400 MW Wind Collection, Substation & Transmission Project

Project Description

Capacity: 400 MW
Year Commissioned:  2019

RRC provided electrical services to a 400 MW wind project located in the Midwest. The facility consists of 163 Vestas V120 (2.2 MW) and 12 Vestas V112 (3.45 MW) wind turbine generators on sixteen (16) collector circuits split evenly between a North and South substation. When completed, the project will be the largest in the state. RRC’s scope included the transmission line design, substation design, SCADA system design, collector system, geotechnical work for the transmission line, and WTG foundation design. The 18-mile 345 kV transmission line is supported by engineered tubular steel poles with drilled pier foundations and direct embedment. The conductor arrangement is bundled. The design included full OPGW communication details. It is broken into two sub-sections with a substation in between. RRC and their partner provided the full construction package to procure and construct the line and provided construction support during construction.

Row of wind turbines in a field of yellow flowers and plants

Meadow Lake Wind Project Phases I-IV

Project Description

Location: White County, Indiana
Installed Capacity: 500.85 MW
Construction Cost: $100,000,000+
Year Commissioned:  2009 – 2010

With over 300 wind turbine generators and a power generating capacity of 500.85 MW for four phases, the Meadow Lake Wind Farm is one of the largest wind farms in the United States. Each phase was supplied with turbines from different manufacturers including Acciona, General Electric (GE), Suzlon, and Vestas, and construction of the individual phases was awarded to different Balance of Plant (BOP) contractors. RRC provided geotechnical engineering, structural engineering, and construction material testing services for the project, covering all stages from planning and final development through construction.

RRC’s geotechnical engineering services included subsurface exploration comprised of conventional soil borings, continuous rock coring, and Cone Penetrometer Tests (CPT), and specialized geophysical surveys comprised of Multi-Channel Analysis of Surface Waves (MASW) surveys, along with engineering analyses and design. Due to the prevalence of shallow groundwater at the project site, numerous temporary piezometers were installed and monitored to facilitate foundation buoyancy calculations and to provide guidelines for site dewatering during construction. Soft or compressive clay soils were encountered during the subsurface investigation phase, requiring deep ground improvement to support the proposed wind turbine generator (WTG) loads at several tower sites. Rammed Aggregate Pier (RAP) systems were utilized to stiffen deep marginal soil deposits. The process involved constructing high density, stiff RAPs to control settlement and improve bearing pressures and rotational stiffness.

Structural engineering services included design and sizing of concrete, reinforcing, embedment rings, and anchor bolts for the WTG foundations to adequately resist the loadings provided by the turbine supplier. Due to the scale of the project, it was important for RRC to create the most economical design possible in order to provide cost savings over the many turbine sites of the project. As part of the effort to economize project construction, each individual phase utilized multiple foundation sizes based on differing soil bearing pressures and groundwater conditions at each turbine site. RRC developed 11 different turbine foundation designs for the four phases.

Coordination of the different foundation sizes, as well as providing necessary provisions for soil corrections and deep soil improvement techniques, was critical to achieving an economical and well-planned project. Working together as a team, RRC’s geotechnical and structural engineers delivered a sound yet economical turbine foundation design for the Meadow Lake project.

Row of wind turbines in a field of yellow flowers and plants
Three wind turbines on a grassy hill with blue skies

Shepherds Flat Wind Farm

Project Description

Location:   Gilliam and Morrow Counties, Oregon
Installed Capacity: 845 MW
Construction Cost: $500,000,000+
Year Commissioned:   2012

The Shepherds Flat Wind Farm is located near the City of Arlington within Gilliam and Morrow Counties, Oregon. As one of the largest wind farms constructed in a single phase in the world at the time of this posting, the project consisted of construction and installation of 338 GE 2.5 MW wind turbine generators with a total nameplate capacity of 845 MW.

RRC provided geotechnical engineering, structural engineering, and construction materials testing for the project. From a geotechnical engineering perspective, the subsurface soils and bedrock conditions were challenging across the site and ranged from collapse-prone soils to basalt bedrock exposed at relatively shallow depths. The design also required implementation of Deep Dynamic Compaction (DDC) to alleviate the subgrade soil collapse potential, as well as providing a plan for the execution of the DDC. Due to the large scale of the project, it was particularly important for RRC to optimize and provide the most economical foundation designs. RRC provided the design and sizing of the concrete, reinforcing, embedment rings, and anchor bolts for the wind turbine foundations to adequately resist the loadings provided by the turbine supplier.

Three wind turbines on a grassy hill with blue skies
Row of wind turbines in a cotton field with a blue sky

Roscoe Wind Project

Project Description

Location:  Mitchell, Nolan, and Scurry Counties, Texas
Installed Capacity: 781.5 MW
Construction Cost: $500,000,000+
Year Commissioned:   2008, 2009

The Roscoe Wind Project is located near the City of Roscoe within Mitchell, Nolan, and Scurry Counties, Texas. The project is divided into four phases comprised of the following: Roscoe Wind Project – Phase I, Champion Wind Project, Inadale Wind Project, and Pyron Wind Project. The total nameplate capacity of all phases is 781.5 MW derived from 406 Mitsubishi 1.0 MW wind turbine generators (WTGs), 55 Siemens 2.3 MW WTGs, and 166 GE 1.5 MW WTGs constructed and installed throughout the entire project. The Roscoe Wind Project is considered one of the largest wind projects in the United States.

RRC provided geotechnical engineering, structural engineering, and construction materials testing for the project. The design team worked and collaborated seamlessly to ensure challenging deadlines and milestones were achieved.

