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Use of a CCB Grout Barrier to Reduce the Formation of Acid Mine Drainage: The Siege of

Acre Project, Kempton, Maryland Robin L. Guynn1, Jason Litten2, Raymond T. Hemmings3, and Paul Petzrick4 1ERM, Inc., 200 Harry S Truman Parkway, Annapolis, MD 21401; 2Frostburg State University, Western Maryland Regional GIS Center, 101 Braddock Rd. Frostburg, MD 21532; 3Hemmings and Associates, LLC, 4100 Lock Ridge Ct. Kennesaw, GA 30152; 4Maryland Department of Natural Resources, Power Plant Research Program, Tawes Office Building, B-3, Annapolis, MD 21401 KEYWORDS: beneficial use, grout, acid mine drainage, Kempton Mine Complex, Siege of Acre ABSTRACT The Maryland Department of Natural Resources Power Plant Research Program (PPRP) has proposed the Siege of Acre Project to demonstrate the feasibility of reducing acid mine drainage (AMD) formation by coating pyritic mine pavement with a CCB-based grout. Use of grout as a surface coating rather than bulk fill will preserve the existing and complex flow system in the mine, decreasing the risk of unintended consequences that can be associated with bulk fills (e.g. blow-outs). The Kempton Mine Complex covers 12 square miles (31 square kilometers) in Maryland and West Virginia and discharges approximately 3.5 million gallons (13.2 million liters) of AMD per day into Laurel Run, a tributary to the Potomac River in Western Maryland. The Siege of Acre segment forms the northern extremity of the Complex in Maryland. Siege of Acre includes an isolated straight run of three parallel tunnels, each 750 feet (229 meters) long by 16 feet (5 meters) wide, running up-dip from the edge of the Kempton mine pool. These tunnels are representative of several hundred acres of mine pavement within the Kempton Mine and in other Upper Freeport mines in Maryland and neighboring states. PPRP has determined the tunnel locations, orientations, and dimensions through desk-top and field investigations. Water quality of the mine pool and flowing across the mine pavement has also been characterized. PPRP has also initiated long-term accelerated weathering experiments that expose cured CCB grout blocks to continuous flows of acidic water to simulate a deep mine environment. The results of these accelerated weathering experiments will be used to determine the durability of a CCB-grout coating of the pavement within mine tunnels, such as those at Siege of Acre.

2009 World of Coal Ash (WOCA) Conference - May 4-7, 2009 in Lexington, KY, USAhttp://www.flyash.info/

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INTRODUCTION The Maryland Department of Natural Resources Power Plant Research Program (PPRP) has partnered with private industry to undertake a series of projects to demonstrate the beneficial application of coal combustion by-products (CCBs) to create flowable grouts for placement in underground coal mines to reduce acid formation. These demonstration projects are a key component of Maryland’s overall ash utilization program to promote and expand the beneficial use of CCBs on a large scale. The ultimate goals of these projects are to utilize CCB-based grouts to effect significant acid reduction at large acid mine drainage (AMD) sources in Maryland and to mitigate subsidence problems associated with lands disturbed by coal mining and natural karst topography. The Siege of Acre Project is a proposed injection project designed to demonstrate the use of a CCB grout to reduce the formation of acid along pyritic mine pavement that is not fully submerged, but is part of a flow path for water running into an acidic mine pool. Previous PPRP demonstration projects have demonstrated the use of CCB grouts to reduce the formation of AMD in other ways. The Winding Ridge Project showed how a CCB grout can be successfully used to reduce acid formation within a small mine by bulk filling of the mine tunnels1. The Kempton Manshaft Project used a CCB grout to attempt to create an impermeable grout curtain around a mine shaft that was acting as a conduit allowing good quality shallow ground water to drain into the acidic Kempton Mine Pool2. Bulk mine filling poses certain challenges for large mines containing large mine pools. Massive quantities of material are needed, which present associated cost, transportation, and storage challenges. In addition, bulk filling of a large mine presents the possibility of blow-outs when mine water becomes impounded behind grout dams. Thus, for the Siege of Acre Site, which is part of the large Kempton Mine Complex, a CCB-grout coating of the mine pavement is proposed as an alternative. Coating the mine floor with CCB grout requires smaller amounts of material to prevent reactions between oxygen, mine water and pyrite (mine pavement and debris) without disrupting the existing water flow patterns within the mine. Figure 1 shows, conceptually, how the grout coating of the mine pavement would be created. As with any underground mine-related project, a significant amount of preparatory work is required before injection can occur. The selected mine, or mine segment must be verified as an acceptable injection site; mine tunnel locations must be accurately determined so that injection boreholes can be placed within the tunnels; pre-injection conditions within the tunnels must be assessed so that any post-injection changes in water quality can be discerned; a suitable grout formula must be developed; and the likely fate of the cured grout in the mine tunnel environment must be considered. This paper presents the methods and findings of investigative activities that have been

