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7 Management of Coal Combustion Residues in Reclamation Activities T his chapter describes the basic principles and minimum standards for reclamation and monitoring that should apply to all large-volume minefill applications of coal combustion residue (CCR) in coal mines. It discusses reclamation planning, bonding requirements, reclamation operations, and how CCRs can be incorporated into the reclamation process. The chapter also dis- cusses the hydrological monitoring that accompanies the use of CCRs in reclama- tion. It outlines the regulatory framework for monitoring at CCR mine placement sites, highlights concerns about existing monitoring programs, and provides rec- ommendations for effective and efficient monitoring programs. It should be noted that the principles and standards for monitoring do not apply to the use of CCR as traction material for haul roads or other incidental low-volume uses. Also, the reclamation section of this chapter does not specifically consider the placement of CCRs in underground mines, which poses more complex technological diffi- culties--especially abandoned underground mines, where there is no practical way to isolate the CCR from the surrounding hydrologic regime. RECLAMATION Reclamation planning is an integral part of the entire mining process and begins before excavation is started. As discussed in Chapter 5, reclamation prac- tices are, by definition, regulated by the SMCRA, which established minimum national standards for coal mining. Thus, the use of CCR for minefill has to be viewed in the context of the general reclamation management activities and re- quirements. 155
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156 MANAGING COAL COMBUSTION RESIDUES IN MINES SIDEBAR 7.1 A Partial List of the Reclamation Plan Requirements Found in Section 508 SMCRA · Identify lands subject to surface coal mining along with the size, sequence, and timing of the subareas; · Document the condition of the land prior to any mining, including the capa- bility of the land to support a variety of uses; · Describe the use that is proposed to be made of the land following reclama- tion, including the utility and capacity of the reclaimed land to support a variety of alternative uses; · Describe how the proposed post-mining land use is to be achieved, includ- ing any necessary support activities; · Provide the engineering techniques proposed for use in mining and recla- mation, and describe the major equipment to be used; included in this requirement are a drainage plan, a backfilling and grading plan, a soil replacement plan, and a revegetation plan; and · Include a timetable for the accomplishment of the plan. Reclamation Planning Requirements The surface mine permit requirements under SMCRA specify the minimum requirements of the reclamation plan (see Sidebar 7.1). The use of CCRs in reclamation would have to be reflected in this plan, especially in the engineering analysis. In general, there are two levels of land-use planning in any reclamation. At the macro level, land-use planning is carried out by government agencies charged with land-use oversight. This results in comprehensive land-use plans that may be accompanied by zoning regulations or other performance standards. However, in many coal mining areas, such an approach to land-use planning does not occur. At the micro level, land-use planning (also called site planning) is driven prima- rily by economic factors that are influenced by natural environmental and cultural conditions in and around the site. The relationship between the two levels of land- use planning is illustrated in Figure 7.1. The reclamation plan that is done at the micro level and is prepared by surface mine operators includes a post-mining environmental site plan. This land-use plan is developed using site planning principles while conforming to any macro-level community plans that may exist. It also must consider the landowner's wishes in the case of leased land. The planning process begins with a thorough analysis of the current site conditions at the mine and the site conditions that are projected to exist following the completion of mining. Site conditions can be categorized as natural environ- mental factors and cultural factors. In general, natural environmental factors tend
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COAL COMBUSTION RESIDUES IN RECLAMATION ACTIVITIES 157 LEVEL I (MACRO SCALE): COMPREHENSIVE COMMUNTIY PLANNING IDENTIFICATION OF DEVELOPMENT OF DEVELOPMENT OF DEVELOPMENT OF OVERALL COMMUNITY PLANNING COMMUNITY ZONING AND GOALS AND CRITERIA MASTER PLAN OTHER ORDINANCES OBJECTIVES SITE EVALUATION IDENTIFICATION OF REVIEW OF DETAILED LAND --------------------------- ALTERNATIVE ALTERNATIVES USE PLAN DESIGN CULTURAL FACTORS LAND USE AND APPROVAL NATURAL FACTORS SCHEMES OF A FINAL LAND USE PLAN PREPARATION OF CONSTRUCTION DOCUMENTS LEVEL 2 (MICRO SCALE): ENVIRONMENT SITE PLANNING FIGURE 7.1 Planning levels involved in the mine and land planning process. SOURCE: Ramani and Sweigard, 1984. Courtesy of the Society for Mining, Metallurgy, and Exploration. to set physical limits on post-mining land-use capability, while cultural factors have a significant impact on the economic feasibility of any post-mining land use. The natural environmental factors that have the greatest impact on land-use capa- bility include topography, climatology, hydrology, geology, and soil properties. A number of these are impacted by the placement of CCR in the mine. The cultural factors that impact economic feasibility include location, surrounding land uses, and local population characteristics. Post-mining land-use plans must take into account both types of factors. The permitee (i.e., the surface mine operator) is responsible for proposing the post-mining land use, considering land- owner wishes and existing macro-level community land-use plans. The SMCRA regulatory agency has the final authority to approve or disapprove of this plan. Use of CCR in Reclamation Operations Coal combustion residues have been used in the reclamation of both aban- doned mines, as defined by Title IV of SMCRA, and active mines that are regulated under Title V. The use of CCR in reclamation is not addressed specifically in the regulatory performance standards derived from SMCRA for either active or aban- doned mines, although the regulations do allow coal mine waste to be discharged into underground mines as long as the plan is approved by the regulatory authority
