ENGINEERING AND ENVIRONMENTAL GUIDANCE ON THE BENEFICIAL USE 

OF COAL COMBUSTION PRODUCTS IN ENGINEERED STRUCTURAL FILL 

PROJECTS 

Purpose Statement: 

This document is intended to provide Coal Combustion Product (CCP) Managers with 

information to ensure that CCP engineered structural fills are planned and implemented in a 

manner that protects the environment and meets regulatory requirements. 

Scope: 

This information is intended to be used in planning and implementing engineered structural fill 

projects associated with the beneficial use of"coal combustion products" including fly ash, 

bottom ash, boiler slag, or flue gas desulfurization (FGD) material produced primarily from the 

combustion of coal. 1 Engineered structural fill projects consist of either an engineered fill or an 

engineered embankment with a beneficial end use. 

2 Engineered structural fills are typically 

constructed in layers of uniform thickness and, where appropriate, compacted to a desired unit of 

density in a manner to control the compressibility, strength, and/or hydraulic conductivity of the 

placed material. 

The generic issues and examples in this Guidance are designed solely to be an educational 

resource for CCP Managers by illustrating the requirements and considerations that may apply to 

engineered structural fill projects and should be taken into consideration depending on the 

quantities of ash used at the site. The Standard Guide for Design and Construction of Coal Ash 

Structural Fills designated ASTM E2277-03 is incorporated herein by reference. Each CCP 

project should be evaluated for site-specific requirements including all permitting requirements 

and the project should be appropriately described. 

Characterization/Testing: 

CCPs should be adequately characterized to ensure that the proposed use of the material does not 

cause environmental or public health problems and has physical properties that are compatible 

with the end use. The characterization, at minimum, should demonstrate the physical 

characteristics, including geotechnical properties, and identifY the primary chemical constituents 

of the CCPs and leaching potential. CCPs should also be sampled and analyzed to verifY that the 

materials meet the applicable regulatory standards for beneficial use. CCP leach testing 

procedures should be selected based on the material used, hydrogeologic setting, and structural 

fill application. See Appendix 1 for a reference to guidelines for potentially applicable leaching 

tests. For assessing engineering properties of the CCP, refer to ASTM E-2777. 

1 Fly ash and bottom ash includes both materials produced by "conventional units" as well as fluidized bed boilers. 2 Examples of engineered structural fill projects include use as fill for building sites and foundations, subbase fill for 

recreational facilities, and as embankments for highways, railroads, dikes and levees. 
Samples should be representative of the CCPs supplied for the engineered structural fill. See 

Appendix 2 for a reference to guidelines for collecting a representative sample. The frequency at 

which the CCPs should be tested is dependent on the variability of the composition of the CCPs.3 

Moisture content of the CCPs should be evaluated in order to determine whether additional 

moisture is needed to condition the ash to help control fugitive dust and to enhance compaction. 

Project Suitability/Qualification: 

In addition to meeting all applicable state standards and guidelines, identifying a suitable site for 

an engineered structural fill using CCPs should include an evaluation of the site commensurate 

with the leaching potential of the CCPs, considering such factors as local zoning and land use 

plans, environmental characteristics of the proposed site, engineering aspects, and proximity to 

and relationship with landowners and neighbors. The historic use of the potential site and 

adjacent properties should be evaluated to assess whether there is potential for existing 

contamination at the site. In addition, consideration should be given to the reasonable future 

uses or planned development of the site and surrounding properties, including the distance 

between the potential site and adjacent properties. 

The soil, geology and groundwater of the proposed site should be evaluated. The site geology 

should be assessed for the presence of any conditions such as sinkholes, karst, or bedrock 

outcrops. Groundwater quality and quantity, the location of groundwater users, groundwater 

flow direction, and depth to the groundwater will be important considerations in the process. 

The evaluation should be done in a manner consistent with ASTM E 2277-03. See Section 7.2 

Site Characterization. 

