In cooperation with the National Park Service 

Assessment of Characteristics and Remedial 


Alternatives for Abandoned Mine Drainage: 


Case Study at Staple Bend Tunnel Unit of 


Allegheny Portage Railroad National Historic 


Site, Cambria County, Pennsylvania, 2004 


By Charles A. Cravotta, III 


Open-File Report 2005-1283 


U.S. Department of the Interior 

U.S. Geological Survey 
U.S. DEPARTMENT OF THE INTERIOR 

GALE A. NORTON, Secretary 

U.S. GEOLOGICAL SURVEY 

P. Patrick Leahy, Acting Director 

U.S. Geological Survey, Reston, Virginia: 2005 

For sale by U.S. Geological Survey, Information Services 


Box 25286, Denver Federal Center 


Denver, CO 80225 


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Although this report is in the public domain, permission must be secured by the individual copyright owners to


reproduce any copyrighted materials contained in the report. 


ii 
Contents 

Abstract ................................................................................................................................................................................................1 


Introduction ..........................................................................................................................................................................................2 


 Selection of a Test Site ..............................................................................................................................................................3 


Purpose and Scope.....................................................................................................................................................................4 


Data Collection and Evaluation .........................................................................................................................................................5 


 Field Methods ..............................................................................................................................................................................5 


 Laboratory Methods ...................................................................................................................................................................6 


 Data Evaluation and Computational Methods ........................................................................................................................7 


Characteristics of Abandoned Mine Drainage.............................................................................................................................10 


Abandoned Mine Drainage Flow Rates and Chemistry......................................................................................................10 


 Pond-Water Volume and Chemistry.......................................................................................................................................12 


Mineralogy and Chemistry of Pond Sediments ....................................................................................................................14 


Considerations for Remediation of the Abandoned Mine Drainage at the ALPO-SBTU Test Site ......................................14 


Mineralogy and Chemistry of Limestone and Steel Slag for Cubitainer Tests ...............................................................15 


Cubitainer Tests of Short-Term Reaction Rates ..................................................................................................................18 


 Cubitainer Estimates of Long-Term Performance ...............................................................................................................21 


Identification of Remediation Strategies at the ALPO-SBTU Test Site............................................................................21 


Summary and Conclusions ..............................................................................................................................................................23 


Acknowledgments.............................................................................................................................................................................24 


References Cited ...............................................................................................................................................................................25 


iii 
Figures 

1.	 Color aerial photograph of the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic 

Site, Pennsylvania, showing locations of water-quality sampling sites..................................................................32 

2.	 Flow chart for selection of passive treatment alternatives .......................................................................................33 


3.	 Graphs showing flow rate and chemistry of abandoned mine drainage, April 7 and 27, 2004, Staple Bend 

Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania .................................................34 

4.	 Graphs showing trace-element concentrations in abandoned mine drainage, April 7 and 27, 200, Staple 

Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania.......................................36 

5.	 Graphs showing rate of change in pH, alkalinity, and calcium concentrations of effluent from sites 1 and 

Fe at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania, 

during cubitainer tests .....................................................................................................................................................38 

6.	 Graphs showing measured and simulated effect of detention time on limestone or steel-slag treatment of 

abandoned mine drainage from sites 1 and Fe at the Staple Bend Tunnel Unit of Allegheny Portage 

Railroad National Historic Site, Pennsylvania, on the basis of cubitainer tests ....................................................39 

7.	 Graphs showing simulation of long-term performance of limestone- or steel-slag substrates for treatment 

of abandoned mine drainage from site 1 at the Staple Bend Tunnel Unit of Allegheny Portage Railroad 

National Historic Site, Pennsylvania, on the basis of cubitainer test data and corresponding first-order or 

second-order rate estimates for limestone or steel slag dissolution and alkalinity production .........................40 

8.	 Graphs showing simulation of long-term performance of limestone- or steel-slag substrates for treatment 

of abandoned mine drainage from site Fe at the Staple Bend Tunnel Unit of Allegheny Portage Railroad 

National Historic Site, Pennsylvania, on the basis of cubitainer test data and corresponding first-order or 

second-order rate estimates for limestone or steel slag dissolution and alkalinity production .........................41 

iv 
Tables 

1.	 Description of abandoned mine drainage and pond sites sampled in April 2004 for the assessment of the 

Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania ..........................42 

2.	 Flow rate, pH, net acidity, and concentrations of dissolved constituents for abandoned mine drainage 

and pond samples collected April 7 and 27, 2004, for assessment of water quality at the Staple Bend 

Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania .................................................43 

3.	 Concentrations of dissolved trace elements in abandoned mine drainage and pond samples collected 

April 7 and 27, 2004, for assessment of water quality at the Staple Bend Tunnel Unit of Allegheny Portage 

Railroad National Historic Site, Pennsylvania..............................................................................................................44 

4.	 Major mineralogical and chemical composition of pond sediment samples from the Staple Bend Tunnel 

Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania, and steel slag and limestone 

obtained from the vicinity and used in cubitainer tests..............................................................................................45 

5.	 Trace-element composition of pond sediment samples from the Staple Bend Tunnel Unit of Allegheny 

Portage Railroad National Historic Site, Pennsylvania, and steel slag and limestone obtained from the 

vicinity and used in cubitainer tests...............................................................................................................................46 

6.	 Cubitainer test data for pH, alkalinity, and calcium concentrations in effluent from reaction between steel 

slag or limestone with abandoned mine drainage from Sites 1 and Fe at the Staple Bend Tunnel Unit of 

Allegheny Portage Railroad National Historic Site, Pennsylvania ...........................................................................47 

7.	 Cubitainer test data for specific conductance, pH, alkalinity, computed acidity, and corresponding 

concentrations of dissolved major cations and anions in effluent from reaction between steel slag or 

limestone with abandoned mine drainage from Sites 1 and Fe at the Staple Bend Tunnel Unit of 

Allegheny Portage Railroad National Historic Site, Pennsylvania ...........................................................................48 

8.	 Cubitainer test data for dissolved trace elements in effluent from reaction between steel slag or limestone 

with abandoned mine drainage from Sites 1 and Fe at the Staple Bend Tunnel Unit of Allegheny Portage 

Railroad National Historic Site, Pennsylvania..............................................................................................................49 

9.	 Summary of cubitainer test conditions and results for rate of reaction between steel slag or limestone 

with abandoned mine drainage from Sites 1 and Fe at the Staple Bend Tunnel Unit of Allegheny Portage 

Railroad National Historic Site, Pennsylvania..............................................................................................................51 

10.	 Rankings of pollutant loading and possible remedial alternatives for abandoned mine drainage at the 

Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania ..........................52 

v 
Conversion Factors 

Inch/Pound to SI 

Multiply By To obtain 

Length 

inch (in.) 2.54 centimeter (cm) 

foot (ft) 0.3048 meter (m) 

mile (mi) 1.609 kilometer (km) 

Area 

square mile (mi2) 2.590 square kilometer (km2) 

Volume 

cubic foot (ft3) 0.02832 cubic meter (m3) 

Flow rate 

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s) 

vi 
Abstract 

This report describes field, laboratory, and computational methods that could be used to assess 

remedial strategies for abandoned mine drainage (AMD). During April-June, 2004, the assessment process 

was applied to AMD from bituminous coal deposits at a test site in the Staple Bend Tunnel Unit of 

Allegheny Portage Railroad National Historic Site (ALPO-SBTU) in Cambria County, Pennsylvania. The 

purpose of this study was (1) to characterize the AMD quantity and quality within the ALPO-SBTU test 

site; (2) to evaluate the efficacy of limestone or steel slag for neutralization of the AMD on the basis of 

reaction-rate measurements; and (3) to identify possible alternatives for passive or active treatment of the 

AMD. The data from this case study ultimately will be used by the National Park Service (NPS) to develop 

a site remediation plan. The approach used in this study could be applicable at other sites subject to 

drainage from abandoned coal or metal mines. 

During April 2004, AMD from 9 sources (sites1, 1Fe, Fe, 2, 3, 3B, 5, 6, and 7) at the ALPO-SBTU test 

site had a combined flow rate of 1,420 gallons per minute (gal/min) and flow-weighted averages for pH of 

3.3, net acidity of 55 milligrams per liter (mg/L) as CaCO3, and concentrations of dissolved sulfate, 

aluminum, iron, and manganese of 694 mg/L, 4.4 mg/L, 0.74 mg/L, and 1.2 mg/L, respectively. These pH, 

net acidity, sulfate, and aluminum values exceed effluent criteria for active mines in Pennsylvania. 

During April-June 2004, limestone and steel slag that were locally available were tested in the 

laboratory for their composition, approximate surface area, and potential to neutralize samples of the 

AMD. Although the substrates had a similar particle-size distribution and identical calcium content (43 

percent as calcium oxide), the limestone was composed of crystalline carbonates and the slag was 

composed of silicate glass and minerals. After a minimum of 8 hours contact between the AMD and 

limestone or steel slag in closed containers (cubitainers), near-neutral effluent was produced. With 

prolonged contact between the AMD and limestone or steel slag, the concentrations of iron, aluminum, and 

most dissolved trace elements in effluent from the cubitainers declined while pH was maintained greater 

than 6.0 and less than 9.0. The cubitainer testing demonstrated (1) lower alkalinity production but higher 

pH of AMD treated with steel slag compared to limestone, and (2) predictable relations between the 

effluent quality, detention time, and corresponding flow rate and bulk volume for a bed of crushed 

limestone or steel slag in an AMD passive-treatment system. 

The process for evaluating AMD remedial strategies at the ALPO-SBTU test site involved the 

computation and ranking of the metal loadings during April 2004 for each of the AMD sources and a 

comparison of the data on AMD flow and chemistry (alkalinity, acidity, dissolved oxygen, ferric iron, 

aluminum) with published criteria for selection of passive-treatment technology. Although neutralization 

Page 1 
of the AMD by reaction with limestone was demonstrated with cubitainer tests, an anoxic limestone drain 

(ALD) was indicated as inappropriate for any AMD source at the test site because all had excessive 

concentrations of dissolved oxygen and (or) aluminum. One passive-treatment scenario that was identified 

for the individual or combined AMD sources involved an open limestone channel (OLC) to collect the 

AMD source(s), a vertical flow compost wetland (VFCW) to add alkalinity, and an aerobic wetland to 

facilitate iron and manganese oxidation and retention of precipitated solids. Innovative passive-system 

designs that direct flow upward through submerged layers of limestone and/or steel slag and that 

incorporate siphons for automatic flushing of solids to a pond also may warrant consideration. 

Alternatively, an active-treatment system with a hydraulic-powered lime doser could be employed instead 

of the VFCW or upflow system. Now, given these data on AMD flow and chemistry and identified 

remedial technologies, a resource manager can use a publicly available computer program such as 

“AMDTreat” to evaluate the potential sizes and costs of various remedial alternatives. 

Introduction 

Abandoned mine drainage (AMD) affects the quality and potential uses of water supplies in coal and 

metal mining regions worldwide (Herlihy et al., 1990; Nordstrom, 2000). AMD ranges widely in quality 

from mildly alkaline to strongly acidic and corrosive, with dissolved solids ranging from about 200 to 

10,000 mg/L (Hyman and Watzlaf, 1997; Rose and Cravotta, 1998; Nordstrom and Alpers, 1999). AMD 

characteristically has elevated concentrations of dissolved sulfate, iron, and other metals. Dissolved metals 

and other constituents in AMD can be toxic to aquatic organisms and ultimately can precipitate forming 

ochreous encrustations that degrade the aquatic habitat (Winland et al., 1991; Bigham and Nordstrom, 

2000). 

The pH and concentrations and loadings of alkalinity, acidity, and metals such as iron (Fe), aluminum 

(Al), and manganese (Mn) in mine effluent and receiving water bodies commonly are measured to identify 

potential for environmental effects (Commonwealth of Pennsylvania, 1998a, 1998b, 2002; U.S. 

Environmental Protection Agency, 2002a, 2002b). These parameters also are measured to identify 

appropriate treatment methods to remove the metals and maintain neutral pH (Hedin et al., 1994; Skousen 

et al., 1998). The pH of AMD is an important measure for evaluating chemical equilibrium, corrosiveness, 

and aquatic toxicity. The severity of toxicity or corrosion tends to be greater under low-pH conditions than 

under near-neutral conditions. For example, Al is soluble at low pH, and compared to Fe and Mn, 

relatively low concentrations of dissolved Al can be toxic (Elder, 1988; Bigham and Nordstrom, 2000). 

Accordingly, the U.S. Environmental Protection Agency (2000, 2002a, 2002b) recommends pH 6.5 to 8.5 

for public drinking supplies and pH 6.5 to 9.0 for protection of freshwater aquatic life. Furthermore, the 

Page 2 
Commonwealth of Pennsylvania (1998a, 1998b, 2002) stipulates that effluent discharged from active 

mines must have pH 6.0 to 9.0 and alkalinity greater than acidity. 

Recently, resource managers have gained access to the publicly available AMDTreat computer 

program for evaluation of the approximate construction and maintenance costs of active or passive systems 

for treatment of AMD (U.S. Office of Surface Mining Reclamation and Enforcement, 2002). Only the 

AMD flow rate and concentrations of acidity, alkalinity, iron, manganese, and aluminum are required as 

input data for this program. However, inappropriate comparisons of remedial strategies and poor decisions 

can result because the AMDTreat program does not consider if the selected AMD treatment technology 

meets recommended criteria for implementation. 

Different alternatives for treatment of AMD could be appropriate depending on the volume of the mine 

discharge, its alkalinity and acidity balance, its concentrations of dissolved oxygen and metals, and the 

available resources for construction and maintenance of a treatment system (Hedin et al., 1994; Skousen et 

al., 1998). If the effluent is “net alkaline,” the alkalinity exceeds the acidity and the pH will remain near 

neutral after complete oxidation of the effluent. In this case, systems that facilitate aeration of the effluent 

and retention of precipitated solids are indicated. On the other hand, if the effluent is “net acidic,” the 

acidity exceeds the alkalinity and the pH will decline to acidic values after complete oxidation and 

precipitation of the dissolved metals. In this case, systems that add alkalinity and that maintain or increase 

pH are indicated. 

Selection of a Test Site 

The Allegheny Portage Railroad in Cambria County, Pennsylvania, was constructed during 1831-1834 

as a 36-mile-long inclined plane railroad over the Allegheny Mountains to connect canal segments along a 

394-mile transportation route between Philadelphia and Pittsburgh, Pa. (Sellards & Grigg, Inc., 1991). 

Hailed as an engineering marvel in 1834, the canal and railroad reduced travel time between Philadelphia 

and Pittsburgh from three weeks by wagon to only four days (VisitPA.com, 2005). The 901-foot long 

Staple Bend Tunnel, excavated at the head of Plane 1 through a promontory that formed a bend in the Little 

Conemaugh River, was the first railroad tunnel to operate in the United States (Sellards & Grigg, Inc., 

1991). Designated a National Historic Site in 1964 and acquired by the U.S. Department of Interior in 1991 

from Bethlehem Steel Corporation, the present site is managed by the National Park Service (NPS) 

(Sellards & Grigg, Inc., 1991; National Park Service, 2005). The site covers 1,249 acres and includes 

various historical attractions plus hiking and biking trails. The site also includes remnants of abandoned 

coal mines and abuts the Cambria steel slag dump that postdate the 1833-1852 period of historical 

significance (Sellards & Grigg, Inc., 1991). 

Page 3 
Historical mining of bituminous coal in the vicinity of the Staple Bend Tunnel Unit of Allegheny 

Portage Railroad National Historic Site (ALPO-SBTU) has caused widespread contamination of water 

resources within the ALPO-SBTU boundaries and surrounding watersheds (Pennsylvania Department of 

Environmental Protection, 2001; Kaktins and Carney, 2002). The ALPO-SBTU is near the eastern limit of 

the Bituminous Coalfield and the northern Appalachian Plateau (Edmunds, 1999). AMD from 

underground and surface mines along the eastern perimeter of the ALPO-SBTU sustains perennial flows in 

several unnamed tributaries that cross the ALPO-SBTU and ultimately discharge into the Little 

Conemaugh River (fig. 1). The AMD within the park was cited as a deficiency in a 2002 NPS 

Environmental Audit (Alan C. Ellsworth, National Park Service, 2004, written commun.). 

Data collected within the ALPO-SBTU test site by Kaktins and Carney (2002) for drought conditions 

in 2000-2001 indicated ranges for AMD flow rates, pH, acidity, and metals loading that could feasibly be 

remediated using passive-treatment technology (Hedin et al., 1994; Skousen et al., 1998). However, the 

flow rates and associated contaminant-loading rates for drought conditions could underestimate the 

average or long-term conditions and, consequently, result in an incorrect basis for design of remediation. 

Nevertheless, the site characteristics are suitable for testing the assessment process for remedial treatment 

of AMD. 