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158 MANAGING COAL COMBUSTION RESIDUES IN MINES (30 CFR. §817.81(f)). However, because SMCRA requires a detailed reclamation plan, including a description of all methods and materials to be used in the reclama- tion of an active mine, the use of CCR becomes part of the permit approval process. The extent to which the use of CCRs in reclamation operations is addressed by state regulations varies considerably from state to state. The disposal of CCRs in coal mines occurs under highly variable conditions, ranging from small quantities to massive minefills, from arid to wet regions, from remote to semiurban locations, from surface to underground mines, and from active to abandoned mines. Because of this variability, reclamation plans have to carefully consider site-specific conditions, such as climate, quantity of CCR to be disposed, and post-mining land uses. The committee endorses the concept of site- specific management plans. A flexible approach to managing CCRs in mine sites has advantages since it can embrace the unique characteristics of the CCRs, the total mass of CCRs, and the environment into which they are placed. However, the need to incorporate site-specific factors should not be a basis for adopting management plans that lack rigor. Such plans should be developed in compliance with management and performance standards for using CCRs in minefilling (see Chapter 8 for a complete discussion of the committee's recommendations on enforceable standards). Primary Reclamation Operations Involving CCRs Although reclamation operations vary regionally, they have several common elements that are conducted regularly as part of the mining cycle. Sidebar 7.2 provides a listing of reclamation operations and the sequence in which they occur for active mines. The primary reclamation operations, whether for active or aban- doned mines, are backfilling and grading, topsoil replacement, and revegetation. These are also the specific reclamation operations most readily impacted by CCR placement and are discussed more fully below. Backfilling and Grading. Surface mining of coal involves the creation of an excavation down to the coal, removal of the coal deposit, and subsequent back- filling of the excavation with overburden from succeeding excavations. Backfill- ing and grading are significant components in satisfying the SMCRA require- ment of returning the land to its approximate original contour following surface mining of coal. The method of backfilling is dependent on the type of mining that is being conducted (Sidebar 7.3). The process of returning the site to its approximate original contour by backfilling and grading is often complicated by either a lack or an overabundance of spoil. A lack of spoil occurs when the coal seam is thick in comparison to the amount of overburden. Conversely, in areas of steep terrain, there may not be enough available space on the bench to contain the rock overburden, which increases in volume when it is fragmented and excavated. In areas of thin over-
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COAL COMBUSTION RESIDUES IN RECLAMATION ACTIVITIES 159 SIDEBAR 7.2 Time Sequence for Reclamation Activities I. During site preparation: 1. Install control measures (water diversion, sediment traps and basins, etc.). 2. Clear and grub, marketing lumber if possible; stockpile brush for use as filters; run brush through wood chipper, and use chips for mulch. 3. Stabilize areas around temporary facilities such as maintenance yards, power stations, and supply areas. II. During overburden removal: 1. Divert water away from and around active mining areas. 2. Remove topsoil or topsoil substitutes and store it if possible and/or nec- essary. 3. Selectively mine and place overburden strata if possible and/or neces- sary. III. During coal removal: 1. Remove all coal insofar as possible. 2. For the purpose of controlling post-mining groundwater flows, break--or conversely prevent damage to--the strata immediately below the coal seam as desired. IV. Immediately after coal removal: 1. Seal the high wall if necessary. 2. Seal the low wall if necessary. 3. Backfill--bury toxic materials and boulders, dispose of waste, ensure compaction. V. Shortly after coal removal: 1. Rough grade and contour, taking the following factors into consideration: a. Time of grading--specific time limit tied to advance of mining; sea- sonal conditions b. Slope steepness c. Length of uninterrupted slope d. Compaction e. Reconstruction of underground and surface drainage patterns 2. If necessary, make mine spoil amendments (root zone), taking the fol- lowing factors into consideration: a. Type of amendment--fertilizers, limestone, fly ash, sewage sludge, or others b. Depth of application c. Top layer considerations--temperature, water retention, mulching, and tacking VI. Immediately prior to first planting season: 1. Fine-grade and spread topsoil, taking seasonal fluctuations into consid- eration. 2. If necessary, manipulate the soil mechanically by ripping, furrowing, deep-chiseling or harrowing, or constructing dozer basins. 3. Mulch and tack. VII. During the first planting season: Seed and revegetate, considering time and methods of seeding, and choice of grasses and legumes. VIII. At regular, frequent intervals: Monitor and control slope stability; water qual- ity, both chemical (pH, etc.) and physical (sediment); and vegetation growth. SOURCE: After Ramani and Clar, 1978.
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160 MANAGING COAL COMBUSTION RESIDUES IN MINES SIDEBAR 7.3 Backfilling Methods for Surface Mining Operations In the midwestern United States and portions of the west where area surface mining is practiced, the overburden is removed using large fixed-base stripping equipment such as draglines or bucket wheel excavators. In those cases, the strip- ping equipment casts the overburden directly into the excavated pit after the coal has been removed. In the steep slope areas of the eastern United States, two different types of surface coal mining methods are commonly practiced. The con- tour mining method utilizes mobile equipment to haul the overburden along the contour from the area of the pit from which it is excavated to the area of the pit where coal has already been removed. The mountaintop removal method always utilizes mobile equipment to haul overburden either to an area on the bench where coal has been removed or to an excess spoil disposal area such as a valley fill. Some mountaintop removal mines also use draglines to remove overburden from lower coal seams. In these cases, the overburden is directly cast by the dragline as it would be in an area mine. In parts of the western United States, an open pit type of surface coal mining method is used. Large trucks haul the overburden around the pit and dump it in the part of the pit where coal has been removed. In almost all cases, some grading with dozers is necessary to achieve the approximate original contour after backfilling is completed. burden, CCRs are used as structural fill material to raise the elevation of the surface and help achieve the approximate original contour. This can reduce the angle of the final slopes and, if necessary, fill in the final cut. In steep terrain, CCRs are used to backfill and seal the holes left in the highwall by augering and highwall mining. If there is sufficient alkalinity in the CCRs, they can be used in backfilling to neutralize acid formed through sulfide oxidation reactions (see Chapter 3). When CCRs are used in mine backfilling, there are important design factors that should be evaluated in the reclamation planning process by considering the site characteristics, the levels of uncertainty in the site conceptual model, and the estimates of risk (see Chapter 6). Emplacement of CCRs can occur above or below the water table and in volumes that range from small to large. As discussed in Chapter 2, CCRs can be disposed as monofills, as layers interbedded with coal spoils, or as blended mixtures with coal spoils (Figure 2.9). Compaction and/or cementation can also be used to increase the strength of the material and decrease its permeability. If CCRs are used to moderate the effects of acid mine drainage, additional factors such as acid-base accounting and blending CCR with spoil will have to be considered. The impacts of various CCR emplacement designs on groundwater flow and contaminant transport are discussed in detail in Chapter 3.
