When executives at Burns & McDonnell signed on to handle construction for a pair of Alliant Energy solar projects in Iowa, they knew they would have to overcome some unique challenges.

The Kansas City, Missouri-based engineer-procure-construct contractor is self-performing construction for two Alliant Energy solar projects in the Hawkeye State:

• The Wever Solar Project is a 150-megawatt (MWac) solar array located in Lee County. The project substation is designed with the flexibility to add a 75-MW battery energy storage system in the future and will connect to the electrical transmission grid. Once completed, it will positively impact the environment and generate enough clean, low-cost energy to power more than 30,000 homes annually.
• The Creston Solar Project is a 50-MWac solar array in Union County. It will connect to the electrical transmission grid directly through the local substation. When it is completed, the project will also positively impact the environment and generate enough clean, low-cost energy to power approximately 11,000 homes annually. It is part of Madison, Wisconsin-based Alliant Energy’s Clean Energy Blueprint, a strategic roadmap to cost-effectively accelerate its transition to renewable energy and reduce carbon emissions.

Construction of both the Wever and Creston projects began in the fall of 2023, and both are expected to be completed by the end of 2024. Each utilized Canadian Solar 660-Watt modules, the highest wattage that Burns & McDonnell has installed to date.

Solar projects are acknowledged to be more cost effective for Alliant than continuing to maintain and operate traditional energy sources, most notably coal. The addition of solar allows the company to avoid additional expenses and investments needed for coal operations in the years to come. Customers, of course, are also able to benefit from long-term savings.

“By adding solar we can avoid ongoing expenses and investments that would be required to keep some units of our coal-generation fleet operational,” said Morgan Hawk, Spokesperson at Alliant Energy. “Transitioning to solar and other renewable sources, it provides long-term savings for our customers moving forward.”

Powered by the sun, both projects will represent a long-term reduction of traditional fossil fuels for energy generation, contributing to a cleaner environment and clean-energy future for Iowa and across the Midwest. Project partners included Alliant Energy, Rachel Inc., and Burns & McDonnell’s wholly owned construction subsidiary, AZCO.

Several earlier Alliant solar projects in Wisconsin began in April of 2021 and were completed in December of 2023.

“We are excited to build on the momentum of the nine sites we successfully delivered for Alliant Energy in Wisconsin,” said Jami Stone, Construction Project Manager at Burns & McDonnell. “We look forward to continuing to build on this trust-based relationship to implement additional renewable energy projects for them.”

Burns & McDonnell is providing fully integrated services for the Iowa projects, which are scheduled to be placed in service later this year. These include in-house engineering and procurement and construction services.

“We handle everything from beginning to end,” Stone said. "Being an integrated team with disciplines across permitting, engineering, and construction, we’re able to work together to solve challenges as they arise to keep the project on schedule.”

The value of an integrated approach of the variety Burns & McDonnell is taking is visible on the 900-acre Wever project, the company noted. Because of its location in a flood plain, extra planning, permitting, and engineered solutions have been involved. Designers collaborated with construction professionals to prepare for 500-year flood levels.

Though AZCO is handling the construction, the majority of the workforce will come from local trades, including carpenters, laborers, operators, and electricians. Peak labor is expected to reach 300 on the Wever project and 120 on the 300-acre Creston project.

Burns & McDonnell proactively designed and installed a drain tile system in-house to accommodate the environmentally sensitive area, reduce the risk of flooding, and mitigate potential challenges. Other project highlights include applying new and innovative technologies to streamline construction, making it more efficient and environmentally sustainable.

The project team will also see the installation of 3 miles of underground cable to interconnect the AC collection system at the Wever site with the closest existing electrical substation.

It did not take long for the twin projects to distinguish themselves as unique — no small task, given that Burns & McDonnell was founded in 1898. Today, it works out of 75 offices globally, and its family of companies includes 14,500 engineers, construction and craft professionals, architects, and more to design and build critical infrastructure.

One of the major challenges at the Wever site involved splitting two groups of panels 4 miles apart.

“With 90 megawatts in one area and 60 megawatts in another, it was challenging for collection systems,” according to Stone, a veteran of the electrical construction industry for more than two decades. Part of the Wever project was also in a flood plain between the Skunk and Mississippi rivers. Because of that, she added, “extra planning, permitting, and engineered solutions have been involved.”

Wever will be among the largest solar facilities in Iowa, a state typically known for its wind installations. With more than 200 people on site, and roughly half of them being from surrounding communities across the river in Illinois, Stone said, “We feel we have added a skillset to local craftspeople.” The number of craftsmen at the Wever project reached 200, while the Creston project peaked at 90.

The AC collection system home run was nearly 4 miles long, Stone explained. It crossed state roads, delineated wetlands, personal drives, and streams.

“Therefore, we installed several thousand feet of directional bores so as not to disturb those features,” she said. “This created a unique situation utilizing several levels of expertise to pull 1250-kcmil cable both below ground in conduit and in open trench.”

The Creston project was built on undulating terrain, which created grade challenges and required erosion management due to the terrain and proximity to the Platte River.

“On both projects, engineers collaborated with construction professionals to account for 500-year flood levels,” Stone explained. Burns & McDonnell proactively designed and installed a drain tile system to account for the environmentally sensitive area, reduce the risk of flooding, and mitigate potential challenges.

Another of the unique aspects of each project site is the planting of native grass and seed mixes around the panels and throughout the solar arrays that will help build soil nutrients and create pollinator-friendly habitats. Pollinator-friendly vegetation has been proven to prevent soil erosion and add benefit to high-value crops.

According to Hawk, the costs for the Wever project are estimated to be approximately $275 million. For Creston, they are about $90 million.

The dollars that Iowa expects to see as a result of the two projects are substantial.

The Wever Project looks to generate over $3.6 million in local school district revenue, more than $700,000 in total county property taxes for Lee County, and over $5.7 million in total property taxes over the project's lifetime.

The Creston Project is expected to provide in excess of $1.2 million in local school district revenue, more than $270,000 in total county property taxes for Union County, and approximately $1.9 million in total property taxes over the project's life. Lease payments to the participating landowners will provide long-term, stable streams of income over the life of the project.

Replacement tax revenue, a state program, will provide annual payments to both Lee and Union counties based on each project’s generation output.

Burns & McDonnell is also actively involved in the communities for both projects, holding food and toy drives for nearby residents and a golf tournament that raised $30,000 for the local Boys & Girls Club.

Photos courtesy of Burns & McDonnell