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undertaken in preparation for grout injection to create a CCB grout barrier coating the mine pavements of the tunnels within the Siege of Acre mine segment.

Figure 1: Creation of a grout coating of mine pavement SELECTION OF SITE

The Siege of Acre Site (the Site) is a part of the Kempton Mine Complex (the Complex), which covers approximately 12 square miles (31 square kilometers) and straddles Maryland and West Virginia (Figure 2). The Complex discharges approximately 3.5 million gallons (13.2 million liters) of AMD per day into Laurel Run, which is a major tributary to the North Branch of the Potomac River in Western Maryland.

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Figure 2: Regional Context of the Kempton Mine Complex.

The Siege of Acre Site forms the northern extremity of the Complex in Maryland. It consists of three mine tunnels that are 16 feet (5 meters) wide. The three tunnels are also interconnected by several crosscuts developed in the conventional method of up dip and pillar mining. The three tunnels extend 750 feet (229 meters) up-dip from the mine pool, with overburden thicknesses ranging from 175 feet (53 meters) near the edge of the mine pool to 140 feet (43 meters) near the high wall, where a surface mine cut into and exposed the underground mine works (Figure 3). Pre-injection characterization of the mine tunnels (which will be further discussed in the next section) has indicated that the three mine tunnels are not permanently submerged in the mine pool. Rather, water flows across the pavement in at least the southernmost tunnel. Figure 4 shows the layout of the three Siege of Acre mine tunnels. The tunnels intercept the mine pool at their eastern end, prior to intersecting the more numerous northeast-southwest running mine tunnels.

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Figure 3: The Kempton Mine Complex, showing both the Kempton and the Coketon mine pools.

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Figure 4: Layout of the Siege of Acre segment of the Kempton Mine Complex.

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Several factors make the Siege of Acre site an attractive location for this type of demonstration project.

• The Siege of Acre mine tunnels are representative of several hundred acres of sub-aerial exposed mine pavement within the Kempton Complex and thousands of acres of sub-aerial mine pavement within Appalachia. Water flowing along the mine pavement becomes acidic as it contacts pyrite and oxygen, and recharges the mine pool.

• Although the Siege of Acre tunnels are part of the large Kempton

Complex and drain directly to the Kempton Mine pool, they are also suitably isolated at the northern extremity of the Complex. Thus the Siege of Acre mine segment can be easily isolated from the pool if leaching of constituents from the grout or any other aspect of the grouting operation required such consideration; and

• Siege of Acre is located in close proximity to sources both of self-

cementing fluidized bed combustion (FBC) products and fly ash. In addition, access to the site is readily available via pre-existing coal haul roads constructed by the Buffalo Coal Mining Corporation.

Empirical data required before completing the engineering design for injection are as follows

• The tunnels must be accurately located in the field. The Siege of Acre site is situated in an isolated location. Although a property corner was located within 300 feet (91 meters) of the site, the nearest georeferenced location (which could be used to correlate surface geography with the tunnel maps) is 4,000 feet (1,219 meters) away. High resolution of the location of the mine tunnels is needed to maximize drilling efficiency (and minimize costs) so that the boreholes can be drilled into the tunnels and not solid coal.

