DNREL
Transforming ENERGY
&EPA
United States
Environmental Protection
Agency
Coal Ash Disposal Sites and Opportunities for Solar Photovoltaic Development
EPA Publication #540-S-23-004
The Office of Land and Emergency Management's RE-
Powering America's Land Initiative is working with the
National Renewable Energy Laboratory (NREL)to evaluate
options for solar development on closed coal combustion
residuals (CCR) landfills and surface impoundments where
site conditions allow for safe development opportunities.
The purpose of this document is to identify closed CCR
units and provide Key Factors to be considered to identify
potential sites for solar photovoltaic (PV) development.
Using the Key Factors, suitability of these sites may be
further evaluated by analyzing site-specific characteristics,
such as site ownership, access to transmission, and current
redevelopment plans.
EPA recognizes the advantages of solar installations on top
of closed CCR landfills because of the potential to make
use of otherwise vacant land area and to connect directly
with existing grid infrastructure. Solar installations on
closed CCR units may have the potential to help manage
the costs of post-closure care and generate local revenue
through generation of clean electricity. In addition,
productive use of CCR units for the generation of clean
energy aligns with President Biden's January 2021
Executive Order1 and its goals of revitalizing coal-based
communities and pursuing environmental justice for
populations negatively impacted by coal mining.2
The U.S. EPA regulates coal ash disposal units under the
Resource Conservation and Recovery Act (RCRA). This
document focuses on closed coal ash disposal units
because they are the best situated for solar energy
development in the near future. All the disposal units
considered in this analysis are currently regulated under
RCRA and the majority are on-site at electric utilities.
Solar on CCR Disposal Sites
Rock River Solar Plant
This 2.25-MW solar installation in Beloit,
Wisconsin, was commissioned by Alliant Energy
in 2016 on a 17-acre capped coal ash landfill
site. Alliant buys the electricity from the facility
under a Power Purchase Agreement (PPA). The
facility uses a pre-cast concrete ballasting
system to anchor the solar system, minimizing
the impacts on the cap.
Orlando Utility Commission (OUC)
Community Solar Plant
This 13-MW community solar facility was
installed in 2017 on a 24-acre site that includes
a coal ash landfill. The solar installed on the
landfill uses a ballasted system, while the
remainder uses a traditional racking structure.
OUC buys electricity from the facility under a
PPA with a private developer.
. V
OUC's Community Solar Plant.
Photo courtesy of Orlando Utility Commission
1 Executive Order (E.O.) 14008: Tackling the Climate Crisis at Home and Abroad. January 27, 2021. https://www.whitehouse.gov/briefing-
room/presidential-actions/2021/01/27/executive-order-on-tackling-the-climate-crisis-at-home-and-abroad/.
2 E.O. 14008 Sections 218 and 220.
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Coal Ash Disposal Sites arid Opportunities for Solar Photovoltaic Development
Coal Combustion Residuals (CCR)
CCR, otherwise known as coal ash,3 is a byproduct of burning coal to generate electricity. According to the EPA,
coal ash is one of the largest industrial waste streams in the United States, generating on average more than a
100 million tons per year that require disposal. Coal ash contains many toxic chemicals harmful to human health
and the environment. EPA's 2015 rule establishes minimum requirements for the management of coal ash which
are intended to address the risks that could result from improper disposal.
Once generated, coal ash may be managed in ponds (where the ash is mixed with water) or landfills (where
the ash remains dry). EPA found that management in unlined ponds poses significant risk of contamination for
groundwater and surface water. As a result, the 2015 rule required all new ponds and landfills to be lined.
Since 2015, a growing number of facilities have converted to dry handling of coal ash, further reducing the
need for ponds.
As an alternative to disposal, CCR may be repurposed under specific RCRA rules to substitute for virgin raw
materials that would otherwise be used. Repurposing can take the form of encapsulated uses, in which coal ash
might be used in production of concrete and drywall, or un-encapsulated uses, in which the coal ash might be
used in construction of roadways or structural fill.4,5 Preliminary efforts to extract rare and critical earth
elements from the ash are also underway.
