The Use of
The Use of
Soil Amendments for Remediation,
Soil Amendments for Remediation,
Revitalization, and Reuse
Revitalization, and Reuse
Foreword
The U.S. Environmental Protection Agency (EPA) hosted a three-day Soil Amendments
for Ecological Revitalization Workshop in August 2006 to assess known problems and
potential solutions related to the use of soil amendments in revitalizing ecosystems on
contaminated lands. This paper is a product of that workshop. Soil amendments of
interest consist of waste residuals such as municipal biosolids, animal manures and litters,
sugar beet lime, wood ash, coal combustion products, log yard waste, neutralizing lime
products, and a variety of composted agricultural byproducts, as well as traditional
agricultural fertilizers. This in situ soil remediation technology can be applied to
Superfund and brownfields sites, large and small mining sites, and other sites with
disturbed or degraded soils. Appropriate application of this technology has the potential
to protect human health and the environment by reducing contaminant bioavailability and
mobility at a considerably lower cost than other available options. This, in turn, allows
for revitalization and reuse of these lands.
Disclaimer
This paper was prepared by the EPA Office of Superfund Remediation and Technology
Innovation (OSRTI), with support under Contract Number 68-W-03-038. Although it has
undergone EPA and external review by experts in the soil amendments field, information
in this paper also was derived from a variety of sources, some of which have not been
peer-reviewed. This document does not reflect Agency policy, nor is it a regulation.
Thus, it does not change or substitute for any legal requirements. It also is not legally
enforceable, and does not confer legal rights or impose legal requirements upon any
member of the public, states, or any other federal agency. For further information, contact
Ellen Rubin, EPA/OSRTI, at 703-603-0141 or, by email, at [email protected].
A PDF version of this paper is available for viewing or downloading at the Hazardous
Waste Cleanup Information System (Clu-In) website at www.clu-in.org/pub1.cfm. A
limited number of printed copies are available free of charge and may be ordered via the
web site, by mail, or by fax from:
EPA/National Service Center for Environmental Publications
P.O. Box 42419
Cincinnati, OH 45242-2419
Phone: 513-489-8190 or 800-490-9198
Fax: 513-489-8695
Cover and document photos courtesy of Dr. Sally Brown, University of Washington;
William Toffey, Philadelphia Water Department; City of Princeton, IN; City of
Shoreview, MN; College of Tropical Agriculture and Human Resources, University of
Hawaii at Mānoa.
i
Acknowledgements
EPA would like to thank all the individuals and organizations that contributed their time,
thought, and effort to the development of this paper. Without their efforts, the paper
would not have come to fruition. The core group includes:
Harry L. Allen, IV, U.S. EPA
Dr. Sally Brown, University of
Washington
Dr. Rufus Chaney, U.S. Department of
Agriculture
Dr. W. Lee Daniels, Virginia Tech
Dr. Charles L. Henry, University of
Washington
Dennis R. Neuman, Montana State
University
Dr. Ellen Rubin, U.S. EPA
Jim Ryan, U.S. EPA
William Toffey, Philadelphia Water
Department
EPA also would like to thank all reviewers and collaborators to this work group:
Harry Compton, U.S. EPA
Ashfaq Sajjad, U.S. EPA
Susan Mooney, U.S. EPA
Mark Sprenger, U.S. EPA
John Oyler, Consultant
Lakhwinder Hundal, Metropolitan Water Reclamation District of Greater Chicago
Heather Henry, National Institute of Environmental Health Sciences
Development of this paper was supported by the U.S. EPA Technology Innovation and
Field Services Division and the U.S. EPA Land Revitalization Office.
ii
Acronyms and Abbreviations
ARARs Applicable or Relevant and Appropriate Requirements
BMP Best management practice
CAFO Concentrated animal feeding operations
CCA Chromated copper arsenate
CCE Calcium carbonate equivalent
CCP Coal combustion products
CERCLA Comprehensive Environmental Response, Compensation, and Liability
Act (Superfund)
C:N Ratio of carbon to nitrogen
Ca:Mg Ratio of calcium to magnesium
Cu:Mo Ratio of copper to molybdenum
EPA U.S. Environmental Protection Agency
FBC Fluidized-bed combustion
FGD Flue gas desulfurization
NA Not applicable
NAS National Academy of Science
OM Organic matter
PAH Polycyclic aromatic hydrocarbon
PCB Polychlorinated biphenyl
PCP Pentachlorophenol
% solids A weight measurement of the amount of solids and liquid in a sample
POTW Publicly Owned Treatment Works
RCRA Resource Conservation and Recovery Act
ppt Parts per thousand
PWD Philadelphia Water Department
SAR Sodium adsorption ratio
SMCRA Surface Mining Control and Reclamation Act of 1977
t/ac Tons per acre
TEQ Toxic equivalent
TPM Technical performance measure
USACE U.S. Army Corps of Engineers
VDMME Virginia Department of Mines, Minerals and Energy
WTR Water treatment residuals
iii
TABLE OF CONTENTS
1.0 INTRODUCTION.................................................................................................... 1
1.1 Background ............................................................................................... 2
1.2 How the Paper Is Organized.................................................................... 3
2.0 TYPES OF PROBLEMS ADDRESSED BY SOIL AMENDMENTS ................ 5
2.1 Exposure Pathways and Adverse Effects................................................ 8
2.1.1 Contaminant Bioavailability/Phytoavailability Problems .................... 8
2.1.1.a Phytotoxicity........................................................................................ 8
2.1.1.b Food Chain Contamination................................................................ 9
2.1.1.c Ingestion of Contaminated Soil ......................................................... 9
2.1.1.d Runoff and Leaching .......................................................................... 9
2.1.2 Poor Soil Health/Ecosystem Function Problems.................................. 10
2.1.2.a High or Low pH ................................................................................ 10
2.1.2.b Sodicity............................................................................................... 10
2.1.2.c Salinity ............................................................................................... 11
2.1.2.d Soil Physical Properties .................................................................... 11
2.1.2.e Nutrient Deficiencies/Low Soil Fertility.......................................... 11
2.2 Interactions .............................................................................................. 12
2.3 Solutions................................................................................................... 12
3.0 TYPES OF SITES WHERE AMENDMENTS CAN BE USED ....................... 13
3.1 Hard Rock Mining Sites ......................................................................... 13
3.2 Coal Mining Sites .................................................................................... 14
3.3 Smelting and Refining Sites ................................................................... 14
3.4 Construction and Mixed-Contaminant Sites........................................ 14
3.5 Other Sites ............................................................................................... 14
4.0 TYPES OF SOIL AMENDMENTS ..................................................................... 17
4.1 Organic Soil Amendments ..................................................................... 17
4.2 Soil Acidity/pH Soil Amendments ......................................................... 24
4.3 Mineral Soil Amendments and Conditioners ....................................... 25
4.4 Application Rates .................................................................................... 26
5.0 LOGISTICS AND OTHER CONSIDERATIONS ............................................. 28
5.1 Availability............................................................................................... 28
5.2 Transportation ........................................................................................ 28
iv
5.3 Storage ..................................................................................................... 31
5.4 Application............................................................................................... 31
5.5 Blending ................................................................................................... 33
5.6 Public Considerations............................................................................. 34
5.7 Costs ......................................................................................................... 35
6.0 REVEGETATION OF AMENDED SOIL .......................................................... 38
6.1 Considerations with Site Revegetation.................................................. 38
6.2 Native Plants............................................................................................ 39
7.0 PERMITTING AND REGULATIONS ............................................................... 40
8.0 BENEFITS OF USING SOIL AMENDMENTS................................................. 42
9.0 MONITORING AND SAMPLING AMENDED SITES.................................... 43
10.0 CONCLUSIONS .................................................................................................... 44
Endnotes........................................................................................................................... 45
Other Resources .............................................................................................................. 49
List of Tables
Table 1. Types of Problems Addressed by Soil Amendments
Table 2. Types of Sites Where Soil Amendments Can Be Used
Table 3. Types of Soil Amendments
Table 4. Logistics and Other Considerations in Using Soil Amendments
Table 5. Comparison of Different Application Systems Used in Remediation
Table 6. Regulatory Requirements for Selected Soil Amendments
List of Figures
Figure 1. The Role of Soil Amendments and Plants in the Amendment of
Metal-Contaminated Soil
v
1.0
INTRODUCTION
Hundreds of thousands of acres of disturbed and contaminated land scar this country‘s landscape.
Some of these lands are in remote locations making cleanup very difficult. Others have minimal
funds for cleanup or are so large that cleanup becomes economically impractical. There is a need
for cost-effective, low energy technologies that can be applied at these sites. This paper provides
information on the use of soil amendments, a cost effective in situ process for remediation,
revitalization, and reuse of many types of disturbed and contaminated landscapes.
This paper focuses on amendments that are generally
residuals from other processes and have beneficial
properties when added to soil. Commonly used
amendments include municipal biosolids, animal
manures and litters, sugar beet lime, wood ash, coal
combustion products such as fly ash, log yard waste,
neutralizing lime products, composted biosolids, and a
variety of composted agricultural byproducts, as well as
traditional agricultural fertilizers. Applied properly, soil
amendments reduce exposure by limiting many of the
exposure pathways and immobilizing contaminants to
limit their bioavailability. The addition of amendments
restores soil quality by balancing pH, adding organic
matter, increasing water holding capacity, re-establishing microbial communities, and alleviating
compaction. As such, the use of soil amendments enables site remediation, revegetation and
revitalization, and reuse.
assist regulators, consultants,
other stakeholders in
understanding the principles of
remediating and revegetating
contaminated sites and to
this alternative to revitalize
and reuse contaminated land.
The purpose of this paper is to
site owners, neighbors, and
soil amendment application for
encourage widespread use of
Superfund sites, large and small mining sites, landfills, and industrial sites such as refineries,
smelters, foundries, milling and plating facilities, and other sites with contaminated or disturbed
soils exhibit a variety of problems that often can be addressed effectively and directly through
the use of soil amendments. These problems include:
• The toxicity
of various soil contaminants, principally metals, can be harmful to plants, soil
animals, and soil microbial populations.
• A higher- or lower-than-normal soil pH range can cause soil infertility and cause soil metals
(low pH) and oxyanions (e.g., arsenate at high pH) to go into solution.
• Excess sodium (Na)
can cause toxicity to plants, a breakdown of soil physical structure, and
dispersion, which limits root growth, aeration, and water infiltration through the soil.
• Excess salts
(e.g., sulfates and chlorides) limit plant rooting and water and nutrient uptake.
• Changes in soil physical properties
, such as density, aggregation, and texture, can reduce
water infiltration and the moisture-holding capacity of the soil and stifle efforts to revegetate
a site.
1
• Deficiencies in essential micronutrients like Zn and Mn can lower soil fertility
; however, the
same elements can be toxic at higher concentrations. In some cases, soil treatments to reduce
phytotoxicity of one contaminant may reduce the phytoavailability of another essential
element. Adding that nutrient as a companion fertilizer can prevent the deficiency due to the
soil treatment.
Although soil amendments and associated enhancements in microbial activity can be used to
address volatile and semivolatile contaminants that have left sites barren of vegetation, this paper
focuses on the use of amendments on sites dominated by inorganic contaminants.
1.1 Background
The bioavailability of contaminants poses a health risk to animals and humans who may be
exposed to contaminated sites. Possible exposure pathways include ingestion of contaminated
soil or water from the site, direct contact with contaminated soil, inhalation of contaminants
adhered to dust in the air, and ingestion of food items (i.e., plants or animals) that have
accumulated contaminants from exposure to contaminated soil or water. Managing the risks
posed by contaminants at a site involves understanding the possible pathways and applying
appropriate remedial measures to mitigate, treat, or remove sources (Ref: 46).
Figure 1 illustrates how soil amendments can help mitigate exposure to contaminants. With the
addition of appropriate soil amendments, metals in the amended area are chemically precipitated
and/or sequestered by complexation and sorption mechanisms within the contaminated substrate.
Metal availability to plants is minimized, and metal leaching into groundwater can be reduced. In
certain cases, metal availability below the treated area is also reduced.
Active plant growth is an integral part of the soil amendment process; vegetation relocates water
in the root zone and can transpire several hundred thousand gallons of water per acre during the
greatly reducing surface water runoff and
sediment loss to receiving streams. Plants
y
wind.
Plants stabilize the landscape from erosion,
also reduce erosion caused b
growing season. This relocation has a
significant impact on the volumes of
water and metals that are able to move
toward the groundwater. The selection of
plant species for amended soil is based on
the availability of seed or seedlings, their
ability to establish and grow in the newly created root zone, the species‘ inability to translocate
(move) metals from roots into the above-ground biomass of the plant, and land use and
management considerations.
Because soil amendments have a wide range of uses, the knowledge presented in this paper may
be applied to various situations ranging from time-critical contaminant removal actions to
ecological revitalization projects. Practitioners can use soil amendments to —jump-start“
ecological revitalization at significant cost savings compared to traditional alternatives. In
addition to eliminating exposure pathways and/or immobilizing metals and other contaminants,
recycling these residual organic byproducts, instead of disposing of them, results in significant
ecological benefits for the hydrosphere and atmosphere.
2
Figure 1. The Role of Soil Amendments and Plants in the Amendment of
Metal-Contaminated Soil (Ref. 3)
1.2 How the Paper Is Organized
This paper is divided into the 10 sections shown below. These sections are structured to expand
on information provided in the quick-reference tables that begin Sections 2, 3, 4, and 5 and
present additional information about the use of amendments in a logical order. Each quick
-
reference table can be used independently, however, depending upon the user‘s primary focus.
• Section 1, Introduction, provides an overview of the soil amendments issue and describes the
organization of the paper.
• Section 2, Types of Problems Addressed by Soil Amendments, describes how soil
amendments can be used to address toxicity, pH, salinity (excess salts), sodicity (excess
sodium), poor soil physical properties, and nutrient and fertility issues.
