By Lucia Woo, Environmental Planner, LaBella Associates

In August of 2018, the Environmental Protection Agency (EPA) identified over 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. According to the data, there are 4,498 sites in New York State alone that have been prescreened and deemed suitable for renewable energy development.

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. Many developers have adopted strategies to cost-effectively provide engineering controls, as well as activity and land use limitations that allow for safe redevelopment.

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.

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 like 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.

Remediation history and ongoing monitoring responsibilities

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.

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.

Civil site design

Landfills and 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.

Identifying favorable interconnection opportunities within various utility territories 

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.

There are many different factors at play when evaluating the feasibility of a landfill or brownfield for solar development. Specialized knowledge of landfills and brownfields — as well as their regulatory requirements and proven engineering solutions — are key to successful development projects.

It is important to note that not all landfills and brownfields are created equal, and different challenges can arise for each project. The site constraints may vary widely depending on the size, topography, microclimate and remediation status. Some sites may contain hazardous waste that requires a health and safety plan and air monitoring for fieldwork that involve excavation. Others may have undergone extensive cleanup activities that preclude the sites from listing on the landfill or brownfield registry. Redevelopment plans need to be addressed on a site-by-site basis to design an economical and functional solar system that carefully balances risks with opportunities.

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Lucia Woo is an environmental planner at LaBella Associates, a full-service engineering firm with renewable energy service offerings from pre-development to post-construction phase. In support of environmental compliance and economic development, Lucia focuses on valuable resource identification and impact analysis for water bodies, wildlife, farmland, public health, environmental remediation, visual impacts, cultural resources and local law/zoning. For primarily solar projects, she performs critical issues analyses, develops permitting applications, and prepares independent engineering reports. Much of her recent attention has been dedicated to leveraging LaBella’s decades of brownfield and landfill expertise for opportune renewable energy site selection, permitting solutions, and engineering design assistance. She holds a Bachelor’s and Master’s in Environmental Science from Yale University.