When a coal plant (or unit) closes, or is converted to natural gas, the utility ceases to generate coal ash as a
waste stream. However, all the coal ash that remains onsite will need to be dewatered (ponds only), capped, and
monitored to ensure the ash remains contained. The continued presence of waste onsite will limit the future
uses of the property to prevent the ash from being disturbed.
Capped coal ash ponds and landfills may present opportunities for solar PV development, particularly when
other productive uses for the land are limited. These sites are typically located near existing utility transmission
facilities which can reduce costs.
In 2022, the EPA's RE-Powering initiative identified 297
existing solar projects on capped landfills with an installed
capacity of 882 MW.7
While these sites aren't expressly identified as capped
coal ash landfills, the data highlights the opportunity that
exists and that many of the challenges associated with
installing solar on such sites have been overcome
Two examples of CCR sites successfully developed with
solar are the Rock River Solar plant in Beloit, Wisconsin,8
and the OUC Community Solar Plant in Orlando, Florida.9
Example of a ballasted racking system for solar.
Photo courtesy of NREL
3 Included in the definition of coal ash are the compounds in the exhaust flue gases captured by scrubbers.
4 These are some of the highest volume uses reported for the different types of coal ash, though other repurpose options exist as well.
5 Coal ash can also be sent to municipal solid waste {MSW) landfills and other off-site landfills that meet minimum requirements for
disposal of CCR; however, these off-site landfills are not the focus of this current effort.
6 https://www.libra.com/en/news-and-insights/greenwood-dedication-of-stanton-ouc-solar-farm/
7 https://www.epa.gov/re-powerine/re-powering-tracking-matrix
8 https://www.hdrinc.com/portfolio/rock-river-solar-project
9 https://www.publicpower.org/periodical/article/ouc-dedicates-solar-farm-former-landfill-site-more-solar-planned
However, capped coal ash ponds and landfills create unique challenges for development given that the integrity
of the caps must be maintained to keep the ash safely in place. As a result, solar installations represent a viable
opportunity to develop at these sites given various racking configurations (including ballasted) that can be used
for this technology.6
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Coal Ash Disposal Sites and Opportunities for Solar Photovoltaic Development
Site List
EPA identified 772 current and former coal combustion residuals (CCR) landfills and surface impoundments subject
to Office of Resource Conservation and Recovery regulations, of which 64 are confirmed to have already
completed closure with waste in place. These 64 units represent CCR from 49 coal-fired power plants across the
United States and are well situated for further renewable energy project development.10 This list of closed CCR
sites is organized by EPA Region. Ownership and redevelopment activity is based on publicly available information
only. A map showing the locations of total and closed CCR sites is provided at the end of this document.
EPA's RE-Powering America's Land Initiative (RE-Powering) has an established methodology to screen
contaminated sites for renewable energy suitability in the RE-Powering Mapper tool. However, given the general
lack of shading or other obstructions around these sites and the close proximity to utility transmission lines,
closed CCR sites would all screen positively for solar under this screening methodology. Therefore, the RE-
Powering Response Team compiled further information about each specific site to further inform stakeholder
engagement on project development activities, such as:
• Site characteristics, such as unit and site acreage, site proximity to nearest body of water, water body
type, distance to urban areas, road, utility transmission and substation interconnection;
• Existence of state policies that support or can be conducive to renewable energy projects;
• Information on annual site solar intensity (kWh/m2/day); and
• Environmental Justice (EJScreen) percentile rankings.
How these types of information may factor into selection of individual sites for a future feasibility study is
outlined in the table provided at the end of this document.