Groundwater modeling is not typically necessary for hydrogeologic characterization in support 

of a structural fill plan. However, in some cases, particularly larger fills, modeling may be useful 

in evaluating the potential for groundwater impacts. Screening models such as EPA's IWEM 

and EPRI's MYGRT are typically sufficient given the nature of the sites and limited availability 

ofhydrogeologic data. Numerical models such as MODFLOW/MT3D are generally not 

warranted for these applications, except for very large sites in complex hydrogeologic 

environments. Brief descriptions of these models are provided in Appendix 3. 

The site should also be evaluated in relationship to its distance from surface waters, including 

wetlands, and the location of floodplains and other environmental regulatory constraints that 

could potentially impact the project. 

While site specific factors including size, rainfall, climate and terrain should always be 

considered, other considerations involving the location of the proposed engineered structural fill 

project include whether the site is: 

• Within floodplain, floodways and ·drainage areas, 

• In or near a wetland area, 

• Near an active fault, 

3 Additional testing should be conducted when conditions change that could significantly impact constituent 

concentrations in the CPP such as, for example, through the use boiler additives and/or changes in coal source or 

type. 

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• In an unstable area (e.g., in a karst area or areas prone to sinkholes), 

• Within a wellhead protection area, 

• Near a drinking water well, or near a public water supply, such as a community 

well, reservoir, or water treatment facility, 

• Near a surface-water body, such as a lake, stream, river, or pond, or 

• An impact on a critical habitat for an endangered or threatened species or an 

historic or archaeological site. 

The landowner(s) should provide written permission for using CCPs on the site. As appropriate, 

the presence of CCPs should be acknowledged on the deed to provide notice to subsequent 

purchasers of the site. 

Current site conditions and engineering and economic considerations, as well as the intended 

future use of the property, should be analyzed to ensure the material can be placed in a manner 

that will achieve needed structural stability. 

The ability of equipment to move on and around the site should be evaluated especially if a 

project will extend over months in which inClement weather is expected. On and offsite traffic 

limitations should be considered. 

Agency Communications: 

The state or local government agency responsible for administering the program for beneficial 

use ofCCPs will vary depending on the nature ofthe beneficial use. Site requirements for 

structural fill projects will also vary by locality. Where appropriate, details of the proposed 

structural fill should be discussed with the appropriate agency for their input. 

These steps may be useful during and after any project. 

1. Draft a plan for the proposed engineered structural fill and identify the agency responsible for 

approving the structural fill if approval is required. 

2. Contact the appropriate agency staff to discuss the proposed engineered structural fill project 

when the detailed plan is complete and approval is required. 

3. Provide the lead agency and other regulatory bodies with information they require to 

understand the project. 

4. Follow-up to ensure the project is meeting State and local government and community 

requirements. Maintain an active dialog with all parties and document all material 

discussions. 

Community Outreach: 

As appropriate, CCP Managers should contact local community officials and offer to meet with 

them to provide information and answer questions that they may have about the proposed 

project. 

After the operations commence, the CCP Manager should remain in contact with the local 

officials and offer to meet with them periodically to provide a project update and to answer 

questions that may be raised. 

Local officials should be provided with a contact name, address and telephone number that they 

may use to inquire about the ongoing project. 

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Contractor Performance Standards: 

CCP Managers should consider the reliability, performance history, compliance and safety 

records of any potential contractor. The contractor selected should have proven technical 

capabilities and experience with CCP placement. The potential contractor's financial resources 

and financial stability should be assessed prior to signing a contract, to ensure that the contractor 

has the ability to fulfill the obligations of the contract. 

The contract should include conditions requiring the contractor to comply with all local, state 

and federal highway regulations during hauling of the CCP, and all local, state and federal 

environmental and occupational safety and health regulations during all of its operations. It 

should also address how the contractor's performance will be assessed. Oversight of contractor 

performance should be ongoing. 

