecrest earthquakes (6.4 and 7.1 magnitude) in July of 2019.  The new piping and V-WrapTM system performed as intended during this seismic activity, and the penstock is in good operating condition.