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COAL COMBUSTION RESIDUES IN RECLAMATION ACTIVITIES 161 However, site-specific conditions and CCR characteristics will ultimately influ- ence the relative importance of each of these factors at a CCR disposal site. Topsoil Replacement. The SMCRA regulations contain specific requirements for the removal, storage, and redistribution of topsoil. The methods used to sat- isfy SMCRA requirements vary depending on site conditions and from region to region. The most stringent topsoil requirements apply to those areas that are designated as prime farmland. In these cases, the mine operator is required to remove, store, and replace a minimum of 48 inches of soil while segregating the topsoil (A horizon) from the lower soil horizons (the B and C horizons). They must be stored in separate stockpiles, temporarily revegetated, and then replaced in the proper order to ensure that the best growing medium is at the surface. In some steep slope areas where topsoil is extremely thin and of low quality, se- lected overburden materials are used as a substitute for topsoil when it can be demonstrated that the resulting medium is equal to or better than the existing topsoil for sustaining vegetation. In some cases, CCR is used as a soil additive to neutralize acidic soil. However, as discussed in Chapter 4 and in the following section, the uptake by vegetation of metals and other contaminants that may be present in CCRs is a concern. Revegetation. Revegetation operations satisfy two separate SMCRA require- ments. The first requirement is stabilization of the surface to prevent erosion and sedimentation. The second requirement is to establish the type of vegetation that is needed for the proposed post-mining land use. If the vegetation does not satisfy the coverage requirements due to climatic conditions, repairs are made to the surface, and seed and mulch are reapplied as needed. Many post-mining land uses, such as prime farmland, commercial forestry, and wildlife habitat, have specific revegetation requirements with very specialized planting practices. The uptake by vegetation of metals and other contaminants that may be present in CCRs is a concern, especially when the reclaimed land will be used as farmland. Sufficient soil cover, which is appropriate for the type of vegetation, is necessary to minimize plant uptake (see Chapter 4). Reclamation of Abandoned Mine Lands The purpose of the Abandoned Mine Land Program is to protect public health and safety and remediate environmental damage caused by coal mining prior to the passage of SMCRA. Abandoned mine sites do not generally have to satisfy the post-mining land-use planning requirements that are part of the permit applications for active surface mines. One of the most common uses of CCR in abandoned mine reclamation is as structural fill material used to backfill aban- doned pits. This has been practiced fairly extensively in the anthracite region of Pennsylvania (Sidebar 2.7). CCRs are also used for stabilization of abandoned
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162 MANAGING COAL COMBUSTION RESIDUES IN MINES highwalls, sealing of abandoned underground mine openings, and capping or encapsulating material in abandoned coal refuse piles. These applications serve the dual purpose of decreasing infiltration into the refuse and helping to neutral- ize acid drainage from the piles. Finally, CCRs are used as either a soil amend- ment or a soil replacement, particularly at abandoned mine sites where topsoil may be totally lacking (see Chapter 2). However, plant uptake of contaminants must be considered when CCRs are used as a soil replacement. Design Considerations to Limit Interactions with the Hydrologic Regime As discussed in Chapter 6, CCR management requires an understanding of risk, and careful placement design can be used to moderate the environmental and human health risks of CCR disposal in mines. Given the known impacts that can occur when CCRs react with water in surface impoundments and landfills, CCR placement in mines should be designed to minimize reactions with water and the flow of water through CCRs. Regardless of whether the CCR is placed in an active or an abandoned coal mine, the issue of limiting the interactions of CCRs with groundwater should be a priority. There are a number of methods for reduc- ing the interactions of CCR with water, although none will guarantee that CCRs remain totally isolated from infiltration. These methods are described below. Many states have specific regulations requiring CCR to be placed at a mini- mum distance above the regional water table and above the floodplain associated with a storm of specified frequency. Appendix F describes both SMCRA and state regulatory requirements for isolation of CCRs from contact with water. This method is sometimes referred to as "high and dry"; however, it must be under- stood that placing CCR above the water table does not guarantee that there will be no interaction with groundwater (see Chapter 3). Many coal seams are underlain by a clay or shale layer. These strata gener- ally behave as an aquitard and can minimize the amount of leachate that migrates from CCR placed above them. The effectiveness of geologic isolation depends on the nature and thickness of the aquitard and the extent of natural fracturing. The aquitard can also be damaged by heavy equipment during the mining process. Compaction and cementation may also be used to minimize the interactions between CCRs and groundwater. Certain types of CCRs can be compacted to achieve a hydraulic conductivity of 10-7 cm/sec when they are properly placed in lifts and compacted, thus creating a zone of lower permeability. Depending on the conductivities of the surrounding strata, effective compaction of CCRs may cause groundwater to be diverted around the CCR. There may remain preferential water movement through compacted CCRs under certain unsaturated zone mois- ture conditions (see Chapter 3). The cementitious properties of some CCRs can also be used to limit the interaction between CCR and groundwater. Concerns have been raised, however, about the long-term stability of cementitious ash when lime is not added to ensure cementation (McCarthy et al., 1997). The
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COAL COMBUSTION RESIDUES IN RECLAMATION ACTIVITIES 163 degree of cementation also influences whether or not the CCR will contribute to acid neutralization reactions. Clay or synthetic liners are often used in landfill settings to minimize the movement of leachate from the site, and liners are design options for CCR dis- posal at higher-risk mine sites. The construction of effective liners in mine set- tings, however, may be operationally challenging. When properly installed and maintained, liners form a barrier between the material placed above the liner and the underlying hydrologic regime. It should be noted, however, that liners have often been known to leak after a number of years. The design and construction of liners must follow strict quality control procedures. For example, clay must be placed in controlled lifts and compacted to meet the specified standard of hydrau- lic conductivity of 10-7 cm/sec or less. Ideally, the entire area to be filled is excavated, smoothed, and leveled before the liner is installed, which is generally not possible in active coal mines. Caps and covers can also be constructed to limit infiltration into the CCR at higher-risk sites. Similar standards for clay liners apply for the design and