What renewable energy developers need to know about siting projects on landfills and brownfields –

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.