CCR sites may also be eligible for additional renewable energy incentives under the Energy Community Tax
Credit Bonus under the 2022 Inflation Reduction Act (IRA). The IRA defines energy communities as:
• A "brownfield site" (as defined in certain subparagraphs of the Comprehensive Environmental Response,
Compensation, and Liability Act of 1980 (CERCLA));
• A "metropolitan statistical area" or "non-metropolitan statistical area" that has (or had at any time after 2009)
o A 0.17% or greater direct employment or 25% or greater local tax revenues related to the extraction,
processing, transport, or storage of coal, oil, or natural gas; and
o An unemployment rate at or above the national average unemployment rate for the previous year; and
• A census tract (or directly adjoining census tract)
o In which a coal mine has closed after 1999; or
o In which a coal-fired electric generating unit has been retired after 2009
An updated Summary of Key Factors project development screening tool tailored to CCR disposal sites is attached to
standardize the collection of relevant site data and site factors for further study of one or more sites.
Next Steps
The RE-Powering Response Team is currently developing a stakeholder engagement outreach plan that will be
designed to engage with utilities, and other stakeholders that may be interested in optimizing land associated with
closed CCR units. The purpose of this outreach effort is to support further project development and feasibility work
based on the site characteristics outlined above at closed CCR sites in line with the RE-Powering Initiative's mission.
Report prepared by Jason Coughlin, William Tokash, and Gail Mosey, June 2023
Produced under direction of the U.S. Environmental Protection Agency (EPA) Office of Land and Emergency
Management by NREL under Interagency Agreement 16-2012-8.
10 EPA identified an additional 87 units that are confirmed to have completed closure through waste removal ("clean closure"). Because
these units no longer have any waste in place, there may be additional opportunities for site redevelopment beyond solar installation.
Therefore, these units were not the focus of this initial evaluation.
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Coal Ash Disposal Sites arid Opportunities for Solar Photovoltaic Development
The U.S. EPA regulates coal ash disposal units under the Resource Conservation and Recovery Act - RCRA in the United States. This map shows coal
ash disposal units that are operational and closed. All of the facilities are currently regulated under RCRA and are onsite at electric utilities.
Power Plants with Operational and Closed Coal Ash Disposal Units
Total Plant Acres
Hawai'i
Alaska
Puerto Rico/Virgin Islands
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Coal Ash Disposal Sites and Opportunities for Solar Photovoltaic Development
Key Factors for Renewable Energy Techno-Economic Feasibility Studies on Closed Coal Ash Disposal Site
These are Key Factors to consider when determining whether a coal ash disposal site should receive a techno-economic feasibility study for renewable
energy technology development. These sites could include both capped coal ash ponds and coal ash landfills.
* Key Factor categories of Environmental Justice, Techno-Economic, and Site Information Provider (item 1 under Other Site Considerations) will receive
priority consideration.
Prepared by: NREL
Prepared: 21-Nov-2021
Updated: April 2023
Name of Unit(s):
Address or Location of Unit(s):
Contact Person Completing Form (Name and Email):
Key Factor Categories
a. Environmental Justice (EJ)*
Environmental justice is the fair treatment and meaningful involvement of all people regardless of race, color, national origin, or income, with respect to the
development, implementation, and enforcement of environmental laws, regulations, and policies. This goal will be achieved when everyone enjoys:
• The same degree of protection from environmental and health hazards, and
• Equal access to the decision-making process to have a healthy environment in which to live, learn, and work. (Source: EPA)
Key Factors
Notes
Response/Input
1. Demographics
Demographics considered are income, presence of
minority, education level, linguistic isolation, and
individuals in household younger than age 5 and older
than age 65.
More detail on EJSCREEN demographic indicators is
included at the end of this table.
2. Environmental
indicators
These include measures related to Air, Waste, Water,
Dust/Lead Paint.
A complete list of indicators and sources is included at
the end of this table.
