Palmers Creek Wind Project – Precast Wind Turbine Foundation

Sargent & Lundy served as independent engineer to develop industry-first modular wind turbine tower base

Palmers Creek Wind Project
Granite Falls, Minnesota
Client: RUTE Foundation Systems, Inc.

Project Highlights:

  • First implementation of proprietary 30BX precast spread footing foundation by RUTE Foundation Systems, Inc.
  • 45MW wind facility.
  • GE 2.3- and 2.5-MW wind turbines on 80- and 90-meter steel tubular towers.

Project Description:

RUTE Foundation Systems, Inc. engaged Sargent & Lundy to perform an independent review of a one-of-a-kind wind turbine foundation concept used to support one of the 18 turbines at Palmers Creek Wind Farm.

The project team tackled a widespread industry problem — with cast-in-place technology, foundation structures can’t be taken apart or moved without destructive demolition. Wind projects sometimes require late-stage changes to turbine locations or the turbines themselves, which can sometimes occur after foundation work has already begun. The team worked to explore a solution to move the structure either prior to turbine tower erection or after 20-year decommissioning.

The project’s 500-foot-tall wind turbine and tower impart significant design loads on the foundation: 584,000 pounds vertical dead load and 45,000,000 pounds-feet overturning moment live load. The large overturning demand provided a design challenge and opportunity for post-tensioning technology.

The project utilized RUTE’s 30BX Foundation technology that consists of a cast-in-place reinforced concrete hub (where the turbine tower is supported) connected to multiple precast concrete box girder sections. Together, these elements form an octagonal spread footing similar in shape to a typical cast-in-place footing built at numerous other wind facilities in the U.S. The 30BX design, however, incorporates novel features intended to maximize material savings and construction efficiency. The RUTE 30BX Foundation cuts the amount of concrete needed by 75% over the life cycle of a wind farm and reduces CO2 emissions.

Taking advantage of well-known technologies such as precast post-tensioned concrete box girders used in bridge design, the 30BX footing allows substantial savings in concrete and reinforcement, and greater resistance to fatigue than typical spread footings used for wind turbines. Precast segmental foundations that use bridge technology are new to the wind industry, and RUTE’s technology allows wind farm owners to reuse the foundation for multiple turbine repowering events.

Project Scope:

Sargent & Lundy provided the following services as independent engineer (IE):

  • Detailed independent review of the various design packages:
    • Preliminary design package, generating comments to improve the design.
    • Final construction documents, to ensure incorporation of IE comments.
  • Review of the project geotechnical report.

The collaboration between RUTE, the engineer of record, and Sargent & Lundy allowed for the successful completion of the foundation in late 2018.

Project Award:

Based on the successful installation of the RUTE 30BX Foundation technology at Palmers Creek Wind Farm, RUTE received the 2019 Merit Award from Post-Tensioning Institute (PTI). The project team, including Sargent & Lundy, was recognized for its input to the design-build success.

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