Geotechnically, the subsurface soils and bedrock conditions were variable across the site. Expansive soils and soft clay layers within some portions of the site required particular attention during the design and construction phases. Due to the large number of turbines and geographic extents of this project, multiple field crews were utilized to shorten the field exploration phase schedule. Additionally, RRC performed seismic refraction surveys to aid in estimating static groundwater levels for some portions of the site. Groundwater is an important factor to consider for turbine foundation design.

Structural engineering services included design and sizing of concrete, reinforcing, embedment rings, and anchor bolts for the wind turbine generator foundations to adequately resist the loadings provided by the turbine supplier. Due to the scale of the project, it was important for RRC to create the most economical design possible in order to provide cost savings over the many turbine sites of the project.

During construction, RRC provided continuous engineering support to effectively provide measures to address issues related to foundation dewatering and unsuitable foundation subgrade. RRC’s remedial measures were efficiently engineered, cost effective, and helped with maintaining the construction schedule.

Row of wind turbines in a cotton field with a blue sky
Wind turbine in a field of blooming cotton
Graphic of wind turbine on orange circle

Highland Wind Project

Project Description

Location:  O’Brien County, Iowa
Installed Capacity: 502.04 MW
Construction Cost: $800,000,000+
Year Commissioned:   2015

The Highland Wind Project is located within O’Brien County, Iowa and includes 214 Siemens 2.34 MW wind turbine generators (WTGs) for a total nameplate capacity of 502.04 MW. RRC provided structural engineering design for 195 of the WTG foundations on the project as well as engineering support during construction.

Structural engineering services included design and sizing of concrete, reinforcing, embedment rings, and anchor bolts for the WTG foundations to adequately resist the loadings provided by the turbine supplier. In order to provide cost-effective structural foundation designs, multiple foundation sizes based on different soil bearing pressures and groundwater conditions were utilized for the project. Additionally, RRC engineers provided support during construction and assisted with resolving field issues in a timely and effective manner resulting in client cost savings.

Graphic of wind turbine on orange circle

Thumb Wind Park

Project Description

Location: Huron and Sanilac Counties, Michigan
Installed Capacity: 129.6 MW
Construction Cost: $200,000,000+
Year Commissioned:   2012

The Thumb Wind Park project is located within Huron and Sanilac Counties, Michigan. The project is divided into three sites comprised of: McKinley Wind Park, Minden Wind Park, and Siegel Wind Park. The total nameplate capacity of the three sites is 129.6 MW derived from 9 GE 1.6 wind turbine generators (WTGs) constructed and installed at McKinley; 32 GE 1.6 WTGs constructed and installed at Minden; and 40 GE 1.6 WTGs constructed and installed at Siegel.

RRC provided geotechnical engineering, structural engineering, and construction materials testing for all three sites included in the project. The wide geographic spread of the three wind park sites, tight design deadlines, and construction schedule constraints promoted members of RRC’s team to work seamlessly to assure deliverables were submitted on time as well as proactively providing support during construction.

The subsurface soils and bedrock conditions along with variable groundwater conditions were challenging throughout the three sites from a geotechnical engineering perspective. The variability of glacial till deposits, soft unsuitable organic soil deposits encountered within some locations, and variable groundwater conditions were carefully reviewed and analyzed during the design phase. Practical remedial measures were provided to address these issues.

Due to the challenging geotechnical conditions encountered, it was particularly important for RRC to collaborate with the geotechnical design team to optimize and provide cost-effective foundation designs. RRC provided design and sizing for concrete, reinforcing, embedment rings, and anchor bolts for the wind turbine foundations to adequately resist the loadings provided by the turbine supplier.

RRC provided continuous engineering support during construction to effectively provide measures to address issues related to foundation dewatering, unsuitable foundation subgrade, and for an access roadway area where peat deposits were exposed. The remedial measures provided by RRC were cost effective, soundly engineered, and helped with maintaining the aggressive construction schedule.

Graphic of wind turbine on orange circle

Alta Wind Energy Center – Phases II-XI

Project Description

Location:   Kern County, California
Installed Capacity: 1,346.45 MW
Construction Cost: $500,000,000+
Year Commissioned:   2010 – 2014

The Alta Wind Energy Center, located near Mojave in Kern County, California, is within one of the largest concentrations of wind farms in the world. Phases 2 through 11 of this project included construction of over 450 wind turbine generators. The Alta Wind Energy Center provides approximately 30 percent of California’s wind-generated electrical power.

RRC was involved with numerous aspects and phases of the Alta project.

RRC’s geotechnical services included conventional soil borings, continuous rock coring, in-situ geophysical surveys, geological hazard studies, slope stability evaluations, and geotechnical engineering/analysis. Collapsible cohesionless soils were encountered in our investigations, requiring remediation measures to reduce the risk of hydro-consolidation at some turbine sites. Portions of the project site are located within the California Alquist-Priolo (AP) Earthquake Fault Zone; therefore, geological fault investigation was conducted to establish appropriate setback distances from active traces of Garlock Fault. In-situ and laboratory thermal resistivity testing was conducted for design of underground electrical cables.

RRC provided extensive foundation designs for the development based upon various configurations of GE and Vestas turbines. Challenges to the structural design included design for high strength tower versions for seismically controlled locations and a standard tower versions for extreme wind-controlled locations. Adding to the challenge, many foundation sites also required coordination of the design for scour protection as well as measures to protect the subgrade against hydro-consolidation concerns.

As with all projects, RRC provided the most economical design to realize maximum cost savings over the project as well as construction support to keep the project on schedule.