By Christina Hebb, SWPPP and vegetation senior manager, McCarthy Building Companies
The reduction of harmful greenhouse gas emissions is an important aspect of our clean energy future. So is fostering healthy ecosystems. In fact, climate change and biodiversity loss are two of the most critical, intertwined crises our planet is facing. As the energy industry works to decrease carbon dioxide emissions from electricity generation, we can also work to help increase the variety of living species on Earth.
Over the next decade, solar development is expected to increase by 69%, due in large part to incentives offered as part of the Inflation Reduction Act of 2022. The land area required to install these large-scale solar farms is estimated to be upwards of 10 million acres, according to the Solar Energy Industries Association. Part of achieving clean energy goals involves converting farmlands, pastures and well-established natural ecosystems to solar farms and other renewable energy developments.
Fortunately, progressive solar developers and EPC contractors are implementing biodiversity strategies to responsibly build utility-scale projects across the country. These strategies are designed to protect and enhance the land, which results in positive impacts on the surrounding environment and helps to promote clean energy initiatives across the U.S.
Utilizing site-specific revegetation strategies
Enhancing biodiversity was a priority at the 293-MW Sun Mountain solar project outside of Pueblo, Colorado; one of the nation’s largest solar farms completed to date. Lightsource bp, the project developer, owner and operator, worked together with EPC McCarthy Building Companies to establish a site-specific revegetation strategy for the more than 1,700 acres of land comprising the project.
The Sun Mountain solar project.
McCarthy’s team of experts developed a site-specific vegetation management plan during the project’s design phase. Implementation of the plan began early in the construction process to best ensure successful revegetation of the land and augment the sustainability and ecological value of the site.
“In-house expertise with our EPC partners is extremely beneficial as they have a thorough understanding of the challenges associated with establishing and maintaining vegetation before, during and after construction. This allows for open dialogue during the planning stage to ensure the correct strategy is being implemented,” said Virginia Brown, director of ecosystem services for Lightsource bp. “Additionally, having the expertise available throughout the process promotes proactive decision-making during the planning and construction phases.”
Site-specific vegetation management plans also aid in restoring natural habitats. In fact, at both Lightsource bp solar farms in Pueblo, including Sun Mountain’s sister project Big Horn, over 3,000 acres of shortgrass prairie are being conserved, creating habitat for wildlife while bolstering the sites’ ability to sequester carbon.
Sun Mountain’s plan also involved weed management, conservation of pre-existing vegetation, and over-seeding to increase the cover of native grassland species. Deep-rooted native grass species are important for water infiltration and storage in an arid climate, and also help to facilitate the capture of carbon from the atmosphere. Research data indicates that over the first 25 years of the Sun Mountain and Bighorn projects’ 40-year lifespan, the on-site prairie habitat will remove and store the equivalent of 36,000 tons of CO2. They also aid in offsetting the carbon dioxide release from construction and operations of the solar farm. And mature stands of native grasses outcompete weeds, preventing weed infestation and spreading in the long-term.
“In Pueblo, the development of solar offered a unique opportunity to enhance the native prairie vegetation within the project boundary without the pressures of agricultural production,” said Brown. “When native grasses are permitted to grow to full maturity without intense grazing pressure, they develop deep root systems, an important component to soil health and stormwater infiltration.”
Spotlight: Sun Mountain Solar Farm
The power generated by the 293-MW Sun Mountain solar farm in Pueblo, Colorado, is capable of powering 53,540 homes and abating 404,080 tons of CO2
The Sun Mountain power purchase agreement between Lightsource bp and Xcel Energy supports Xcel energy’s Colorado Energy Plan to delivery 55% renewable energy to the grid and reduce carbon emissions 60% by 2026.
Sun Mountain supports Colorado’s clean energy goal to reduce emissions statewide 26% by 2025, 50% by 2030 and 90% by 2050 – creating cleaner and healthier communities across Colorado, while contributing to local economies.
Why topsoil matters
Topsoil salvaging at Sun Mountain.
Successful solar development begins with the soil. Proper planning, sequencing, handling and storage of soil materials prior to breaking ground can drastically improve the establishment of healthy vegetation on and around solar farms during and after construction. Reducing site grading can help preserve topsoil, which is the most fertile layer of land for vegetation.
At Sun Mountain, topsoil management was implemented on areas with soil disturbance and excavation. This practice is particularly important in arid areas with thinner topsoils as the subsoil layers are not suitable for establishing or supporting healthy vegetation. A suitable native seed mix was planted early in the project timeline and during the preferred season to maximize successful growth.
“By producing a topsoil map for the property and accurately quantifying topsoil depths via a survey prior to earthwork, we optimized grading and pile designs to mitigate impacts to valuable topsoil during construction,” said Justin Peterson, VP of operations for McCarthy’s national renewable energy and storage team.
Establishing vegetation after construction disturbance can be challenging. Most native species take two to three years to become fully established, which is why preserving topsoil is a critical element of any biodiversity strategy.
How revegetation supports stormwater
Managing stormwater on solar sites is a key goal within site-specific revegetation strategies for a number of reasons, primarily in order to meet or exceed stormwater permit requirements. For EPCs, rapid revegetation leads to safer, more productive working conditions for solar installation crews, and later, operations and maintenance staff.
Native grasses at Sun Mountain.
“Nobody likes working in mud,” said Peterson. “By effectively managing stormwater, the risk for erosion and degradation onsite is exponentially reduced.”
During civil design of the Sun Mountain solar project, McCarthy’s stormwater management experts were able to eliminate sediment basins and instead manage water on the site and provide filtration to allow continued flow to the landowner’s nearby ranch, ultimately reaching his grazing cattle.
“Landowners are generally a great resource when it comes to understanding the land, particularly in terms of stormwater, hydrology and water flows,” Brown said. “Conversations with landowners provide insight on where erosion-prone areas are located, areas that hold water, or where water flows during storm events. This information facilitates the generation of an effective engineered stormwater plan for the site, which helps to ensure long-term site stability.”
The overarching goals of successful biodiversity strategies on solar sites are facilitating sustainable, environmentally responsible renewable energy projects, and managing risks associated with vegetation and stormwater. Plans developed with a scientific approach, incorporating principles of soil science and ecology as well as practical field experience, yield the most success.
Christina Hebb is a Storm Water Pollution Prevention Plan Preparer and vegetation senior manager for McCarthy Building Companies. As a certified professional soil scientist, she brings more than a decade of experience to her roles.