con- struction of clay caps. Normally caps consist of a layer of soil covered with vegetation. There are also alternative designs to caps and barriers, including geomembrane covers, evapotranspiration covers, and capillary barriers. Evapo- transpiration covers are designed to hold any infiltrating water in the soil zone until it is removed by evapotranspiration. Capillary barriers utilize differences in pore-size distributions and the corresponding differences in capillary (suction) forces to prevent percolation of water into the CCR so that no leachate is gener- ated (USDOE, 2000). However, the design of these covers requires careful analy- sis of the various parameters involved and is specific to a given location (ITRC, 2003). The idea of using evapotranspiration covers or capillary barriers has not been applied to CCR backfills to date but has been successfully employed in several landfills. An issue associated with any cap or cover is whether parts may eventually become saturated and allow infiltration. If substantial reductions in across-site recharge occur as a result of CCR isolation management strategies, it is assumed that appropriate engineered recharge augmentation will occur to com- pensate (see NRC, 1990). Reclamation Bonding Before a mine permit can be issued and mining begun, a surface coal mine operator is required to post a reclamation bond. The purpose of the bond is to ensure that the approved reclamation plan will be completed in its entirety. If the operator defaults on the conditions of the permit, the bond amount is forfeited and the regulatory authority can use the funds to contract with a third party to com- plete the reclamation according to the approved plan. The regulatory authority has the responsibility for determining the bond amount based on the specific conditions of the site and holds the bond until the completion of reclamation. The
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164 MANAGING COAL COMBUSTION RESIDUES IN MINES SIDEBAR 7.4 Bond Release Phases · Phase I requires the completion of all backfilling, grading (including topsoil replacement), and drainage control; 60 percent of the bond amount can be re- leased at this point. · Phase II requires that revegetation be established according to the ap- proved reclamation plan; the amount of the bond released at this point may vary from state to state but is typically in the range of 25 percent. · Phase III requires the successful completion of all specified reclamation activities at which point the final portion of the bond can be released except that the final bond release cannot occur before the minimum required liability period has ended. regulations derived from SMCRA allow for a phased bond release after reclama- tion milestones are achieved (see Sidebar 7.4). The minimum liability period commences "after the last year of augmented seeding, fertilizing, irrigation or other work in order to assure compliance" (Sur- face Mining Control and Reclamation Act of 1992, H.R. 4381, 102d Cong. 2d sess., 4 March 1992). It is specified as five years except where the average annual precipitation is 26 inches or less, in which case the minimum liability period is ten years. In all cases the actual amount of time that a surface mine is covered by a reclamation bond will exceed the minimum, since the liability period is related to revegetation and this is not started until all coal removal, backfilling, grading, and topsoil replacement have been done. Surface mine operators seek bond release to unencumber financial resources that are committed to reclamation bonds. However, the reclamation bond require- ments established by SMCRA present another strong incentive for the operator to satisfy all reclamation performance standards. If a company defaults on a recla- mation bond, that company or any successor companies involving officers of the defaulting company are prohibited from obtaining another surface mine permit in any state. The name of the company and its officers are entered into the Office of Surface Mining (OSM) Applicant Violator System, which is used to screen any new permit applications. The use of CCRs in active coal mines has raised questions regarding the adequacy of current SMCRA reclamation bond requirements. Specifically, con- cern has been expressed about the length of the liability period and the adequacy of the remaining reclamation bond to treat any groundwater impacts that may occur after the bond is released. This issue is discussed further in Chapter 8. Possible parallels exist between impacts from CCRs and the formation of
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COAL COMBUSTION RESIDUES IN RECLAMATION ACTIVITIES 165 acid mine drainage (AMD) at surface coal mines requiring long-term treatment. If AMD is detected before final bond release, OSM has the authority to require the bond amount to be adjusted accordingly and held indefinitely until it is replaced by some other enforceable contract or mechanism to ensure continued treatment (USDOI, OSM, 2003). Secondly, if any violation of the reclamation standards becomes apparent after final bond release (i.e., after jurisdiction has been terminated), OSM has the authority to reassert jurisdiction if there was "misrepresentation of material fact" at the time jurisdiction was terminated. MONITORING Proper waste characterization, site characterization, placement design, and reclamation practices, which have been discussed earlier in this report, contribute to the process of reducing environmental impacts from the use of CCRs in recla- mation. Monitoring is an essential tool to confirm predictions of contaminant behavior and detect if and to what extent CCR constituents are moving off-site and into the surrounding environment. In this manner, monitoring is an important tool to help protect ecological and human health at CCR placement sites. This section outlines the regulatory framework for monitoring at CCR mine placement sites, highlights concerns about existing monitoring programs, and provides rec- ommendations for effective and efficient monitoring programs. Regulatory Framework for Monitoring Current monitoring programs associated with the placement of CCRs in mines have been developed and implemented by states as stipulated by SMCRA (30 CFR §700). In general, SMCRA monitoring regulations are not very pre- scriptive (see Appendix E). Thus, the states have a large degree of flexibility and control, and the monitoring programs required at CCR mine placement sites vary widely by state. According to an analysis of regulations from 23 states by the Environmental Protection Agency (EPA), five states have monitoring require- ments for CCR disposal at mine sites that are substantially similar to SMCRA (USEPA, 2002c). Ohio and Pennsylvania have monitoring requirements for CCRs that are substantially greater than SMCRA requirements. The additional regula- tions that states have added to SMCRA monitoring requirements at CCR mine placement sites vary in stringency and specificity. Many states simply have pro- visions that allow increased monitoring or additional parameters on a site-by-site basis. Some states, such as Indiana and Pennsylvania, specifically require moni- toring for particular CCR parameters. State requirements on monitoring frequency for CCR parameters vary from quarterly to annually. Additionally, some states specify a minimum number of downgradient monitoring wells, such as North Dakota and Washington, which require at least two downgradient wells, and Indiana and Pennsylvania, which require at least one.