• Section 3, Types of Sites Where Soil Amendments Can Be Used, discusses hard rock mining
sites, coal mining sites, refining and smelting sites, and construction sites and includes
information on individual contaminants that may be present, the problems associated with
them, and options for remediating them.
• Section 4, Types of Soil Amendments, describes soil amendments suitable for use in
remediating and restoring sites, including their availability, potential uses, and issues
regarding public acceptance issues, costs, advantages, and disadvantages.
3
• Section 5, Logistical and Other Considerations, focuses on a range of issues (e.g., site
characteristics and operations, issues related to the public, and cost) that may need to be
addressed in using soil amendments for remediation and revitalization at a specific site.
• Section 6, Revegetation of Amended Soil, provides helpful information about planning for
and implementing site revegetation efforts.
• Section 7, Permitting and Regulations, reviews the regulatory requirements and authorities
that may pertain to the use of soil amendments to remediate and revitalize sites.
• Section 8, Benefits of Using Soil Amendments, summarizes the environmental, human
health, economic, and other advantages of soil amendments in remediating and revitalizing
sites.
• Section 9, Monitoring and Sampling Amended Sites, describes an ongoing effort to delineate
technical performance measures for use in verifying the effectiveness of soil amendments.
• Section 10, Conclusions.
In addition, this paper provides references to documents and Internet resources used in the
preparation of this document, other relevant references, and useful links for obtaining additional
information.
4
2.0
TYPES OF PROBLEMS ADDRESSED BY
SOIL AMENDMENTS
Soil amendments can be used to address two primary categories of problems at contaminated
sites: (1) contaminant bioavailability/phytoavailability and (2) poor soil health and ecosystem
function. Solutions to the specific types of problems within these categories depend on the nature
of specific contaminants, known exposure pathways and adverse effects, and specific
interactions involved with the various recommended soil amendments and other contaminants
(see Table 1).
Table 1: Types of Problems Addressed by Soil Amendments
Exposure Pathways and
Adverse Effects
Interactions Solutions
Contaminant Bioavailability
/Phytoavailability Problems
Aluminum (Al)
Toxicity (inorganic)
Phytotoxicity
Runoff
Leaching
Low pH
2
= more
toxic; Low P = more
toxic; High calcium
(Ca) = less toxic
Raise pH greater than 6.0, add
OM and P; add gypsum or
other high soluble Ca source
Arsenic (As) Soil Ingestion
Runoff
Leaching
High pH
2
= more
toxic; High P = more
soluble
Add organic matter (OM) and
adjust pH to between 5.5-6.5
Borate (BO
3
3
-
) Phytotoxicity Low and High pH
2
=
more toxic
Add iron oxide and acidify
(pH between 6.0-7.0)
Cadmium-to-Zinc Ratio
(Cd:Zn)
1
Food chain High ratio = greater
bioavailability (risk)
of Cd
Add Zn to reduce the Cd:Zn
ratio
Chromate (CrO
4
2
-
) Phytotoxicity
Runoff
Leaching
High pH
2
= more
toxic
Add reductants, e.g., OM,
biosolids; also acidify to less
than 6.5
Copper (Cu) Phytotoxicity
Runoff
Leaching
Aquatic receptors
Low pH
2
= more
toxic; low OM =
more toxic
Raise pH (6.0-7.0), add P,
OM, and sorbents
Lead (Pb) Soil ingestion Low phosphorus (P)
= more toxic
With no As present, raise pH
to 6.0 or greater; with As
present, raise pH to 5.5-6.5;
add P, and iron oxide
Manganese (Mn) Phytotoxicity
Runoff
Leaching
Low pH
2
= more
toxic
Raise pH greater than 7.0
Molybdenum (Mo) Food chain
Cu:Mo ratio
High pH
2
= more
toxic; Low Cu =
more toxic
Acidify (pH between 5.5- 6.5)
and add Cu
5
Exposure Pathways and
Adverse Effects
Interactions Solutions
Nickel (Ni) Phytotoxicity Low pH
2
= more
toxic; low P = more
toxic
Raise pH (7.0-8.0), add P,
OM, and sorbents
Selenium (Se) Food chain
Runoff
Leaching
High pH
2
= more
toxic
Acidify (pH between 5.5-6.5)
Sulfate (SO
4
2
-
) Phytotoxicity to salt effects NA Irrigate soil
Zinc (Zn) Phytotoxicity Low pH
2
= more
toxic; low P = more
toxic
Raise pH (7.0-8.0), OM, and
sorbents
3
, e.g., iron and
manganese oxides, WTR
4
Toxicity (organic)
Polycyclic Aromatic
Hydrocarbon (PAH)
Soil Ingestion Low OM
5
= more
bioavailable
Add OM and tillage
Polychlorinated Biphenyl
(PCB)
Soil Ingestion Low OM
5
= more
bioavailable
Add OM and tillage
Poor Soil Health/Ecosystem Function
Problems
High or Low pH
Active Acidity (as
measured directly in a
water:soil mixture)
Runoff
Leaching
Controls metal
solubility and
microbial activity;
increases metal
availability
6
Add lime and/or other alkaline
soil amendments
Alkalinity Anion solubility and metal
micronutrient availability
See Mo, Se, As listed
above
Add acid equivalent
Potential Acidity (total acid
production capacity with
time; largely from
unreacted sulfides)
Runoff
Leaching
Metal and salt evolution and
associated phytotoxicity
Similar to active
acidity (above)
6
Estimate total lime demand
and add 1.25 to 1.5 times the
demand
Sodicity or Salinity
Electrical Conductivity Phytotoxicity, plant water
stress, nutrient uptake
imbalances
High Na = more toxic Irrigate; OM may help
Sodium (Na) Phytotoxicity
Sodicity
7
High SAR = high soil
dispersion
Add any Ca:Mg-rich
material
1
; OM
Changes in Soil Physical Properties
Aggregation Rooting and moisture-
holding capacity
Low OM
4
= poor
aggregation
Add OM and gypsum
Bulk Density Limits rooting and
infiltration
Low OM
4
= high
bulk density
Add OM and deep tillage
Texture Moisture-holding and soil
strength
High clay = poor
tilth; High sand = low
moisture-holding
Modify with mineral soil
amendments and add OM
6
Exposure Pathways and Interactions Solutions
Adverse Effects
Nutrient Deficiencies and Low Fertility
High Calcium-to-
Magnesium Ratio (Ca:Mg)
1
Induced Mg deficiency in
plants; Can reduce growth
or kill plants
Very strong acidity
causes loss of
exchangeable cations
(Ca, K, Mg), which
makes Mg deficiency
more likely; Addition
of only calcitic
limestone to acidic
site can more easily
induce Mg
deficiency. Dolomitic
or Mg-containing
calcitic limestones do
not cause this Mg
deficiency risk
Add Mg
High C:N
1
ratio Limits nitrate availability to NA Add N or high-N soil
plants/limits growth amendments, e.g., manures,
biosolids
High N Nitrate leaching;
NA Add cellulosic carbon, e.g.,
Suppresses legumes and
sawdust, rice hulls, or wood
conifers
chips
High P Runoff of soluble P or
movement of soil particles
to water can cause
eutrophication; Limits Pb
bioavailability; Reduces Cu,
Cd, Ni, Zn
Increases As
availability
9
Add Al or Fe to acid soils or
Ca to alkaline soils to bind P;
Drinking Water Residuals may
be an effective source of Al or
Fe for this purpose
phytoavailability; Supports
legumes
Low Carbon-to-Nitrogen
Ratio (C:N)
1
Runoff
Nitrate leaching
NA Add cellulosic C e.g., sawdust,
rice hulls, or wood chips
Low Nitrogen (N) Limits growth High C:N
1
ratio = Add N and/or high-nitrogen
low N availability OM
Low P Limits growth Increases metal
availability
8
Add P or high-P organic soil
amendments
Manganese (Mn) Limits growth NA Add Mn or lower pH to less
deficiency than 6.0
1
Ratios:
C:N ratio = 15-40:1
Ca:Mg ratio = no greater than 20:1
Cd:Zn = <0.015 on weight basis
Cu:Mo = >2:1 for cattle and >5:1 for sheep. Recommended Cu levels in feed/forages are 8 to 11 mg/kg.
This amount should provide adequate copper if the diet does not exceed 0.25 percent sulfur and 2 mg
Mo/kg diet. In a Cu-deficient diet, Mo can be toxic. Sulfur status of feed and forage also is a co-factor (Ref.
30, 26). Cu deficiency in cattle and sheep is easy to correct with mineral salt licks or supplements.
2
Low pH = <5.5; High pH = >8
3
WTR = water treatment residuals
4
Target OM% for soil = >2.5%; target OM% for contaminated soil = >5%
7
5
The term sorbents, as used here, describes materials that can hold on to or sorb different contaminants. There are a
range of these materials, with different materials better suited for absorption of different contaminants. Some
examples of sorbents include charcoal for different organic contaminants, water treatment residuals for excess P
and some heavy metals, and high surface area iron oxides for heavy metals including Pb and As.
(Refs. 6, 13, 14, 58)
6
All severely acidic soil systems are detrimental to plant growth because of Al and Mn toxicity. In cases where
metal contaminants are present, acidity will increase metal availability. The toxicity of Al may be corrected by
adding residuals high in cations such as Mg, Ca and K, even if these are in a form that does not increase soil pH. It
is important in remediating these types of systems to make sure that sufficient Mg is available for plants. In cases
where metal contaminants are present, acidity will increase metal availability.
7
A measure of the excess sodium in a soil which imparts a poor physical condition to the soil. (Ref. 31)
8
In cases where metal contaminants are present, insufficient P increases metal availability. Metals that are critical
include Pb, Zn, and Cd. Agronomic tests for P availability to crops are useful to determine P status in soil where
low P is suspected.
9
High P is a concern in cases of As contamination. Since P and As are chemically related, high P increases As
availability. Tests, including water soluble P and Fe strip P, are available to determine P status in cases where high
P is suspected. For more information, see http://www.sera17.ext.vt.edu.
2.1 Exposure Pathways and Adverse Effects
2.1.1 Contaminant Bioavailability/Phytoavailability Problems
Although chemicals may be present in soils, not all of them may be bioavailable or
phytoavailable. Bioavailability and phytoavailability are terms used to describe the degree to
which contaminants are available for absorption or uptake by and interaction with the
metabolism of organisms that are exposed to them. These processes are quantifiable through the
use of multiple tools (Ref. 23, 33). Several types of exposure pathways and/or adverse effects
may need to be addressed to solve bioavailability and/or phytoavailability problems.
2.1.1.a Phytotoxicity
Harmful substances can accumulate in plant tissue to a level that affects its growth and
development (Refs. 2, 8). Metal toxicity can occur when a metal (often a necessary plant
nutrient) is present in high concentrations. Toxicity becomes more severe at acidic soil pH or
when coupled with other nutrient
deficiencies.
Certain metals are more toxic to plants than
they are to humans. An example of this is Zn.
It will kill plants in concentrations that are too
low to cause any negative human health
effects. Some metals are necessary nutrients
for animals. Plants with elevated
concentrations of these nutrient metals
generally will not cause detrimental effects to
the animals that ingest them. These elements,
even when essential for plants, can cause
plant toxicities. Other metals, such as Pb, are
8
generally not toxic to plants but can cause negative human health effects when soil is ingested
directly. Most metals that are a threat to humans and wildlife are not necessary nutrients. For the
majority of these (including Cr, As, and Hg) uptake by plants is minimal. The exception is Cd,
due to its chemical similarity to Zn, a necessary nutrient. Cadmium is the most important
example of a metal that is toxic to plants only at very high concentrations. Plants can take up Cd
into foliar tissue. Foliar concentrations of Cd can be high enough to cause harm to wildlife
before plants show any toxicity symptoms. Plant tissue tests can help to determine if there is
metal toxicity. Commercial labs and land grant universities can generally do plant tissue
analysis. Grab samples from young leaves of several plants in a field can be combined for
analysis. They should be washed in soapy water, rinsed and air-dried before being sent to a lab.
While toxic concentrations of metals in the above-ground portion of plants, including leaves and
stems, vary across plant species, generally Zn > 400 mg/kg, Mn > 1000 mg/kg, and Cu > 40
mg/kg are potentially toxic.
2.1.1.b Food Chain Contamination
When plant cover is restored to a site, the potential for food chain contamination should be
considered. Food chain contamination refers to the potential for the soil metals to cause harm to
animals that feed off of the plants and soil mesofauna (animals living among the litter and inside
the microscopic crevices of the site soil). Soil particles on the plants or the soil mesofauna may
result in high enough levels of contaminants that are toxic to animals that consume them. For
example, if shrews at a restored site feed largely on earthworms, the shrews will be exposed to
high concentrations of contaminants in the soils. This is the case because earthworms generally
consist of over 50% soil by weight. Consumption of soil through earthworm ingestion has the
potential to result in high body burdens for shrews. This then could lead to an increase in body
burden for birds that prey on the shrews. Soil extractions, such as dilute Ca(NO
3
-1
)
2
, have been
shown to be related to earthworm available metals and offer one way to evaluate this risk.
2.1.1.c Ingestion of Contaminated Soil
Ingestion of contaminated soil may result in an increased exposure to most elements. Examples
of inorganic elements that may pose a risk include fluorine (F), lead (Pb), arsenic (As), and
cadmium (Cd). Direct ingestion of soil by
humans is generally not a risk for adults.
Consumption of soil on an empty stomach
will also result in greater contaminant
adsorption due to the acidic gastric
environment and a lack of competing ions. For wildlife, the situation is different. As stated
earlier, some animals normally ingest high volumes of soil. Examples include worms and some
water fowl. If the area that is being restored is expected to provide habitat to water fowl that
dive into and feed on food, such as worms, in the sediment, the potential for contaminants to
enter the food chain or to harm animals through direct ingestion is increased.