• The quality and quantity of mine water produced in this portion of the mine must be determined;

• A grout formula must be developed that of adequate viscosity to flow along 750-foot (229 meter) long, debris-littered tunnels, but with sufficient durability to cure into a competent and impermeable barrier along the mine pavement.

The remainder of this paper presents the investigative activities performed to address these challenges in preparation for grout injection activities at the Site.

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INVESTIGATION TO-DATE Location of Tunnels To assess water quality and quantity within the mine tunnels and ultimately to perform injection, it is necessary to drill boreholes into the mine tunnels. To accurately drill boreholes into the 16-foot (5-meter) wide mine tunnels situated 140 to 175 feet (43-53 meters) below ground surface, the locations of the tunnels were first determined as accurately as practical. Specifically, preparation for borehole drilling began with a detailed desktop study, as well as non-intrusive field reconnaissance of the Siege of Acre segment of the mine. Four important pieces of information were used in the assessment of the location of the tunnels:

• The landowner, Western Pocahontas Properties (WPP), provided a digitized version of the original large scale Davis Coal & Coke (DC&C) mine map to the Geospatial Research Group (GRG) at Frostburg State University (FSU). (This group has since been renamed the Western Maryland Regional GIS Center).

• In 1999, GRG contracted with 3DI of Easton, Maryland to obtain very high quality aerial photographs of the surface over the Kempton Mine Complex. The resulting digitized aerial photographs were available for use in the project.

• GRG personnel discovered that many of DC&C’s local records were stored in their former headquarters building, now known as the Railroad Building, in Thomas, West Virginia. These assets were controlled by the Thomas Historical Society. The Society Director agreed to share access to these records, as well as the rock cores remaining in the building. This diverse material included detailed maps, engineering memos, and survey notes; information that has proven to be invaluable in the characterization of the Kempton Mine Complex. These records are referred to collectively as the DC&C Records.

• During field reconnaissance conducted along a logging trail, which was known to cross the three mine tunnels near their eastern ends, three large depressions were observed at uniform intervals corresponding to the dimensions and spacing of the mine tunnels, ascertained from the other available materials. These depressions were successfully used to site the boring locations.

Based on the principles of mine subsidence, the depressions noted on the logging trail were believed to be the result of sag subsidence over the mine tunnels and thus, surface expressions of the mine tunnels. To check this hypothesis, the location of the

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depressions was surveyed and compared with the tunnel locations as shown on the mine maps, georeferenced to the aerial photographs. The mine maps and aerial photographs showed the tunnels to be approximately 30 feet (9 meters) northwest of the depression locations. However, distances between other geospatial reference points, as measured on mine maps are frequently longer than the same displacements measured in aerial photography, or as determined from differences in latitude and longitude. Thus, it was reasoned that there may be a systematic error in the mine maps. Using the empirical data, drilling proceeded on the assumption that the depressions marked the true tunnel locations, and this assumption was found to be correct when boreholes installed in the depressions encountered the mine tunnels. The mine tunnel maps and georeferencing to the aerial photographs were adjusted using additional survey data as well as borehole information, once it had been obtained. Exploratory drilling was conducted in November 2002, with additional drilling and retrofitting of boreholes for sampling purposes conducted in June 2003. A total of nine boreholes were installed, as described below and in Figure 5. Figure 5: Location of all nine exploratory boreholes installed at the Siege of Acre Site and final mapped (and corrected) location of mine tunnels

• The first borehole (LTBE-3) encountered the mine pool; • The second, third, and fourth boreholes (LTB-3, LTB-2, and LTB-1,

respectively) encountered the mine tunnels just up-dip of the mine pool;

• The fifth and sixth boreholes (UTB-4 and UTB-5) were targeted at

locating the mine tunnels further up-dip of the LTB boreholes, but these boreholes encountered only coal at the expected tunnel elevation (these boreholes were subsequently abandoned). Re-

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assessment of the original mine maps, borehole camera observations, and georeferenced mine workings indicated that a one-degree rotation of the maps provided the best fit to all of the data collected. This rotation showed that UTB-4 and UTB-5 had actually been drilled into pillars located southwest of Tunnels 3 and 2. This information was used to determine the locations of the remaining boreholes;

• The seventh and eighth boreholes (UTB-6 and UTB-7) encountered

the mine tunnels up-dip of the LTB boreholes. • The ninth borehole (LTBE-1) was drilled during the second mobilization

in 2003 and encountered the mine pool. Figure 6 shows the adjustment that was made (based on the results of the desktop study, GIS mapping, and initial borehole drilling) to the georeferenced mine tunnel maps to show the true locations of the tunnels.