Transportation on Public Roadways: 

Possible community concerns associated with transportation routes should be identified, 

reviewed and properly addressed prior to project implementation. Access routes to the project 

site should consider: 

• Impact on local communities. 

• Road conditions. 

• Timing of transportation. 

• Volume oftraffic. 

• Noise. 

• Vehicle operational condition and cleanliness (free of dust and dirt). 

Drivers or other personnel should ensure that vehicles are loaded and unloaded in a manner that 

minimizes the generation of dust and should ensure that all trucks are covered while in transit. 

Vehicles must be operated and maintained in a safe working order and in compliance with all 

applicable federal, state, and local requirements. They should not negatively impact road 

conditions or safety, especially at project ingress and egress locations. 

For examples, see Appendix 3. 

Project Operation Controls and Security: 

Site Access Controls- To the extent possible, access controls should be utilized at the placement 

site to discourage unauthorized entrance to the site. Controls should be implemented to ensure 

appropriate pickup and delivery of CCPs. 

The construction of engineered structural fills should follow the procedures described in Sections 

7.7.6 & 8 "Construction" of the ASTM E 2277-03 Standard Guide for Design and Construction 

of Coal Ash Structural Fills. The ASTM standard includes operating procedures for weather 

restrictions, dust control, erosion control, source and delivery, on-site storage, site preparation, 

placement and compaction, cover and quality control. These standards are incorporated herein 

by reference. 

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Spill/Off-Site Release Response: 

Trucks hauling CCPs on public roadways should have a Material Safety Data Sheet and should 

be responsible for responding to spills. All CCPs spilled during transit should be cleaned up and 

either taken to the placement site or returned to the plant of origin. 

A plan should be developed for potential off-site releases. The plan should identify the 

individual who is responsible for implementing response actions and notifying appropriate 

regulatory officials, contact information for response assistance, procedures to follow in the 

event of an offsite release, and an inventory of response equipment/services. In the event of an 

off-site release, all discharges of CCPs should be cleaned up and returned to the placement site. 

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APPENDIXl 

Characterization/Testing: 

Examples of leaching procedures: 

• EPA SW846 Method 1313- 1316, 

Methods 1313 through 1316 are a recently developed set of procedures designed to fully 

evaluate leaching potential under a wide range of potential environmental conditions, 

sometimes collectively referred to as the Leaching Framework. The framework includes 

batch leaching as a function ofpH (1313), column leaching (1314), mass transfer leaching 

for monolithic materials (1315), and batch leaching as a function of solid-liquid ratio (1316). 

Selection of tests depends on the CCP material and the expected range of environmental 

conditions associated with the structural fill application. 

• EPA SW846 Method 1312, Synthetic Precipitation Leaching Procedure (SP LP) 

The SPLP is a single point batch leaching test similar to the TCLP but uses a nitric and 

sulfuric acid leachant to simulate acid rain. SPLP is commonly used to assess infiltration and 

leaching at CCP sites. 

• ASTM D3987, Shake Extraction of Solid Waste with Water 

ASTM D3987 is a single point batch leaching test similar to the SPLP but uses a deionized 

water leachant. ASTM D3987 is commonly used to assess infiltration and leaching at CCP 

sites. 

APPENDIX2 

Collecting Representative Samples: 

Examples of reference guidelines for collecting a representative sample. 

• EPA SW846 Test Methods for Evaluating Solid Waste, Physical/Chemical Methods 

http://wvvw.epa.gov/epaoswer/hazwaste/test/sw846.htrn 

• ASTM D75 Practice for Sampling Aggregates 

• ASTM C311 Test Methods for Sampling and Testing Fly Ash or Natural Pozzolans for Use 

as a Mineral Admixture in Portland-Cement Concrete. 