Children, who are growing will absorb a
greater portion of the ingested contaminant
(particularly true for Pb) than adults.
2.1.1.d Runoff and Leaching
Soils devoid of vegetation are especially prone to water and wind erosion. Runoff refers to the
movement of materials over the soil surface. Actual particles of soil can erode off of the surface.
In addition, contaminants can come into solution and flow over the surface soils and off site.
Leaching refers to the movement of contaminants through the soil profile. Although it is possible
for contaminated particles to move through the soil though large pores, it is much more common
9
for contaminants to come into solution and travel downwards through the soil with soil water.
Runoff from these barren landscapes may contain contaminants, for example, copper (Cu) and
Zn, at concentrations that may be lethal to aquatic resources in receiving streams. This problem
is exacerbated if the runoff water is acidic.
At many mine sites, the formation of acid rock or acid mine drainage is common. During mining,
uncovered rock may be exposed to oxidation processes, and this rock can remain exposed after
the mine is abandoned. The oxidation of sulfide minerals in the rock, especially iron sulfide
(FeS
2
) produces acid that can solubilize metals. These low pH waters with elevated bioavailable
metals can adversely impact receiving streams and aquatic receptors. Mine wastes and
contaminated soil can be amended and vegetated to limit the loss of acidic, metal-rich runoff
water to adjacent receiving streams. Studies compared 26 runoff events involving non-amended
and contaminated soil to one event from lime-amended soil at a large Superfund site in Montana.
The pH of runoff water from the untreated areas typically ranged from 3.8 to 5.3, while pH from
the remediated soil was 6.2 during the single runoff event. Copper (Cu) and Zn levels in runoff
water from the non-amended soil were several orders of magnitude higher than those observed
from the treated site (Ref. 1).
2.1.2 Poor Soil Health/Ecosystem Function Problems
It is critical to revitalize soil health following drastic disturbance of a site through mining or
other industrial activity. In most cases, appropriate organic and/or inorganic soil amendments can
All components of an ecosystem
are dependent on healthy soil for
the system to function optimally.
be used to revitalize soil by increasing water holding
capacity, re-establishing microbial communities, and
alleviating compaction. Refer to The Nature and
Property of Soil by Brady and Weil for more details
on soils (Ref. 4).
2.1.2.a High or Low pH
A higher- or lower-than-normal pH range (typically <5.5 or >8.5) in the soil, which could result
from the runoff or leaching of industrial contaminants, acidic deposition, or exposure of acid- or
alkaline-reactive geologic materials, can cause soil infertility and limit the microbial activity.
Phytotoxicity is more likely with strongly acidic soil, such as soil where pyritic (containing
sulfides) ores or acidic smelter emissions have caused local contamination. Pyrite and other
sulfides in soil generate large amounts of sulfuric acid when they are oxidized. For example, in
Butte, MT, and Leadville, CO, mine wastes reached a pH < 3.5 due to oxidation of pyrite in the
soil. When soil is high in Zn, Cu, or nickel (Ni) contamination, soil pH may have to be raised to
above 7.0 to reduce metal solubility enough to protect plant health and ensure food-chain safety.
On the other hand, exposure of high Na subsoil or mine spoils can generate very high pH
conditions that drastically limit phosphorus (P) availability and may induce high As, selenium
(Se), and molybdenum (Mo) solubility. Similar problems may be found where waste limes (burnt
lime and hydrolysis products) are found at elevated levels.
2.1.2.b Sodicity
Sodicity (high concentrations of Na) and/or high levels of exchangeable Na+ in soil has a
detrimental affect on plants and, therefore, limit the use of salt-affected soils. Detrimental effects
of sodicity or sodic soils are due to toxicity of Na+, HCO
3
-, and OH- ions and to reduced water
infiltration and aeration. Excess Na can cause soil dispersion, which inhibits plant growth by
10
hardening soil and blocking water infiltration, reducing soil hydraulic conductivity, and creating
a cement-like surface layer that blocks growth of root systems and water infiltration through the
soil (Ref. 22). Soil with an accumulation of exchangeable sodium is often characterized by poor
tilth (physical condition of soil related to its ease of tillage, fitness as a seedbed, and its
favorability to seedling emergence and root penetration
) and low permeability making it
unfavorable for plant growth (Ref. 21).
2.1.2.c Salinity
Salinity, or excess salts, such as chlorides and
sulfates in the root zone limits the ability of
plants to withdraw water and nutrients from the
soil.
In this hypertonic micro-environment,
water is lost from the roots to achieve osmotic
equilibrium with the surrounding environment.
In effect, the salts physically draw out water
from the plant root leading to desiccation. Salts
also interfere with active ion uptake
mechanisms at the root interface requiring
plants to exert more energy to extract water and
nutrients. This decrease in plant-available water
and nutrients in saline environments causes
plant stress.
2.1.2.d Soil Physical Properties
Soil physical properties refer to the physical characteristics of the soil including, increased bulk
density, poor aggregation, and textures that are too sandy or clayey. If a soil has a high bulk
In order for the soil to support a healthy
the soil must be able to maintain a sufficient
vegetative cover and microbial community,
amount of oxygen when wet and hold onto a
sufficient amount of water during a dry spell.
density (high weight per unit volume), it
is generally too dense to contain enough
pore space to allow oxygen to diffuse
through a soil and keep it well aerated. In
addition, pore space allows water to enter
and move through a soil, helping avoid
waterlogged conditions. A soil with high
bulk density generally will have high clay content. Soils that consist of rocks and coarse
fragments can have too much pore space, which allows water to flow through the soil very
quickly. Roots have difficulty anchoring, and there is no habitat for soil microorganisms.
Another important property is water infiltration capacity. If the soil surface is too crusted, water
will pond or run off the surface. This increases the potential for the soil to be droughty.
2.1.2.e Nutrient Deficiencies/Low Soil Fertility
Striking the appropriate balance in metal concentrations is essential, since many of these metals
also are toxic in high concentrations. Deficiencies in phosphorus (P) and nitrogen (N) limit
growth. It is important to maintain sufficient available or labile N, P and K for the species of
interest based on local (state) soil testing laboratory guidance. Deficiencies in Zn, Cu, manganese
(Mn), and other metals that are necessary micronutrients also can lower soil fertility. In addition,
proper ratios of Ca to Mg and carbon (C) to N are necessary for plant growth. As a rule-of-
thumb, the C:N ratio is 15-40:1; the ideal Ca:Mg ratio is no greater than 20:1 (Ref. 5). Higher
11
C:N ratios will lead to immobilization of N. Soil microbes will scavenge for nitrogen and limit
its availability for plants. In the case of lower C:N ratios, N will be in excess. This can lead to N
leaching through the soil. While a wider range for acceptable C:N ratios is shown above, an
optimal range would be 20-30:1. Refer to Soil Fertility and Fertilizers by Havlin and Tisdale for
more details (Ref. 18).
2.2 Interactions
Contaminants can be, and generally are, co-occurring. For example, Pb and Zn commonly occur
together in sulfide ores, and there may be significant As and Se in the material as well.
When two or more contaminants are present, the more protective solution should be applied. For
example, Cd is almost always present at Zn-contaminated sites. Solutions to elevated Zn include
raising soil pH. Adding sufficient P fertilizer also will reduce the bioavailability of Cd.
Sometimes two solutions may be antagonistic or contradictory. In such cases, one should
proceed based on the primary driver for ecosystem health. A good example would be a site that
is co-contaminated with Pb and As. If the site were contaminated by Pb alone, addition of high
rates of P would reduce Pb bioavailability. However, where As is a co-contaminant, adding high
rates of P may increase As solubility. Here, if Pb is the primary driver and As concentrations are
relatively low in comparison, P addition should be the preferred solution. When both Pb and As
concentrations are high and both contaminants are risk drivers, an alternative solution, such as
addition of a high-surface-area iron (Fe) oxide, such as ferrihydrite or high Fe biosolids compost,
which is effective for both contaminants, would be the preferred alternative.
2.3 Solutions
Most of the solutions to the various problems presented in Table 1 include raising or lowering
the pH of the soil; adding organic matter, phosphate and /or sorbents; tillage; and other listed
management alternatives. Table 3 lists soil amendments that can be used to adjust the pH, add
organic material, and act as a sorbent. Sorbents are a subset of amendments and have desirable
chemical properties for reducing the solubility and bioavailability of various toxic elements or
compounds.
12
3.0
TYPES OF SITES WHERE
AMENDMENTS CAN BE USED
Many contaminated sites that would benefit from revitalization fall into four broad
categorieshard rock mining sites, abandoned coal mines, refining and smelting sites, and
construction sites. Some of these categories can be further divided into specific site types. For
each site type, Table 2 shows the contaminants and problems that are likely to be found and
suggests soil amendments to solve the problems. For example, all types of sites within the hard
rock category potentially will have mine wastes onsite or nearby. They also may have tailings
present. Soils at these sites generally are infertile with poor physical properties. The general
solution for revitalization of these sites is to add an organic soil amendment mixture rich in N
and P, adjust the pH using neutralizing lime, followed by seeding and planting of vegetation
species appropriate for the land use.
3.1 Hard Rock Mining Sites
Hard rock mining sites are sites where the desired mineral must be extracted from rock hosts.
Examples of common hard-rock derived metals include Fe, Zn, Pb, cobalt (Co), Cu, gold (Au),
and Mo, although some of these are mined from sedimentary deposits as well. The desired metal
is present at an elevated concentration in a mineral matrix (ore) that is sufficiently above
background to make extraction of the metal economically viable. In addition to the mined ore,
hard rock mining sites must move large amounts of non-mineralized rock (overburden) to get to
and remove the ore. These sites can include open pit and underground mining operations. In both
cases, overburden or waste rock with low mineral concentration frequently makes up a large
portion of the waste material onsite. Tailings, created when the ore-rich rock is ground up and
the economic mineral is extracted via flotation or screening, also can be present onsite or in
adjacent tailing disposal facilities. Adjacent soil also may be contaminated from fluvial
deposition or, in some instances, the use of historical irrigation practices. For most of these sites,
overburden or waste rock, which often is acidic and has elevated contaminant concentrations, is
the material left that needs to be revegetated.
Since many hard rock mining sites generate acidic soil conditions in their overburden and waste
rock, addition of liming materials is usually an essential first step to site remediation. However,
there are limitations associated with lime treatment of acid-forming mine waste. Problems
achieving adequate mixing are commonly encountered in excessively rocky materials.
Lime is not well mixed into the full depth of the profile, and tillage equipment tends to create a
rock pavement veneer with repeated incorporation passes of soil with more than 40% rock. A
second limitation encountered with lime treatment relates to contamination levels. When levels
of trace metals are modest, bulk alkaline addition can neutralize pH enough to precipitate toxic
metals and control phytotoxicity. However, when high levels of metals are present in the
neutralized root zone following treatment, residual phytotoxicity has caused apparent vegetation
failure. No rigid criteria have been developed to address this issue. Progressively more intensive
treatments, adding more organic matter and fertilizer, have been employed with modest success.
13
At the highest levels of total metals in the treated soil profile, very few plants will survive (Ref.
29).
3.2 Coal Mining Sites
This category includes both eastern (dominantly acid-forming) and western (high salt and
sodium) coal mining sites. It also includes piles of coal processing waste piles and fills, which
tend to be much more difficult to reclaim and revegetate than the mine sites.
Sand and gravel mining sites are included within this category, because vegetation challenges are
similar to those at coal mining sites. For most of the sites within this category, contaminant
concentrations are low. Obstacles to ecosystem revitalization are related to undesirable pH
levels, low fertility, and poor soil physical properties.
3.3 Smelting and Refining Sites
Smelting and refining sites are facilities where different ores or fuels have been processed.
Contaminated waste materials at these sites are confined to a smaller area than at hard-rock
mining sites or coal mining sites; however, aerial deposition of contaminants at the processing
facility can spread contamination over a very wide area. Localized and aerially dispersed
contaminants or wastes are the two broad categories within this category of sites. Complex
organic compounds are common contaminants at refining sites and these issues are not
specifically addressed in this paper.
3.4 Construction and Mixed-Contaminant Sites
Construction sites are very common and include urbanized and industrialized areas, highway and
utility corridors, and airports. Revitalization of these sites is significantly improved when soil
amendments are used. Mixed-contaminant sites are those with elevated but relatively low
concentrations of multiple metals and organics. Common examples include urban brownfields
sites.
3.5 Other Sites
While the range of soil amendments listed in Table 2 can restore ecosystem function and a self-
sustaining plant cover on the majority of sites, some disturbed sites do not respond to the
addition of amendments. Sites with excess amounts of soluble salts or pyretic materials are
examples. In both cases, the recommended approach is to cap the disturbed site and create a new
soil horizon above the cap. This approach was used at a smelter waste site in Poland where
excessive salts prevented plant establishment despite high application rates of biosolids and a
high calcium carbonate residual (Ref. 11). As an alternative, the site was capped with 10 inches
of the high lime material, and a new soil horizon was created with biosolids incorporated into the
upper portion of the lime cap. For such highly contaminated sites, residuals and soil amendments
are excellent alternatives to clean fill for building a new soil above the barrier to the damaged
soil.
14
Table 2: Types of Sites Where Soil Amendments Can Be Used
Site Contaminant Problem Solution
Mining
Hard Rock
(Ferrous and non
-
ferrous)
There are some common
mixtures of contaminants at
these sites. See below for
specific combinations.
Metal contamination; Soil generally is highly infertile; Acid
mine drainage possibility; Poor physical properties
1
.
Commonly requires nitrogen (N) and phosphorus (P) rich
organic soil amendment at high rate to improve soil
physical properties and nutrient status; Neutralizing soil
amendments may be necessary to raise pH.