Figure 6: Location of first six boreholes installed at Siege of Acre and adjustment of mine tunnel locations on the map.

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Determination of Water Quality To assess the potential benefits of grouting the mine pavement for the Siege of Acre mine tunnels, and to assess the likely longevity of any grout injected into the tunnels, the water quality within the mine tunnels and in the adjacent mine pool was evaluated. The collection of water samples from the mine pool was relatively simple, as boreholes LTBE-3 and LTBE-1 allowed access to the mine pool, which is deep enough to be sampled with conventional methods (i.e. bailers). Sampling of water within the mine tunnels was more complicated because water is not pooled within the tunnels, but rather flows along the pavement toward the mine pool at a depth insufficient for conventional sampling techniques. Initially, at borehole LTB-1 a hydrophilic pad was used to collect a sample of the water flowing along the mine pavement. The pad was covered by a shroud as it was lowered into and removed from the borehole to protect the sample from condensate on the well casing walls (Figure 7)

Figure 7: Hydrophilic pad sampling device used temporarily to sample location LTB-1. During the second round of drilling and borehole retrofitting in 2003, a sump was installed at LTB-1 to allow mine pavement water to collect to a depth that could be sampled with a conventional bailer. Monitoring wells LTBE-3, LTBE-1, and LTB-1 comprise the mine pool and mine tunnel water quality monitoring network for the Site. Monitoring has been performed regularly (first on a monthly basis and later reduced to a quarterly basis) from June 2002 through August 2008. The available data is summarized in Table 1 and key parameters are shown graphically in Figure 8. In general, the mine pavement water has lower pH,

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higher acidity, and higher concentrations of iron, sulfate, and other metals than the mine pool water. This is consistent with the concept that AMD forms readily as water flows along the mine pavement where water, pyritic debris, and air are readily in contact. AMD then flows into the Kempton mine pool, where there is less contact between these three components, and is diluted.

Pre-Injection Pre-Injection Pre-Injection LTB-3E (Mine Pool) LTB-1E (Mine Pool) LTB-1(Mine Tunnel) Parameter Units