Treatment systems require a neutralization media that is economical to use. An important factor in 

selection of this site for study is that limestone and steel slag are locally available and potentially useful for 

mine-drainage treatment. Calcium-bearing compounds in the limestone and steel slag can neutralize AMD, 

increasing pH and alkalinity (Ziemkiewicz and Skousen, 1998; Simmons et al., 2002a, 2002b; Cravotta, 

2003). However, equal amounts of limestone or slag could have different neutralizing capacities and rates 

of reaction because limestone predominantly is composed of crystalline carbonates and slag predominantly 

is composed of silicate glass. Furthermore, the pH, dissolved carbon dioxide (CO2), and other solutes in 

AMD could affect the rates of reaction in a treatment system (Cravotta and Watzlaf, 2002; Cravotta, 2003). 

Hence, investigation of these factors is warranted to determine potential effectiveness of using limestone or 

steel slag for treatment of the AMD at the ALPO-SBTU test site. 

Purpose and Scope 

This report outlines a process to assess remedial alternatives for treatment of AMD. The ALPO-SBTU 

test site in Cambria County, Pennsylvania, is used to illustrate how the process can be applied. The report 

summarizes (1) the quantity and quality of the AMD within the ALPO-SBTU test site during April 2004, 

(2) the efficacy of limestone and steel slag for treatment of the AMD on the basis of laboratory reactionrate measurements, and (3) possible remediation strategies for passive and active treatment of the AMD on 

Page 4 
the basis of the April 2004 water-quality data and available criteria for identification of passive-treatment 

technologies. Synoptic field surveys and laboratory studies were conducted by the U.S. Geological Survey 

(USGS) in cooperation with the NPS in April 2004, to acquire data for nondrought, high base-flow 

conditions and to evaluate limestone and steel slag for treatment of the AMD at the ALPO-SBTU test site. 

The approach used in this study could be applicable at other sites subject to drainage from abandoned coal 

or metal mines. 

Data Collection and Evaluation 

Data were collected by the USGS on the flow rates and composition of AMD and associated pond 

water and sediment, and the rate of reaction between AMD and limestone or steel slag. Methods used to 

collect and evaluate these data are summarized below. 

Field Methods 

Synoptic surveys were conducted by the USGS during high base-flow conditions on April 7 and 27, 

2004, to characterize the inorganic chemistry of all known AMD, including 12 sites previously sampled by 

Kaktins and Carney (2002), 1 previously unsampled discharge site, and 6 sites on two previously 

unsampled ponds downstream from AMD sources within the ALPO-SBTU boundaries (table 1). At each 

sample site, temperature, pH, specific conductance (SC), dissolved oxygen (DO), and redox potential (Eh) 

were measured using a multiparameter, submersible sonde calibrated in the field in accordance with 

standard field methods (U.S. Geological Survey, 1997 to present). Field pH and Eh were determined using 

a combination Pt and Ag/AgCl electrode with a pH sensor. The electrode was calibrated in pH 2.0, 4.0, and 

7.0 buffer solutions and in ZoBell solution (Wood, 1976, p. 18-22; U.S. Geological Survey, 1997 to 

present). Values for Eh were corrected to 25 °C relative to the standard hydrogen electrode in accordance 

with methods of Nordstrom (1977). Where weirs were intact, the flow rate was estimated on the basis of 

the water depth flowing through the weir notch and the appropriate weir equation given the notch geometry 

(Rantz et al., 1982b; Kaktins and Carney, 2002). Where weirs were absent or damaged, the flow rate was 

measured using a wading rod and pygmy current meter or a bucket and stop watch (Rantz et al., 1982a). 

Unfiltered and filtered (0.45-micrometer (μm) pore size) samples of water from each AMD source and 

pond sampling point were processed in the field, transferred to polyethylene bottles, preserved as 

appropriate, and transported on ice to the laboratory. 

On April 27, 2004, a canoe was used to access each pond for sampling of water and bottom sediment. 

The temperature, pH, and SC near the top and bottom of the water column were measured while sampling 

locations were recorded with a global positioning system (GPS) and electronic depth indicator. Near the 

Page 5 
upstream (inflow) and downstream (outflow) ends of each pond, a clamshell dredge device was suspended 

from the canoe to collect bottom sediments for analysis of chemistry and mineralogy. The wet sediment 

was transported on ice in a sealed polyethylene bag to the laboratory. 

Laboratory Methods 

The alkalinity and “hot” acidity of the unfiltered water samples were titrated using standard methods to 

fixed endpoint pH of 4.5 and 8.3, respectively, within 48 hr of sampling at the USGS New Cumberland 

laboratory (American Public Health Association, 1998a, b). Concentrations of sulfate, chloride, and nitrate 

in filtered, unpreserved subsamples were analyzed by ion chromatography (IC), and concentrations of 

dissolved metals in filtered, acidified subsamples were analyzed by inductively coupled plasma emission 

mass spectrometry (ICP-MS) at the Actlabs laboratory in Toronto, Ontario (Crock et al., 1999). 

The pond-bottom sediments and samples of limestone and steel slag used for cubitainer testing 

(described below) were air dried and pulverized in the laboratory prior to analysis of mineralogy and 

chemistry. The mineralogy was analyzed by X-ray diffraction (XRD) at the USGS Minerals Resources 

laboratory in Reston, Virginia (Whittig and Allardice, 1986; Taggart, 2002). The XRD patterns were 

collected on a Scintag theta-theta diffractometer using copper radiation over the range of 3° to 70° with a 

0.02° step size and a count time of 1 second per step (Nadine Piatak, U.S. Geological Survey, written 

commun., 2004). Major, minor, and trace elements in a 1-gram subsample of the dried sediment were 

analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES) and ICP-MS after 

lithium metaborate-tetraborate fusion and decomposition with a mixture of hydrochloric, nitric, perchloric, 

and hydrofluoric acids (Lim and Jackson, 1982; Crock et al., 1999) at the Actlabs laboratory in Ontario, 

Canada. 

“Cubitainer” tests were conducted during May 3-17, 2004, in the USGS New Cumberland laboratory 

to evaluate quantities of limestone or steel slag needed for AMD treatment using methods of Cravotta 

(2003) and Cravotta and others (2004). Following the synoptic survey on April 27, water samples from 

sites Fe and 1 were collected into separate 5-gallon polyethylene containers, sealed without headspace, 

immediately transferred on ice to the laboratory, and then refrigerated. In the laboratory, the untreated 

water from each site was transferred to a 1-gallon collapsible polyethylene container (cubitainer) 

containing 2 kilograms (kg) of limestone or steel slag particles that had been sieved to nominal diameters 

ranging from 0.5 to 1.5 inches (1.3 to 3.8 centimeters (cm)). AMD from site 1 was added to one cubitainer 

filled with limestone and a second filled with steel slag, and AMD from site Fe was added to a third 

cubitainer filled with limestone and a fourth filled with steel slag. Effluent samples from each of the four 

cubitainers were collected at progressively longer detention times, starting at 0.5-hour (hr) intervals, over 2 

Page 6 
weeks total elapsed time. Each effluent sample was withdrawn using a 120-milliliter (mL) syringe, and a 

60-mL aliquot was pushed through a 0.45-μm pore-size nylon filter. The first 10-mL filtrate of the 60-mL 

aliquot was discarded and the remaining 50-mL filtrate was analyzed immediately for pH, alkalinity, and 

calcium concentrations by electrometric and colorimetric titration methods (American Public Health 

Association, 1992a, 1998b). A subset of the effluent samples collected after 1 hr, 8 hr, and 336 hr elapsed 

detention time also was analyzed for trace metals by ICP-MS to assess potential for contaminants to be 

derived from, or removed by, reaction with the limestone and steel-slag substrates. 

The limestone and steel slag used for the laboratory rate tests were obtained from commercial sources 

near the ALPO-SBTU test site with the expectation that the same materials could be used for construction 

of a treatment system. The limestone, with a reported CaCO3 content of 83 weight percent, was obtained 

from the Ashcom Quarry, near Everett, Bedford County, through New Enterprise Stone and Lime Co., Inc., 

of New Enterprise, Pa. According to O’Neill (1964), this quarry is in the undivided Middle Ordovician 

Coburn through Loysburg Formations. The Johnstown limestone that can be present locally with coalbearing strata of the Pennsylvanian System (Brady et al., 1998) is not quarried because it is relatively thin 

and impure (Keith B. C. Brady, Pennsylvania Department of Environmental Protection, oral commun., 

2004). The steel slag, originally produced as a blast-furnace byproduct, was obtained through Rollock Inc., 

of Johnstown, Pa., from stockpiles near the ALPO-SBTU test site (fig. 1). Commercial uses of the 

stockpiled slag include railroad ballast, slope protection, anti-skid material, roofing granules, 

embankments, and fills (Simmons et al., 2002a). The slag had been sieved and cleaned commercially by 

magnetic separation to eliminate stray scraps of iron and steel. 

Data-Evaluation and Computational Methods 

Various water- and sediment-quality guidelines are relevant for evaluating the quality of the AMD and 

the pond water and sediment at the ALPO-SBTU test site. Effluent from a coal mine that was permitted 

after passage of Public Law 95-87, the Surface Mining Control and Reclamation Act of 1977 (SMCRA), 

must have alkalinity that exceeds its acidity concentration and must not have an instantaneous maximum 

concentration of iron, manganese, or aluminum that exceeds 7.0 milligrams per liter (mg/L), 5.0 mg/L, or 

0.75 mg/L, respectively (Commonwealth of Pennsylvania, 1998a, b). Additionally, the average daily 

concentration of sulfate must not exceed 250 mg/L for discharges that could affect public water supplies 

(Commonwealth of Pennsylvania, 1998a, b). Although these effluent criteria generally are not enforced for 

discharges from coal mines in Pennsylvania that were abandoned before 1977, in-stream criteria for 

chemical constituents have been incorporated in recent “total maximum daily loads” (TMDLs) for miningaffected watersheds (Commonwealth of Pennsylvania, 2001a; Pennsylvania Department of Environmental 

Page 7 
Protection, 2002, 2004). The criteria for TMDLs generally are consistent with those established to meet the 

warm-water fishery (WWF) or cold-water fishery (CWF) designation of a stream or other freshwater body 

(Commonwealth of Pennsylvania, 2002): 

• temperature during July and August not to exceed 66°F (18.9°C) or 87°F (30.6°C) for CWF and WWF, 

respectively; 

• dissolved oxygen concentration greater than 5.0 mg/L for CWF and 4.0 mg/L for WWF; 

• alkalinity not less than 20 mg/L as CaCO3, except where natural conditions are less; 

• pH not less than 6.0 or greater than 9.0; 

• total iron concentration not to exceed 1.5 mg/L as a 30-day average; 

• dissolved iron concentration not to exceed 0.3 mg/L; 

• total manganese concentration not to exceed 1.0 mg/L; and 

• total aluminum concentration not to exceed 0.75 mg/L. 

TMDLs for the Little Conemaugh River are proposed for development during 2007-2009 (Pennsylvania 

Department of Environmental Protection, 2004). Additional water-quality criteria established by the U.S. 

Environmental Protection Agency (2004) for the protection of freshwater aquatic life also have been 

adopted by the Commonwealth of Pennsylvania (2001b). These criteria include recommended continuous 

and maximum exposure limits for trace metals and other constituents in water that could be present in 

AMD. Finally, criteria for protection of benthic aquatic organisms from metals in streambed or lakebed 

sediments are available (MacDonald et al., 2000), but these sediment-quality guidelines have not been 

adopted by regulatory authorities in the United States. 

Following methods of Cravotta and Kirby (2004), the net-acidity concentrations for the AMD and 

pond-water samples were computed as the difference between the computed acidity based on the pH and 

the concentrations of dissolved aluminum, iron, and manganese and the measured alkalinity. Generally, 

with aeration and aging of AMD, the pH can decrease because of oxidation and hydrolysis of dissolved 

ferrous (FeII) and manganous (MnII) species and the consequent precipitation of solid phases. 

Fe2+ + 0.25 O2 + 2.5 H2O Æ Fe(OH)3 (s) + 2 H+ (1) 

Mn2+ + 0.5 O2 + H2O Æ MnO2 (s) + 2 H+ (2) 

Precipitation of Fe(OH)3, MnO2, and associated solids, such as FeOOH and Al(OH)3, will consume some 

or all available alkalinity. The net acidity (= computed acidity - measured alkalinity) indicates the potential 

for the pH to decrease to acidic values because of the oxidation and hydrolysis of dissolved metals 

(Cravotta and Kirby, 2004). The computed net acidity of AMD is equivalent to the measured hot acidity 

Page 8 
(Cravotta and Kirby, 2004). If the net acidity is negative (< 0), the effluent ultimately will be near neutral 

(pH = 6 to 8) and some alkalinity will remain after complete oxidation and hydrolysis of the dissolved 

metals. However, if the net acidity is positive (> 0), the effluent ultimately will be acidic (pH < 4.5) and an 

additional source of alkalinity would be needed to neutralize the excess acidity. 

The maximum measured flow and maximum concentrations of net acidity, dissolved oxygen, and 

metals for the April 2004 high base-flow samples were used to estimate relative contributions of AMD 

pollutants and to identify possible remedial alternatives for each of the AMD sources at the ALPO-SBTU 

test site on the basis of published criteria for selection of passive-treatment technology (fig. 2). The netacidity and metals loading for each AMD source were computed as the product of flow rate and the 

relevant constituent concentrations to indicate the environmental significance of the sources. These 

loading computations also could be useful to evaluate sizing of possible AMD treatment systems. For 

example, the iron-loading rate can be used to estimate the size of an aerobic wetland (Hedin and others, 

1994; Pennsylvania Department of Environmental Protection, 1999), and the annual net-acidity loading 

(net acidity > 0) can be used to indicate the annual quantities of limestone required for a passive 

neutralization within an anoxic limestone drain (ALD) or vertical flow compost wetland (VFCW) (Watzlaf 

and others, 2000; Rose, 2004) or for active treatment with hydrated lime (U.S. Office of Surface Mining 

Reclamation and Enforcement, 2002). Nevertheless, such sizing estimates based on loading rates ignore 

characteristics of the water quality and available substrates that can affect reaction rates and, consequently, 

treatment-system performance. 

Following methods of Cravotta and others (2004), the titration data for the cubitainer tests were used to 

derive first-order and second-order rate equations to estimate the rates of substrate dissolution and of 

increases in alkalinity and calcium concentrations as a function of the detention time within a limestone or 

steel-slag bed used for a passive-treatment system. By combining the cubitainer rate estimates with 

estimates for the initial mass of limestone or steel slag, the porosity of the bed (assumed to be 45 percent), 

and the reported AMD discharge rate, exponential decay models were obtained. These models indicate 

possible long-term trends, on a decadal scale, for changes in mass of limestone or slag, detention time, and 

corresponding concentrations of alkalinity of the effluent with age of the treatment system. Calcite 

saturation index (SI) and partial pressure of carbon dioxide (Pco2) were computed using measured values 

for temperature, SC, pH, alkalinity, and calcium (Langmuir, 1997; American Public Health Association, 

1992b); van't Hoff temperature-corrected equilibrium constants from Ball and Nordstrom (1991); and 

Debye-Huckel activity coefficients on the basis of ionic strength estimated from SC (Langmuir, 1997). The 

concentration of dissolved FeII was computed on the basis of the measured Eh, temperature, and ionic 

strength of fresh samples (Nordstrom, 1977, 2000). 

Page 9 
Characteristics of Abandoned Mine Drainage 

Data on the flow rates and composition of AMD, pond water and sediment, and the effluent and solids 

from cubitainers were used to assess the characteristics, possible ecological effects, and to identify possible 

alternatives for passive remediation of the AMD within the ALPO-SBTU test site. These data are 

summarized and evaluated below and, ultimately, will be used by resources managers of the NPS to 

develop a site remediation plan. 

Abandoned Mine Drainage Flow Rates and Chemistry 

Water-quality data for the field and laboratory analyses of the AMD and pond samples collected April 

7 and 27, 2004, are summarized in tables 2 and 3 and figures 3 and 4. A total of 13 samples were collected 

from known AMD sources and selected downstream locations on April 7, 2004. A subset of these sites was 

resampled on April 27, 2004, with additional sampling conducted within the two ponds near the southwest 

boundary of the ALPO-SBTU test site. Data collected on April 7 (tables 2 and 3) and previously by 

Kaktins and Carney (2002) indicated similar chemistry for upstream and downstream pairs of samples, but 

larger flow rates at the downstream sites. Thus, sites U, 3A, and 4 were excluded from the second set of 

samples on April 27 because these were upstream of sites 1, 3B, and 5, respectively. Site 2 was excluded 

from the second set of samples because it is not a separate flow, but represents combined seepage from 

sites 1Fe, Fe, and other diffuse discharges associated with an iron mound; samples from sites 1Fe and Fe 

were presumed representative of the chemistry of this seepage. Nevertheless, to account for the combined 

seepage flow volumes, data for site 2 were included in various computations. 