Copper (Cu)/Arsenic(As)/Pb/
Molybdenum (Mo)
Existing and potential acidity; Soil ingestion risk from As
and Pb; Possible food chain risk from Mo; Aquatic risk
from Cu
Add lime to correct potential and existing acidity; Final
target pH is 5.5 to 6.5 to limit As bioavailability. In cases
where Mo is primary concern, final pH is <5.5.
Cyanide (CN) Groundwater contamination and residual CN from leaching
of gold (Au) using cyanide solutions
Oxidation of cyanide solutions; Cover or cap waste piles
with cover soils.
Lead (Pb)/Zinc (Zn)/
Cadmium (Cd)
Zn induced phytotoxicity; P deficiency; Low pH acid
generating potential; Soil ingestion Pb risk; Cd food chain
risk
Add lime to correct potential and active acidity plus
additional 25 to 50% reserve factor; ensure sufficient P to
inactivate Pb and provide fertility to support legumes.
Mercury (Hg)/As Food chain (aquatic) risk from Hg; Soil ingestion risk from
As; Concerns about volatilization of Hg.
Surface apply organic or organic-mineral soil amendments
without incorporation to eliminate volatilization potential
and provide a barrier against soil ingestion.
Nickel(Ni)/Cobalt(Co) Ni induced phytotoxicity; P deficiency; Existing and
potential acidity
Add lime to correct potential and active acidity plus
additional 25 to 50% reserve factor; Ensure sufficient P to
provide fertility to support legumes.
Pyrite (FeS2)/As/Selenium
(Se)/Ni/Cu
Existing and potential acidity; Soil ingestion risk from As;
Se leachability and food chain risk; Wide range of other
metals possible
Add lime to correct active and potential acidity plus 25 to
50% reserve factor (this will also reduce availability of
other metals); If high As, lower target pH to less than 6.5.
Selenium (Se) Increased Se solubility and bioavailability at phosphate
mines due to changes in oxidation state of Se
Achieve reducing conditions; Cover and cap waste piles.
Coal Pyrite-based acidity and
exchangeable Sodium (Na)
and salts, soluble Se
Metal contamination; Rocky, compacted and infertile soil See below
Coal waste piles Pyrite-based acidity Existing and potential acidity; physical problems; acid mine
drainage; Dark color (which causes heat kill of seedlings);
low moisture-holding
Add lime to correct existing and potential acidity plus
additional safety factor of 20 to 30% is sufficient; Add
organic soil amendments to revitalize soil; Modify surface
texture by adding OM or adding amendment with sand or
clays, such as biosolids; Lighten surface color of pile to
prevent heat-kill of seedlings.
15
1
Poor soil physical properties, such as density, aggregation, and texture, can reduce water infiltration and the moisture-holding capacity of the soil and stifle efforts to
revegetate a site.
2
Modify Physical Properties = If the soil is too coarse, add fines, sand or silt. If the soil is too fine, add OM or a course material.
Site Contaminant Problem Solution
Eastern (acid-
forming)
Pyrite and associated metals Existing and potential acidity; Physical problems; Acid
mine drainage
Add lime to correct existing and potential acidity plus
additional 25 to 50% safety factor is sufficient; Add organic
soil amendments to revitalize soil; Modify surface texture
where possible.
Sand/Gravel
mines
In Eastern sites, may have
associated acidity problems
Coarse texture or rocky and very infertile; Heavy soil
compaction and low water retention and/or rooting depth
Add lime and organic soil amendment (generally high
application rate beneficial) with appropriate C:N ratio to
minimize nitrate leaching.
Western (Na and
salts)
Na, salts, Se Salinity, sodicity, and physical problems; Se leaching and
aquatic biomagnification
Add OM and Ca-rich soil amendments; Irrigate to remove
salts where possible; Segregate Se bearing materials and
avoid Se accumulating plant species for revegetation.
Refineries/Smelters
Aerial Deposition Metals (see mining sites
above)
Metal toxicity; Acidity, Possible infertility; In urban
environment, soil ingestion may be dominant risk
See metals-specific remedies above.
Smelter Process
Waste/Slag
Metal acidity; Salts; Dark color (which causes heat kill of
seedlings); Cementation
See metals-specific remedies above; For color, surface
mulch to modify temperature or surface apply light-colored
mixtures of alkaline fly ash and biosolids; For cementation,
modify physical properties; For salts, irrigate and if
electrical conductivity (EC) is excessive, capping may be
necessary.
Tailings Metals (see mine sites
above); Cyanide
Metal toxicity; Acidity (associated acid drainage) or
alkalinity; Infertility; Physical properties; Cyanide in gold
(Au) tailings
See metals-specific remedies above; modify physical
properties.
1
Construction
Sites
See sand and gravel; urban
contaminants
See sand and gravel; Compaction, mixed soil and geologic
materials, imbalanced pH and low fertility all common
Site-specific remedies based on contaminants.
Mixed
Contaminants
Low levels of metals and
organics
Often former industrial sites will have soil physical and
nutrient problems
Soil amendments to improve nutrient and physical
characteristics and pH adjustment as needed can often
reduce contaminant availability; Site-specific evaluation
necessary.
16
4.0
TYPES OF SOIL AMENDMENTS
This section briefly describes soil amendments and organizes them by use: organic soil
amendment, pH soil amendment, and mineral soil amendment. Table 3 lists the various soil
amendments along with their availability, uses, public acceptance, cost, advantages, and
disadvantages. Note that specific regulatory or permitting requirements for various types of
amendments are addressed in Section 7 of this document.
The type, mix, and amounts of soil amendments will vary from site to site in response to the
local mix of site contaminants, soil conditions, and type of desired vegetation. The first and most
essential components of any soil amendment strategy are an accurate assessment of existing site
-
soil conditions and knowledge of the range of target soil conditions appropriate for the
revegetation species of interest. Post-revitalization land use also is an important consideration in
choosing soil amendments and remedial strategies. Additionally, it is essential that potential soil
amendments be carefully characterized for all important physical, chemical and microbiological
properties.
4.1 Organic Soil Amendments
A wide array of organic soil amendments, with varying levels of processing and characterization
is available in most regions. Organic amendments most frequently are used to provide essential
nutrients (such as N and P), to rebuild soil organic matter content, and re-establish microbial
populations. Benefits directly associated with improved organic matter content are: enhanced
water infiltration and moisture-holding, aggregation, aeration, nutrient supply for plant growth,
and microbial activity (Refs. 44, 56, 57).
Biosolids. Biosolids are the primary organic solid byproduct produced by municipal wastewater
treatment processes that have been treated to meet federal and state land-application standards
(Refs. 25, 53). Over 7 million tons of biosolids are
generated annually by municipal wastewater
treatment plants in the United States, and about 55%
of this material is land applied in one form or another,
primarily to agricultural land (Ref. 32). Compared to
many other organic soil amendments, biosolids are
highly characterized and often are readily available at
low cost for use as a soil amendment on disturbed lands (Ref. 17). Biosolids characteristics can
be quite variable between sources, but are very predictable from any one source. In addition to
available nutrient and organic soil amendment benefits, biosolids often possess significant liming
and sorbent properties as well. Use of biosolids may be limited by excessive nutrient loading
concerns at higher loading rates, and odors occasionally cause public acceptance issues. The
nitrogen content of biosolids is generally of the —slow-release“ type and becomes available to
vegetation slowly over several years following application. For more information on biosolids,
go to http://www.epa.gov/waterscience/biosolids/.
industrial pretreatment programs
over the years, biosolids tend to
have metal concentrations much
Because of advancements in
lower than regulations require.
17
Table 3: Types of Soil Amendments
Amendment Availability Uses Public
Acceptance
Cost Advantages Disadvantages
Links
Organics
Biosolids Sustainable
supply; Higher
quantities in
urban areas
Nutrient source;
Organic matter
(OM) source;
Sorbent
1
properties
increase with
increasing iron
content.
Largely odor-
driven;
Pathogen
concerns;
Concerns
largely driven
by perception.
Materials
generally free;
Municipalities
may pay for
transport and
use.
Multi-purpose, multi-
benefit soil
amendment; highly
cost-effective; EPA
regulated
2
; well
characterized
consistent quality.
Public concern/public
perceptions; High
nutrient loadings in
some settings; Some
sources have high
moisture content.
National Biosolids
Partnership
(http://www.biosolids.org/in
dex.asp)
Manures Sustainable
supply; Higher
quantities near
CAFOs
Nutrient source;
OM source.
Well accepted. Materials
generally free;
Transport and
application fee.
Widespread and
readily available.
Not consistently
regulated
2
; Variable
quality; Not routinely
treated for pathogen
reduction; Generally
uncharacterized.
Industry Residuals: How
They Are Collected, Treated
and Applied
(http://www.clu-
in.org/studentpapers/)
Compost Location-
dependent;
Volumes limited;
Competing users
Nutrient source;
OM source.
Readily
accepted.
Product and
transport costs
can be high.
Readily accepted;
Stable product; Can
be used in or near
water.
High cost; Limited
availability; N
quantity usually
significantly lower
than non-composted
materials.
U.S. Composting Council
(http://www.compostingcou
ncil.org/section.cfm?id=37)
Association of Compost
Producers
Digestates
3
New material;
Very location
dependent
Nutrient source;
OM source.
May have odor
problems.
To be
determined;
Transport and
application fee.
New enough so that
not regulated
2
;
Variable quality; Not
routinely treated for
pathogen reduction;
Generally
uncharacterized.
18
Amendment Availability Uses Public
Acceptance
Cost Advantages Disadvantages
Links
Pulp Sludges Material
available locally
(Northwest and
East)
OM source; Slope
stabilizer.
May have odor
problems; May
have dioxins;
May be
nutrient
limiting.
Materials
generally free;
Transport and
application fee.
High C content;
Large volumes;
Locally available.
Highly variable
quality; May contain
other residuals, e.g.,
fly ash, waste lime,
clay, which can be
benefit or detriment
for intended use.
Total C may not
reflect available C.
Very low nutrient
value.
American Forest and Paper
Association
(http://www.afandpa.org/Te
mplate.cfm?section=Pulp_a
nd_Paper)
Yard/Wood
Waste
Material
available locally
OM source; Can be
high C; Can be
used for bulking
and structure.
Yard waste
can be
odorous.
Materials may be
free; Transport
may be partially
covered.
May be used to
control erosion;
Variable sizes
available.
Large category; High
variability; May be
hard to obtain; Can
contain herbicides.
Ethanol
Production
Byproducts
New material;
Very location
dependent
Nutrient source;
OM source.
May have odor
problems.
To be
determined;
Transport and
application fee.
New, not regulated
2
;
Variable quality; Not
routinely treated for
pathogen reduction;
Generally
uncharacterized.
pH
Lime Widespread Increase pH;
Increase Ca.
Highly
accepted.
Product,
transport and
application is $8-
30/ton based on
transport
distances.
Regulated
2
; Well
characterized; Very
uniform; soil
aggregation.
Agricultural
limestone has low
solubility and can
become coated and
ineffective at
severely acidic sites.
Can be source of
fugitive dust.
National Lime Association
(http://www.lime.org/ENV0
2/ENV802.htm#BioS)
19
Amendment Availability Uses Public
Acceptance
Cost Advantages Disadvantages
Links
Wood Ash Locally available Increase pH;
Source of mineral
nutrients, Ca, Mg,
K; Can work for
odor control.
Accepted. Materials
generally free;
Locally variable
cover and
transport costs.
Acceptance; Cost;
Multi-purpose; Can
limit odor of organic
soil amendments.
Highly variable;
Lime equivalent will
vary by burn
temperature and age
of material; Dioxins
should not be a
problem but tests
should be conducted
to verify.
Coal
Combustion
Products
Most available in
eastern U.S.
Increase pH;
Source of mineral
nutrients (e.g., Ca).
Variable. Materials
generally free;
Transport and
application fee.
Regulated
2
; Well
characterized; Soil
aggregation; Light
color reduces surface
temperature for
seedlings; Increases
moisture-holding
capacity; Reduces
odor of organic soil
amendments.
Varies plant to plant;
can be high B and
salts; can leach Se
and As.
American Coal Ash
Association (http://fp.acaa-
usa.org/CCP.htm)
The Fly Ash Resource
Center
(http://www.geocities.com/c
apecanaveral/launchpad/209
5/mar_index.html)
Sugar Beet
Lime
Locally available
- primarily in
west
Increase pH. Accepted. Materials
generally free;
Transport and
application fee.
More reactive than
agricultural
limestone.
Potential fugitive
dust.
Cement Kiln;
Lime Kiln
Locally available Increase pH; High
Ca.
Variable. Materials can
have associated
cost; Transport
and application
fee.
Highly soluble and
reactive.
Potential fugitive
dust; Highly caustic;
Variable content;
May contain
contaminants.
20
Amendment Availability Uses Public
Acceptance
Cost Advantages Disadvantages
Links
Red Mud Locally available
in TX and AR in
U.S.
Increase pH;
Sorbent.
Variable. Commercial
product from a
residual under
development.
Demonstrated
effective in limited
testing in Australia
and other sites at
moderating pH and
sorbing metals.
Potentially costly,
High salt content;
Variable CCE.
I-99 ARD Remediation
Status, June 8, 2005
(http://www.dep.state.pa.us/
dep/deputate/fieldops/nc/I_9
9/Reports_Documentation/5
_PennDOT_Acid_Rock_Re
mediation_Plan/I-
99_ARD_Pres._Tran_Sub_
Final.ppt#274 ,8,Interim
Remediation Measures)
International
Aluminum Institute
(http://www.world-
aluminium.org/environment
/challenges/residue.html)
Red Mud Project
(http://www.redmud.org/ho
me.html)
Lime-stabilized
Biosolids
Locally available Increase pH; OM
and nutrient
source; Potential
sorbent.
See biosolids. See biosolids. See biosolids;
Potential multi
-
purpose soil
amendment.
Can have high odor;
Lower N content than
conventional
biosolids; Variable
lime content.