Min Max Average Min Max Average Min Max Average Metals Aluminum mg/L 0.54 4100 138.20 11 38 19.40 13.00 94.00 43.39 Antimony mg/L 0.002 0.02 0.01 0.004 0.027 0.01 0.00 0.10 0.02 Arsenic mg/L 0.0005 0.13 0.02 0.005 0.76 0.05 0.01 1.90 0.37 Barium mg/L 0.0025 442 97.48 0.009 0.92 0.12 0.01 0.66 0.16 Beryllium mg/L 0.005 0.025 0.01 0.005 0.017 0.01 0.01 0.09 0.02 Boron mg/L 0.02 0.1 0.05 0.02 0.16 0.05 0.02 0.50 0.11 Cadmium mg/L 0.0016 0.012 0.01 0.0005 0.026 0.01 0.00 0.05 0.01 Calcium mg/L 40 185 61.94 47 170 68.02 52.00 260.00 188.08 Chromium mg/L 0.002 0.11 0.01 0.002 0.052 0.02 0.01 0.08 0.05 Cobalt mg/L 0.01 0.87 0.18 0.016 0.84 0.22 0.16 1.40 0.89 Copper mg/L 0.004 0.2 0.03 0.008 0.2 0.05 0.02 0.29 0.16 Lead mg/L 0.002 0.068 0.01 0.003 0.29 0.03 0.01 0.67 0.14 Magnesium mg/L 19.7 79 28.57 20 62 33.16 25.00 130.00 68.53 Manganese mg/L 1.43 4.3 2.86 2.1 4.7 3.40 2.80 6.01 4.86 Mercury mg/L 0.0002 0.002 0.0003 0.0002 0.0002 0.0002 0.0002 0.0004 0.0002 Nickel mg/L 0.15 1.9 0.35 0.27 1.5 0.40 0.28 2.50 1.68 Potassium mg/L 0.9 6.5 3.17 2 11 3.46 2.30 29.00 8.68 Selenium mg/L 0.005 0.04 0.01 0.005 0.04 0.01 0.01 0.20 0.02 Silver mg/L 0.001 0.005 0.00 0.001 0.005 0.00 0.00 0.05 0.01 Sodium mg/L 1.2 13.5 6.99 0.53 17 6.80 0.50 8.20 2.56 Thallium mg/L 0.002 0.025 0.01 0.002 0.025 0.01 0.00 0.13 0.02 Zinc mg/L 0.12 59 2.59 0.62 90 4.86 0.74 8.70 4.96 Other Acidity mg/L 10 840 163.96 10 580 207 10.00 1400 769 Alkalinity mg/L 0 82 12.08 10 80 12.92 10.00 82.00 13.00 Chloride mg/L 4.4 70 14.03 4.5 120 13.47 0.50 50.00 11.95 Conductivity umho 650 3000 939 800 2500 1108 990 4600 2968 Iron (mg/L) mg/L 0.1 200 28.78 0.1 300 66.92 0.40 510 258 Nitrate-Nitrogen mg/L 0.1 0.7 0.41 0.1 7.7 1.03 0.10 30.00 1.91 Nitrite- Nitrogen mg/L 0.1 0.5 0.43 0.1 0.5 0.42 0.10 0.50 0.42 pH su 2.7 6.9 3.86 2.9 5.6 3.43 2.40 5.10 2.91 Sulfates mg/L 79 1700 434 80 1500 506 390 3300 1845 Dissolved Solids mg/L 466 810 637 --- --- --- --- --- --- Suspended Solids mg/L 2 318 75.33 --- --- --- --- --- ---

Table 1: Summary of water quality analysis for the Kempton mine pool and water flowing along tunnels at the Siege of Acre site.

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Figure 8: Selected water quality data for the mine pool and water flowing along the mine pavement at the Siege of Acre site. Grout Development In general, the design of grout (whether made from Portland cement or CCBs) for injection into abandoned mine workings for the purpose of reducing AMD formation or preventing subsidence due to mine tunnel collapse must balance the fluidity of the grout during injection with its strength after curing3. Fluidity is important because the grout must be pumped, often through long lengths of hose or piping. In addition, because drilling into abandoned mine workings is expensive and boreholes may not always penetrate the mine workings, it is most practical to be able to use as few injection locations as possible. Thus, the grout must be of low viscosity to be able to flow long distances and around and over debris and other obstacles, while retaining its cohesiveness. In the case of Siege of Acre, the goal is to inject grout at the upper end

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of the mine tunnels and allow the grout to flow via gravity down the 15-30% slope of the 750-foot (229-meter) long tunnels. Grout strength is of obvious importance in cases where grout is intended to prevent mine tunnel collapse and associated surface subsidence. In the case of Siege of Acre, the strength of the grout is primarily important because a strong grout tends to be more cohesive and less permeable. Low permeability is of high importance to the success of the grout in preventing water in the mine tunnels from contacting the acid-producing pavement covered by the grout. Successful grout mixes for injection were developed for the Winding Ridge and the Kempton Manshaft Projects1,2. The Winding Ridge grout mix contained:

• 60% fluidized bed combustion ash (FBC) from the Morgantown Energy Associates power plant;

• 20% flue gas desulfurization product, from the Virginia Power Company’s Mt. Storm; power plant;

• 20% Class F fly ash, also from Mt. Storm • 47% water (primarily pumped from the mine being grouted)1.