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166 MANAGING COAL COMBUSTION RESIDUES IN MINES The monitoring requirements under SMCRA can be contrasted with the more specific monitoring requirements that exist in the Resource Conserva- tion and Recovery Act (RCRA) Subtitle D (40 CFR. §257-258) (see Appen- dix E). The differences between the monitoring requirements for SMCRA and RCRA stem in part from the basic objectives of these different statutes: SMCRA is motivated by the reclamation of mine lands, whereas RCRA is motivated by the containment of contaminated wastes. The relevant aspect of RCRA for such a comparison is the Subtitle D requirements designed for municipal solid waste landfills, which regulate CCRs disposed in landfills and surface impoundments. Although SMCRA and RCRA regulations both provide ample authority to address the surface and groundwater monitoring demands of CCR disposal, RCRA regulations impose more specific require- ments on the groundwater monitoring network design, sampling, and analysis procedures; surface-water monitoring; and constituents sampled. For ex- ample, while the RCRA rules require the rate and direction of groundwater flow to be determined each time groundwater is sampled, SMCRA rules are more general, requiring a groundwater monitoring plan that is based on the determination of probable hydrologic consequences. SMCRA and its imple- menting regulations allow the regulatory agency to impose requirements simi- lar to those established under RCRA, but they do not require it (see 30 CFR §§780.21(h), 816.41(c)). In terms of parameters monitored, RCRA requires the analysis of a wide suite of inorganic constituents commonly found in landfills. SMCRA requires monitoring to include those parameters that relate to the suitability of the groundwater for current and approved post-mining land uses and, at a minimum, total dissolved solids or specific conductance, pH, total iron, and total manganese. Assessment of Existing Monitoring Programs As discussed previously, monitoring programs and requirements vary sub- stantially from state to state, and the committee observed a range of monitoring programs in its study. Nevertheless, some broad concerns emerged in the committee's general assessment of monitoring activities at CCR mine place- ment sites. These concerns, which emerged from observations made during the committee's open meetings and site visits, include the appropriate placement of monitoring wells based on the location of CCRs and the characterization of subsurface flow paths and whether there were an appropriate number of moni- toring wells to characterize and sample groundwater along these flow paths. Other concerns related to whether there was adequate characterization of field leachate concentrations, adequate analysis of constituents in surface and ground- water, adequate length of monitoring, and ongoing and timely data processing (including review, analysis, and distribution).
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COAL COMBUSTION RESIDUES IN RECLAMATION ACTIVITIES 167 Defining Subsurface Flow Paths Mine permits require an assessment of the groundwater resources that could be affected by mining operations, including the determination of probable hydro- logic consequences and cumulative hydrologic impact assessments (OSM, 2002). Under the current regulatory system, mine permits require that background hydrogeological and geochemical conditions are established through the integra- tion of lithological information from drill cores, hydraulic data, and groundwater chemistry. Identification of distinct geologic units is required, and the impact of these units on groundwater flow paths is incorporated into the permit. The result of this analysis is typically a general discussion of reported aquifer characteris- tics, hypothesized or measured flow directions, and water quality at sites spread out across the permit area. Much of the information gathered for the coal mining permit is not substantially refined for the placement of CCRs, even though sig- nificantly more information is needed to understand potential contaminant flow paths resulting from their placement. Often the process of mining disturbs ground- water flow pathways, such that the original permit data are not sufficiently accu- rate to site monitoring wells for CCR placement. The result is a monitoring well network that may not intersect a contaminant plume if it were to occur or a network that generates data that lead only to confusion over the source of el- evated concentrations. Number and Placement of Wells and Length of Monitoring The committee is concerned about the number and placement of monitoring wells at CCR mine placement sites. In general, monitoring networks were found to be inadequate to assess accurately the movement of contaminants within a reasonable time frame. The committee notes that at some sites visited, monitoring was focused at the mine permit boundary, with large distances (up to a mile) between the CCR placement site and the monitoring network. In cases where there was a large distance between the location of CCRs and monitoring wells, monitoring over a limited time frame (e.g., <10 years) might not detect any problem, even if one existed. Early detection of any problem is highly desirable to minimize possible impacts of CCRs and reduce potential remediation costs. Additionally, the committee observed sites at which background or upgradient wells were not situated in appropriate locations to achieve long-term baseline data for comparison. Monitoring well data from mine placement of CCRs is often difficult to interpret due to the influences of the mining process itself and the large volumes of spoil, which can impact water quality in ways similar to CCR. Nearly all sites face the difficulty of siting wells in locations where the background influences of mining operations can be separated from the influence of CCRs, even somewhat simple sites. Substantial pre-CCR-placement monitoring data (or background data) are needed to discern the contributions of