On April 7 and 27, 2004, the AMD flow rates ranged from 0.4 gal/min to 498 gal/min (table 2, fig. 

3A), with the largest flows, exceeding 350 gal/min, at sites 1, 3, and 5. Previously reported maximum 

flows at sites 1, 3, and 5 were 232, 73, and 105 gal/min, respectively (Kaktins and Carney, 2002). All the 

known AMD sources were flowing in April 2004; however, previously, some of the small AMD sites had 

been reported as intermittent (Kaktins and Carney, 2002). 

With the exception of site 8, the AMD samples for April 2004 were net acidic and had elevated 

concentrations of dissolved sulfate, silica, and metals compared to background. Site 8 had net-alkaline 

water quality with near-neutral pH, moderate concentrations of sulfate (from 317 to 351 mg/L), and low 

concentrations of dissolved metals, consistent with background (table 2, figs. 3 and 4). The pH ranged 

from 2.3 at site 2 to 7.8 at site 8 (table 2, fig. 3B). Net acidity ranged from -45 mg/L as CaCO3 at site 8 to 

322 mg/L as CaCO3 at site 2. Concentrations of sulfate ranged from 317 to 1,090 mg/L and silica ranged 

from 5.8 to 34.7 mg/L at site 8 and site Fe, respectively. Except for sites Fe, 1Fe, and 2, the concentrations 

Page 10 
of dissolved aluminum exceeded those of iron and manganese (table 2). Concentrations of dissolved 

aluminum ranged from <0.02 mg/L at site 8 to 15.9 mg/L at site 6. Concentrations of dissolved iron ranged 

from <0.1 mg/L at site 8 to 76.4 mg/L at site Fe. Concentrations of dissolved manganese ranged from 

<0.01 mg/L at site 8 to 4.95 mg/L at site 1Fe. 

Although concentrations of manganese for all the AMD sources were less than the 5-mg/L effluent 

limit for active mines in Pennsylvania (fig. 3G), concentrations of aluminum for most of the AMD sources 

exceeded the 0.75-mg/L effluent limit (fig. 3F). Additionally, AMD at sites Fe, 1Fe, and 2 had 

concentrations of iron that exceeded the 7.0-mg/L effluent limit (fig. 3E). Furthermore, all the AMD 

samples, including site 8, had concentrations of sulfate that exceeded the 250-mg/L limit that applies for 

mine discharges that could affect public water supplies (fig. 3D). 

The quality of all the AMD sources combined was approximated by the computation of the flowweighted average concentrations of constituents and the sum of flow and loading rates. The cumulative 

flow rate for the combined AMD sources was 1,420 gal/min on April 7 and 1,231 gal/min on April 27. 

This calculation excludes site 8 (fig. 1), because it is isolated from other sources and is not representative 

of AMD, and sites U, 3A, and 4, because these sites are redundant with downstream sites. The relevant 

sources had a flow-weighted average pH of 3.3 (determined on the basis of flow-weighted hydrogen-ion 

concentration) and net acidity of 55 mg/L as CaCO3. The flow-weighted average concentrations of sulfate, 

silica, aluminum, iron, and manganese were 694 mg/L, 17.2 mg/L, 4.4 mg/L, 0.74 mg/L, and 1.2 mg/L, 

respectively. On the basis of these values, the pH, net acidity, sulfate, and aluminum concentrations would 

exceed relevant effluent criteria for active mines (Commonwealth of Pennsylvania, 1998a, b) (fig. 3). 

The sum of iron, aluminum, and manganese loading for the combined AMD sources was 19.7 and 

16.6 tons per year (ton/yr) on April 7 and 27, 2004, respectively (table 2). Site 1 had the largest metals 

loading rate, discharging an average of 6.5 ton/yr of iron, aluminum, and manganese (table 2, fig. 3H). 

Sites 3, 5, 6, and 7 each discharged approximately half that load, largely from dissolved aluminum (table 2, 

fig. 3H). 

In addition to aluminum, iron, and manganese, dissolved trace metals were present in the AMD at the 

ALPO-SBTU test site (table 3, fig. 4). Concentrations of arsenic, cadmium, chromium, copper, lead, and 

zinc in the AMD did not exceed relevant U.S. Environmental Protection Agency (2002b) drinking-water 

standards (fig. 4); however, drinking-water standards are not available for cobalt, nickel, and various other 

metals. Nevertheless, concentrations of cobalt, nickel, and zinc in the AMD samples (figs. 4C, 4G, 4H) 

consistently exceeded continuous concentration criteria for protection of freshwater aquatic life (CCCF) 

(U.S. Environmental Protection Agency, 2002a; Commonwealth of Pennsylvania, 2001b). Additionally, 

Page 11 
chromium, copper, and lead concentrations in several of these samples exceeded relevant CCCF values 

(figs. 4D, 4E, 4F). 

The water-quality samples collected April 27 had higher pH and lower concentrations of net acidity, 

sulfate, and most dissolved metals compared to samples collected April 7 (tables 2 and 3, figs. 3 and 4). 

Furthermore, the samples collected in April 2004 generally had lower concentrations of net acidity and 

dissolved metals than the samples reported by Kaktins and Carney (2002) for lower flow conditions than 

the present study. Hence, the data from Kaktins and Carney (2002) along with the data for April 2004 

indicate a general decline in the concentrations of acidity and metals associated with increased flow rate. 

Dilution of mineralized ground water with meteoric water (rainwater, snowmelt) could explain the 

relatively low concentrations of dissolved sulfate and metals for the high base-flow samples. Kaktins and 

Carney (2002) noted that acidity concentrations for the AMD sources tended to be larger during fall lowflow conditions compared to spring high-flow conditions during their study, but acidity loading was larger 

in the spring. If dilution or evaporation was the sole process causing changes in flow rate and associated 

chemical concentrations, the chemical load would not change. The increase in acidity loading associated 

with higher flow conditions in the spring during 2001 and the current study implies that the meteoric water 

is a dilute acidic solution that adds some acidity, sulfate, and metals, likely due to atmospheric aerosols 

(acid rain) and dissolution of pyrite-oxidation products along the recharge pathway (Cravotta, 1994, 2000). 

Pond-Water Volume and Chemistry 

The two ponds near the southern limit of the ALPO-SBTU test site are bounded on the east bank by the 

hillside leading to the historical rail trail and abandoned mines and on the west by the active railroad and 

the Little Conemaugh River (fig. 1). Although water from the upper pond (pond #1) is presumed to flow to 

the lower pond (pond #2), no direct spillover or surface flow was apparent from either pond in April 2004. 

Seepage to pond #2 is likely to take place through the earthen berm separating the two ponds. Likewise, 

water is likely to seep from both ponds to the Little Conemaugh River through the adjacent railroad bed. 

Elevation surveys were not conducted to determine precise volumes or capacity. However, based on the 

GPS coordinates and water-column depth readings completed on April 27, 2004, the upper pond has a 

surface area of approximately 1.5 acres with a volume of approximately 4.47 acre-feet (acre-ft) based on 

its length of 860 feet (ft), average width of 75 ft, and average depth of approximately 3 ft. The lower pond 

has a surface area of approximately 0.9 acres with a volume of 4.29 acre-ft, based on its length of 440 ft, 

average width of 85 ft, and average depth of approximately 5 ft. 

The chemistry of water from the upper pond indicated it originated as a mixture of AMD from various 

sources (sites 3, 3B, 5, 6, 7, and other unidentified seeps) plus smaller quantities from non-AMD or 

Page 12 
alkaline sources (site 8 and other associated seeps). Samples from the upper pond (pond #1 outflow) on 

April 7 and 27, 2004, had pH of 3.8 and 3.5, net acidity of 38 and 41 mg/L as CaCO3, and concentrations 

of dissolved sulfate of 356 and 358 mg/L, silica of 15.7 mg/L, aluminum of 5.07 and 3.94 mg/L, iron of 

0.25 and 0.41 mg/L, and manganese of 0.84 and 0.91 mg/L, respectively (table 2). In comparison, the main 

tributary to the upper pond (pond #1 inflow) had flow rates of 260 and 324 gal/min with corresponding pH 

of 3.2 and 3.6, net acidity of 90 and 60 mg/L as CaCO3, and concentrations of dissolved sulfate of 536 and 

499 mg/L, silica of 22.7 and 24.0 mg/L, aluminum of 9.25 and 7.62 mg/L, iron of 0.45 and 0.60 mg/L, and 

manganese of 1.48 and 1.46 mg/L, respectively (table 2). Combining data for April 7 and 27, 2004 (table 

2), the AMD sampled at sites 3, 3B, 5, 6, and 7 had a combined average flow rate of 955 gal/min (average 

of combined flow rates of 1,042 and 868 gal/min for April 7 and 27, respectively) with flow-weighted 

average values for pH of 3.7, net acidity of 32 mg/L as CaCO3, and concentrations of sulfate, silica, 

aluminum, iron, and manganese of 706 mg/L, 15.8 mg/L, 3.87 mg/L, 0.35 mg/L, and 0.93 mg/L, 

respectively. These flow-weighted average values do not change substantially if data for site 8 are 

included, because of its small flow rate, but would tend to approach measured values in the pond if 

proportionally greater volumes of such non-AMD were combined with the AMD. Thus, although the pond 

water was similar in composition to that computed for combined AMD sources, the computed volume of 

the combined AMD sources was three times larger than the measured inflow to pond #1. The relatively 

small inflow volume entering pond #1 compared to the combined AMD volume indicates a large fraction 

of the upstream AMD at sites 3, 3B, 5, 6, and 7 exits the ALPO-SBTU test site boundaries, possibly as 

seepage through the railroad bed, between the AMD sources and pond #1. Furthermore, additional nonAMD sources that were not sampled or quantified flow to the ponds as surface runoff and seepage. 

Although contributions from the non-AMD sources tend to have a diluting effect on sulfate and metals 

concentrations, they have little effect on the pH of the ponds. 

In April 2004, the chemistry of water from the lower pond (pond #2 inflow and outflow) was similar to 

that for the outflow of pond #1 (tables 2 and 3). Except for arsenic and chromium, the outflow samples 

from pond #1 and pond #2 had lower concentrations of net acidity, sulfate, and dissolved metals than the 

inflow to pond #1 (tables 2 and 3). Lower concentrations of sulfate and dissolved metals in the outflow 

from pond #1 and pond #2 compared to the inflow to pond #1 and the average for sites 3, 3B, 5, 6, and 7 

indicate that attenuation of these constituents by dilution and precipitation is likely to occur within the 

ponds. For example, mixing of the alkaline water from site 8 with acidic water from sites 3, 3B, 5, 6, and 7 

results in intermediate net acidity, sulfate, and metals concentrations, with potential for precipitation of 

iron and aluminum hydroxide, hydroxysulfate, and (or) silicate minerals. Nevertheless, dissolved cobalt, 

chromium, nickel, and zinc in both ponds were consistently greater than the relevant CCCF values for 

Page 13 
protection of aquatic life (table 3). Concentrations of copper and lead were similar to the CCCF values, and 

arsenic and cadmium were less than the CCCF values (table 3). 

Mineralogy and Chemistry of Pond Sediments 

Aluminum-rich precipitate with a light-brownish color accumulated on the bottom of the upper pond 

where the metal-laden AMD (sites 3, 3B, 5, 6, 7, and other unidentified seeps) mixed with alkaline water 

from various sources (site 8 and other associated seeps). The precipitate, which was thickest near the 

inflow to pond #1, was composed predominantly of aluminum- and silica-bearing compounds, such as 

quartz (SiO2), muscovite (KAl3Si3O10(OH)2), kaolinite (Al2Si2O5(OH)4), chlorite (Mg5Al2Si3O10(OH)8), 

and poorly crystalline or amorphous aluminum-hydroxysulfate minerals (table 4). The same minerals were 

present in sediment samples near the outflow of pond #1 and the inflow of pond #2. Although XRD 

patterns did not reveal iron minerals, trace quantities of ferrihydrite (Fe(OH)3; nominally Fe5HO8·4H2O), 

goethite (α−FeOOH), schwertmannite (Fe8O8(OH)6SO4), and other FeIII minerals (Winland et al., 1991; 

Bigham et al., 1996) likely imparted the rusty brownish colors to the sediments. 

The bottom sediments sampled from both ponds at the ALPO-SBTU test site were enriched in various 

metals (tables 4 and 5). The pond sediments had as much as three times higher concentrations of 

aluminum, arsenic, and chromium, but equivalent or lower concentrations of iron, copper, nickel, lead, and 

zinc compared to median concentrations for streambed sediments across the conterminous United States 

that were reported by Rice (1999) for aluminum (Al2O3 = 12.1 weight percent (wt%)), iron 

(Fe2O3 = 5.0 wt%), arsenic (As = 6.3 parts per million (ppm)), chromium (Cr = 64 ppm), copper 

(Cu = 27 ppm), nickel (Ni = 27 ppm), lead (Pb = 27 ppm), and zinc (Zn = 110 ppm). Of the metals 

detected in the pond sediments, only the concentration of iron in pond#1 outflow exceeded available 

sediment-quality guidelines for protection of freshwater benthic organisms reported by Persaud and others 

(1993) for iron (Fe2O3 = 5.72 wt%) and manganese (MnO2 = 0.142 wt%) and by MacDonald and others 

(2000) for arsenic (As = 33 ppm), chromium (Cr = 111 ppm), copper (Cu = 149 ppm), nickel 

(Ni = 48.6 ppm), lead (Pb = 128 ppm), and zinc (Zn = 459 ppm). 

Considerations for Remediation of the Abandoned Mine Drainage at the ALPO-SBTU Test Site 

Data on the characteristics of AMD sources at the ALPO-SBTU test site indicate the extent and 

severity of the AMD, as described above, and can be evaluated to identify possible passive treatment 

alternatives for the AMD sources (fig. 2). Combined with empirical tests on the rates of neutralization of 

AMD samples by locally available substrates, described below, site-specific strategies for remediation of 

Page 14 
the AMD can be considered. In the case of the ALPO-SBTU test site, limestone and steel slag substrates 

were evaluated to determine their potential for use in AMD treatment. 

Mineralogy and Chemistry of Limestone and Steel Slag for Cubitainer Tests 

The mineralogical and chemical compositions of the limestone and steel slag used in cubitainer tests 

are summarized in tables 4 and 5. The limestone was dark gray with minor white and black veins. On the 

basis of XRD and chemical analyses of finely crushed samples (table 4), the limestone was composed of 

calcite (CaCO3) with minor dolomite (CaMg(CO3)2), quartz (SiO2), and muscovite (KAl3Si3O10(OH)2). 

The chemical analysis indicated the limestone contained mostly calcium (CaO = 42.58 wt%) with smaller 

amounts of magnesium (MgO = 6.38 wt%), silicon (SiO2 = 7.15 wt%), aluminum (Al2O3 = 1.63 wt%), 

iron (Fe2O3 = 0.68 wt%), and potassium (K2O = 0.56 wt%). The concentrations of calcium and 

magnesium equate to 76.0 wt% as CaCO3 and 13.4 wt% as MgCO3. However, the XRD patterns did not 

reveal dolomite peaks (Jane Hammarstrom, U.S. Geological Survey, written commun., 2004). Hence, 

dolomite and (or) magnesian calcite probably were present but not in sufficient quantity to be detected by 

XRD. Silicon, aluminum, and potassium in the limestone could be explained by the presence of quartz and 

small amounts of muscovite. Except for strontium (Sr = 905 ppm) and barium (Ba = 133 ppm), the 

limestone was relatively free of trace-element impurities (table 5). Trace amounts of strontium and barium 

could substitute for calcium in major carbonate minerals (Hanshaw and Back, 1979). 

The steel slag had the appearance of porous cement or volcanic tuff; it was pale gray with a powdery 

white surface and numerous air vesicles ranging to 1 millimeter (mm) diameter. XRD analysis indicated 

the slag was composed predominantly of gehlenite (Ca2Al(AlSi)O7) and larnite (Ca2SiO4) with minor 

ettringite (Ca6Al2(SO4)3(OH)12.

26 H2O), gypsum (CaSO4

.

2H2O), and calcite (table 4). Non-crystalline 

phases (glasses) are probable in the slag because the peak-to-noise ratio on the XRD pattern was relatively 

low, suggesting an XRD-amorphous component (Jane Hammarstrom, U.S. Geological Survey, written 

commun., 2004). Additionally, zeolites could be present at low concentrations resulting from weathering 

of the slag minerals and glass (Nadine Piatak, U.S. Geological Survey, written commun., 2004). The 

calcium-silicate minerals and glasses of similar composition are typical of steel slag (Bayless and Schulz, 

2003; Ceramics Research Center, 2003) and account for the bulk composition (Ca2SiO4 = 2 CaO + SiO2; 

Ca2Al(AlSi)O7 = 2 CaO + Al2O3 + SiO2). The white surface coating on the slag samples consisted of 

ettringite, gypsum, and calcite, which are common minerals in portland cement and alkaline fly ash 

(Myneni et al., 1998; Loop et al., 2003). 