National Lime Association
(http://www.lime.org/ENV0
2/ENV802.htm#BioS)
Mineral
Foundry Sand Large quantities
locally available
Modifies texture;
Sorbent.
Variable. Materials
generally free;
transport and
handling fee.
Good filler; Sand
replacement.
Can have trace
metals, Significant
Na; Only Fe and steel
sands currently
acceptable.
21
Amendment Availability Uses Public
Acceptance
Cost Advantages Disadvantages
Links
Steel Slag Locally available CCE, sorbent, and
Mn fertilizer.
Accepted. Materials
generally free;
Transport and
grinding fee.
Combination of CCE
and sorbent,
including Mn.
May volatilize
ammonia.
National Slag Association
(http://www.nationalslag.or
g/slagsites.htm)
Dredged
Material
Large quantities
locally available
Modifies texture;
Top soil substitute
useful for covering
sites.
Variable. Materials
generally free;
Transport may
be paid by
generator.
Can be top soil
substitute; Ideal for
blending with other
residuals.
Needs dewatering;
Can have wide range
of contaminants; Can
have Na.
Gypsum Large quantities
locally available
Good for sodic
soil; Good for low
pH soil; Good for
soil structure.
Variable. Materials
generally free;
Transport fee.
Improves
aggregation; Offsets
aluminum toxicity.
Different sources of
waste gypsum and
wide range of
potential
contaminants, many
of which are
regulated
2
.
Water
Treatment
Residuals
(WTR)
Available
wherever water
is treated
Good for binding
P; Potential
sorbent.
Accepted. Materials
generally free;
Transport costs
may be covered
by generator.
Moderates P
availability when
mixed with high P
soil amendments.
Different materials
have variable
reactivities; May
contain As and
radioactive isotopes.
Coal
Combustion
Products (CCP)
Available where
coal is burned
Sorbent; Improve
water-holding
capacity; Excellent
mix for biosolids;
Compost to create
cover soil.
Variable. Materials
generally free;
Transport and
application fee.
May have CCE
value; Large volumes
available.
Large quantities
generally necessary
to achieve benefits;
Can have
contaminants
including Se, B, As
and metals.
1
The term sorbents, as used here, describes materials that can hold on to or absorb different contaminants. There are a range of these materials, with different materials better suited
to absorption of different contaminants. Some examples of sorbents include charcoal for different organic contaminants, water treatment residuals for excess P and some heavy
metals and high surface area iron oxides for heavy metals including Pb and As (Refs. 6, 13, 14, 58).
2
See Table 6. Regulatory Requirements for Sites Using Selected Soil Amendments
3
Digestate, as used here, is defined as a general category for organic wastes that have been partially treated through anaerobic digestion.
22
Manures. Over 25 million tons of animal manures are generated annually in the United States
(Ref. 57). Manures vary widely in moisture, nutrient content, and relative stability. Some
manures are dewatered or otherwise stabilized for beneficial use, but most are applied —as is“ on
nearby agricultural lands as nutrient and organic matter amendments. The nitrogen content of
manures is usually readily available to vegetation and does not persist in the soil as long as the
nitrogen from biosolids or other types of manures.
Composts. Compost is the stable soil conditioning product that results from aerobically
decomposing raw organic materials, such as yard trimmings, food residuals, or animal
byproducts (http://www.epa.gov/compost/). The composting process involves a proper carbon-
to-nitrogen ratio, a favorable temperature regime, water, and air to yield the compost end-product
that is less in volume than the original material and free from offensive odors. Composting is
used frequently to significantly reduce pathogens in organic waste streams since the process
generates temperature hot enough to achieve this reduction. Compost availability and
composition varies widely, but in general, compost is generated in much smaller volumes
nationally than manures or biosolids. Composts generally have a lower N content than biosolids
or manures.
Digestates. The term —digestates“ is used in this paper as a general category for organic wastes
that have been partially treated through anaerobic digestion. Anaerobic digestion of organics is a
way to reduce volume, destroy pathogens, and generate methane for energy recovery. This type
of digestion is status quo for many municipal biosolids and is becoming increasingly common
for animal manures and food residuals. The material that comes out of digesters typically is a
high-organic-matter semi-solid that can have a relatively high nutrient content. This type of
treatment is commonplace for municipal biosolids; however, biosolids are considered separately
from digestates in this paper, even though their properties and potential uses are likely to be
similar.
Papermill Sludges. Papermill (pulp) sludges also are available for use as soil amendments on
disturbed lands (Refs. 16, 40), but tend to vary from source to source. In general, papermill
sludges are much lower in N and P than biosolids and composts, but can provide large amounts
of organic matter. Many papermills also combine other residuals such as waste lime, fly ash, or
kaolin with their pulp sludges, which may greatly enhance their soil amendment potential (Ref.
20).
Yard and Wood Waste. Many localities collect yard waste (lawn, garden, shrub/tree trimmings,
etc.) and make it available for local reuse. Similarly, large amounts of wood waste (bark chips,
sawdust, whole tree chips, etc.) may be available from wood processing facilities or from right-
of-way maintenance activities. Collectively, these materials tend to vary greatly in composition,
size, and relative decomposition/stability, but can serve as significant and beneficial organic
matter amendments or mulching materials. In recent years, wood products have been
increasingly utilized as fuel in industrial boilers and, therefore, are not as readily available.
Ethanol Production Byproducts. Because this is a relatively new source of soil amendments, its
availability is very location specific. It is generally uncharacterized and there is very little
information available about it.
23
4.2 Soil Acidity/pH Soil Amendments
Many degraded sites are plagued by low soil pH conditions and associated problems, including
heavy metal bioavailability and direct toxicity to microbes. Fortunately, a wide array of alkaline
soil amendments is available. All liming/alkaline soil amendments should be tested for their net
neutralizing power. This is commonly expressed on a calcium-carbonate-equivalent (CCE) basis.
The particle size of liming materials also is very important in that sand-sized or larger (>
0.05
mm) particles are much slower to react than finer-textured materials.
Many soil amendments (e.g., lime)
have important positive effects on
runoff and leachate water quality in
addition to ameliorating adverse
plant growth conditions.
Lime. pH-neutralizing soil amendments include
ground calcium carbonate (CaCO
3
), or limestone;
calcium oxide (CaO), or burnt lime; calcium
hydroxide (Ca(OH)
2
), or hydrated lime; and
industrial waste products, such as cement kiln dust
and sugar beet precipitated calcium carbonate, are
widely available. The applicability of each soil
amendment is subject to chemical analysis of CCE, moisture content, and particle size.
Additionally, lime amendments should not contain phytotoxic characteristics. Phytotoxicity
effects of industrial waste products can be determined by greenhouse testing, and should not be
determined by chemical analysis alone. Pure alkaline products such as ground limestone, calcium
oxide, and calcium hydroxide do not need independent greenhouse evaluation prior to field use
(Ref. 29). Liming is commonly used to reverse phytotoxicity of Zn, Cu, or Ni. However,
excessive liming may reduce phytoavailability of soil Mn and other essential micronutrients, and
induce Mn deficiency depending on Mn levels present in the contaminated soil.
Wood Ash. Wood ash is locally available in small to moderate amounts from wood-fired utilities.
Wood ash provides K and certain micronutrients to the treated soil/plant system. CCE varies by
source and the degree to which the ash product has been weathered and hydrated. Wood ash may
contain contaminants if other fuels, such as tires or waste oil, have been co-combusted with the
wood. The ash of wood treated with chromated copper arsenate (CCA) or pentachlorophenol
(PCP) is not acceptable for use on land because of the contaminants present in these materials.
Coal Combustion Products (CCPs). Over 100 million tons of coal fly ash and flue gas
desulfurization (FGD) lime sludge are produced annually in the United States (Ref. 24). These
products can provide a low-cost alkaline alternative to conventional lime sources. The CCE of
fly ash can vary from 0 to > 50%, so appropriate testing of all land-applied materials is essential.
FGD materials typically are higher in CCE than fly ashes, and the two are commonly co-mingled
at generating facilities. Gypsum also is commonly a major component of FGD. High levels of
soluble salts and boron (B) in both products may limit the application rate. Boron and soluble
salt levels are reduced in weathered material, if this is locally available. Heavy metal
concentrations should be determined in these materials prior to use. Metals levels can vary
considerably between sources.
Sugar Beet Lime. During purification of sugar from sugar beets or cane, lime is added to
neutralize organic acids present in the plant materials along with sugar. Sugar beet lime, the
limestone byproduct of this process, is available wherever sugar is produced or packaged. It
usually has a fine particle size, and may include byproduct organic matter needing application.
These byproduct limestones contain organic matter and have relatively high CCE values. They
24
are an underutilized resource mainly because of additional transportation costs resulting from
remote locations and relatively high water content.
Cement Kiln Dust. A highly soluble and reactive byproduct of the cement industry, kiln dust is
also locally available in moderate quantities. This product may contain higher than desirable
concentrations of contaminants. Like all lime substitutes, these materials should be carefully
characterized before use. This material can vary considerably between sources.
Red Mud. Red mud is a highly alkaline byproduct of the aluminum industry found in very large
quantities near active refineries in Arkansas, Texas, and other states. Several commercial
products (e.g. Bauxsol
TM
), based on processed red
mud, are currently available. Bauxsol has been
pilot tested on three acid rock drainage (ARD) sites
in Pennsylvania (Ref. 38).
Red mud is known for its combined
liming and sorbent properties.
Lime-stabilized Biosolids. This is a product of secondary treatment of biosolids via addition of
CaO or other lime (alkaline)-based reactive products. Lime-stabilized biosolids have a variable
CCE (10 to > 50%) but also contribute significant nutrient and organic-matter benefits. Lime
-
stabilized biosolids may be available in large quantities near cities that use lime stabilization in
their wastewater treatment facilities.
4.3 Mineral Soil Amendments and Conditioners
While organic matter and lime/alkaline soil amendments are used most often, a wide range of
mineral byproduct materials with significant soil amendment, conditioning, or even soil
substitute properties may be available locally (Ref. 56). All materials should be characterized
prior to use.
Foundry Sand. A byproduct of the metal casting industry, foundry sand is available locally in
moderate amounts. It is used primarily as a soil conditioner to improve texture but may contain
various heavy-metal residues from the casting process.
Steel Slag. Steel slag is available locally in moderate quantities. It often is used as a combined
alkaline soil amendment, sorbent, and micronutrient source.
Dredged Materials. Available in very large quantities near commercial waterways and estuaries,
dredged materials may be used to modify surface soil texture or, in thicker lifts, to form an entire
soil profile. Dredged materials can be highly variable in physical and chemical properties and
may contain organic contaminants, including herbicides.
Gypsum. Very large amounts of gypsum are produced in the manufacturing of P fertilizers,
titanium pigment production, and a range of other industries that neutralize sulfuric acid extracts
in their processes. Gypsum is used to enhance soil aggregation, offset aluminum (Al) toxicity,
and ameliorate sodic soil conditions. The product varies by industrial process and location and
can contain trace contaminants of concern, such as Cd, F, and uranium (U).
Water Treatment Residuals (WTR). Alum and other compounds are used in drinking water
plants to flocculate or precipitate P, fine clays, silts, and organics from the raw water feed. The
25
resultant water treatment sludges can be used as a soil conditioner to improve texture, or as a
sorbent for excess P or other contaminants of concern.
Coal Combustion Products (CCPs). CCPs are generated in large volumes nationwide and are
frequently employed as liming alternatives for ameliorating acidic soil. However, CCPs also are
used for their metal-sorption ability, as soil conditioners to modify soil texture and improve
water-holding, or as simple dry-bulking agents to improve the handling properties of wetter
byproducts such as biosolids.
4.4 Application Rates
There are several approaches that can be used to determine the appropriate application rate for
the soil amendments to be used.
depend on the specific
Appropriate application rates
concern to be addressed.
One approach is to look at healthy soil in the environment
at the site. The total organic matter of such soil can be used
as a target value for the target site. If this approach is
taken, a significant portion of the organic matter applied
will decompose to carbon dioxide (CO
2
) and water in a
relatively short time frame. If a nearby soil has 2% organic matter, adding 4% to the site is a way
to compensate for the initial rapid decomposition. Another approach is to look at rates that have
been used at similar sites. For example, coal mining sites have been successfully restored with a
range of biosolids products added at 22 to about 100 dry tons per acre (Ref. 17). Metal
-
contaminated sites (primarily hard rock mining sites) have been restored with mixtures of
biosolids and lime, with biosolids added at rates of about 25-100 tons per acre and higher. The
appropriate rates at other hard rock sites with low probability of metal toxicities where soil
fertility and poor physical properties are the primary impediments to plant growth will be similar
to those for coal sites.
A heavily contaminated, barren mountainside adjacent to a large smelting complex in Palmerton,
PA. was revegetated using a blend of 105 wet tons/acre anaerobically digested biosolids (21 dry
tons/acre), 52.5 tons/acre fly ash and 10 tons/acre agricultural limestone (Ref. 37). In this case,
the application rates were determined primarily based on the organic nitrogen content of the
biosolids, then using half that amount of fly ash and twice the required amount of limestone
needed to neutralize the soil (pH 7.0). The blend, 167.5 dry tons/acre, was surface applied with
seed mixed in. It provided a uniform cover about 2 inches in depth and was very successful. The
organic nitrogen content of the biosolids was used as a determining factor because that nitrogen
component would provide the slow-release nitrogen needed by the vegetation. The 2000 lbs/acre
applied would be slowly mineralized by soil bacteria to plant-available nitrate and ammonia,
providing an annual amount of 100 œ 200 lbs/acre for a five to seven year period. This was the
amount of nitrogen required by the grass/legume vegetation that was seeded, preventing a loss of
nitrogen from the site. The fly ash amount was determined based on lab, greenhouse and field
trials, and supplied numerous benefits to the blend. The heavy metal content of the fly ash was
added to the metals content of the biosolids for the metals loading calculations for the project and
none exceeded the amounts allowed by Pennsylvania regulations (Ref. 35).