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Coal Ash Disposal Sites and Opportunities for Solar Photovoltaic Development
Note: EJ will be evaluated using EPA's EJSCREEN tool. EJSCREEN is an environmental justice mapping and screening tool that provides EPA with a nationally consistent
dataset and approach for combining environmental and demographic indicators. In situations where the data from EJSCREEN is outdated or does not apply (e.g., for
tribes) we will look at the same indicators with new or appropriate data. EPA should identify the community that would likely be impacted by the project within a
certain distance of the site, for example, a two-mile buffer around the site point. Indicators that fall within a 70th percentile category would be flagged as potential
for EJ concerns based on historical information. EPA will need to consider values across the state, region, and nation to compare indicators. For example, if a site in
Missoula, Montana, was in the 86th percentile of the state for linguistically isolated, but that indicator dropped significantly when compared to the Region (57th
percentile) or Nation (46th percentile) based on the fact that Montana as a state has very few linguistically isolated people, but Missoula (relatively speaking) has
more than most Montana areas, then it would be considered an area with EJ concerns.
b. Energy Equity (EE)
Energy equity is the fair distribution of benefits and burdens from energy production and consumption. (Source: The Partnership for Southern Equity)
We will look to encourage a feasibility study at sites that are under-represented for renewable energy.
Key Factors
Notes
Response/Input
1. Percent renewables
in the state/region/
area
These are examples of factors that can be reviewed and
considered as part of the assessment for Energy Equity.
Additional or different factors may be available and site
specific.
2. State Renewable
Portfolio Standard (RPS)
3. Access to clean energy
options from the utility
4. Access to power at a
reduced price
c. Techno-Economic Criteria*
Techno-economic criteria considers site characteristics that may determine the success of a renewable energy installation.
Key Factors
Notes
Response/Input
1. Renewable resource
availability
Threshold for each of these varies by renewable energy
technology.
These five factors are assessed using the RE-Powering
Mapper. Or when a site is not listed in the mapper, by
evaluating the site using comparable information.
2. Useable acreage
3. Slope
4. Proximity to
transmission
5. Proximity to roads
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Coal Ash Disposal Sites and Opportunities for Solar Photovoltaic Development
Key Factors
Notes
Response/Input
6. Shading and other
No substantial shading or other obstructions like
obstructions
buildings and vegetative conditions as assessed by
reviewing Google Earth images.
7. Electricity Price
Moderate electric rates as determined through U.S.
Utility Rate Database. Note that very low rates may make
the economics challenging for an economically viable
renewable energy project.
8. Proximity to
Generating electricity close to larger population centers
population centers
can be attractive as it creates a potential market for the
power. Being close to the end users of the electricity also
limits line losses due to transmission.
9. Proximity to
Alternative development options may exist if the site is
waterways/bodies of
located near or along a body of water. Water quality
water?
considerations also play a factor in determining the best
use of the site.
10. IRA Energy
Might the site meet Energy Community Tax Credit Bonus
Community Tax
applies a bonus of up to 10% (for production tax credits)
Credit Bonus
or 10 percentage points (for investment tax credits) for
eligible?
projects, facilities, and technologies located in energy
communities.
d. Coal Combustion Residuals (CCR) Disposal Sites - Specific Considerations
Given the unique nature of coal ash disposal sites, the following factors seek to identify considerations, risks, and opportunities specific to these
locations.
Key Factors
Notes
Response/Input
1. Site information
Is there someone sufficiently familiar with the site who
and data provider*
can and is willing to provide the necessary data and
information to conduct a feasibility study?
2. Utility
Who is the local utility, and do they own the CCR site?
Considerations
Have they been approached about a project on the site?
If so, are they receptive?
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Coal Ash Disposal Sites and Opportunities for Solar Photovoltaic Development
Key Factors
Notes
Response/Input
3. Ownership
Who owns the site? Will site ownership be a favorable or
complicating factor to re-developing the site with
renewable energy? A simple ownership structure paves
the way toward a more straightforward arrangement.
Does the site owner have previous experience with solar
energy facilities on its property?
4. Property Status
Are there on-going activities at the site (i.e., mining,
generation, or other)?
5. On-site Electricity
Demand
Is there a need for on-site electricity?
6. Status of Coal Ash
Disposal Site(s)
What is the status of the disposal site? Active, Inactive,
Scheduled for Closure, or Closed? What is the Closure
type? What is the regulatory status?
7. Champion forthe
Site (Driver)
Is there someone associated with the site who is driven to
make a renewable energy installation a reality? A
Champion is often a key determinant of success.