Like the limestone, the steel-slag sample contained mostly calcium (CaO = 42.69 wt%) with smaller 

amounts of magnesium (MgO = 3.57 wt%), iron (Fe2O3 = 0.47 wt%), and potassium (K2O = 0.32 wt%), 

Page 15 
but it also contained substantial silicon (SiO2 = 32.79 wt%), aluminum (Al2O3 = 13.12 wt%), manganese 

(MnO = 0.68 wt%), and titanium (TiO2 = 0.44 wt%) (table 4). Minor elements, such as iron, manganese, 

magnesium, and titanium (table 4) and trace elements, such as barium, strontium, and zirconium (table 5) 

could be in glass and (or) spinels, olivines, or pyroxenes that are present in concentrations too low to be 

confidently identified by XRD (Jane Hammarstrom, U.S. Geological Survey, written commun., 2004). 

Except for strontium (Sr = 662 ppm) and rubidium (Rb = 3 ppm), the slag contained higher concentrations 

of trace metals than the limestone, but it had equivalent or lower concentrations of most trace metals 

detected in the pond sediments (table 5). 

The calcite, gypsum, and ettringite that were identified in the white surface coatings on the slag 

represent weathering products that could form by reaction of the calcium-silicate minerals or glass with 

acidic rainfall. For example, with prolonged exposure to atmospheric CO2 (as H2CO3) and SO3 (as 

H2SO4), larnite and gehlenite could spontaneously convert to calcite, gypsum, and ettringite: 

Ca2SiO4 (s) + 2 H2CO3 ↔ 2 CaCO3 (s) + SiO2 (am) + 2 H2O (3) 

Ca2SiO4 (s) + 2 H2SO4 + 2 H2O ↔ 2 CaSO4

.

2H2O (s) + SiO2 (am) (4) 

2 Ca2SiO4 (s) + Ca2Al(AlSi)O7 (s) + 3 H2SO4 + 29 H2O ↔

Ca6Al2(SO4)3(OH)12.

26 H2O (s) + 3 SiO2 (am). (5) 

In reactions (3) through (5), atmospheric acids represented by H2CO3 and H2SO4 are neutralized, and only 

solid products are formed. Crystalline and amorphous solids are denoted by (s) and (am), respectively. 

The principal calcium-bearing minerals in limestone and steel slag also can be effective for 

neutralization of AMD as demonstrated by cubitainer tests described below. For example, the dissolution 

- of calcite can increase pH, alkalinity (predominantly HCO3 + OH-

), and calcium concentration by the 

following reactions or some combination thereof: 

CaCO3 (s) + 2 H+ ↔ Ca2+ + H2O + CO2 (6) 

- CaCO3 (s) + H2O + CO2 ↔ Ca2+ + 2 HCO3 (7) 

- CaCO3 (s) + H+ ↔ Ca2+ + HCO3 . (8) 

Hence, the stoichiometric dissolution of 1 mole CaCO3 will produce 1 mole Ca2+ and up to 2 moles 

- alkalinity as HCO3 . However, the relative quantities of H+ reacted and alkalinity produced per mole Ca2+ 

released vary depending on the predominant reaction. According to Plummer and others (1979), reaction 

(6) is predominant at pH values less than 5, whereas reaction (7) is predominant at pH values greater than 

Page 16 
6 and becomes increasingly important with increased Pco2. At pH values of 5 to 6, both reactions (6) and 

(7) are important. Reaction (8) is an overall reaction derived by the addition of reactions (6) and (7). 

As indicated by reactions (3) and (4), calcium-silicate minerals and associated glass in steel slag can 

neutralize acid, with calcite or gypsum as possible products. Nevertheless, with the addition of AMD to 

steel slag, solid calcium-bearing products initially would be undersaturated in the aqueous phase (leachate) 

and only “non-carbonate” alkalinity as OH-

 would be produced. Initially, when low-pH AMD (pH 3 to 4) 

contacts larnite and gehlenite, only the component CaO is presumed to be reactive: 

Ca2SiO4 (s) + 2 H+ ↔ 2 Ca2+ + 2 OH- + SiO2 (s) (9) 

Ca2Al(AlSi)O7 (s) + 2 H+ ↔ 2 Ca2+ + 2 OH-

 + SiO2 (s) + Al2O3 (s) (10) 

In accordance with reactions (9) and (10), solid silica and alumina (or related phases) will accumulate as 

the pH and alkalinity increase. Without carbonate buffering, described below, the pH of slag leachate can 

increase to highly alkaline levels (pH > 9) (Ziemkiewicz and Skousen, 1998; Loop et al., 2003). Although 

dissolved silicon and aluminum concentrations could be limited by equilibrium with solid SiO2, Al2O3, 

Al(OH)3, and (or) kaolinite, the solubility of these phases increases at high pH (Ball and Nordstrom, 1991; 

Langmuir, 1997). At alkaline pH, the residual silica and alumina can dissolve: 

- SiO2 (s) + H2O + OH- ↔ H3SiO4 (11) 

Al - 2O3 (s) + 3 H2O + 2 OH- ↔ 2 Al(OH)4 . (12) 

Hence, dissolved silica concentrations could be expected to increase at alkaline pH by a combination of 

reactions (9), (10), and (11). Nevertheless, concentrations of dissolved aluminum in solutions containing 

sulfate and calcium may actually decline with continued increases in pH owing to the precipitation of 

“alkaline” solids, such as ettringite: 

- 6 Ca2+ + 2 Al(OH)4 + 3 SO42- + 4 OH-

 + 26 H2O ↔ Ca6Al2(SO4)3(OH)12.26 H2O. (13) 

The precipitation of ettringite by reaction (13) represents a sink for alkalinity, calcium, aluminum, and 

sulfate concentrations in leachate. Likewise, the precipitation of other silicate, hydroxide, or carbonate 

solids, such as kaolinite, Al(OH)3, Fe(OH)3, and (or) CaCO3, could remove alkalinity plus aluminum, iron, 

and (or) calcium in the leachate from steel slag or limestone. 

The pH of a solution in contact with steel slag or limestone will be determined by the relative rates of 

mineral dissolution and precipitation and atmospheric exchange. Eventually, as atmospheric CO2 diffuses 

into an alkaline solution, “bicarbonate alkalinity” will form: 

- CO2+ OH- ↔ HCO3 . (14) 

Page 17 
- - -

As reaction (14) proceeds to the right, pH will decline, but total alkalinity will be unaffected. Forward 

reactions (11) and (12) also could cause pH to decline without affecting the total alkalinity. Total alkalinity 

will be conserved if an equal number of moles of HCO3 , H3SiO4 , or Al(OH)4 is produced for each mole 

of OH-

 reacted because these dissolved species have equal molar capacities to neutralize H+. Hence, pH 

and alkalinity can increase by forward reactions (6) through (10), pH can decrease by forward reactions 

(11) through (13), and the precipitation of solids, such as forward reactions (1), (2), and (13) and the 

reverse of reaction (8), can cause pH and alkalinity to decrease. 

As the steel slag ages in piles on the land surface or the leachate from steel slag equilibrates with the 

atmosphere, carbonate reactions become important. Eventually, equilibrium can be established with 

atmospheric CO2 and various calcium-bearing minerals, including calcite, gypsum, and ettringite. Once 

established, these equilibrium reactions will buffer the pH and impose upper limits on the alkalinity and 

concentrations of dissolved calcium, sulfate, and aluminum. With the establishment of carbonate 

equilibrium, the neutralization capacity of the slag and (or) final composition of slag leachate (treated 

effluent) could approach that of limestone. Nevertheless, rates of neutralization could be distinctive for 

limestone and steel slag because of differences in their compositions, crystallinities, and surface areas. 

Cubitainer Tests of Short-Term Reaction Rates 

Cubitainer tests were conducted using AMD collected April 27 from sites 1 and Fe as the influent 

because these represented “end-member” compositions for the AMD at the ALPO-SBTU test site (table 2). 

Site 1 AMD was saturated with oxygen (DO = 11.2 mg/L) and contained moderate concentrations of 

dissolved aluminum (Al = 4.96 mg/L) and relatively low concentrations of dissolved iron and manganese 

(Fe = 0.96 mg/L, Mn = 1.48 mg/L). In contrast, site Fe AMD contained negligible dissolved oxygen 

(DO = 0.7 mg/L) but high concentrations of dissolved aluminum, iron, and manganese (Al = 9.31 mg/L, 

Fe = 71.3 mg/L, Mn = 4.40 mg/L). Aqueous speciation computations with the computer program 

WATEQ4F (Ball and Nordstrom, 1991) using measured pH, Eh, and analytical concentrations of chemical 

constituents (tables 2 and 3) indicated the dissolved iron proportion in the influent AMD from sites 1 and 

Fe on April 27, 2004, was 19 and 100 percent FeII, respectively. 

The chemical evolution of the AMD from sites 1 and Fe with elapsed time in the cubitainers and the 

corresponding rates of reaction between the AMD and limestone or steel slag are summarized in tables 6, 

7, 8, and 9 and figures 5, 6, 7, and 8. Generally, for all four test conditions (site 1 AMD + limestone, site 1 

AMD + steel slag, site Fe AMD + limestone, site Fe AMD + steel slag), the pH, alkalinity, and calcium 

concentrations in the effluent increased (fig. 5, tables 6 and 7), whereas the acidity and concentrations of 

dissolved aluminum and iron progressively decreased (tables 7 and 8). After prolonged contact with steel 

Page 18 
slag, manganese concentrations in the AMD from sites 1 and Fe declined to less than 1 mg/L; however, 

they did not change after equivalent contact with limestone. Nevertheless, manganese is not considered 

toxic at concentrations observed at the ALPO-SBTU test site (fig. 3G), and the regulation of manganese in 

coal-mine effluent is subject to debate (Kleinmann and Watzlaf, 1986). The concentration of magnesium 

increased for tests with limestone, while the concentration of silica increased for tests with steel slag (table 

7). Except for increases in strontium and barium, which substitute for calcium in limestone and steel-slag 

minerals, and, to a lesser extent, chromium, titanium, lithium, and vanadium, the concentrations of most 

dissolved trace elements in effluent declined after prolonged contact with the limestone or slag (table 8). 

Hence, use of steel slag or limestone could be effective for increasing pH and alkalinity while decreasing 

concentrations of dissolved metals of concern. 

The pH and dissolved calcium concentrations increased asymptotically with elapsed contact time 

(detention time) between the AMD and limestone or steel slag (figs. 5 and 6, table 6). These trends 

indicated progressive declines in the rates of dissolution of the limestone or steel slag with increased pH 

and an approach to “steady-state” or equilibrium conditions after approximately 2 weeks (336 hr). At each 

time step for the same AMD influent (site 1 or site Fe), the pH and concentrations of calcium were greater 

for tests with steel slag than limestone (fig. 5). At the start of the tests, the AMD influent from sites 1 and 

Fe had pH of 3.7 and 4.0, respectively. However, after only 1 hour of contact between the AMD and the 

limestone or slag substrates, the pH for all tests increased to values ranging from 4.9 to 5.1 (tables 6 and 7). 

After 8 hr of contact, three of the four tests produced net-alkaline effluent (net acidity < 0 for site 1 AMD 

with limestone and with steel slag and site Fe AMD with steel slag; net acidity > 0 for site Fe with 

limestone); all four effluents had pH values of 6.1 to 6.7. After 2 weeks of contact, the effluent for all tests 

was net alkaline, with pH values ranging from 6.5 to 7.4 for limestone and from 8.5 to 8.6 for steel-slag 

substrates. 

The trends for alkalinity, net acidity, and dissolved iron were more complex than those for pH and 

calcium. Short-term trends for alkalinity production and acidity removal were distinctly different between 

the limestone and steel-slag tests with site Fe AMD and, to a lesser extent, with site 1 AMD (fig. 5, table 

7). Generally, the pH and alkalinity increased progressively with elapsed contact time in cubitainers filled 

with limestone. Although the effluent contacting steel slag ultimately had the highest pH values and 

calcium concentrations, the highest alkalinities were produced by limestone (fig. 5, table 6). After 2 weeks 

contact with limestone, concentrations of calcium increased by 124 and 248 mg/L as CaCO3 and alkalinity 

increased to 45.5 and 108 mg/L as CaCO3 for tests with AMD from sites 1 and Fe, respectively (fig. 6, 

table 6). However, after 2 weeks contact with steel slag, concentrations of calcium increased by 466 and 

730 mg/L as CaCO3 and alkalinity peaked and then declined to 18.6 and 25.8 mg/L as CaCO3 for tests 

Page 19 
with AMD from sites 1 and Fe, respectively (fig. 6, table 6). If dissolved calcium resulted from dissolution 

of gypsum instead of calcite, gehlenite, or larnite, alkalinity would not increase with calcium 

concentration. Nevertheless, supersaturation with calcite could result because of increased calcium 

concentration at near-neutral or alkaline pH. The final effluents in contact with steel slag were 

supersaturated with calcite; those effluents in contact with limestone were undersaturated with calcite 

(table 9). Although apparent steady-state conditions had been achieved, the lack of equilibrium after 2 

weeks of contact between the AMD and substrate implies that solution compositions could continue to 

change, albeit gradually, as carbonate reactions continued toward equilibrium conditions. 

The initial rates of alkalinity production for site Fe AMD in contact with limestone or steel slag 

exceeded those for the same substrates in contact with site 1 AMD (fig. 5). Two possible explanations for 

this difference are (1) greater initial Pco2 (table 9) and (2) greater initial “available” acidity as H+ and Al3+ 

for site Fe AMD (59 mg/L as CaCO3) compared to site 1 AMD (37 mg/L as CaCO3). Elevated quantities 

of H+ and CO2 in the influent would tend to make the site Fe solution more aggressive or reactive than the 

site 1 solution. Other differences in the relative rates of change in pH, calcium, alkalinity, acidity, and 

metals concentrations for individual tests and among tests warrant additional discussion, but speculation 

on these differences is beyond the scope of this report. 

Dissolved iron initially present as FeIII precipitated rapidly after contact of the solutions with limestone 

or steel slag. Although the reaction with limestone had little effect on the concentration of any dissolved 

iron that was initially present as FeII for both AMD sources (table 7), dissolved FeII was substantially 

removed from the effluent in contact with steel slag. The steel-slag tests exhibited a rapid alkalinity 

increase, peaking at 24 hr for site Fe and at 72 hr for site 1, followed by a gradual decrease, presumably 

associated with the removal of the dissolved iron and manganese (fig. 5, tables 6 and 7). The decrease 

following the alkalinity peak indicates consumption of initial alkalinity and is consistent with an increased 

rate of oxidation of dissolved Fe2+ and Mn2+ at neutral or alkaline pH values. Higher rates of oxidation and 

hydrolysis are expected with increased pH and increased availability of oxygen (in pores and on surfaces) 

in the steel slag compared to the limestone substrate. Precipitate formed a pale orange coating on the steel 

slag and, eventually, the limestone substrates in the cubitainers. 

The calcium and alkalinity concentration data for the first 7 hr of cubitainer testing and the maximum 

concentrations observed during the tests were used to compute first-order and second-order estimates of 

the concentration as a function of detention time (fig. 6, table 9). Generally, second-order models 

approximated the calcium concentration changes with detention time, whereas first-order models 

approximated the alkalinity concentration trends (fig. 6). 

Page 20 
Cubitainer Estimates of Long-Term Performance 

The results of computations to simulate long-term, decadal-scale mass decay and associated 

alkalinities for porous beds of limestone or steel-slag substrates for treatment of AMD from sites 1 and Fe 

(figs. 7 and 8) are based on the cubitainer concentration data and associated dissolution rate estimates (fig. 

6, table 9). The initial masses of substrate for site 1 (8,800 ton = 8,000 tonne) and site Fe (500 ton = 455 

tonne) were selected to achieve a minimum detention time of 8 hr and (or) a minimum net-alkalinity 

concentration of 20 mg/L for a 20-yr life span. Instead of the maximum flow rate measured for site Fe 

(0.9 gal/min), the flow rate for site 2 (18 gal/min) was used to estimate the size of the limestone or steelslag bed for treatment of AMD from site Fe, because the site 2 flow measurement accounts for various 

additional diffuse seepage sources from the iron mound represented by site Fe influent. Decreases in the 

substrate mass and associated detention time with increased age of the treatment system were estimated on 

the basis of the concentration and flux of calcium as CaCO3 at the maximum measured flow rate (table 2). 

As the limestone mass decreased with age, its total volume was assumed to decrease proportionally, 

whereas the porosity (42 volume percent (vol%)) and flow rates for site 1 (360 gal/min) and site Fe 

(18 gal/min) were assumed to remain constant. Calculations of detention time and corresponding 

concentrations and fluxes of alkalinity and calcium as CaCO3 were repeated for sequential time steps to 

simulate the long-term performances. 