The Kempton Manshaft grout mix contained:

• 50% FBC ash from the Dominion Power Company’s North Branch power plant and from the AES Warrior Run power plant;

• 50% Class F fly ash, also from the North Branch power plant; and • Water sufficient to create a solids to water ratio of 60% to 70% (ratios

had to be field-adjusted to maintain grout fluidity2. Based on the results of these previous injection projects, and the results of the CCB block weathering study (discussed below), it is anticipated that the grout mixture to be used for injection at Siege of Acre will contain:

• Approximately 50% FBC from the Warrior Run power plant (baghouse material);

• Approximately 50% Pulverized Fly Ash (PFA) from the R. Paul Smith power plant; and

• Water sufficient to create a solids to water ratio of approximately 60%. The final grout mix will depend upon the availability of materials, field conditions, and the field equipment to be used.

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CCB Block Weathering Study

Experimental Design As part of the grout development process for the Siege of Acre project, a bench study has been conducted to study the weathering of CCB grouts under conditions anticipated in the mine tunnels at the site4. The study is currently on-going, but only the first year of data is presented here. Many studies have performed the standard Toxicity Characteristic Leaching Procedure (TCLP) and Synthetic Precipitation Leaching Procedure tests on CCBs (both stabilized and unstabilized). These leaching procedures simulate the potential of the tested substance to leach under non-hazardous landfill conditions or under exposure to atmospheric precipitation, respectively; however, few studies have been conducted that have attempted to simulate the exposure of CCB-based grouts to conditions anticipated in underground mines. The CCB Block Weathering Study is a bench-scale CCB-grout weathering experiment designed to subject the CCB grout blocks to flowing water that simulates subsurface mine conditions. The Block Weathering Study was initiated in 2005. Four blocks were formed from 100 percent CCBs. The blocks were formed with a 0.79 inch (2 centimeter) deep groove in which pH-adjusted running water is allowed to flow continually. Table 2 details the composition of each block and the pH condition of the water it is exposed to.

Block Number

Dry Wt% Warrior Run

Baghouse FBC

Dry Wt% Warrior Run

Bed Drain FBC

Dry Wt% R. Paul Smith

PFA

% Water Content

pH

1 52.5 22.5 25 60 7 2 70 30 0 57.5 3 3 52.5 22.5 25 60 3 4 52.5 22.5 25 60 4

Notes: Dry Wt% - Dry weight percent. Grout mixes were formulated by Hemmings & Associates. Table 2: Weathering Block composition and pH exposures. The four blocks were allowed to cure in their molds at ambient temperature and 100% relative humidity in a sealed plastic container for 28 days before initiating exposure testing. During the study, the blocks have been inclined at a 30° angle to simulate the pavement slope in the Siege of Acre mine tunnels. The water is recycled through the system using fish pond pumps. Water is occasionally added to the system to compensate for evaporative losses. The pH of the water is adjusted daily with sulfuric acid. Samples of the circulating water are collected periodically and analyzed for the parameters listed in Table 3. In addition, one sample of the tap water supply used for the experiment has been analyzed for the same suite of parameters to provide a baseline for comparison.

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Major Ions Trace Elements Other Parameters Aluminum Arsenic Mercury Alkalinity Calcium Barium Manganese Silica Sodium Boron Molybdenum Total Dissolved Solids