8. Community
Intention/Planning for
the Site
Is the community in favor of a renewable energy project
at the site or do they have another re-use in mind? What
re-use was planned for the site? A supportive community
can determine the success of a renewable energy project.
9. Zoning and
Permitting
Are there any specific code requirements or restrictions?
Is the site in an area already zoned for a renewable energy
installation? Zoning already in place that permits a
renewable energy installation can make the permitting
process less complex. What agencies have jurisdiction
over the site?
10. Complexity of the
Site
Are there any other complexities, site liabilities, or other
risks not already captured that may be associated with the
site?
11. Other Sensitivities
with the Site
Are there any other sensitivities not already captured that
may be impactful to the success of the project?
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Coal Ash Disposal Sites and Opportunities for Solar Photovoltaic Development
EJSCREEN Demographic Indicators
Demographics
Low Income:
Household income is less than or equal to twice the federal "poverty level."
Minority:
The number or percentage of individuals in a block group who list their racial
status as a race other than white alone and/or list their ethnicity as Hispanic
or Latino.
Education:
The number or percentage of people age 25 or older in a block group whose
education is short of a high school diploma.
Linguistic isolation:
The number or percentage of people age 25 or older in a block group whose
education is short of a high school diploma.
Individuals under age 5:
The number or percentage of people in a block group under the age of 5.
Individuals over age 64:
The number or percentage of people in a block group over the age of 64.
Source:
American Community Survey (ACS) 5-year summary file, which the U.S. Census
Bureau compiles yearly.
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Coal Ash Disposal Sites and Opportunities for Solar Photovoltaic Development
EJSCREEN Tool Environmental Factors
Key Medium
Indicator
Details
Source
Data
Year
Air
National-Scale Air Toxics Assessment
(NATA) air toxics cancer risk
Lifetime cancer risk from inhalation of air toxics
EPA NATA
2014
Air
NATA respiratory hazard index
Air toxics respiratory hazard index (ratio of
exposure concentration to health- based
reference concentration)
EPA NATA
2014
Air
NATA diesel PM
Diesel particulate matter level in air, ng/m3
EPA NATA
2014
Air
Particulate matter
PM2.5 levels in air, ng/m3 annual average
EPA, Office of Air and
Radiation (OAR) fusion of
model and monitor data
2017
Air
Ozone
Ozone summer seasonal average of daily
maximum 8- hour concentration in air in parts
per billion
EPA, OARfusion of model and
monitor data
2017
Air/other
Traffic proximity and volume
Count of vehicles (AADT, average annual daily
traffic) at major roads within 500 m, divided by
distance in meters(not kilometers)
Calculated from 2017 U.S.
Department of
Transportation (DOT) traffic
data, retrieved 2019
2017
Dust/lead paint
Lead paint indicator
Percent of housing units built pre-1960, as
indicator of potential lead paint exposure
Calculated based on
Census/American Community
2014-2018
Survey (ACS) data, retrieved
2020
Waste/air/water
Proximity to Risk Management Plan
(RMP) sites
Count of RMP (potential chemical accident
management plan) facilities within 5 km (or
nearest one beyond 5 km), each divided by
distance in kilometers
Calculated from EPA RMP
database, retrieved
04/05/2020
2020
Waste/air/water
Proximity to Hazardous Waste
Facilities
Count of hazardous waste facilities (TSDFs and
LQGs) within 5 km (or nearest beyond 5 km),
each divided by distance in kilometers
TSDF data calculated from EPA
2020
RCRAInfo database, retrieved
07/06/2020
Waste/air/water
Proximity to National Priorities
List (NPL) sites
Count of proposed or listed NPL—also known as
superfund—sites within 5 km (or nearest one
beyond 5 km), each divided by distance in
kilometers
Calculated from EPA
CERCLIS database,
retrieved 04/22/2020
2020
Water
Wastewater Discharge Indicator
(Stream Proximity and Toxic
Concentration)
RSEI modeled Toxic Concentrations at stream
segments within 500 m, divided by distance in
kilometers
Calculated from RSEI modeled
2020
toxic concentrations to stream
reach segments, created
07/06/2020
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