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168 MANAGING COAL COMBUSTION RESIDUES IN MINES CCR from other influences. The problem is particularly severe in densely mined regions, such as the anthracite region of Pennsylvania, where several active or abandoned mines may contribute flow to a single monitoring point. Characterization of Field Leachates As noted in Chapter 6, more information is needed to relate CCR character- ization data obtained in the laboratory to the behavior of CCRs in field settings. While the committee saw some sites where monitoring wells were placed within the CCR itself to obtain field leaching data, such data were not universally col- lected. Field leaching data provide the best assessment of the potential for off-site migration of the contaminants and the information necessary to distinguish the contributions of CCR from other influences. This information will also be valu- able for testing the efficacy of laboratory leachate tests. Field leachate data can be combined with hydraulic conductivity and hydraulic head data to provide an approximate assessment of contaminant flux. Comparing these data with ground- water quality and flow rates from nearby downgradient wells could provide infor- mation on adsorption, precipitation, and other attenuation processes. Constituents Analyzed in Surface and Groundwater For the sites reviewed in the course of this study (which represent only a subset of the sites at which CCR mine placement is occurring), most of the monitoring programs appeared to be analyzing for appropriate constituents to assess the movement of CCR-related contaminants. While SMCRA surface- water monitoring requirements are focused upon traditional mine reclamation constituents such as iron, manganese, acidity, and sediment, most of the sites reviewed sampled for a more extensive suite of contaminants, including trace metals. However, some sites did not include an analysis of boron or selenium concentrations, even though these constituents are commonly elevated in loca- tions where CCR is present and are rather mobile in the subsurface. Boron or selenium may be viewed as a good indicator of the presence of CCR-related contaminants in both groundwater and associated downgradient surface water bodies. Information and Data Management While reviewing CCR placement sites across the country, the committee observed many instances in which the utility of analytical data was questioned, related in part to possible failures in quality assurance and quality control (QA/ QC). There appeared to be an absence of clearly defined QA/QC protocols prior to project implementation, which led to disagreements about which monitoring data were to be considered in post-placement data analyses. QA/QC plans are
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COAL COMBUSTION RESIDUES IN RECLAMATION ACTIVITIES 169 valuable for addressing systematic errors in analytical procedures, data validation problems, and information management. With regard to information management, the committee observed that the results from field measurements were not consistently given the level of attention and scrutiny required to recognize CCR contamination problems in their early stages of development. Coal companies supply large amounts of data to state agencies as part of the reporting requirements for CCR placement related to ground- and surface-water monitoring and waste characterization. Most of these data are required to be submitted on paper, creating a challenge for data manage- ment and interpretation because the data analysis involves wading through many pages of data or requires the time-consuming step of first entering these data into a central data management system. Some states have moved to electronic report- ing data methods, which can speed the review process. Electronic reporting can also facilitate closer attention to water quality concerns if the data management system is capable of flagging exceedances for attention by state water quality staff. To ensure early recognition of CCR contamination, QA/QC plans and information and data management plans should be developed prior to CCR place- ment. These plans should inform the decision-making process in a timely manner and should include how the data will be made available to the public. Recommended Monitoring Strategies As noted above, the committee had several concerns regarding the effective- ness of existing monitoring programs. General issues related to long-term moni- toring, liability, and oversight are discussed in Chapter 8. The discussion below highlights general recommendations for a more robust and consistent monitoring program needed in situations involving CCR mine placement. In general, the overall extent of monitoring (number of sampling points, frequency and duration of sampling, and constituents analyzed) should be customized to address the level of estimated risk and the uncertainties associated with the estimate. Higher levels of potential risk (i.e., more dire consequences) warrant greater investments in field monitoring to ensure adequate protection of human and ecological health. Because uncertainty exists in CCR characterization methods and site character- ization, monitoring plans should also be designed to compensate for the level of uncertainty about contaminant behavior in the local environment (i.e., more moni- toring when uncertainties are large). Groundwater Monitoring The monitoring network should be designed based on a careful assessment of site characterization data, CCR characterization data, and the design of the CCR emplacement and subsequently should be certified by a regulatory official expe- rienced in contaminant transport processes. The number of monitoring wells and
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170 MANAGING COAL COMBUSTION RESIDUES IN MINES the spatial coverage of wells should be consistent with the potential for material damage to groundwater. For example, sites with large masses of CCR that exhibit high rates of contaminant leaching would warrant substantial engineering con- trols together with detailed monitoring, whereas sites with relatively inert CCR disposed in small quantities would warrant a simpler approach. An ideal groundwater monitoring system should include wells installed at multiple depths and multiple locations, concentrated primarily in the probable directions of groundwater flow with additional wells to characterize upgradient water quality. Overall, well screens should be placed in a range of materials, including coal spoils, CCRs, blended materials, and undisturbed geologic materi- als, to provide information that is representative of variations present at the site. Downgradient wells should be sited with an understanding of the travel times for contaminants to reach these monitoring points. Several monitoring points should be established along predicted flow paths at distances downgradient from CCR emplacement that will yield early (i.e., during the established bonding period) confirmatory information regarding predicted CCR leachate transport (e.g., ad- vection, dispersion, dilution, attenuation). If uncertainty exists regarding the di- rections of groundwater flow or if ongoing mining and associated groundwater pumping could disrupt groundwater flow, additional wells may be necessary to capture the movement of any contaminant plume. As discussed above, if wells are placed only at the permit boundary, water quality monitoring for the length of the bonding period may not detect a contamination problem, even if one exists. If downgradient contamination is detected, additional wells may have to be in- stalled to assess the impact of CCR on groundwater resources. At least one well (or a suction or pan lysimeter for unsaturated conditions), and preferably two wells, should be placed directly in the CCR to monitor local porewater chemistry and assess the field leaching behavior. These data should then be compared to the predicted flux rates in the site conceptual model. The effects of mining on groundwater levels and flow normally occur rela- tively quickly while changes in groundwater quality can take several decades (NRC, 1981). Depending on the individual site characteristics and the distances to downgradient wells, terminating groundwater monitoring at the time of bond release may lead to an underestimation of contaminant release from many sites. The duration of groundwater monitoring will have to be addressed on a site- specific basis to adequately assess the temporal release of contaminants. A longer field-monitoring period will likely be needed in some situations in recognition of the fact that subsurface migration of potential contaminants can occur over time periods in excess of a decade. A large portion of the investment in groundwater monitoring is currently being directed at collection and analysis of groundwater samples from a very small number of wells at a high frequency (monthly to quarterly). The frequency of monitoring should be selected to more accurately reflect the variation in chem- istry that is expected at a site. Monitoring of groundwater chemistry should be