The simulation of long-term performance of a treatment system on the basis of short-term cubitainer 

tests (figs. 7 and 8) should be considered only as a crude guide of possible field performance because few 

variables could be evaluated and (or) were assumed constant. Additional bench-scale testing using 

cubitainers or pilot-scale testing in the field could be helpful to refine models of long-term performance 

and to optimize the design of a treatment system. For example, tests could evaluate the effects of mixing or 

layering steel slag, limestone, and (or) compost on alkalinity production and metals removal. Such testing 

could evaluate the effects of particle sizes and mineral coatings on dissolution rates. Specific data on the 

potential for discharging solids from these packed beds and data on the porosity and permeability of 

different substrates also could be obtained. 

Identification of Remediation Strategies at the ALPO-SBTU Test Site 

Water-quality criteria for identification of AMD treatment alternatives (fig. 2) were considered with 

data on the flow and concentration of net acidity, dissolved oxygen, and dissolved iron, manganese, and 

aluminum to rank the AMD sources at the ALPO-SBTU test site by their pollutant loadings and to indicate 

possible passive-treatment alternatives. Sites 1, 7, and 6 had the largest loadings of dissolved metals 

among the AMD sources and were the first-, second-, and third-ranked pollutant sources, respectively, on 

Page 21 
this basis (table 10). These sources had moderate flows (50 to 500 gal/min) with very high concentrations 

of dissolved aluminum (Al > 4 mg/L) and low-to-moderate concentrations of dissolved iron and 

manganese (1 < Fe < 3 mg/L and 1 < Mn < 2 mg/L). Because these and the other AMD sources at the 

ALPO-SBTU test site were net acidic, treatment steps or components that add alkalinity to the AMD and 

that facilitate removal of precipitated metal-rich solids from the alkalinity-producing system were 

identified as potentially appropriate (fig. 2, table 10). Because the AMD sources were oxygenated or 

contained more than 2 mg/L of dissolved aluminum, none met criteria for an ALD (Hedin et al., 1994). 

Cravotta and Trahan (1999) and Cravotta and Watzlaf (2002) suggested that aluminum concentrations less 

than 5 mg/L may be treated with underground anoxic or oxic limestone drains that are flushable. Hence, 

appropriate passive-treatment alternatives included the VFCW for most AMD sources or a flushable oxic 

limestone drain (OLD) and (or) open limestone channel (OLC) for AMD sources with low to moderate 

concentrations of metals (table 10) (Skousen et al., 1998; Cravotta and Trahan, 1999). In addition to the 

alkalinity-producing VFCW, OLD, or OLC, an aerobic pond or wetland was indicated as an additional 

component to facilitate iron and manganese oxidation and retention of precipitated solids (table 10). The 

combination of a VFCW and aerobic pond also was identified as a possible treatment option for treatment 

of combined AMD from sites 1, 1Fe, Fe, and 2 and from sites 3, 3B, 5, 6, and 7 based on their combined 

flows and volume-weighted average compositions (table 10). 

Although beyond the scope of this investigation, the publicly available computer program AMDTreat 

(U.S. Office of Surface Mining Reclamation and Enforcement, 2002) could be used with the flow and 

water-quality data collected for this project to evaluate differences in costs among various possible 

passive-treatment and active-treatment scenarios. For example, a resource manager may wish to compare 

the costs for construction and maintenance of a passive-treatment system consisting of an OLC to collect 

the AMD, a VFCW as the primary source of alkalinity, and then an aerobic wetland to remove iron 

precipitate with an active treatment system that uses a hydraulic powered lime-dosing system to add 

alkalinity instead of a VFCW. Options to collect precipitated solids generated by passive or active AMD 

treatment also would need to be considered. 

Although basic VFCW designs could be applicable for passive treatment of the AMD at the ALPOSBTU test site, consideration could be given to innovative passive-system designs that direct flow upward 

through the treatment bed and that incorporate siphons for automatic flushing of solids to a pond (Vinci 

and Schmidt, 2001; Weaver et al., 2004; Schueck et al., 2004). Siphons and associated plumbing 

components could be incorporated in a modified VFCW design that includes or excludes the compost 

layer. Also, it may be advantageous to include a layer of steel slag on top of limestone for an upflow 

treatment system, on the basis of cubitainer testing that showed potential for lower alkalinity production 

Page 22 
but higher pH of AMD treated with steel slag compared to limestone. The slag appears to offer greater 

short-term benefit with initially high pH, whereas the limestone appears to offer greater long-term benefit 

with greater alkalinity and possibly greater longevity. A combination of limestone and steel-slag substrates 

in the treatment system may take advantage of these differing, complementary properties. Burial of the 

limestone and steel-slag beds could be advantageous to increase Pco2 and alkalinity concentrations and to 

minimize potential for entry of debris or animals. 

Summary and Conclusions 

This report, prepared by the U.S. Geological Survey (USGS) in cooperation with the National Park 

Service (NPS), describes field, laboratory, and computational methods that, when combined, can be used 

to assess possible remedial alternatives for abandoned mine drainage (AMD). During April-June, 2004, an 

assessment process was applied to AMD from bituminous coal deposits at the Staple Bend Tunnel Unit of 

Allegheny Portage Railroad National Historic Site (ALPO-SBTU) in Cambria County, Pennsylvania. The 

approach used at this test site could be applicable at other sites subject to drainage from abandoned coal or 

metal mines. 

Data on the flow rates and composition of AMD, pond water and sediment, and the effluent and solids 

from cubitainers were used to assess the characteristics, possible ecological effects, and possible 

alternatives for remediation of the AMD at the ALPO-SBTU test site. During April 2004, the combined 

AMD sources had a total flow rate of 1,420 gallons per minute (gal/min) and flow-weighted averages for 

pH of 3.3, net acidity of 55 milligrams per liter (mg/L) as CaCO3, and concentrations of dissolved sulfate 

and aluminum of 694 mg/L and 4.4 mg/L, respectively, which exceeded effluent criteria for active mines in 

Pennsylvania. Flow-weighted average concentrations of dissolved iron and manganese of 0.74 mg/L, and 

1.2 mg/L, respectively, met these effluent criteria and met criteria for protection of freshwater aquatic 

organisms. The sum of iron, aluminum, and manganese loading for the combined AMD sources was 19.7 

and 16.6 tons per year (ton/yr) on April 7 and 27, 2004, respectively, predominantly because of aluminum. 

Elevated concentrations of dissolved trace metals were present in the AMD and downstream pond 

sediments at the ALPO-SBTU test site. Concentrations of cobalt, nickel, and zinc in the AMD samples 

consistently exceeded continuous concentration criteria for protection of freshwater aquatic life. 

Additionally, chromium, copper, and lead concentrations in several of the AMD samples exceeded relevant 

continuous concentration criteria. The pond sediments had as much as three times higher concentrations of 

aluminum, arsenic, and chromium, but equivalent or lower concentrations of iron, copper, nickel, lead, and 

zinc compared to median concentrations for streambed sediments across the conterminous United States. 

Page 23 
Nevertheless, of the metals detected in the pond sediments, only the concentration of iron in pond#1 

outflow exceeded available sediment-quality guidelines for protection of freshwater benthic organisms. 

Limestone and steel slag were tested in the laboratory for their composition, approximate surface area, 

and potential to neutralize samples of the AMD from the ALPO-SBTU test site. The substrates had a 

similar particle-size distribution and identical calcium content (43 percent as calcium oxide); however, the 

limestone was composed of carbonates and the slag was composed of silicates. After a minimum of 8 

hours contact between the AMD and limestone or steel slag in closed containers (cubitainers), net-neutral 

effluent was produced, and the concentrations of iron, aluminum, and most dissolved trace elements in 

effluent from the cubitainers declined relative to influent concentrations. The steel slag produced lower 

alkalinity concentrations but higher pH compared to limestone. Ultimately, the pH of AMD in contact with 

limestone or steel slag was maintained greater than 6.0 and less than 9.0. The cubitainer test results 

extrapolated over a decadal time scale indicated that passive treatment of the AMD at the ALPO-SBTU 

test site may be feasible with limestone and (or) steel slag substrates. 

The process for evaluating AMD remedial strategies at the ALPO-SBTU test site involved the 

computation and ranking of the metal loadings during April 2004 for each of the AMD sources and a 

comparison of the data on AMD flow and chemistry (alkalinity, acidity, dissolved oxygen, ferric iron, 

aluminum) with published criteria for selection of passive-treatment technology. Although neutralization 

of the AMD by reaction with limestone was demonstrated with cubitainer tests, an anoxic limestone drain 

(ALD) was indicated as inappropriate for any AMD source at the test site because all had excessive 

concentrations of dissolved oxygen and (or) aluminum. One possible passive-treatment scenario that was 

identified for the individual or combined AMD sources involved an open limestone channel (OLC) to 

collect the AMD source(s), a vertical flow compost wetland (VFCW) to add alkalinity, and an aerobic 

wetland to facilitate iron and manganese oxidation and retention of precipitated solids. Using the 

AMDTreat computer program with the flow and water-quality data collected for this study, resource 

managers may compute and compare the costs for implementation, long-term operation, and maintenance 

of a passive-treatment system with those for an active-treatment system. 

Acknowledgments 

Suzanne J. Ward of the USGS and Kathy A. Penrod and Alan Ellsworth of NPS provided critical 

assistance with the planning and implementation of this study. Mineralogical and chemical analyses of 

limestone and steel slag used in cubitainer tests were provided by Jane Hammarstrom and Nadine Piatak of 

USGS. The draft report benefitted from reviews by Nadine Piatak and Kevin Breen of USGS and Brent 

Page 24 
Means of the Office of Surface Mining, Reclamation and Enforcement. Support for the study was provided 

by the NPS and the USGS. 

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of Mining and Reclamation, Lexington, Ky., June 9-13, 2002: American Society of Mining and 

Reclamation, p. 527-538. 

Simmons, J., Ziemkiewicz, P., and Black, D. C., 2002b, Use of steel slag leach beds for the treatment of 

acid mine drainage: Mine Water and the Environment, v. 21, p. 91-99. 

Skousen, J. G., Rose, A. W., Geidel, G., Foreman, J., Evans, R., Hellier, W., and others, 1998, Handbook of 

technologies for avoidance and remediation of acid mine drainage: Morgantown, W.Va., National 

Mine Land Reclamation Center, 131 p. 

Taggart, J. E., Jr., 2002, Analytical methods for chemical analysis of geologic and other materials, U.S. 

Geological Survey: U.S. Geological Survey Open-File Report 02-0223 (http://pubs.usgs.gov/of/2002/ 

ofr-02-0223/). 

U.S. Environmental Protection Agency, 2002a, National recommended water quality criteria--2002: U.S. 

Environmental Protection Agency EPA 822-R-02-047, 33 p. 

U.S. Environmental Protection Agency, 2002b, National primary drinking water standards: U.S. 

Environmental Protection Agency EPA 816-F-02-013, July 2002, 7 p. (accessed December 15, 2002, 

on the World Wide Web at http://www.epa.gov/safewater). 

U.S. Geological Survey, 1997 to present, National field manual for the collection of water-quality data: 

U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chaps. A1-A9, 2 vols., 

variously paged (http://pubs. water. usgs. gov/twri9A). 

U.S. Office of Surface Mining Reclamation and Enforcement, 2002, AMDTreat 3.1: Washington, D.C., 

U.S. Office Surface Mining Reclamation and Enforcement (accessed June 15, 2003, on the World Wide 

Web at http://amd.osmre.gov). 

Vinci, B. J., and Schmidt, T. W., 2001, Passive, periodic flushing technology for mine drainage treatment 

systems, In Proceedings of the 18th Annual Meeting of American Society for Surface Mining and 

Reclamation, Albuquerque, New Mexico, June 3-7, 2001: American Society for Surface Mining and 

Reclamation, p. 611-625. 

Page 30 
VisitPA.com, 2005, Attraction details--Allegheny Portage Railroad National Historic Site (accessed 

August 4, 2005, on the World Wide Web at http://www.visitpa.com/ 

visitpadetails.pa?name=Allegheny+Portage+Railroad+National+Historic+Site) 

Watzlaf, G. R., Schroeder, K. T., and Kairies, C., 2000, Long-term performance of alkalinity-producing 

passive systems for the treatment of mine drainage, In Proceedings of the 2000 National Meeting of the 

American Society for Surface Mining and Reclamation: American Society for Surface Mining and 

Reclamation, p. 262-274. 

Weaver, K. R., Lagnese, K. M., and Hedin, R. S., 2004, Technology and design advances in passive 

treatment system flushing, In 2004 National Meeting of the American Society of Mining and 

Reclamation and the 25th West Virginia Surface Mine Drainage Task Force, April 18-24, 2004: 

American Society of Mining and Reclamation, p. 1974-1989. 

Whittig, L. D., and Allardice, W. R., 1986, X-ray diffraction techniques, In A. Klute (ed.), Methods of soil 

analysis, Part 1, Physical and Mineralogical Methods (2nd): Madison, Wisc., American Society of 

Agronomy, p. 331-362. 

Winland, R.L., Traina, S.J., and Bigham, J.M., 1991, Chemical composition of ochreous precipitates from 

Ohio coal mine drainage: Journal of Environmental Quality, v. 20, p. 452-460. 

Wood, W. W., 1976, Guidelines for the collection and field analysis of ground-water samples for selected 

unstable constituents: U.S. Geological Survey Techniques of Water Resources Investigations, Book 1, 

Chapter D2, 24 p. 

Ziemkiewicz P. K., and Skousen, J. G., 1998, The use of steel slag in acid mine drainage treatment and 

control, In, Proceedings 19th Annual West Virginia Surface Mine Drainage Task Force Symposium, 

Morgantown, West Virginia, April 7-8, 1998: Charleston, W.Va., West Virginia Mining and Reclamation 

Association. 

Page 31 
Mineral

Point

Figure 1. Color aerial photograph of the Staple Bend Tunnel Unit of Allegheny Portage Railroad (ALPO-SBTU) National Historic 

Site, Pennsylvania, showing locations of water-quality sampling sites. Aerial photography mosaic created by North Carolina 

State University Center for Earth Observation. ALPO-SBTU Park boundary and trace of drainage are approximate. 

Page 32 
Figure 2. Flow chart for selection of passive treatment alternatives modified from Hedin and others (1994), Skousen and others 

(1998), and Pennsylvania Department of Environmental Protection (1999). Vertical flow compost wetland (VFCW) also known as 

SAPS or RAPS. Less than (<), greater than (>), milligrams per liter (mg/L). 

Page 33 
Figure 3. Flow rate and chemistry of abandoned mine drainage, April 7 and 27, 2004, Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, 

Pennsylvania: A, Flow rate; B, pH; C, Net acidity (= acidity, computed - alkalinity); D, Sulfate concentration; E, Dissolved iron concentration; F, Dissolved aluminum concentration; G, Dissolved manganese concentration; H, Loading of dissolved iron, aluminum, and manganese. Water-quality standards (WQstd) at left; green is criteria continuous concentration for protection of freshwater aquatic life (U.S. Environmental Protection Agency, 2002a) and orange is standard for mine effluent (Commonwealth of 

Pennsylvania, 1998a). 

Page 34
Figure 3. Flow rate and chemistry of abandoned mine drainage, April 7 and 27, 2004, Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, 

Pennsylvania: A, Flow rate; B, pH; C, Net acidity (= acidity, computed - alkalinity); D, Sulfate concentration; E, Dissolved iron concentration; F, Dissolved aluminum concentration; G, Dissolved manganese concentration; H, Loading of dissolved iron, aluminum, and manganese. Water-quality standards (WQstd) at left; green is criteria continuous concentration for protection of freshwater aquatic life (U.S. Environmental Protection Agency, 2002a) and orange is standard for mine effluent (Commonwealth of 

Pennsylvania, 1998a) (continued). 

Page 35
Figure 4. Trace-element concentrations in abandoned mine drainage, April 7 and 27, 200, Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, 

Pennsylvania: A, Arsenic; B, Cadmium; C, Cobalt; D, Chromium; E, Copper; F, Lead; G, Nickel; H, Zinc. Water-quality standards (WQstd) at left; green is criteria continuous 

concentration for protection of freshwater aquatic life (U.S. Environmental Protection Agency, 2002a; Commonwealth of Pennsylvania, 2001b) and yellow is drinking-water standard (U.S. Environmental Protection Agency, 2002b). 

Page 36
Figure 4. Trace-element concentrations in abandoned mine drainage, April 7 and 27, 2004, Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, 

Pennsylvania: A, Arsenic; B, Cadmium; C, Cobalt; D, Chromium; E, Copper; F, Lead; G, Nickel; H, Zinc. Water-quality standards (WQstd) at left; green is criteria continuous 

concentration for protection of freshwater aquatic life (U.S. Environmental Protection Agency, 2002a; Commonwealth of Pennsylvania, 2001b) and yellow is drinking-water standard (U.S. Environmental Protection Agency, 2002b) (continued). 