Another approach is to follow laboratory protocols. For example, laboratory protocols for
calculating the acid-base account from field soil samples; determining lime-quality CCE,
26
moisture content, and particle size; and delineation of spatial variation in the lime rate observed
in the field, are used for determining the application rate for neutralizing acid-forming mine
waste to ensure that appropriate amounts of soil amendments are applied spatially at proper
depths. Analytical tests that measure active and potential acidity have been documented (Refs.
42, 43).
In other cases, however, the amount of amendments added to the soil can be a qualitative rather
than a quantitative decision. This is generally the case for amendments used to increase soil
organic matter or to rebuild soil.
Some states regulate the use of different soil amendments. These regulations often are
formulated to protect against excessive leaching of N to groundwater while still allowing
application of soil amendments at high enough rates to assure success of the revegetation effort.
For example, Virginia Department of Mines Minerals and Energy (VDMME) developed
guidelines limiting application of biosolids for revitalization to 33 tons per acre for class B
biosolids or 51 tons per acre if the C:N ratio of the soil amendment was 25:1 or greater (Ref. 55).
Similar maximum rates are in place for reclamation of mined land in Maryland and
Pennsylvania.
In rebuilding soil, it is important to
include a mixture of N-rich materials with
C-rich materials to reduce the potential for
N leaching while providing sufficient
organic matter. In general, a bulk
amendment C:N ratio between 20:1 and 40:1 is recommended, but higher C additions may be
viable in certain scenarios. It also may be appropriate to include a mineral soil amendment like
foundry sand or wood ash as part of the amendment mixture respectively for inorganic bulk and
plant nutrients. Here, operational considerations and budget often can be the limiting factors in
determining appropriate application rates. The functional A horizon, also called topsoil, is where
seeds germinate and plant roots grow. It is made up of a mineral particle matrix with a significant
(1 to 10%) humus (decomposed organic matter) content. This layer is generally > 4 inches. The
goal should be to create a surface layer (A horizon) that is close to or greater than this depth.
Higher application rates of soil amendments
are required when rebuilding soil rather
than simply enhancing damaged soil.
27
5.0
LOGISTICS AND OTHER
CONSIDERATIONS
Availability, transportation, storage, and blending are the key logistical issues to evaluate when
using soil amendments for site remediation and revitalization (see Table 4). Other essential
concerns discussed in this section are public acceptance and cost.
5.1 Availability
Soil amendment materials are available almost everywhere. Sources include Publicly Owned
Treatment Works (POTWs), concentrated animal feeding operations (CAFOs), coal-fired power
plants, and pulp and paper mills, as well as retail sources. A limited list of sources for various
types of soil amendment materials is available on U.S. EPA‘s Clean-Up Information System
website at www.clu-in.org (Ref. 9). Also see the links to sources of information on the various
types of amendments in Table 3.
5.2 Transportation
Truck-delivery of residuals to a project site requires good access including roads kept clear of
snow and ice during periods of delivery, roads built to withstand heavy truck weights, bridges
when planning for the use of soil
and reuse of disturbed sites.
Transport logistics (identifying sources and
delivery costs) should be considered first
amendments for remediation, revitalization,
that legally can carry truck weights, and
sites with unloading areas that are level
and firm for safe truck dumping. Other
project-specific considerations may
include the need for a truck scale,
sampling apparatus and an on-site lab for
rapid field characterization of material.
Specialized transport vehicles may be needed for soil amendments that are highly hydroscopic
(have high moisture content), caustic, or have other special characteristics
. This can translate to
high unit costs for transportation. Liners should be considered for loads of high-moisture
materials for safer dumping.
Where sources of soil amendments are within 200 miles of a project site, dump trailers or dump-
truck delivery of amendments is economically viable. Longer distances make rail hauling
practical, but development of short-line rail service, or rail-to-truck transfer, can be costly. The
potential impact of concentrated truck traffic on homeowners directly adjacent to the haulage
route, including access, also should be considered.
28
Table 4: Logistics and Other Considerations in Using Soil Amendments
Amendment Transport On-site Storage Blending Application Application
Equipment
Organics
Biosolids Can be costly
due to high
Extended storage
of high moisture
Can be mixed
with high C
Industrial disks will
be needed for surface
Range of options
available.
moisture materials can
material to
or incorporated high Generators may
content for generate offensive
reduce N
moisture content of have expertise.
some odors. Can use
leaching
some materials, Options include
materials;
High potential
storage as
treatment with
potential. Can
also be mixed
chisel plow or
rippers; Material can
dump truck +
dozer, side cast
for cost-share onsite processing
with lime
be surface applied spreader,
with to compost or
materials for
and allowed to dry aerospreader™,
municipality; stabilize with lime.
complete
before incorporation; and custom
Rail haul is Blending with fly
amendment or
If blended with dry biosolids
possible; Intra-
modal
ash prior to storage
can reduce odors.
CCPs.
mineral materials,
e.g., fly ash, the
application
vehicles
transport
moisture content is including
containers
similar to topsoil (50- terragators. May
(rail/truck)
55%) and can be also be bulldozed
may simplify
surface applied down steep
transfers from
rail to truck.
without
incorporation.
slopes.
Manures See biosolids. See biosolids. See biosolids;
See biosolids; less See biosolids;
less stable than
stable than biosolids. less stable than
biosolids.
biosolids.
Compost Due to low
bulk density
and high water
content, high
transport costs.
See biosolids. Blowers,
pneumatic
spreaders,
manure
spreaders,
aerospreader™,
etc.
Digestates
1
See biosolids. See biosolids. See biosolids. See biosolids.
Pulp Sludges See compost. Can become
anaerobic and
odorous.
Can have very
high C:N ratio
2
which may
necessitate
See biosolids. See biosolids.
blending with N-
rich material for
plant growth.
Yard/Wood
Waste
See biosolids. See pulp sludges. Check C:N ratio.
If >30:1, will
See compost;
Standard
necessitate
mixing with a
high N material
like manure or
agricultural
tillage to12
inches.
biosolids.
Ethanol
See pulp sludges. Too new.
Production
Byproducts
29
Amendment Transport On-site Storage Blending Application Application
Equipment
pH
Lime Cost varies
with distance
and water
Lime pile should
be covered to avoid
dusts and
Can be blended
with an organic
soil amendment.
Lime spreader. Lime spreader;
aerospreader™;
hydro-mulcher;
content;
Usually by
precipitation.
Rip prior to
incorporation;
truck or rail.
Incorporation
equipment may
include tillage to
12 inches, rotary
mixers (24
inches), or
specialized
plows (up to 47
inches).
Wood Ash pH will decrease to
8.3 as material is
Can also be a
source of K and
See lime.
exposed to air; Will
be slower reacting
and less soluble;
P; If pH is > 8.3
can drive off N
from manures or
This process will
occur quickly if
lime material is
biosolids and
decrease nutrient
value; If blended
mixed with an
with manures or
organic residual for
storage.
biosolids and
seeded
immediately, the
ammonia
generated can
kill the seed.
Fly Ash See wood ash. Can be source of
K.
Sugar Beet See compost. See wood ash. See lime.
Cement Kiln
Dust
See lime. See wood ash; In
addition nutrient
Can also be a
source of K and
Can be caustic. See lime.
value, N can
decrease with
P; If pH is > 8.3
can drive off N
volatilization over
from manures or
time.
biosolids and
decrease nutrient
value.
Red Mud Can be salty.
Lime-
See biosolids. See biosolids.
stabilized
Biosolids
Mineral
Foundry Sand Generally high
application
rates will
High volume soil
amendments; Should
be handled in bulk.
Loaders, haulers,
pans, dozers.
involve high
cost; Cost may
be covered by
generator.
30
Amendment Transport On-site Storage Blending Application Application
Equipment
Dredged See foundry See foundry sand. See foundry
Material sand. sand.
Gypsum See foundry
sand.
See lime. See lime.
Water
See lime.
Treatment
Residuals
1
Digestate, as used here, is defined as a general category for organic wastes that have been partially treated through
anaerobic digestion.
2
Ratio of carbon to nitrogen; C:N ratio is 15-40:1
5.3 Storage
Temporary stockpiling of soil amendments in advance of application is often necessary. The
stability of a soil amendment is an important factor in planning for on-site storage. Exposure to
rainfall while in storage may affect the quality of some soil
amendments. Other amendments are biologically active,
and their nutrient properties or odor characteristics may
change while in storage. Some materials may be composted
at an on-site storage facility, but regulatory restrictions may
apply. In some states, on-site storage for any protracted
period of time (e.g., > 14 days or over winter) may require
a compacted pad below and low berms around the base of
the stockpile to retain leachates and seepage. In some
instances, blending two soil amendments prior to storage
(e.g., biosolids and fly ash) can overcome odor problems
and alleviate reduced usability due to rainfall exposure
while being stored. Other admixtures likely will show
similar characteristics if the soil amendments are paired to
be synergistic, i.e., each overcoming negative aspects of the
other.
5.4 Application
For some materials, such as biosolids, regulatory requirements may limit the steepness of a site
that can be approved for reclamation. In other cases, using soil amendments on sites with
The gradient or slope of a
project site influences
selection of soil amendments.
unusually steep gradients may have advantages. For
example, a blend of fly ash and biosolids has been shown
to become partially cemented onto a hillside at slopes
approaching 1:1 (100%) and, hence, highly resistant to
movement. Many of the state regulatory requirements for
maximum slope on a project site were developed with equipment limitations and runoff
considerations in mind. If a project can be designed to allow the equipment to remain on fairly
moderately sloping access roads on an otherwise steep site and limit surface water impacts, it
may be possible to obtain regulatory approval.
31
Project plans should reflect seasonal differences in potential adverse impacts from soil
amendment use. For example, excessive nitrate-N loss in winter may occur if nutrient-rich soil
amendments are applied after the growing season. The workability of the land surface may
degrade if soil amendments are applied during a rainy season, and seedling germination may be
inhibited by excessive drought if applied in the dry season. In addition, temperature may impact
the feasibility of onsite composting.
The amount of moisture in the soil amendment, commonly reported as % solids, is the
predominant characteristic that dictates application procedures and timing. Typical ranges of
solids content of biosolids applied to revitalization sites have included liquid sludge at 2-8%
solids, which can be pumped easily; semi-solid biosolids at 8-18% solids, which also can be
pumped (though less efficiently than liquids); and solid biosolids cake at 20-40% solids, which
may be flung from a manure-type spreader or end-dumped (Ref. 5).
Application rates typically are calculated on a dry-weight basis. This means that, for an average
dewatered biosolids (20% solids), application of 90 dry tons per acre would involve applying
450 tons per acre of material. This is a significant amount of material that can complicate
incorporation efforts. A variety of equipment technologies are available to perform direct
spreading, including farm manure wagons, all-terrain vehicles with rear tanks, and dump trucks.
Heavy applications like these can be accomplished using two basic techniques, both of which are
relatively easy and relatively inexpensive.
• Single application. The fastest and most cost-effective method is to make the total
application in a single —lift“ (an application that is immediately incorporated into the soil).
Depending upon the application rate and % solids, this may be as little as 1 to 30 inches in
depth. Soil amendment mixtures can be allowed to dry on the surface before incorporation.
This may take a complete summer period. Drying can be enhanced by seeding with a grass
that can germinate and withstand the
anaerobic conditions of the soil
amendments. A cereal grass such as
annual rye or wheat generally is very
effective for this purpose. Once the
soil amendment has dried, normal
farm disks or chisel plows can be used
to incorporate the mixture into the
subsoil. If the amendments are
incorporated into the soil when wet,
high moisture materials added at high
application rates will involve use of
heavy duty equipment (e.g., mine
disks) capable of deep mixing and
incorporation.
• Multiple lifts. Soil amendment applications also can be made in smaller or partial lifts. In
fact, some states require incorporation of biosolids within a certain time period. When
multiple heavy applications are needed within a short period of time, working the soil
becomes a challenge, because repeated applications followed by mixing without drying will
32
turn the soil into a deep quagmire (potentially far deeper than the actual depth of amendment
added). Costs will be significantly higher, because the soil is worked many more times in this
method.
There are several technologies that are effective for applying and incorporating materials at these
rates. Site topography, soil strength, evenness (including debris), and proximity to waterways are
the physical features that affect equipment selection. Easy access, stable soil, and a clear site
favor the simple methods, while rockiness, obstructions, or steep slopes necessitate special
equipment. The application rate also is important, as light applications need a more precise
method. Table 5 summarizes the common types of equipment available to make applications to
disturbed soil (Ref. 5).
• Incorporation. Incorporation of high rates of biosolids mixtures similarly require the
proper equipment and equipment operators. The low % solids of the biosolids means that
when making a 100 dry t/ac application, more than 500 wet t/ac of material may actually
be applied. Generally a large track bulldozer pulling a 36-inch disk is required. Smaller
equipment will just float on the surface of the biosolids mixture. Large chisel plows also
are capable of incorporating amendments. Achieving a completely homogenous mixture
is not possible when incorporating high rates of amendments. Although not always
necessary, maximizing soil-amendment contact whenever possible can increase the
effectiveness of the amendment.
In most cases, the municipality or private contractor that has applied the soil amendments for a
municipality or generator will have appropriate application equipment and operators. Arranging
for application and incorporation as part of the agreement to use biosolids from a municipality
may be the best way to ensure appropriate and cost effective application of the materials. If the
particular municipality does not have the appropriate equipment, others will. Examples of
municipalities and states that have large scale application equipment include: Chicago (contact
Thomas Granato, (708)222-4063); Virginia (contact Lee Daniels, [email protected]); Denver
(contact Bob Brobst, [email protected].gov); and Philadelphia (contact Bill Toffey,
[email protected]). Bob Bastian (U.S. EPA Washington, DC,
[email protected]) also has information on application equipment across the
country. For more information on application equipment go to
http://faculty.washington.edu/clh/whitepapers/biosolidswhite.pdf.