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COAL COMBUSTION RESIDUES IN RECLAMATION ACTIVITIES 171 carried out more frequently at sites where groundwater velocities are high and less frequently at sites where groundwater velocities are low. For example, sam- pling of porewater within the CCR could be frequent in the first few years after placement but be reduced in frequency once flow conditions stabilize. Rigorous CCR characterization studies should give an initial indication of the potentially leachable contaminants that should serve as the basis of the field monitoring program. Ongoing field sampling of the CCR porewater will charac- terize the actual field leaching behavior. Analysis of these results can guide the development of a list of the most mobile contaminants that should be analyzed for samples from upgradient and downgradient wells. Surface Water Monitoring Surface-water monitoring is a key component of any monitoring program to protect the ecosystem from potential adverse impacts of CCRs. Appropriate un- derstanding of the connectivity between local groundwater and receiving surface water bodies, however, should allow groundwater monitoring to forewarn the arrival of mobile CCR constituents through the subsurface. As described in Sidebar 4.5, contaminant levels needed to adequately protect ecological health can be significantly lower than those prescribed to protect human health (e.g., drinking water maximum containment levels). Beyond the difference in concen- trations, different analytical techniques (sample collection and laboratory method) are sometimes necessary to measure these lower, yet environmentally relevant concentrations. Coal combustion residue monitoring programs have to identify surface water bodies (streams, lakes, and wetlands) that might receive either direct surface or indirect subsurface discharge of CCR leachate. Direct surface discharges from mine sites are typically monitored in accordance with associated National Pollu- tion Discharge Elimination System permit requirements. Surface-water monitor- ing should be conducted with a frequency that will adequately capture the tempo- ral variation of the upgradient (background) condition as well as the variation of any point- and/or non-point-source loading. Surface monitoring for rivers and streams should continue at upgradient, point-source, and downgradient locations for the same duration as groundwater monitoring. At all surface monitoring loca- tions, background water-quality data should also have been collected prior to CCR placement through the site characterization process (see Chapter 6). Parameters for effective surface-water monitoring would include hydraulic data in addition to water chemistry. Necessary hydraulic monitoring data include flow velocity, cross-sectional area, average water depth, and reach length, as well as a calculation of hydraulic residence time for lakes or wetlands. Hydraulic monitoring data may be needed at every surface-water sampling site where water chemistry is monitored if there are important loading issues to be addressed. Water chemistry parameters include pH, temperature, conductivity, major cat-
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172 MANAGING COAL COMBUSTION RESIDUES IN MINES ions and anions, hardness, total organic carbon, and CCR-related metals, which should be analyzed on both filtered and unfiltered samples. Suspended sediment should also be sampled at each site to estimate contaminant accumulation in sediments and the sediment-associated transport and to assess impacts on aquatic biota (USEPA, 2004a). Ecological Monitoring Existing SMCRA regulations include the monitoring of water and sediment as it moves from mines to surface waters, but the potential impact of either direct surface or indirect subsurface discharge of CCR-related contaminants on receiv- ing water biota is not specifically addressed within SMRCA. In the event that surface-water quality impacts are detected, they should be promptly verified with more intensive water sampling to determine the magnitude of the problem. How- ever, such sampling may not be sufficient to detect elements like selenium that may occur in low concentrations in water, yet high concentrations in tissues due to its bioavailability, and additional ecological monitoring may be needed. Monitoring tissue concentrations in biota upstream and downstream of CCR placement sites may be a necessary first step towards understanding potential ecological impacts of CCR-related contaminants. For example, selenium is one the CCR constituents of greatest ecological concern. Because water concentra- tions of selenium are often not indicative of concentrations bioaccumulated in fish, invertebrates, and wildlife (Hamilton, 2002, 2003; Lemly, 2002), the EPA is currently replacing its water quality criterion for Se with a tissue-based crite- rion (Federal Register EPA-822-D-04-001, Draft Aquatic Life Criteria for Sele- nium-2004). Tissue residues provide a valuable integrative metric of the bio- available fraction of contaminants entering the impacted community and are especially useful for elements such as selenium that have complex biogeochem- istry. Thus, tissue sampling may provide the most sensitive monitoring index for some elements associated with CCRs, and may eventually be required by EPA regulations. If tissue residues are elevated above reference conditions, additional ecological variables, such as measures of reproductive performance and/or in- vertebrate diversity and abundance, should be considered. Reproductive indices are among the most sensitive end points of toxicity for highly teratogenic ele- ments such as selenium and mercury that are readily maternally transferred. Measures of animal abundance and diversity can provide insight into the eco- logical consequences of changes in stream water chemistry resulting from CCR contamination. As discussed in Chapter 4, macroinvertebrate and zooplankton assemblages have commonly been impacted by CCRs at surface impoundment sites, and these compositional changes appear to be a good metrics of unin- tended ecological impacts.