Page 37
Figure 5. Rate of change in pH, alkalinity, and calcium concentrations of effluent from sites 1 and Fe at the Staple Bend Tunnel 

Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania, during cubitainer tests: A, pH; B, Alkalinity 

concentration; C, Calcium concentration. Tests were conducted in May 2004 with 2 kilograms uncoated limestone or steel slag 

under closed, circulated conditions. Data on compositions of effluent from cubitainers are shown in tables 6-9. Data on 

composition of slag and limestone are shown in tables 4 and 5. 

Page 38 
Figure 6. Measured and simulated effect of detention time on limestone or steel-slag treatment of abandoned mine drainage 

from sites 1 and Fe at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania, on the 

basis of cubitainer tests: A, Calcium concentration for site 1; B, Alkalinity concentration for site 1; C, Calcium concentration for 

site Fe; D, Alkalinity concentration for site Fe. Cubitainer test data are shown in figure 5 and tables 6 and 9. First-order curve 

dashed; second-order curve solid. 

Page 39 
Figure 7. Simulation of long-term performance of limestone- or steel-slag substrates for treatment of abandoned mine drainage 

from site 1 at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania, on the basis of 

cubitainer test data and corresponding first-order or second-order rate estimates for limestone or steel slag dissolution and 

alkalinity production (table 9). Computations assume constant flow rate of 359 gal/min, limestone porosity of 0.42 , steel slag 

porosity of 0.55., and surface area of 0.72 cm2/g for limestone and steel slag. 

Page 40 
Figure 8. Simulation of long-term performance of limestone- or steel-slag substrates for treatment of abandoned mine drainage 

from site Fe at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania, on the basis of 

cubitainer test data and corresponding first-order or second-order rate estimates for limestone or steel slag dissolution and 

alkalinity production (table 9). Computations assume constant flow rate of 18 gal/min, limestone porosity of 0.42 , steel slag 

porosity of 0.55., and surface area of 0.72 cm2

/g for limestone and steel slag. 

Page 41 
Table 1. Description of abandoned mine drainage and pond sites sampled in April 2004 for the assessment of the Staple Bend 

Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania 

[n.a., not applicable; latitude and longitude listed without degree, minute, and second symbols; 402228.7 represents 40°22'28.7” 

north latitude and 785105.8 represents 78°51'05.8” west longitude] 

Local Identification 

Numbera Weirb U.S. Geological Survey Station Identificationc Latitude Longitude 

Latitude, 

decimal 

degrees 

Longitude, 

decimal 

degrees 

Abandoned Mine Drainage 

U 1 402229078510601 402228.7 785105.8 40.3747 -78.8516 

1 1A 402229078510602 402229.0 785110.4 40.3747 -78.8529 

1Fe n.a. 402232078510901 402231.7 785109.3 40.3755 -78.8526 

Fe n.a. 402223078511001 402223.4 785110.0 40.3732 -78.8528 

2d UPJ2 402225078511201 402225.1 785111.9 40.3737 -78.8533 

3 3 402221078510701 402221.4 785107.4 40.3726 -78.8521 

3A n.a. 402221078510702 402220.2 785107.7 40.3723 -78.8522 

3B 4 402221078510703 402219.1 785110.8 40.3720 -78.8530 

4 n.a. 402214078510901 402213.9 785108.8 40.3705 -78.8525 

5 5 402218078511101 402218.2 785111.2 40.3717 -78.8531 

6 UPJ6 402212078511601 402212.0 785116.2 40.3700 -78.8545 

7 7 402210078511701 402210.1 785117.2 40.3695 -78.8548 

8 n.a. 402151078511001 402151.0 785110.0 40.3642 -78.8528 

Upper Pond (Pond #1) 

Inflow (Pond1.In) n.a. 402143078511204 402148.0 785115.6 40.3633 -78.8543 

Al (Pond1.Al) n.a. 402143078511201 402146.4 785116.0 40.3629 -78.8544 

Middle (Pond1.Middle) n.a. 402143078511202 402144.4 785117.0 40.3623 -78.8547 

Outflow (Pond1.Out) n.a. 402143078511203 402141.6 785119.6 40.3616 -78.8554 

Lower Pond (Pond #2) 

Inflow (Pond2.In) n.a. 402139078512401 402140.1 785120.3 40.3611 -78.8556 

Outflow (Pond2.Out) n.a. 402139078512501 402138.5 785125.4 40.3607 -78.8571 

a. Local site identification numbers used to indicate site location in figure 1. 

b. Weir identification from Kaktins and Carney (2002). 

c. Formal USGS station identification number based on latitude and longitude. 

d. Site 2 in this study was not identical to site 2 of Kaktins and Carney (2002). In this study, samples were collected at the outflow of a 

pipe that collected AMD from sites 1Fe, Fe, and other diffuse seepage from an iron mound before this seepage commingled with water from site 

1. Although sampling points were only feet apart, Kaktins and Carney (2002) sampled the water at a culvert under the railroad, inclusive of sites 

1, 1Fe, and Fe (sites 1 and 2 of this study). 

Page 42 
Table 2. Flow rate, pH, net acidity, and concentrations of dissolveda

 constituents for abandoned mine drainage and pond samples 

collected April 7 and 27, 2004, for assessment of water quality at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National 

Historic Site, Pennsylvania 

[0, not flowing or dry; n.d., no data; <, less than; <, less than or equal to ; >, greater than or equal to; gal/min, gallons per minute; mg/L, 

milligrams per liter; ton/yr, tons per year] 

Local 

Site 

Name 

Flow rate 

(gal/min) 

4/07 4/27 

pH, Field 

(units) 

4/07 4/27 

Net 

Acidityb 

(mg/L 

CaCO3) 

4/07 4/27 

Dissolved 

Oxygen 

(mg/L) 

4/07 4/27 

Dissolved 

Nitrate 

(mg/L N) 

4/07 4/27 

Dissolved 

Sulfate 

(mg/L SO4) 

4/07 4/27 

Dissolved 

Silica 

(mg/L 

SiO2) 

4/07 4/27 

Dissolved 

Aluminum 

(mg/L Al) 

4/07 4/27 

Dissolved 

Iron 

(mg/L Fe) 

4/07 4/27 

Dissolved 

Manganese 

(mg/L Mn) 

4/07 4/27 

Dissolved 

Al, Fe, and 

Mn loadc 

(ton/yr) 

4/07 4/27 

Abandoned Mine Drainage 

U 175 n.d. 2.9 n.d. 109 n.d. 10.3 n.d. 0.35 n.d. 689 n.d. 22.2 n.d. 6.77 n.d. 1.43 n.d. 1.75 n.d. 3.83 n.d. 

1 359 360 2.7 3.4 150 51 10.4 11.2 .37 .53 687 612 21.6 18.8 6.40 4.96 1.01 0.96 1.78 1.48 7.24 5.85 

1Fe .9 1.8 2.8 3.3 222 142 1.8 1.0 <.04 <.04 754 722 32.1 29.7 9.82 8.00 48.2 36.7 4.95 4.23 .11 .2 

Fe .4 .9 3.6 3.9 221 194 1.2 .7 <.05 <.05 1,090 1,080 34.7 31.0 11.2 9.31 76.4 71.3 4.82 4.40 .11 .15 

2 18 n.d. 2.3 n.d. 322 n.d. 9.7 n.d. .09 n.d. 940 n.d. 32.5 n.d. 9.76 n.d. 11.2 n.d. 4.40 n.d. 1.00 n.d. 

3 498 104 3.8 4.7 20 8 10.2 10.5 .55 .56 779 773 14.3 12.7 1.81 1.16 .25 .21 .93 .93 3.27 .53 

3A 23 n.d. 3.2 n.d. 57 n.d. 8.8 n.d. .54 n.d. 763 n.d. 15.7 n.d. 3.47 n.d. .19 n.d. .95 n.d. .23 n.d. 

3B 24 60 3.1 3.5 63 36 9.6 9.9 .50 .54 738 697 17.1 15.5 3.62 2.84 1.60 1.75 1.06 .98 .33 .74 

4 20 n.d. 4.7 n.d. 29 n.d. 10.5 n.d. .48 n.d. 737 n.d. 15.2 n.d. 5.18 n.d. .21 n.d. .83 n.d. .27 n.d. 

5 404 404 4.7 6.5 16 -2 10.7 11.0 .52 .55 676 587 13.6 10.2 3.04 .06 .13 .11 .72 .55 3.45 .64 

6 58 120 3.1 3.3 137 93 11.1 11.2 .71 .67 700 659 30.5 27.6 15.9 11.9 .21 .19 1.93 1.66 2.31 3.62 

7 58 180 3.0 3.4 118 80 10.5 10.7 .66 .63 828 792 26.3 23.3 12.1 10.0 1.08 .96 1.42 1.28 1.87 4.83 

8 20 3.1 7.1 7.8 -44 -45 11.9 11.0 .92 .75 351 317 5.8 5.9 <.02 .12 <.10 .23 <.01 .03 <.01 <.01 

Upper Pond (Pond #1) 

Inflow 260 324 3.2 3.6 90 60 11.4 11.1 0.74 0.68 536 499 22.7 24.0 9.25 7.62 0.45 0.60 1.48 1.46 6.39 6.88 

Al n.d. n.d. n.d. 3.3 n.d. 47 n.d. 9.9 n.d. .77 n.d. 345 n.d. 14.9 n.d. 3.47 n.d. .30 n.d. .74 n.d. n.d. 

Middle n.d. n.d. n.d. 3.5 n.d. 42 n.d. 9.7 n.d. .72 n.d. 396 n.d. 17.3 n.d. 4.57 n.d. .45 n.d. 1.00 n.d. n.d. 

Outflow n.d. n.d. 3.8 3.5 38 41 11.2 9.3 .96 .84 356 358 15.7 15.7 5.07 3.94 .25 .41 .84 .91 n.d. n.d. 

Lower Pond (Pond #2) 

Inflow n.d. n.d. 3.7 4.0 33 30 11.1 7.2 1.01 0.80 334 360 15.1 16.1 4.12 4.17 <0.10 0.13 0.77 0.91 n.d. n.d. 

Outflow n.d. n.d. n.d. 3.6 n.d. 41 n.d. 7 n.d. .74 n.d. 383 n.d. 18.3 n.d. 4.54 n.d. .19 n.d. 1.03 n.d. n.d. 

Criteria for Drinking Water, Mine Effluent, and Protection of Freshwater Aquatic Lifed 

Drink 

Mine 

CCCF 

n.d. 

n.d. 

n.d. 

6.5<pH<8.5 

6.0<pH<9.0 

6.5<pH<9.0 

n.d. 

<0 

<-20 

n.d. 

n.d. 

>5.0 

<10.0 

n.d. 

n.d. 

<250 

<250 

n.d. 

n.d. 

n.d. 

n.d. 

<0.20 

<0.75 

<0.087 

<0.30 

<7.00 

<1.00 

<0.05 

<5.0 

n.d. 

n.d. 

n.d. 

n.d. 

a. Concentration data for dissolved oxygen are for in-situ measurement. Concentration and loading data for “dissolved” nitrate, sulfate, and metals 

are for filtered (0.45-micrometer pore size) samples. 

b. Net acidity = computed acidity - measured alkalinity. Positive value indicates acidity exceeds alkalinity and the ultimate pH after complete 

oxidation and hydrolysis of metals will be acidic (pH < 4.5). Negative value indicates alkalinity exceeds acidity and the ultimate pH will be near neutral or 

alkaline (pH > 6). Acidity computed on the basis of the pH and dissolved metals concentrations where CAl, CFe, and CMn indicate aluminum, iron, or 

manganese concentration, respectively, in milligrams per liter as: Acidity ) computed (mg/L CaCO3) = 50.

(10(3-pH + 3CAl/26.98 + 2.CFe/55.85 + 2CMn/54.94). 

c. Dissolved metals loading was computed as the product of the instantaneous flow rate (Q) and the sum of concentrations of the metals as: Metal 

load = f.

Q.(CAl + CFe + CMn), where C with a subscript Al, Fe, or Mn indicates aluminum, iron, or manganese concentration, respectively. For flow rate in 

gallons per minute and concentrations in milligrams per liter, the conversion factor, f = 5.45, yields daily loading in grams (g/d), whereas f = 0.00219, yields 

annual loading in short tons (ton/yr). 

d. Drink = drinking-water standard (U.S. Environmental Protection Agency, 2002b). Mine = mine effluent standard (Commonwealth of Pennsylvania, 

1998a). CCCF = criteria continuous concentration for protection of freshwater aquatic life based on hardness of 100 mg/L; values for arsenic, cadmium, 

chromium, copper, lead, nickel, and zinc from U.S. Environmental Protection Agency (2002a) and for cobalt from Commonwealth of Pennsylvania (2001b). 

Page 43 
Table 3. Concentrations of dissolveda trace elements in abandoned mine drainage and pond samples collected April 7 and 27, 


2004, for assessment of water quality at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, 


Pennsylvania


[n.d., no data; <, less than; mg/L, milligrams per liter]


Local 

Site 

Name 

Dissolved 

Arsenic 

(mg/L As) 

4/07 4/27 

Dissolved 

Cadmium 

(mg/L Cd) 

4/07 4/27 

Dissolved 

Cobalt 

(mg/L Co) 

4/07 4/27 

Dissolved 

Chromium 

(mg/L Cr) 

4/07 4/27 

Dissolved 

Copper 

(mg/L Cu) 

4/07 4/27 

Dissolved 

Lead 

(mg/L Pb) 

4/07 4/27 

Dissolved 

Nickel 

(mg/L Ni) 

4/07 4/27 

Dissolved 

Zinc 

(mg/L Zn) 

4/07 4/27 

Abandoned Mine Drainage 

U 0.0013 n.d. 0.0006 n.d. 0.0721 n.d. 0.0107 n.d. 0.0086 n.d. 0.0010 n.d. 0.127 n.d. 0.244 n.d. 

1 .0008 0.0017 .0005 0.0004 .0680 0.0620 .0062 0.0090 .0076 0.0069 .0011 0.0008 .123 0.107 .238 .200 

1Fe <.0003 .0007 .0007 .0006 .156 .139 <.0050 .0056 .0051 .0046 .0021 .0024 .231 .205 .549 .492 

Fe <.0003 .0004 .0006 .0005 .165 .159 <.0050 <.0050 <.0020 <.0020 .0019 .0014 .261 .247 .605 .574 

2 <.0003 n.d. .0006 n.d. .138 n.d. .0060 n.d. .0023 n.d. .0010 n.d. .224 n.d. .504 n.d. 

3 .0006 <.0003 .0003 .0002 .0365 .0379 .0073 <.0050 <.0020 <.0020 .0002 <.0001 .081 .086 .116 .101 

3A .0009 n.d. .0004 n.d. .0388 n.d. .0106 n.d. .0037 n.d. .0009 n.d. .084 n.d. .139 n.d. 

3B .0007 .0004 .0004 .0003 .0465 .0418 .0063 <.0050 .0042 .0039 .0013 .0012 .098 .090 .186 .161 

4 .0012 n.d. .0003 n.d. .0378 n.d. .0126 n.d. .0051 n.d. .0003 n.d. .080 n.d. .139 n.d. 

5 .0022 .0005 .0003 .0002 .0327 .0264 .0225 <.0050 .0040 <.0020 .0003 <.0001 .071 .057 .126 .089 

6 .0016 .0004 .0008 .0008 .0937 .0884 .0165 <.0050 .0154 .0148 .0059 .0056 .159 .145 .394 .330 

7 .0011 .0008 .0005 .0005 .0796 .0808 .0143 .0073 .0090 .0083 .0018 .0016 .154 .149 .359 .308 

8 .0014 .0008 <.0001 <.0001 <.0001 .0003 .0134 .0060 <.0020 <.0020 <.0001 .0008 <.003 <.003 .013 .016 

Upper Pond (Pond #1) 

Inflow 0.0011 0.0019 0.0006 0.0008 0.0667 0.0679 0.0116 0.0173 0.0103 0.0108 0.0037 0.0034 0.113 0.111 0.268 0.253 

Al n.d. .0015 n.d. .0004 n.d. .0312 n.d. .0166 n.d. .0047 n.d. .0017 n.d. .054 n.d. .134 

Middle n.d. .0044 n.d. .0005 n.d. .0421 n.d. .0476 n.d. .0063 n.d. .0019 n.d. .066 n.d. .170 

Outflow .0011 .0017 .0005 .0005 .0359 .0378 .0110 .0190 .0054 .0054 .0026 .0018 .063 .064 .149 .148 

Lower Pond (Pond #2) 

Inflow 0..0013 0.0018 0.0004 0.0005 0.0320 0.0377 0.0125 0.0195 0.0036 0.0046 0.0008 0.0014 0.053 0.064 0.147 0.151 

Outflow n.d. .0034 n.d. .0004 n.d. .0443 n.d. .0344 n.d. .0050 n.d. .0012 n.d. .069 n.d. .161 

Criteria for Drinking Water, Mine Effluent, and Protection of Freshwater Aquatic Lifeb 

Drink <0.0100 <0.0050 n.a. <0.1000 <1.300 <0.0150 n.a. <5.000 

Mine n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. 