5.5 Blending
Individual soil amendments can be combined with other residuals to produce characteristics
optimal for revitalization of a particular type of site. For example, the target may be to produce a
blend containing a full range of nutrients with optimal soil pH and texture, or to moderate the pH
of an amendment mix or achieve a desired balance of C and N in order to reduce the risk of
nitrate leaching. Blending equipment may be required to achieve proper soil conditions when
using amendments. Two basic approaches are in situ mixing of soil amendments into the
receiving surface or a priori blending of a soil mix made from amendments followed by
emplacement onto the receiving surface. Both operations involve large-scale equipment. The
former requires large fixed pieces, such as pug mills or tub grinders, which may be movable
around the site but essentially blend and shred from a designated location that has a power
source. The use of tracked or wheeled vehicles to pull farm-like equipment for spreading and
33
plowing also can be used for in situ blending of amendments and soil. In either case, care should
be taken to avoid over mixing, particularly with biosolids, as this can result in a loss of flocculent
structure that makes the material difficult to apply. Operators also should monitor closely to
verify that proper ratios of materials are maintained. Experience with one large-scale remedial
action using blends of biosolids and fly ash in Pennsylvania revealed that the use of a large, fixed
mixing station was detrimental to the vegetation process, because the material was over-blended.
The resulting mix was difficult to apply and crusted after application, which slowed vegetation
emergence significantly. This was overcome by using a front-end loader to do much reduced
blending and by placing alternating buckets of amendments into the spreader truck. The action of
being thrown from the spreader achieved a uniform mixing of the amendments when applied
(Ref. 37).
Table 5. Comparison of Different Application Systems Used in Remediation (Ref. 5)
System Range
*
%
Solids**
Relative Costs Advantages Disadvantages
Biosolids dump truck
discharge, spreading
with dozer
10-15‘ > 12% Low capital, low
O&M
Simple to operate, fast
for high application
rates.
Need cleared, relatively
flat site, acceptable to
heavy equipment, difficult
to get even applications
for low application rates.
Application vehicle
with mounted cannon
Up to
125‘
< 12% Moderate capital,
high O&M
Can make even
applications for low
rates, any terrain.
May need special trails
with strength for repeated
trips, slow.
Application vehicle
with rear splash plate
10‘ 15-35% Moderate capital,
moderate O&M
Can make even
applications for low
rates, moderate terrain.
May need special trails
with strength for repeated
trips, slow.
Application vehicle
with side discharge
Up to
200‘
15-90% Moderate capital,
moderate O&M
Can make even
applications on any
terrain and at any rate,
including low rates.
May need special trails
with strength for repeated
trips, moderate speed.
Manure-type spreader -
rear discharge
10‘-30‘ > 25% Low capital, low
O&M
Can make even
applications for low
rates, moderate terrain.
Limited to high % solids,
trails may need to be close
together, moderate speed.
* Range is defined as the distance away from the equipment that the amendment material can be thrown.
** It is best to check with POTW about the equipment they use, because % solids may vary for different equipment.
NOTE: Injection may be applicable in particular situations, and should be evaluated on a case-by-case basis.
5.6 Public Considerations
Issues affecting the community living near or affected by a site where soil amendments will be
used should be taken into account when planning and implementing remediation and
revitalization plans. These include:
stakeholders in the decision-making
process is a key element in projects
to remediate and revitalize a site
using soil amendments.
The involvement of community
Public outreach. Public outreach in projects
involving the use of soil amendments should
include two-way communicationcommunicating
with/informing affected stakeholders about plans
and soliciting/listening to input from the
community on project plans. This is particularly
34
important when remedial or revitalization work is to be done on private property. Effective
public outreach can include the use of site tours, fact sheets, public meetings, media tours of
project sites, websites, and telephone hotlines. Public outreach is very important for projects with
significant potential for community impact, where health and environmental concern is high,
where costs and complexity are extraordinary, and where the final use of the site is a matter of
community concern.
Odor. Odor emissions can be a major cause of public dissatisfaction with projects using soil
amendments. Selection of amendments should take into account the potential for release of
odorants at malodorous intensities beyond the project boundary. Odor management, including
applying well stabilized material, avoiding land application when wind conditions favor transport
of odors to residential areas, minimizing the length of time that amendment materials are stored,
reducing visibility, maximizing the distance of the storage area from occupied dwellings, and
training all staff to identify and mitigate odors, should be a high priority throughout the project if
odorous soil amendments are used. More information on the causes of odor and a comparison of
various odor treatments can be found in EPA‘s Biosolids and Residuals Management Fact Sheet:
Odor Control in Biosolids Management (Ref. 51).
Demonstrations. Because revitalization projects frequently focus on sites of heightened
community or regulatory concern, and project managers may be held to a high standard of proof
when selecting amendments for in situ treatment, demonstrations of different residuals and
different ratios of residual mixtures may be warranted. Reviewing demonstration projects or pilot
studies in which various types of soil amendments have been used also may be helpful in
determining whether a particular type of amendment is appropriate for a similar site.
5.7 Costs
The volume of soil amendments needed, their availability, transportation, and onsite storage
issues are among the most important factors in determining per-acre costs of using soil
amendments to remediate and revitalize a site. These costs can vary widely. A project in which
amendments suitable for revitalization are already on site may cost up to $1,000 per acre treated;
a project requiring organic material alone to be delivered may cost $10,000 per acre treated; and
a site requiring a variety of soil amendments to cover and treat may exceed $100,000 per acre
treated.
One of the first large-scale demonstration of biosolids and lime addition at a Superfund site was
conducted in 2005 on about 40 acres at the California Gulch Superfund Site, Operable Unit 11,
in Leadville, CO (Ref. 49). The cost of the one-year field demonstration was estimated at about
$100,000 per acre. This cost included road construction through remote areas and extensive hard
engineering with rip-rap boulders, root wads, and bend-way weirs in areas that were treated. As
with many large demonstration projects, the cost of this demonstration included the capital
expended learning the best management practices (BMPs) that would serve to bring costs down
in future projects.
The Philadelphia Water Department (PWD) has used at least some of its biosolids for reclaiming
coal mines in Pennsylvania for over 25 years. Reclamation project sites receive approximately
200 tons (60 dry tons) of biosolids per acre. PWD uses contracted services on behalf of the
landowner, and these services include transporting biosolids to the site, final grading, liming,
35
temporary product storage, spreading, disking, seeding, and other services. Environmental
monitoring is not usually required, although the contractor should ensure that an adequate
vegetative cover is achieved across the entire treatment area and that soil pH is maintained for
two years after treatment. This bundle of services is charged to the city on the basis of the unit
cost of biosolids handled. The range in prices over the past ten years has been $40 to $50 per ton
of biosolids. At typical application rates, this converts to a cost of $8,000 to $10,000 per acre
(Ref. 45).
Similarly, costs for in-place treatment of acid metalliferous mine wastes using lime and compost
at the Clark Fork Superfund site in Missoula County, MT, are estimated to be in the range of
$6,000 to $10,000 per acre (Ref. 28). Costs for using soil amendments to reclaim approximately
1,000 acres of the Blue Mountain Operable Unit at the Palmerton Zinc Superfund Site in
Palmerton, PA, in the 1990s, ranged from $4,500 to $5,500 per acre (Refs. 36, 41).
In some cases, the cost of treatment can be reduced significantly if soil amendments can be
obtained without cost. For example, construction of the Stafford Regional Airport between 1998
and 2000 disturbed over 400 acres of land. Approximately 300 of these acres were contaminated
by sulfidic Coastal Plain sediments, which were intentionally spread across the final surface due
to their dark —organic-like“ color. These materials contained approximately 1% reactive iron
sulfides with virtually no inherent neutralizing capacity (Refs. 34, 15). By the fall of 2001, the
average soil pH across the site was around 3.0 with many locations having a pH of less than 2.0.
The main stem of the Potomac Creek, the second-order stream draining the airport‘s watershed,
was high in Fe and S and had an in-stream pH of 3.7.
Over the fall and winter of 2001, three rehabilitation alternatives were considered for this site. In
all cases, it was estimated that seed and mulch would add no cost. Alternative 1 involved the use
of lime stabilized biosolids. The biosolids sources bore the cost of the biosolids utilization
through biosolids management, transportation, and utilization contractual arrangements already
in place, resulting in a net price per acre of this option of $0 (Ref. 39). Alternative 2 involved the
use of agricultural lime and compost (Ref. 12). Studies on revegetation of sulfidic materials
indicated that these materials could be successfully revegetated/remediated via the application
and incorporation of 15 tons per acre of lime plus 35 tons per acre of yard waste compost (or
similar high quality organic soil amendment), plus minimal additional N-P-K fertilizer.
Estimated costs for these combined soil amendments (based on Virginia Tech Extension Service
Farm Budgets and proprietary information from the contractor would be $330,000, or about
$1,100 per acre. Alternative 3 involved use of an agricultural lime (applied at 100% of potential
acidity) treated/barrier layer in the surface of the acid-forming materials under a reduced
thickness (6 inch) soil cover for revegetation. Such covers are now routinely used in the
coalfields of southwestern Virginia on similar materials and have been quite successful. The
estimated cost for this conventional option would be $6,793,500, or $22,645 per acre (Ref. 10).
The utilization of lime-stabilized biosolids was elected as the optimal remedy due to obvious
economies, the presence of able and willing contractors, and the willingness of regulatory
agencies to allow Virginia Tech to monitor the site remediation as a research project. In the
spring of 2002, lime-stabilized biosolids from Blue Plains (Washington, D.C.), Upper Occoquan
(VA), and several smaller plants in Maryland were applied to various areas of the site according
to predicted potential acidity/lime demand of the upper 6 inches of the soil (Ref. 35). Due to
36
biosolids management and utilization arrangements with the contractors, all land application and
incorporation costs were borne by the biosolids sources (Ref. 10).
Even in cases where soil amendments themselves are donated, other costs may be incurred. Daily
cost for hiring a tractor trailer is about $600 (2006). The typical load capacity for a trailer over
the highway is about 23 tons. The number of daily
delivery trips and the possibility of splitting costs
with back-hauled deliveries are factors that
influence the unit charge for residual delivery to a
reclamation project. Distances of over 150 miles
between the origin of the residual and its destination make two deliveries per day unlikely;
distances less than 50 miles make three deliveries daily a possibility. As a result, unit costs may
range from $10 per ton for short haul, to $20 per ton for medium range, and $30 or more per ton
for long haul. Congestion in urban areas, tolls, traffic restrictions, and special truck equipment
needs may add a premium to vehicular costs (Ref. 45).
The cost of transporting residual
amendments may be the largest
budget item in a remediation project.
Costs for handling residuals at an application site will depend on the size of the field crew and
the number of pieces of equipment. An operator with a piece of field equipment (e.g., spreader or
front-end loader) may cost about $1,000 per day. Depending on the complexity of a field
operation (e.g., the extent of final grading and the number of passes with incorporation
equipment), a team of three operators may complete work at a rate of between 1 and 10 acres a
day. As a result, the cost per acre for equipment operation has a wide range of costs, from $300
to $3,000 per acre, with higher costs reflecting sites with extreme conditions of slope, poor soil
cover, or inadequate drainage (Ref. 45).
Costs for administrative and monitoring tasks also should be considered. These expenses will
vary considerably. At sites where contamination is not the primary issue, little environmental
monitoring is needed. At sites where daily testing is undertaken, as may be the case where
regulated residuals are used, the costs of monitoring may be significant, and the cost of
monitoring and administration may be $100 to $500 per acre (Ref. 45).
37
6.0
REVEGETATION OF AMENDED SOIL
While ecological function should be considered early in the site remediation process to ensure it
is properly implemented, revegetation is one of the final actions taken at a site. All site
revegetation involves careful planning that considers soil conditions, plant species, and past
experiences. Plans should address land uses that affect plant establishment. In addition, the post
-
revitalization land use will have a significant influence on designs, implementation, and costs.
6.1 Considerations with Site Revegetation
A variety of issues should be considered when revegetating sites where soil amendments have
been used. These include:
• Seedbed preparation is necessary to facilitate seeding and improve the probability of seeding
success. This includes leveling, breaking up large clods, and reducing soil seedbank and
competitive plants.
• Obtaining plants, from seed or growing stock, is best done with as much lead time as
possible. The availability of native plant materials from reliable sources is often limited.
Also, plants should be planted at the most opportune time. The Natural Resources
Conservation Service (NRCS) has Plant Material Centers which can augment commercial
nurseries, but need advance notice (Ref. 27). The Lady Bird Johnson Wildflower Center
(Ref. 19) and NRCS both maintain a list of native plant suppliers.
• Seeding of vegetation without supplemental irrigation should be done either in the spring, in
advance of wet weather, or in the fall after the growing season. Three principal seeding
methodsdrilling, broadcasting, and hydraulic seedingcan be used. Certified weed-free
seed with known germination rates should be used to avoid introduction of weeds or invasive
species that are difficult to eliminate after the fact. The seed source and quality should be
reported in post construction documentation.
• Including legumes in the seeding mixtures can prevent N deficiency. Legume species are
adapted to different soil conditions, so regional and soil-specific characteristics may have to
be taken into consideration in selecting legumes for the seeding mixture. Legumes should be
inoculated with their specific Rhizobium symbiont prior to application.
• Mulch can be used to stabilize reseeded areas prior to establishment of the seeded vegetation.
Mulch serves to decrease water erosion, reduce wind velocity, reduce soil crusting, decrease
rainfall impact, and decrease soil surface temperature and evaporation.
• Irrigation may need to be considered in planning for revegetation in some regions to ensure
successful plant establishment and avoid the potential for replanting in case of drought.