APPENDIX3 

Site Modeling Tools 

• Industrial Waste Management Evaluation Tool ("IWEM") 

IWEM (USEPA, 2002) was developed by EPA as a screening tool to evaluate industrial 

waste disposal and use applications. IWEM is easy to use and can be run with very little sitespecific hydrogeologic data. The core model in IWEM is the EPACMTP (USEPA, 2003) 

analytical model, which simulates the migration of dissolved constituents through soil and 

groundwater. The model accepts input values describing geology and infiltration at the site, 

and then performs a Monte Carlo analysis using a range of values for attenuation parameters 

and hydrogeologic parameters, producing over 10,000 realizations. For each of the Monte 

Carlo realization, IWEM allows up to 10,000 years to reach a maximum concentration. 

Output for individual realizations are not provided. A facility design is deemed "protective" 

if90 percent of the IWEM realizations predict maximum concentrations at the compliance 

point that are lower than the appropriate health-based number or water quality standard. 

• MYGRT 

MYGRT Version 3.1 (EPRI, 2005) is a collection of22 analytical models that calculate the 

transport of organic or inorganic constituents in the unsaturated and saturated zone, 

accounting for the processes of advection, dispersion, retardation, and decay. All of these 

models are based on analytical solutions to the 1D, 2D, and 3D mass transport equations. 

Inputs are specified by the user, and output is provided for each set of input parameters 

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provided. The model will accept time-varying leachate concentrations, and can be run for 

any length time period. MYGRT is easy to use and requires minimal or estimated sitespecific data; it is most appropriate for screening level applications and relatively simple 

hydrogeologic settings. 

• MODFLOW/MT3D 

MODFLOW is a numerical groundwater flow code developed by the United States 

Geological Survey (McDonald and Harbaugh, 1988) that uses a finite difference 

approximation to solve a three-dimensional head distribution in a multi-layered aquifer. The 

program also calculates water balance at wells, rivers, and drains. MT3DMS (Zheng and 

Wang, 1998) is a transport code that uses a finite difference solution to calculate 

concentration distribution for a single dissolved solute as a function oftime and space. 

MT3DMS accounts for advection, dispersion, diffusion, first-order decay, and sorption. 

Sorption can be calculated using linear, Freundlich, or Langmuir isotherms. 

MODFLOW/MT3D are relatively time consuming codes to set up and calibrate, and are most 

applicable for large sites with complex and well characterized hydrogeology. 

APPENDIX4 

Transportation on Public Roadways: 

Examples to consider: 

1. Ensure vehicles, company and contractor, are in safe working order and associated 

inspections are up-to-date. 

2. Ensure contractors are adequately insured. 

3. Investigate compliance history of contractors. 

4. Ensure proper vehicle washing at loading and unloading areas. 

5. Proper vehicle covering: 

• The cover must be made of a solid or close weave mesh material. 

• The cover must be large enough to enclose the top of the entire load. 

• The cover must be sufficiently secured. 

• The cover must be kept in good repair 

6. Ensure proper construction and maintenance of access and egress points to public roadways. 

This could include construction of temporary roadways and use of flagmen or other traffic 

flow devices. 

7. Evaluate whether water must be added to condition the ash to help control fugitive dust. 

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References 

USEPA, 2002. Industrial Waste Management Evaluation Model (IWEM) Technical Background 

Document. Office of Solid Waste and Emergency Response, EPA530-R-02-012. 

USEPA, 2003. EPACMTP Technical Background Document. Office of Solid Waste and 

Emergency Response, EPA530-R-03-006. 

McDonald, M.G. and A.W. Harbaugh, 1988, A Modular Three-Dimensional Finite-Difference 

Ground-Water Flow Model: Techniques of Water-Resources Investigations, Techniques of 

Water-Resources of the United States Geological Survey, Book 6, Chapter AI. 

Zheng, C., and P.P. Wang, 1998, MT3DMS, A Modular Three-Dimensional Multispecies 

Transport Model, Model documentation and user's guide prepared by the University of Alabama 

Hydrogeology Group for the U.S. Army Corps of Engineers. 

EPRI, 2005. MYGRT Version 3.1. EPRI, Palo Alto, CA: 2005. 1010066 

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