CCCF <0.1500 <0.0220 <0.0190 <0.0110 <0.0090 <0.0025 <0.052 <0.120 

a. Concentration data are for “dissolved” constituents in filtered (0.45-micrometer pore size) samples. 

b. Drink = drinking-water standard (U.S. Environmental Protection Agency, 2002b). Mine = mine effluent standard (Commonwealth of 

Pennsylvania, 1998a). CCCF = criteria continuous concentration for protection of freshwater aquatic life; values for arsenic, cadmium, chromium, 

copper, lead, nickel, and zinc from U.S. Environmental Protection Agency (2002a) and for cobalt from Commonwealth of Pennsylvania (2001b). 

Page 44 
Table 4. Major mineralogical and chemical composition of pond sediment samples collected April 27, 2004, from the Staple Bend Tunnel Unit 

National Historic Site, Pennsylvania, and steel slag and limestone obtained from the vicinitya and used in cubitainer tests 

[tr, trace; wt%, weight percent] 

Sample 

Identification Mineralsb 

Constituent Concentration as Oxide in W

SiO2 Al2O3 Fe2O3 MnO MgO CaO Na2O K2O 

Pond #1 Inflow quartz, muscovite, kaolinite, chlorite, amorphous aluminum & iron hydroxides 56.30 18.97 5.65 0.07 0.92 0.22 0.26 2.74 Pond #1 Outflow quartz, muscovite, kaolinite, chlorite, amorphous aluminum & iron hydroxides 52.79 18.66 6.17 0.02 0.95 0.25 0.20 2.7

Pond #2 Inflow quartz, muscovite, kaolinite, chlorite, amorphous aluminum & iron hydroxides 49.19 13.45 3.19 0.01 0.48 0.18 0.18 1.5Steel slag gehlenite, larnite, ettringite(tr), gypsum(tr), calcite(tr) 32.79 13.12 0.47 0.68 3.57 42.69 0.13 0.3

Limestone calcite, dolomite(tr), quartz(tr), muscovite(tr) 7.15 1.63 0.68 0.01 6.38 42.58 0.08 0.5

a. Steel slag was aged blast-furnace byproduct from Johnstown, Pa.; limestone was from Ashcom Quarry, near Everett, Bedford County, Pa. b. Mineralogy identified by X-ray diffraction (XRD): Quartz (SiO2), muscovite (KAl3Si3O10(OH)2), kaolinite (Al2Si2O5(OH)4), chlorite (Mg5Al2Si3O10(OH)8)

(Ca2Al(AlSi)O7), larnite (Ca2SiO4), ettringite (Ca6Al2(SO4)3(OH)12.26 H2O), calcite (CaCO3), dolomite (CaMg(CO3)2). Trace quantities of a mineral (less than 5 

amorphous materials may not be detected by XRD owing to low peak to background ratios for such phases (J. M. Hammarstrom, U.S. Geological Survey, writt

c. Major elements analyzed by inductively coupled plasma atomic emission spectroscopy after lithium metaborate/tetraborate fusion. Loss on ignition ind

H2O, CO2, and SO3. 

d. Comparable values for median concentrations in streambed sediments across the conterminous United States were reported by Rice (1999) for alum

(Fe2O3 = 5.00 wt%). Sediment-quality guidelines for protection of benthic freshwater organisms were reported by Persaud and others (1993) for iron (Fe2O3 = 

(MnO = 0.142 wt%). 

Page 45 
Table 5. Trace-element composition of pond sediment samples collected April 27, 2004, from the Staple Bend Tunnel Unit of Allegheny Portag

Site, Pennsylvania, and steel slag and limestone obtained from the vicinitya and used in cubitainer tests 

[<, less than; ppm, parts per million] 

Sample Identification Element Concentration in Parts per Millionb , c 

Ag As Ba Be Bi Ce Co Cr Cs Cu Dy Er 

Pond #1 Inflow <0.5 15 583 3 <0.4 93.3 13 75 7.0 23 5.8 3.7 Pond #1 Outflow <.5 10 603 3 <.4 92.4 21 79 6.7 27 6.0 3.8 Pond #2 Inflow <.5 21 433 3 <.4 63.9 28 110 4.4 50 6.1 3.6 Steel slag <.5 <5 993 8 <.4 140 <1 22 <.5 17 8.4 5.6 Limestone <.5 <5 133 1 <.4 8.7 <1 <20 .5 17 .6 .4 

Ge Hf Ho In La Lu Mo Nb Nd Ni Pb Pr 

Pond #1 Inflow 2 5.8 1.2 <0.2 44.5 0.50 <2 19 38.5 33 10 10.2 Pond #1 Outflow 1 5.2 1.2 <.2 44.6 .50 <2 18 39.3 44 10 10.5 Pond #2 Inflow 1 5.4 1.2 <.2 30.3 .50 <2 15 28.4 25 <5 7.22 Steel slag <1 4.2 1.8 <.2 44.4 .67 <2 1 41.9 30 <5 10.3 Limestone <1 .9 .1 <.2 4.1 .05 <2 1 3.7 <20 <5 .95 

Sm Sn Sr Ta Tb Th Tl Tm U V W Y 

Pond #1 Inflow 7.9 5 94 1.5 1.1 13.7 1.3 0.54 3.9 119 2 31 Pond #1 Outflow 8.0 5 90 1.4 1.1 13.4 1.5 .56 3.7 118 2 31 Pond #2 Inflow 6.6 9 75 1.2 1.1 11.5 1.6 .55 4.8 89 2 28 Steel slag 9.2 2 662 .2 1.5 10.3 <.1 .81 8.5 8 <1 53 Limestone .8 2 905 <.1 .1 1.2 <.1 .05 .8 <5 <1 4 

a. Steel slag was aged blast-furnace byproduct from Johnstown, Pa.; limestone was from Ashcom Quarry, near Everett, Bedford County, Pa. b. Trace elements analyzed by inductively coupled plasma emission mass spectrometry after lithium metaborate/tetraborate fusion. c. Comparable values for median concentrations in streambed sediments across the conterminous United States were reported by Rice (1999) for arse

(Cr = 64 ppm), copper (Cu = 27 ppm), nickel (Ni = 27 ppm), lead (Pb = 27 ppm), and zinc (Zn = 110 ppm). Sediment-quality guidelines for protection of benthic f

by MacDonald and others (2000) for arsenic (As < 33 ppm), chromium (Cr < 111 ppm), copper (Cu < 149 ppm), nickel (Ni < 48.6 ppm), lead (Pb < 128 ppm), a

Page 46 
Table 6. Cubitainera

 test data for pH, alkalinity, and calcium concentrationsb in effluent from reaction between steel slag or 

limestone with abandoned mine drainage (AMD) from Sites 1 and Fe at the Staple Bend Tunnel Unit of Allegheny Portage 

Railroad National Historic Site, Pennsylvania 

[hr, hour; mg/L, milligrams per liter; additional data for shaded cells, including calcium analysis by inductively coupled plasma 

emission mass spectrometry, are shown in subsequent tables] 

Elapsed 

Time 

(hr) 

Site 1 AMD + Slag 

pH, Lab Alkalinity Calciumc 

(units) (mg/L as CaCO3) 

Site 1 AMD + Limestone 

pH, Lab Alkalinity Calcium 

(units) (mg/L as CaCO3) 

Site Fe AMD + Slag 

pH, Lab Alkalinity Calcium 

(units) (mg/L as CaCO3) 

Site Fe AMD + Limestone 

pH, Lab Alkalinity Calcium 

(units) (mg/L as CaCO3) 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

3.7 0.0 312 

4.8 3.8 434 

5.1 4.2 464 

5.2 3.6 472 

5.4 4.1 498 

5.6 5.6 512 

5.7 6.6 522 

3.7 0.0 312 

4.4 0.0 358 

5.0 3.1 374 

5.0 3.6 374 

5.2 4.7 380 

5.2 4.2 384 

5.6 5.8 386 

4.0 0.0 540 

4.8 4.3 630 

5.0 7.2 652 

5.1 9.4 680 

5.2 12.0 694 

5.4 14.4 742 

5.7 19.8 770 

4.0 0.0 540 

4.8 5.7 420 

4.9 8.8 434 

5.0 9.4 520 

5.2 12.6 526 

5.3 12.6 546 

5.4 16.0 560 

3.5 

4.0 

4.5 

5.0 

5.5 

6.0 

5.9 8.3 536 

6.1 9.8 560 

6.2 11.8 576 

6.4 13.1 570 

6.5 14.6 592 

6.6 18.8 600 

5.6 7.2 388 

5.8 8.4 396 

6.0 11.6 428 

6.0 11.8 410 

6.2 13.8 412 

6.3 16.0 410 

5.8 28.4 810 

6.0 31.6 786 

6.2 39.6 818 

6.1 44.4 838 

6.3 50.6 872 

6.4 54.4 888 

5.6 17.8 564 

5.6 21.0 574 

5.8 24.4 580 

5.8 27.2 584 

6.0 33.2 594 

6.0 41.1 610 

7.0 

8.0 

24 

72 

168 

264 

336 

6.7 18.0 582 

6.7 18.8 610 

6.9 20.5 638 

7.3 21.2 708 

8.2 19.7 742 

8.5 17.6 772 

8.6 18.6 778 

6.3 19.4 416 

6.5 22.3 422 

6.6 29.4 430 

7.1 39.1 426 

7.2 41.9 426 

7.2 41.3 438 

7.4 45.5 436 

6.3 64.0 916 

6.5 70.6 948 

6.8 84.6 1,054 

6.9 64.4 1,108 

7.3 41.6 1,166 

8.2 28.9 1,244 

8.5 25.8 1,270 

6.0 43.0 612 

6.1 48.2 628 

6.3 61.7 636 

6.4 77.8 690 

6.4 93.6 722 

6.5 90.8 766 

6.5 108 788 

a. Conducted at U.S. Geological Survey, New Cumberland, Pennsylvania, laboratory May 3-17, 2004, following methods of Cravotta 

(2003). Each test used 2 kilograms of sieved limestone or steel-slag fragments and untreated effluent from the respective site. Composition of 

steel slag and limestone indicated in tables 4 and 5. Data for elapsed time = 0 represented by samples for sites 1 and Fe that were collected 

April 27, 2004 (table 2). 

b. Concentrations and pH measured after filtration through 0.45-micrometer pore-size filter. 

c. Calcium concentration determined by colorimetric titration (American Public Health Association, 1992a); alkalinity determined by 

electrometric titration to pH 4.5 endpoint (American Public Health Association, 1998b). 

Page 47 
Table 7. Cubitainera test data for specific conductance, pH, alkalinity, computed acidity, and corresponding concentrations of dissolvedb majo

from reaction between steel slag or limestone with abandoned mine drainage (AMD) from Sites 1 and Fe at the Staple Bend Tunnel Unit of AlNational Historic Site, Pennsylvania [hr, hours; <, less than; >, greater than; μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; n.d., no data] 

Elapsed Time 

Specific

Conductance 

pH

Alkalinity

Acidity 

computed

Net Acidity

computed

Aluminum

as Al

Iron

as Fe 

Manganese

as Mn

Calcium

as Ca

c

Calcium

as CaCO

3

Magnesium

as Mg

Sodium

as Na

Potassium

as K

Silica 

as SiO 

2

Sulfate

as SO

4

Nitrate 

as N

Nitrite

as N

Phosphate

as P

(hr) (μS/cm) (units) (mg/L as CaCO3) (mg/L) (mg/L) (m

Site 1 AMD + Steel Slag 

0 990 3.7 0.0 56 56.0 4.96 0.96 1.48 121 303 47.6 4.08 1.47 18.8 612 0.53 <0.04 <0.08 

1 950 5.1 4.2 20 15.8 3.05 <.10 1.41 197 493 50.8 5.03 1.67 24.2 .n.d. .n.d. .n.d. .n.d8 1,200 6.7 18.8 2 -16.8 .10 .12 .92 >200 >500 46.5 5.11 1.76 33.2 .n.d. .n.d. .n.d. .n.d

336 1,700 8.6 18.6 1 -17.6 <.02 .15 .24 >200 >500 35.2 4.52 1.53 57.8 .n.d. .n.d. .n.d. .n.d

Site 1 AMD + Limestone 

0 990 3.7 0.0 56 56.0 4.96 0.96 1.48 121 303 47.6 4.08 1.47 18.8 612 0.53 <0.04 <0.08 1 900 5.0 3.1 25 21.9 3.94 .18 1.51 147 368 52.2 4.85 1.68 19.0 .n.d. .n.d. .n.d. .n.d8 1,250 6.5 22.3 3 -19.3 .08 <.10 1.46 169 423 53.7 4.74 1.68 17.1 .n.d. .n.d. .n.d. .n.d

336 1,790 7.4 45.5 2 -43.5 <.02 .16 1.12 175 438 51.8 4.89 1.73 14.0 .n.d. .n.d. .n.d. .n.d

Site Fe AMD + Steel Slag 

0 1,610 4.0 0.0 194 194.0 9.31 71.3 4.40 191 478 71.6 4.29 2.14 31.0 1080 <0.05 <0.05 <0.1 

1 1,600 5.0 7.2 169 161.8 7.21 64.1 7.22 >200 >500 80.0 5.22 2.36 34.2 .n.d. .n.d. .n.d. .n.d8 1,900 6.5 70.6 64 -6.6 .32 23.1 11.7 >200 >500 74.6 5.20 2.37 35.3 .n.d. .n.d. .n.d. .n.d

336 2,230 8.5 25.8 2 -23.8 <.02 .22 .99 >200 >500 52.4 4.11 1.77 58.0 .n.d. .n.d. .n.d. .n.d

Site Fe AMD + Limestone 

0 1,610 4.0 0.0 194 194.0 9.31 71.3 4.40 191 478 71.6 4.29 2.14 31.0 1080 <0.05 <0.05 <0.1 

1 1,610 4.9 8.8 183 174.2 7.14 74.8 4.60 >200 >500 82.1 4.91 2.46 32.9 .n.d. .n.d. .n.d. .n.d8 1,700 6.1 48.2 140 91.8 .81 70.9 4.57 >200 >500 80.0 4.93 2.39 31.0 .n.d. .n.d. .n.d. .n.d

336 1,870 6.5 108 64 -44.0 <.02 31.6 4.14 >200 >500 80.3 4.95 2.36 23.1 .n.d. .n.d. .n.d. .n.d

a. Conducted at U.S. Geological Survey, New Cumberland, Pennsylvania, laboratory May 3-17, 2004, following methods of Cravotta (2003). Each test us

or steel-slag fragments and untreated effluent from the respective site. Data for elapsed time = 0 represented by samples for sites 1 and Fe that were collected 

b. Cations analyzed by inductively coupled plasma emission mass spectrometry and anions by ion chromatography (Crock and others, 1999) after 0.45

c. Calcium concentration as CaCO3 computed by multiplying Ca determined by inductively coupled plasma emission mass spectrometry by 2.5. 