• Weed species represent one of the greatest threats to long-term success of soil-based
revitalization efforts. Close monitoring of the habitat during establishment and control of
invasive species is important because weeds and other invasive species can quickly disperse
and invade disturbed land, causing problems ranging from destruction of habitat for animals
native to the area, to pushing out native plants that help control erosion, to impacting land
value by limiting its use (Ref. 47, 48). Developing a weed management plan is
recommended.
38
• Managing wildlife, such as deer and beavers, is often overlooked but can be an issue.
Wildlife can over-browse a newly planted site and leave it vulnerable to invasive species.
Control options should be identified and explored with the local community to ensure they
are acceptable.
6.2 Native Plants
An Executive Order signed April 12, 1994, recognizes the need to conserve the biodiversity and
health of native plants to sustain the natural resource base in the United States. The
Native plant communities are best in
providing the ecological diversity and
long-term sustainability of the landscape.
reestablishment of native species and plant
communities should be emphasized where
appropriate and if commensurate with post
-
revitalization land use. However, for
landscapes that have been severely disturbed,
it is ecologically unrealistic to expect a return to baseline biological conditions. In some
situations, use of native plants in revitalizing a site may not be possible. One example is a site
that had heavy metal contamination of the soil. The native soil was very acidic, with a pH of 3.5
to 4.5. Following remediation, a soil pH of 6.5 or higher had to be maintained to prevent the
metals from going into solution. Even though the site was revegetated, the species that
previously existed there could not remain due to the dramatic soil pH change. The objective of in
situ treatment of contaminated lands using soil amendments is to establish a self-sustaining
system that does not rely on artificial inputs and, ideally, is similar to and provides nearly equal
ecological value as the undisturbed adjacent landscape. The production of native plant materials
for use in revitalizing lands is a rapidly expanding industry (Refs: 7, 47, 48).
The U.S. Department of Agriculture‘s Natural Resource Conservation Service Plant Material
Centers (http://www.nrcs.usda.gov/programs/plantmaterials/) provide native plants that can be
used in many revitalization projects (Ref. 27).
Scientists at the centers seek out and test the
performance of plants that show promise for
meeting an identified conservation need. After
species are proven, they are released to the
private sector for commercial production. The
work at the 26 centers is carried out
cooperatively with state and federal agencies,
commercial businesses, and seed and nursery
associations.
39
7.0
PERMITTING AND REGULATIONS
A variety of regulatory requirements may pertain to the use of soil amendments for ecological
revitalization (see Table 6). The type of amendment chosen will determine the pertinent
regulatory authorities. For example, biosolids are regulated under a "self implementing" rule
issued by U.S. EPA (40 CFR Part 503) under the joint authority of the Clean Water Act (CWA),
the Resources Conservation and Recovery Act (RCRA), and the Clean Air Act (CAA). At the
federal level, regulations are implemented by the EPA‘s Water Program, while the states regulate
and implement biosolids management programs through their water and/or solid waste
management programs. The federal biosolids rule (40 CFR Part 503) requires that land-applied
biosolids meet these strict regulations and quality standards (Refs. 50, 54). The 503 rule governs
the use and disposal of biosolids. It also specifies numerical limits for metals in biosolids and
pathogen reduction standards, site restrictions, crop harvesting restrictions and monitoring, and
record-keeping and reporting requirements for land applied biosolids, as well as similar
requirements for biosolids that are surface disposed or incinerated.
Soil amendments, such as foundry sand, may be regulated as hazardous wastes under the
Resource Conservation and Recovery Act (RCRA), but are exempt from Subtitle C restrictions if
they pass certain screening tests such as the Toxicity Characteristic Leaching Procedure (TCLP).
Regulations for these types of nonhazardous soil amendments are implemented primarily by state
solid waste programs. While federal RCRA regulations do not address using these materials as
soil amendments for revitalization, many states do regulate land application or beneficial
utilization of these products. In addition, the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA), also known as Superfund, or state cleanup
requirements should be addressed.
Beware of regulatory situations when two or more soil amendments are blended for use as a
remedial material. For example, when blending biosolids with fly ash, the biosolids are regulated
under the Clean Water Act self-implementing Part 503 rule as well as state water and/or solid
waste programs, and the fly ash is regulated as a solid waste under RCRA. If these types of
blends are envisioned, regulatory issues should be identified early in the project. At the
Palmerton, PA Zinc Smelter Superfund Project, which revegetated approximately 1,000 acres of
the nearby Blue Mountain, issues were identified concerning the blending of not only biosolids
and fly ash, but also blending the regulatory impact due to the biosolids being regulated under
the Clean Water Part 503 regulations, fly ash being regulated under RCRA, and the entire project
being regulated under Superfund. This site was on the Superfund list for excessive zinc, lead and
cadmium contamination of the soil. All biosolids and fly ash contain zinc, lead and cadmium.
The final resolution of the regulatory dilemma was to count the metals concentration contributed
by the fly ash added to the metals in the biosolids, and require that the total metals loading of the
blend could not exceed the maximum amount of metals allowed under the Part 503 biosolids
regulations for land application. It was also important to have this codified in a Consent Decree
to protect all parties involved (Ref.36).
40
Table 6: Regulatory Requirements for Sites Using Selected Soil Amendments
Organics
Biosolids Clean Water Act (40 CFR Part 503) Class B permit required (site restrictions); may be
possible to compost or otherwise treat the biosolids on site to reach Class A quality
(with no site restrictions);
For CERCLA actions, no permit required, but should adhere to spirit of state and local
permit requirements (ARARs) when possible;
State-specific regulations also may apply.
Manures Federal and state BMP nutrient management;
CAFOS may have bookkeeping requirements.
Pulp Sludges Dioxin concentrations restricted - voluntary or required by state standard 10 ppt TEQ
(toxic equivalent) for dioxin incorporated; may have high sodium which can limit
applications.
pH
Lime State-specific lime labeling requirements.
Wood Ash May be regulated as a caustic material; pH will decrease to 8.3 with exposure to air;
state-specific soil amendment or liming material regulations.
Coal Combustion
Products
State-specific regulations; NAS recommended increased study; coal mining site
regulation under SMCRA expected by 2008.
Red Mud Regulated as mining waste in situ, but labeled for application as soil amendment by
many states/localities.
Mineral
Foundry Sand and
Steel Slag
State-specific; different states may have restriction by grade.
Dredged Materials USACE regulations (to pull out of waterway) as well as State-specific (to land apply).
WTR State solid waste permits may be required to land apply.
41
8.0
BENEFITS OF USING SOIL
AMENDMENTS
The use of soil amendments has the potential to protect human health and the environment and
allows remediation, revitalization, and reuse of disturbed sites by reducing contaminant
bioavailability at lower cost than other available options. At many sites, this technology may be
the only economically viable treatment option. In addition, this approach offers the benefit of
recycling municipal and industrial residuals to reclaim damaged or disturbed land rather than
disposing of what is generally considered to be waste in landfills or by incineration.
The benefits of restoring contaminated land to natural habitats include: creating green space such
as wildlife sanctuaries; improving the aesthetic beauty and cultural stimulation for communities;
improving economic value; cleansing air and water; mitigating flooding; reducing wind and
water erosion of contaminated soil; generating and preserving soil; increasing evapotranspiration
of water from a site and reducing the amount of potentially contaminated water recharging
aquifers; cycling and moving nutrients; and partially stabilizing climate (carbon sequestration).
Benefits of Amendments
• Restore soil health and structure
vegetation
• Recreate ecological function of
soils
• Decrease bioavailability of toxic
pollutants
•
• Decrease erosion and improve
soil drainage
• Reduce costs compared to
traditional remediation
techniques
• May abate acid mine drainage
Benefits of Revitalized Land
• Provides wildlife habitat
• Provides improved water quality
in receiving streams
•
• Reuses of devoid and damaged
lands
• Improves property values
• Reduces wind- and water-borne
contaminants leaving the site
•
• Reduces the amount of possibly
contaminated water recharging
allowing establishment of
Decrease leachability and
mobility of contaminants
Sequesters carbon
Increases evapotranspiration
local aquifers
42
9.0
MONITORING AND SAMPLING
AMENDED SITES
EPA has developed a Web-
based tool to help site project
managers select appropriate
technical performance
measures (TPMs) for use in
demonstrating whether soil
amendments are functioning
as designed to reduce
contaminant mobility and/or
bioavailability. Remediation,
Revitalization, and Reuse:
Technical Performance
Measures contains a range of
potentially applicable TPMs.
These measures draw on the
collective knowledge and
experience of experts to
identify and document a core
set of commercially
available, cost effective, and
proven measures that are
consistent from region to
region, state to state, and site
to site. The range of TPMs
provides site managers the flexibility they need to design the most appropriate testing for their
sites while providing consistency and comparability between sites. Users can search a database
of TPMs by using criteria relevant for their particular sites. The search results provide
information about each TPM method that matches the selection criteria and provides comments
on issues to consider when using the method and references for additional information. These
TPMs will help site managers and other stakeholders assess if and when sites, where soil
amendments have been used for remediation, are ready for reusethat is, to determine when
contaminant bioavailability and or mobility are reduced such that the remediation is protective of
human health and the environment. To view or use the TPM tool, visit http://www.clu-
in.org/products/tpm/.
43
10.0
CONCLUSIONS
Many soils, particularly those found in urban, industrial, mining, and other disturbed areas suffer
from a range of physical, chemical, and biological limitations. These include soil toxicity, too
high or too low pH, lack of sufficient organic matter, reduced water-holding capacity, reduced
microbial communities, and compaction. Appropriate soil amendments may be inorganic (e.g.,
liming materials), organic (e.g., composts) or mixtures (e.g., lime-stabilized biosolids). When
specified and applied properly, these beneficial soil amendments limit many of the exposure
pathways and reduce soil phytotoxicity. Soil amendments also can restore appropriate soil
conditions for plant growth by balancing pH, adding organic matter, restoring soil microbial
activity, increasing moisture retention, and reducing compaction. However, the appropriate use
of soil amendments is completely dependent upon appropriate characterization of both the site
and the residual materials to be employed.
Soil amendments can reduce the bioavailability of a wide range of contaminants while
simultaneously enhancing revegetation success and, thereby, protecting against offsite movement
of contaminants by wind and water. As such, they can be used in situations ranging from time
-
critical contaminant removal actions to long-term ecological revitalization projects. Using these
residual materials (industrial byproducts) offers the potential for significant cost savings
compared to traditional alternatives. In addition, land revitalization using soil amendments has
significant ecological benefits including benefits for the hydrosphere and atmosphere.
44
Endnotes
1. ARCO. 2000. Clark Fork River Governor‘s Demonstration Project Monitoring Report
(1993-1996). Prepared for Atlantic Richfield Company (AERL), Anaconda, MT.
Administrative Record for the Clark Fork River OU of the Milltown Reservoir NPL Site.
U.S. EPA Region 8 Montana Office, Helena, MT.
2. Beckett, P.H.T. and R.D. Davis. 1977. Upper critical levels of toxic elements in plants.
New Phytologist 79: 95-106.
3. Berti, W.R. and S.D. Cunningham. 2000. Phytostabilization of Metals. pp. 71-88. In:
Raskin, I., and B. D. Ensley (Eds.) Phytoremediation of Toxic Metals-Using Plants to
Clean Up the Environment. John Wiley & Sons, New York. 234 pp.
4. Brady, N.C. and R.R. Weil. 2002. The Nature and Properties of Soils (13
th
Edition).
Prentice Hall, Upper Saddle River, NJ. 960 pp.
5. Brown, S.L. and C.L. Henry. Not dated. Using Biosolids for Reclamation/Remediation of
Disturbed Soils (White Paper). University of Washington. Seattle, WA. 26 pp.
6. Brown, S.L., R.L. Chaney, J. Halfrisch, and Q. Xue. 2003. Effect of Biosolids Processing
on Lead Bioavailability in an Urban Soil. J. Environ. Qual. 32:100-108.
7. Brown, S.L. and J. Dorner. 2000. A Guide to Restoring a Native Plant Community (White
Paper) University of Washington. Seattle, WA. 59 pp.
8. Chaney R.L. 1993. Zinc phytotoxicity. pp. 135-150. In A.D. Robson (ed.) Zinc in Soils and
Plants. Kluwer Academic Publ., Dordrecht.
9. Corker, A. 2006. Industry Residuals: How They Are Collected, Treated and Applied. Intern
Paper. Prepared for U.S. EPA Office of Superfund Remediation and Technology
Innovation. 52 pp. http://www.clu-in.org/studentpapers/
10. Daniels, W. L. 2006. Personal Communication.
11. Daniels, W.L., T. Stuczynski, R.L. Chaney, K. Pantuck and F. Pistelok. 1998. Reclamation
of Pb/Zn smelter wastes in Upper Silesia, Poland. pp. 269-276 In: H.R. Fox et al. (Eds.),
Land Reclamation: Achieving Sustainable Benefits. Balkema, Rotterdam.
12. Daniels, W.L., B.R. Stewart and D.C. Dove. 1995. Reclamation of Coal Refuse Disposal
Areas. Va. Coop. Ext. Pub. 460-131. 15 pp. http://www.ext.vt.edu/pubs/mines/460-
131/460-131.html
13. Dayton, E.A. and N.T. Basta. 2005a. Using Drinking Water Treatment Residuals as a Best
Management Practice to Reduce Phosphorus Risk Index Scores. J. Environ. Qual. 2005 34:
2112-1117. Invited manuscript for the special JEQ publication —Phosphorus Workshop: 4th
International Phosphorus Workshop: Critical Evaluation of Options for Reducing
Phosphorus Loss from Agriculture, Wagingenen, The Netherlands, August, 2004.“
14. Dayton, E.A. and N.T. Basta. 2005b. A method for determining phosphorus sorption
capacity and amorphous aluminum of Al-based drinking water treatment residuals. J.
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