Magnesium Cadmium Nickel Potassium Cobalt Lead

Iron Chromium Zinc Chloride Copper

Nitrate/Nitrite Sulfate

Table 3: Parameters of concern analyzed in Weathering Block Study. Results Figure 9 presents the analytical results for potassium, sodium, calcium, aluminum, iron, sulfate, chloride, and TDS in the water that has been allowed to run over the blocks. The experimental CCB blocks have been found to have significant buffering capacity, as indicated by the fact that the recycled water for the low pH experiments (pH 3 and 4) requires the daily addition of acid to maintain the desired pH. The concentrations of all analytical parameters increased sharply above the tap water concentration at the initiation of the experiment. For all four blocks, calcium, potassium, sodium, sulfate, and total dissolved solids concentrations decreased over time to levels lower than the initially observed levels, but higher than the initial tap water levels. This same pattern of concentration was also observed for aluminum and iron in Blocks 2 and 3. Aluminum and iron in Blocks 1 and 4 also increased initially, but eventually decreased to levels similar to the original tap water concentration. The pattern of chloride concentrations is slightly different from the other parameters in that an initial release of chloride was observed, followed by a decrease and finally a steady increase above the original tap water concentration and the initially observed concentrations. The data appear to indicate that upon first exposure of the CCB-grout to water, there is an initial release of certain parameters, possibly due to surface-held ions or easily soluble surface minerals. Over time, the observed concentrations appear to stabilize (with the exception of chloride, for which the continued increase in concentration may be due to external factors, such as evaporation). This observation is consistent with field data observed at the Winding Ridge injection site where, after an initial concentration spike for certain parameters related to the grout rather than to AMD (calcium, potassium, sodium, and chloride), the concentrations of these parameters gradually decreased, but in many cases remained elevated relative to pre-injection conditions for several years1.

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Among the trace elements analyzed in the water, cadmium, cobalt, mercury, nickel, and lead have never been detected. Copper has been detected in the water samples, but at levels below those detected in the tap water sample. Among the remaining trace metals that have been detected in one or more water samples from the weathering block experiment at levels above the tap water level, only arsenic has been detected at a level above its maximum contaminant level (MCL). The concentrations of arsenic in the Weathering Block Study samples ranged from non-detect to 0.031 mg/L. These levels are lower than the levels of arsenic detected in samples from the Kempton mine pool (non-detect to 0.76 mg/L) and in the water flowing along the mine pavement at Siege of Acre (non-detect to 1.9 mg/L). This data suggests that although some release of trace metals from the CCB grout could occur in the presence of acidic mine water, the levels are expected to be low compared to the levels already present in the AMD. Overall, the Weathering Block study data indicate that limited dissolution of the grout has occurred. The grout dissolution that occurs produces elevated pH levels (if acid is not added continuously, as was done in the study), and elevated levels of total dissolved solids and major ions. While limited leaching of trace metals has been observed in the analytical results, the levels appear to be very low, especially when compared to the levels of trace metals generally observed in typical AMD environments4. STEPS FORWARD The initial proposal for the Siege of Acre injection project divided the project into 5 phases:

• Phase 1 – Characterization of Siege of Acre • Phase 2 – Materials Research • Phase 3 – Engineering Design – Assimilate the results of Phase 1 and

Phase 2 to prepare a final engineering design and bid package for the project.

• Phase 4 – CCB Grout Injection; and • Phase 5 – Post-Injection Monitoring

The activities detailed in this paper represent the completion of Phases 1 and 2, and work is slated to begin on Phase 3 – Engineering Design in the near future. The Final Engineering Design will include identification and procurement of necessary federal, state, and local permits as well as the preparation of a conceptual engineering design for bid by qualified contractors. REFERENCES [1] Guynn, R.L., R.L. Rafalko, and P. Petzrick (2007). Use of a CCP Grout to Reduce the Formation of Acid Mine Drainage: 10-Year Update on the Winding Ridge Project. Presented at the 3rd World of Coal Ash Conference, Covington, Kentucky.

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[2] Warner, N.R., L. Rafalko, B. Williams, P. Petzrick, and R.T. Hemmings (2005). The Kempton Man Shaft Project: Application of CCP Grout as a Seepage Barrier. Presented at the 2nd World of Coal Ash Conference, Lexington, Kentucky. [3] Hemmings, R.T., P. Petzrick, J. Sherwill, and B.J. Cornelius (2002). Beneficial Use of CCPs in Maryland in Large-Scale Engineering Applications: Design and Development of CCP Grouts. Presented at the 19th Annual International Pittsburgh Coal Conference, Pittsburgh, Pennsylvania. [4] Warner, N. J. Giacinto, G. Reeves, A. Albirght, and P. Petzrick (2007). Effects of Acid Mine Drainage on CCP Grout: A Bench-Scale Weathering Experiment. Presented at the 3rd World of Coal Ash Conference, Covington, Kentucky.