Two years ago, the Environmental Protection Agency (EPA) identified more than 80,000 brownfields and municipal solid waste landfills across the country that could be used for renewable energy facilities. This screening included maps depicting locations of EPA tracked sites and their potential for supporting renewable energy generation.
Clean energy development, especially when constructed on underutilized sites like landfills and brownfields, can present economic recovery opportunities for many U.S. communities. Many states offer financial incentives for these developments like investment tax credits, state tax credits, cash rebates, or even performance-based incentives that, when coupled with Brownfield Cleanup Programs, can provide enhanced financial benefits for renewable energy developers. On the local level, many communities are more willing to host renewable projects as they can provide a new source of revenue such as payments in-lieu of taxes (PILOTS).
With many of the country’s brownfields, closed landfills, and underutilized former industrial complexes ripe for redevelopment, there are some important factors developers should consider when reviewing ideal sites for solar development.
1. Remediation history
It is imperative to identify, evaluate, and preemptively address the existing and future environmental issues and liabilities associated with these impaired properties that may contain hazardous waste. Environmental due diligence is key to accomplishing these objectives by building a thorough understanding of the site’s contamination history, governing regulatory program requirements, and ongoing environmental management and monitoring obligations.
Performing an All Appropriate Inquiry (AAI) Phase I Environmental Site Assessment (ESA) prior to land lease or purchase is an effective initial step. The AAI ESA process should be performed in accordance with a national standard established by the American Society for Testing and Materials (ASTM) to ensure consistency in terms of the depth and breadth of due diligence completed.
Information garnered from the ESA process should also be considered when negotiating lease or purchase terms to ensure that the developer is properly indemnified from potential environmental liabilities associated with the site. Lastly, defining all ongoing site management and monitoring requirements can put a developer in a position to establish the owner’s continued accountability and financial responsibility for compliance with these requirements in the lease or purchase agreement.
2. Landfill/brownfield cover type and post-closure status
Landfills and other disturbed sites such as brownfields present unique challenges when placing structures on top of them. Landfill capping systems are mainly engineered to isolate the buried waste from the environment, provide a stable barrier to rainfall, and minimize the escape of landfill gasses. Brownfields and other formerly used industrial properties may have been filled with heterogeneous materials, which present stability issues for future construction and may have been capped as part of regulatory closure requirements.
It is important when considering solar development on top of these sites to review any available closure and post-closure care plans. Landfills and sometimes brownfield caps are constructed of several different layers of materials such as low permeability clays, geomembranes and topsoil.
Poorly designed caps can, over time, lead to surface water infiltration that can cause uneven settlement and produce a hummocky pattern on the surface. Soil settlement analysis should also be reviewed to document historical settlement, as well as predict potential for future settlement. If no information on how the cap was constructed is available, an intrusive investigation via borings or trenches can be done to document cap construction methods and thickness, which may include geotechnical testing of soil samples.
3. Ecological considerations
Often, solar developers will overlook wetland and ecological concerns for their landfill or brownfield sites, when in reality, these should be among the first considerations at the beginning of the development process. Both landfills and brownfield sites can have cap issues, such as settling caused from lack of proper maintenance that can create jurisdictional wetlands over time.
In addition, some states regulate upland buffer areas adjacent to wetlands to protect the valuable upland habitat surrounding wetlands. These regulated buffer areas can (and often do) impede on the developable area within a landfill or brownfield. These sites can also provide unique and protected habitat for endangered or threatened species such as migratory birds, waterfowl, grassland birds, butterflies, and dragonflies.
Wetland and ecological regulations differ from state to state and are forever changing at the federal level. As such, it is best practice to involve the right experts to properly address potential wetland and ecological concerns on a landfill or brownfield site to understand any possible project implications a site may have before proceeding.
4. Civil site design
Landfills and some brownfields have several features that require deviations from standard civil engineering design for solar arrays. For instance, landfills are typically capped with liners and soils that cannot be disturbed with a pile-driven racking system. Instead they require a ballasted system, where the solar panels are held in place by concrete blocks — light enough to prevent unacceptable settlement, but heavy enough to prevent movement or uplift of the solar tables from wind and snow.
Accurate slope analysis is critical, especially for landfills in defining the buildable area since ballasted arrays are suited to more gentle slopes than their pile-driven counterparts. Landfills also typically have monitoring wells and gas vents across the site, for which the solar site design needs to provide adequate clearance for long-term maintenance of the landfill.
When these contaminated sites go through the closure process, stormwater management on a site-wide level should be developed to direct stormwater away from capped areas and to outfalls. This is a benefit since stormwater management has already been considered and might require little to no adjustments for the development of a solar array and associated infrastructure.
5. Interconnection opportunities
Recognizing and evaluating capacity and suitability for interconnection to the utility distribution system is an essential factor in the assessment of siting solar arrays. In comparison to rural greenfield locations, brownfield sites are typically vacated facilities that were large net energy consumers and in the majority of cases comprise an existing electrical service of significant capacity and infrastructure to reduce potential interconnection costs.
Depending on location of the site, utility distribution system resilience is a potential prospect to interconnect a larger capacity distributed energy resource. In many cases, a landfill site will contain a dedicated electrical distribution service that can be assessed as a feeder for a dedicated interconnection.
Evaluating contaminated or former industrial sites for solar development is a multi-faceted challenge that requires specialized knowledge of landfills and brownfields. Developers working on underutilized sites must come fully equipped to evaluate all environmental risks, recognize any remedial or monitoring requirements, and propose a solar design that will be protective of the existing cover system. They also should have a deep understanding of various financial incentives available from both brownfield redevelopment and renewable energy development angles.
Not all redevelopments come with the same challenges, and there are many benefits to reusing contaminated land for renewable energy, such as: greater community support, protection of open space and valuable farmland and possibly shorter project approval timeframes.
Given the availability of these sites across the country and the financial benefits that could accompany them, repurposing contaminated sites for solar energy generation is a win-win for both communities and developers alike.