Page 48 
Table 8. Cubitainera test data for dissolved trace elementsb in effluent from reaction between steel slag or limestone with abandoned mine dr

Fe at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania [hr, hours; <, less than] 

Elapsed 

Time (hr) Element Concentration in Micrograms per Liter Ag As Au Ba Be Bi Cd Ce Co Cr Cs Cu Dy Er Eu Ga Gd Ge Hf Hg Ho In La 

Site 1 AMD + Steel Slag 

0 <2 1.66 <0.02 12.5 1.97 <3 0.41 3.93 62 9.0 0.03 6.86 1.6 0.81 0.25 0.10 1.57 <.10 0.04 <2 0.31 <0.01 1.31 <2 3.06 <.02 36.7 1.29 <3 .40 3.99 50 29.9 .04 4.69 1.17 .64 .21 <.10 1.22 <.10 .03 <2 .23 <.01 2.08 <2 1.35 <.02 37.5 <1.00 <3 .17 .41 23 22.2 .05 <2.00 .07 .05 .02 <.10 .09 <.10 <.01 <2 .02 <.01 .3

336 <2 .78 .28 23.5 <1.00 <3 <.10 .02 4 12.0 .04 <2.00 <.01 <.01 <.01 <.10 <.01 <.10 <.01 <2 <.01 <.01 .0

Site 1 AMD + Limestone 

0 <2 1.66 <0.02 12.5 1.97 <3 0.41 3.93 62 9.0 0.03 6.86 1.6 0.81 0.25 0.10 1.57 <0.10 0.04 <2 0.31 <0.01 1.31 <2 2.31 <.02 19.2 1.33 <3 .41 2.87 58 21.1 .01 5.53 1.08 .62 .19 <.10 1.07 <.10 .04 <2 .23 <.01 1.08 <2 1.36 <.02 27.9 <1.00 <3 .32 .66 58 20.3 .01 <2.00 .19 .09 .03 <.10 .20 <.10 <.01 <2 .04 <.01 .3

336 <2 <.30 <.02 43.1 <1.00 <3 .17 .09 43 9.9 .01 <2.00 <.01 <.01 <.01 <.10 .01 <.10 <.01 <2 <.01 <.01 .0

Site Fe AMD + Steel Slag 

0 <2 0.36 <0.02 7.15 7.86 <3 0.54 13.1 159 <5.0 0.07 <2.00 7.25 3.71 1.18 0.20 6.88 0.11 0.14 <2 1.39 <0.01 3.41 <2 <.30 <.02 37.3 6.07 <3 .55 14.5 144 16.8 .08 2.43 5.3 2.88 .90 .20 5.37 .14 .11 <2 1.02 <.01 4.28 <2 <.30 <.02 55.7 <1.00 <3 .24 4.51 108 11.7 .08 <2.00 .57 .32 .10 .24 .64 <.10 .02 <2 .12 <.01 1.9

336 <2 1.83 <.02 22.3 <1.00 <3 <.10 .02 4 16.6 .06 <2.00 <.01 <.01 <.01 <.10 <.01 <.10 <.01 <2 <.01 <.01 .0

Site Fe AMD + Limestone 

0 <2 0.36 <0.02 7.15 7.86 <3 0.54 13.1 159 <5.0 0.07 <2.00 7.25 3.71 1.18 0.20 6.88 0.11 0.14 <2 1.39 <0.01 3.41 <2 <.30 <.02 16.9 7.12 <3 .67 10.1 160 13.9 .06 3.39 5.41 2.74 .88 .14 5.19 .12 .12 <2 1.04 <.01 3.08 <2 <.30 <.02 29.8 2.30 <3 .62 6.02 158 12.1 .05 <2.00 2.15 1.15 .33 .12 2.34 <.10 .05 <2 .45 <.01 2.2

336 <2 <.30 <.02 39.5 <1.00 <3 .34 .19 144 9.0 .04 <2.00 .08 .06 <.01 <.10 .06 <.10 <.01 <2 .02 <.01 .1

a. Conducted at U.S. Geological Survey, New Cumberland, Pennsylvania, laboratory May 3-17, 2004, following methods of Cravotta (2003). Each test us

or steel-slag fragments and untreated effluent from the respective site. 

b. Concentration determined by inductively coupled plasma emission mass spectrometry (Crock and others, 1999) after 0.45-millimeter pore-size filtrat

Page 49 
Table 8. Cubitainera test data for dissolved trace elementsb in effluent from reaction between steel slag or limestone with abandoned mine dr

Fe at the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania (continued) [hr, hours; <, less than] 

Elapsed 

Time (hr) Element Concentration in Micrograms per Liter Ni Os Pb Pd Pr Pt Rb Re Ru Sb Sc Se Sm Sn Sr Ta Tb Te Th Ti Tl Tm U V 

Site 1 AMD + Steel Slag 

0 107 <0.02 0.84 <0.10 0.59 <3 2.30 <0.01 <0.1 <0.1 <10 7.14 0.91 <1 204 <.01 0.29 <1 0.02 <1.00 0.48 0.11 0.49 21 99 <.02 .10 <.10 .61 <3 5.91 <.01 <.1 <.1 <10 14.1 .76 <1 294 <.01 .21 <1 <.01 1.72 .21 .08 .55 98 62 <.02 .02 <.10 .05 <3 8.30 <.01 <.1 <.1 <10 7.44 .05 <1 360 <.01 .01 <1 <.01 2.45 .03 <.01 .37 6

336 19 <.02 <.10 .69 <.01 <3 8.33 <.01 <.1 <.1 <10 6.97 <.01 <1 524 <.01 <.01 <1 <.01 4.33 <.01 <.01 .37 5

Site 1 AMD + Limestone 

0 107 <0.02 0.84 <0.10 0.59 <3 2.30 <0.01 <0.1 <0.1 <10 7.14 0.91 <1 204 <0.01 .29 <1 0.02 <1.00 0.48 0.11 0.49 21 103 <.02 .93 <.10 .41 <3 2.05 <.01 <.1 <.1 <10 8.20 .65 <1 229 <.01 .20 <1 <.01 <1.00 .42 .08 .43 68 106 <.02 <.10 <.10 .08 <3 1.68 <.01 <.1 <.1 <10 4.30 .10 <1 270 <.01 .04 <1 <.01 <1.00 .33 .01 .08 5

336 75 <.02 <.10 <.10 <.01 <3 1.23 <.01 <.1 <.1 <10 <2.00 <.01 <1 404 <.01 <.01 <1 <.01 <1.00 .16 <.01 .42 2

Site Fe AMD + Steel Slag 

0 247 <0.02 1.37 <0.10 2.02 <3 5.73 <0.01 <0.1 <0.1 <10 <2.00 4.14 <1 407 0.02 1.30 <1 <0.01 2.10 0.22 0.47 0.50 11 234 <.02 .51 <.10 1.73 <3 10.7 <.01 <.1 <.1 <10 <2.00 3.22 <1 524 .01 .97 <1 <.01 3.03 .10 .37 .75 48 186 <.02 <.10 <.10 .31 <3 14.8 <.01 <.1 <.1 <10 2.79 .33 <1 675 <.01 .10 <1 <.01 2.94 .01 .03 2.39 3

336 18 <.02 <.10 .72 <.01 <3 10.6 <.01 <.1 <.1 <10 8.85 <.01 <1 851 <.01 <.01 <1 <.01 4.28 <.01 <.01 1.42 5

Site Fe AMD + Limestone 

0 247 <0.02 1.37 <0.10 2.02 <3 5.73 <0.01 <0.1 <0.1 <10 <2.00 4.14 <1 407 0.02 1.30 <1 <0.01 2.10 0.22 0.47 0.50 11 250 <.02 1.08 <.10 1.55 <3 5.57 <.01 <.1 <.1 <10 <2.00 3.08 <1 452 .01 .96 <1 <.01 2.32 .19 .36 .39 48 255 <.02 <.10 <.10 .77 <3 5.01 <.01 <.1 <.1 <10 <2.00 1.15 <1 514 <.01 .40 <1 <.01 2.63 .16 .14 .10 3

336 227 <.02 <.10 <.10 .02 <3 3.67 <.01 <.1 <.1 <10 <2.00 .01 <1 697 <.01 .01 <1 <.01 1.91 .08 <.01 .20 2

a. Conducted at USGS New Cumberland, Pennsylvania, laboratory May 3-17, 2004, following methods of Cravotta (2003). Each test used 2 kilograms 

fragments and untreated effluent from the respective site. 

b. Concentration determined by inductively coupled plasma emission mass spectrometry (Crock and others, 1999) after 0.45-millimeter pore-size filtrat

Page 50 
Table 9. Summary of cubitainer test conditions and results for rate of reaction between steel slag or limestone with abandoned mine drainag

the Staple Bend Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania [hr, hours; mg/L, milligrams per liter; L/mg/hr, liters per milligram per hour; cm2/mg/hr, square centimeters per milligram per hour; cm2/g, squa

ion activity product; Kt, equilibrium constant at temperature indicated; atm, atmospheres; <, less than; >, greater than] 

Site/Testa 

pH 

(units) 

Calcite Saturation Indexb,c 

(log IAP/Kt) 

Carbon Dioxide Pressureb,c 

(log atm) 

Alkalinity Rate Constantsd 

C0 CS k' (x102) K' (x105) k'' (x104) K'' (x106) 

C0 

0 hr 

Elapsed Time 

1 hr 4 hr 8 hr 336 hr 

Elapsed Time 

0 hr 1 hr 4 hr 8 hr 336 hr 

Elapsed Time 

0 hr 1 hr 4 hr 8 hr 336 hr 

(mg/L 

CaCO3) (1/hr) 

(L/ 

cm2/ 

hr) 

(L/mg/ 

hr) 

(L2/ 

cm2/ 

mg/hr) 

(mg/L 

CaCO

Site 1 AMD + Steel Slag 3.7 5.1 6.1 6.7 8.6 <-4.0 -3.7 -2.2 -1.3 0.7 >-1.3 -1.5 -2.2 -2.4 -4.4 0.0 21.2 -27.66 -31.72 389.54 44.67 312 7Site 1 AMD + Limestone 3.7 5.0 5.8 6.3 7.2 <-4.0 -4.0 -2.7 -2.0 -.6 >-1.5 -1.5 -1.9 -2.1 -2.6 .0 45.5 -7.51 -9.01 21.21 2.55 312 4Site Fe AMD + Steel Slag 4.0 5.0 6.0 6.5 8.5 <-3.9 -3.4 -1.7 -.8 .8 >-1.2 -1.2 -1.6 -1.7 -4.1 .0 84.6 -19.13 -21.94 43.43 4.98 480 12Site Fe AMD + Limestone 4.0 4.9 5.6 6.1 6.5 <-3.9 -3.6 -2.4 -1.5 -.8 >-1.1 -1.0 -1.4 -1.5 -1.6 .0 107.6 -6.98 -8.37 8.37 1.00 480 7

a. All tests conducted in laboratory May 3-17, 2004, using collapsible 1-gallon nominal polyethylene containers filled with fresh influent from the discharge 

(0.5 to 1.5 inches) of limestone or steel slag with effluent recirculated under closed conditions. Cubitainer test data used for rate estimates are shown in figure 

of steel slag and limestone are shown in tables 4 and 5. 

b. Calcite saturation index (SI) and partial pressure of carbon dioxide (Pco2) computed using measured temperature, specific conductance (SC), pH, a

Ca (Langmuir, 1997; American Public Health Association, 1992b); van't Hoff temperature-corrected equilibrium constants from Ball and Nordstrom (1991); and on the basis of estimated ionic strength, I = 1.88.(10-5).SC (Langmuir, 1997). SC values are shown in table 7. 

c. Alkalinity value greater than 0 is needed to compute SI and Pco2. Numerical values for SI and Pco2 at 0 h are given for first sample (at 0.5 or 1.0 h) w

d. First-order rate equation, Ct = CS - [(CS - C0)·exp{-k'·td}], or second-order rate equation, Ct = CS - {1/[k''·td + 1/(CS - C0)]}, used to estimate alkalinity or 

of detention time on the basis of the initial and steady-state concentration (C0 and CS) and the overall first- and second-order rate constants (k’ and k") derived 

rate constant (K' or K'') was computed as the product of the overall rate constant and the initial solution volume divided by the surface area of substrate in the cub

surface area was estimated as the product of the mass and unit surface area of the solid substrate. The unit surface areas of the limestone and steel-slag subswere estimated on the basis of the measured dimensions, weight, and volume of 50 samples of each substrate. Assuming an ellipsoidal sphere as the geomet

limestone and steel slag was 1.53 and 1.52 cm2/g, respectively (appendix C). The overall rate constant for other particle sizes can be computed as the product o

the surface area of that particle divided by the solution volume. Because alkalinity values initially were less than 0 but were positive after 0.5 hr detention time, a 

the estimated alkalinity concentration. Substituting td = (td - 0.4) in the rate equations yields alkalinity values less than zero for detention times less than 0.4 hr, 

detention times greater than 0.4 hr. 

Page 51 
Table 10. Rankings of pollutant loading and possible remedial alternatives for abandoned mine drainage at the Staple Bend 

Tunnel Unit of Allegheny Portage Railroad National Historic Site, Pennsylvania 

[Priority rankings based on instantaneous loadings of dissolved iron, aluminum, and manganese during April 7 and 27, 2004. 

Remedial alternatives are not identified in order of preference; any treatment design would require additional data and specific 

analysis; VFCW, vertical-flow compost wetland; ALD, anoxic limestone drain; OLD, flushable oxic limestone drain; OLC, open 

limestone channel; X, applicable; +, additional; - not applicable] 

Local Site Name 

Pollutant 

Loading 

Ranka 

Principal Characteristicsb 

Remedial Alternativesc 

Remine/Reclaim 

VFCW

ALDOLD

OLC

Aerobic Pond(s)

Active Treatment 

U 4 Moderate flow; moderate Fe, Mn; very high Al; net acidic; oxic X X - - - + X 

1 1 Moderate flow; moderate Fe, Mn; very high Al; net acidic; oxic X X - - - + X 

1Fe 10 Small flow; very high Fe, Mn; very high Al; net acidic; oxic X X - - - + -

Fe 12 Small flow; very high Fe, Mn; very high Al; net acidic; suboxic X X - - - + -

2 7 Small flow; high Fe, Mn; very high Al; net acidic; oxic X X - - - + -

3 6 Moderate flow; low Fe, Mn; moderate Al; net acidic; oxic - - - X X + -

3A 11 Small flow; low Fe, Mn; high Al; net acidic; oxic X X - X X + -

3B 8 Moderate flow; moderate Fe, Mn; high Al; net acidic; oxic X X - X X + -

4 9 Small flow; low Fe, Mn; very high Al; net acidic; oxic - X - - - + -

5 5 Moderate flow; low Fe, Mn; moderate Al; net acidic?; oxic - X - X X + -

6 3 Moderate flow; moderate Fe, Mn; very high Al; net acidic; oxic X X - - - + X 

7 2 Moderate flow; moderate Fe, Mn; very high Al; net acidic; oxic X X - - - + X 

1+1Fe+Fe+2d n.a. Moderate flow; moderate Fe, Mn; very high Al; net acidic; oxic X X - - - + X 

3+3B+5+6+7 n.a. Very large flow; moderate Fe, Mn; very high Al; net acidic; oxic X X - - - + X 

1+1Fe+Fe+2+ 

3+3B+5+6+7 n.a. Very large flow; moderate Fe, Mn; very high Al; net acidic; oxic X X - - - + X 

a. Rankings based on loading computed as product of maximum flow rate and maximum concentrations of dissolved iron, aluminum, and 

manganese for samples collected on April 7 and 27, 2004 (table 2). Rank of 1 for greatest loading; rank value increases with decreased loading. 

b. Principal characteristics based on maxima and minima for flow rate and concentrations of alkalinity, dissolved metals, and oxygen 

(in mg/L) for samples collected on April 7 and 27, 2004 (table 2). Flow (gal/min): "very large" if minimum > 1,000; "large" if maximum > 500 and 

< 1,000; "moderate" if maximum > 50 and < 500; "small" if maximum < 50; "intermittent" if maximum or minimum = 0. Iron and manganese 

(mg/L): "very high" if minimum Fe > 12 and minimum Mn > 4; "high" if minimum Fe < 12 and minimum Mn < 4; "moderate" if minimum Fe < 6 and 

minimum Mn < 2; "low" if maximum Fe < 3 and maximum Mn < 1. Aluminum (mg/L): "very high" if maximum > 4; "high" if maximum > 2 and < 4; 

"moderate" if maximum > 0.2 and < 2; "low" if maximum < 0.2. Net alkalinity (alkalinity - computed acidity; mg/L as CaCO3): "net acidic?" if 

maximum < 5; "net acidic" if maximum < 0; "net alkaline?" if minimum > 0 or no data and minimum pH > 6.4; "net alkaline" if minimum > 5. 

Dissolved oxygen (mg/L): "anoxic" if maximum < 1; "suboxic" if maximum < 2; "oxic" if minimum > 2. 

c. Remedial alternatives initially identified on the basis of maxima and minima for flow rate (in gal/min) and water quality (in mg/L): 

"Remine/reclaim" if maximum pH < 4.0; "Aerobic pond" if minimum net alkalinity > 5; "VFCW and aerobic pond" if minimum net alkalinity < 5, 

maximum dissolved oxygen > 1, maximum Al > 2, and maximum flow < 300; "ALD and aerobic pond" if minimum net alkalinity < 5, maximum 

dissolved oxygen < 1, maximum Al < 2, and maximum flow < 300; "OLD and aerobic pond" if minimum net alkalinity < 5, maximum dissolved 

oxygen > 1, maximum Al < 3, and maximum flow < 300; "OLC" if minimum net alkalinity < 5, maximum Fe < 10, maximum Al < 5, and maximum 

flow < 4,500; "Active Treatment" if minimum flow > 2 or maximum net alkalinity < -300. The option to "Remine/reclaim" with respect to the ALPOSBTU AMD sources would require this activity outside of the ALPO-SBTU boundaries and, thus, is beyond the authority or responsibility of the 

National Park Service. 

d. AMD sites were combined considering possible flow paths and potential for merging or aggregation of AMD. The cumulative flow rate 

and flow-weighted average concentrations were used to estimate combined AMD characteristics. The combinations exclude sites U, 3A, and 4 

because these are above sites 1, 3B, and 5, respectively. Site 8 was excluded because, on the basis of its chemistry, it is not AMD. 

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