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COAL COMBUSTION RESIDUES IN RECLAMATION ACTIVITIES 173 Performance Standards for Monitoring Performance standards should be established for the aforementioned ground- water and surface-water monitoring points to ensure adequate protection of groundwater and surface-water quality. Performance standards associated with SMCRA regulations are discussed in Chapter 5 and should be followed to de- velop specific metrics. These performance standards could be based on best available data, model predictions, and relevant water quality standards (including tissue-based standards developed for elements such as selenium), considering pre-placement water quality conditions. Indications that the established perfor- mance standards have not been met should trigger more intensive monitoring and, if warranted, the development of a remediation plan. SUMMARY Reclamation planning and monitoring are essential components of risk-in- formed CCR management at coal mine sites. Reclamation planning is an integral part of the mining process, and the use of CCRs for minefill should be viewed in the context of general reclamation management activities. The reclamation plan- ning process begins with a thorough analysis of current site conditions at the mine and the site conditions projected to exist following the completion of min- ing. The disposal of CCRs in coal mines occurs under highly variable conditions, ranging from small quantities to massive minefills, from arid to wet regions, from remote to semiurban locations, from surface to underground mines, and from active to abandoned mines. Because of this variability, the committee endorses the concept of site-specific management plans, including site-specific perfor- mance standards. A flexible approach to managing CCRs in mine sites has advantages since it can embrace the unique characteristics of CCRs, the total mass of CCRs, and the environment into which they are placed. However, the need to incorporate site-specific factors should not be a basis for adopting man- agement plans that lack rigor. The primary reclamation operations most readily impacted by CCR place- ment, whether for active or abandoned mines, are backfilling and grading, topsoil replacement, and revegetation. Reclamation requirements and potential concerns for CCR for these operations are described in this chapter. CCR management requires an understanding of risk, and careful CCR placement design can be used to moderate the human health and environmental risks of CCR disposal in mines. The committee recommends designing CCR placement in mines to minimize reactions with water and the flow of water through CCRs. Several methods are described for reducing the interaction of CCRs with water, including place- ment well above the water table, compaction and cementation, liners, and low- permeability covers. However, none of these methods will guarantee that CCRs remain completely isolated from infiltrating water.
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174 MANAGING COAL COMBUSTION RESIDUES IN MINES Monitoring is an essential tool to confirm predictions of contaminant behav- ior and detect if and to what extent contaminants are moving into the ambient environment. SMCRA monitoring regulations provide the regulatory agency with sufficient authority to require adequate ground- and surface-water monitoring. However, while the monitoring rules at 30 CFR §780.21(i), (j) and §816.41(c), (e) require mine operators to establish and implement ground- and surface-water monitoring plans, they do not specifically address the number and location of wells, spatial coverage of wells, and duration of monitoring. Furthermore, al- though they require monitoring "at a minimum" for total dissolved solids, spe- cific conductance corrected to 25°C, pH, total iron, total manganese, and water levels, they do not address the full suite of contaminants that might possibly be expected to leach from CCRs in a minefill setting. Because SMCRA monitoring regulations are not very prescriptive, states have a large degree of flexibility and control, and monitoring programs required at CCR mine placement sites vary widely by state. Based on its reviews of CCR post-placement monitoring, the committee concludes that the number of monitoring wells, the spatial coverage of wells, and the duration of monitoring at CCR minefills are generally insufficient to accurately assess the migration of contaminants. Additionally, the committee found quality assurance and control and information management procedures for water quality data at CCR mine placement sites to be inadequate. This chapter highlights general recommendations for a more robust and consistent monitoring program needed in situations involving CCR mine place- ment. Downgradient wells should be sited with an understanding of the travel times for contaminants to reach these monitoring points. Depending on the indi- vidual site characteristics and the distances to downgradient wells, a longer dura- tion of groundwater monitoring may be necessary at some sites to adequately assess the temporal release of contaminants, which can occur over periods in excess of a decade. To address these concerns, several monitoring points should be established along predicted flow paths that will yield early (i.e., during the established bonding period) confirmatory information regarding predicted CCR leachate transport. At least one well or lysimeter, and preferably two, should be placed directly in the CCR to assess the field leaching behavior and confirm predicted contaminant flux. As part of the monitoring plans, quality assurance and control plans should be developed prior to CCR placement with clearly defined protocols for sampling and analysis, data validation, and managing sys- tematic errors in analytical procedures. In general, the committee recommends that the number and location of monitoring wells, the frequency and dura- tion of sampling, and the water quality parameters selected for analysis be carefully determined for each site, in order to accurately assess the present and potential movement of CCR-associated contaminants. Such an approach will also allow the specifics of the monitoring plan to be tailored to accommodate the unique combination of particular CCR characteristics, emplacement tech-
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COAL COMBUSTION RESIDUES IN RECLAMATION ACTIVITIES 175 niques, and overall site characteristics, considering estimates of ecological and human health risks and uncertainties in the site conceptual model. Surface-water and ecological monitoring are key components of any moni- toring program to protect the ecosystem from potential adverse impacts. It is important to note that chemical levels adequate to protect environmental health can be significantly lower than those prescribed to protect human health. For surface-water, the frequency of sampling should adequately capture temporal variations in the background conditions as well as variations in any point- and/or non-point-source loading. Tissue residue monitoring provides valuable insights into the bioavailability of certain contaminants that can be present at low concen- trations in water but accumulate in living organisms (e.g., selenium). The dura- tion of surface-water monitoring should be consistent with the duration of ground- water monitoring. In the event that surface-water quality impacts are detected, appropriate ecological monitoring may need to be implemented. Performance standards should be established for the aforementioned ground- water and surface-water monitoring points to ensure adequate protection of groundwater and surface-water quality. Indications that the established perfor- mance standards have not been met should trigger more intensive monitoring and, if warranted, the development of a remediation plan.
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Representative terms from entire chapter: