|
|
RESEARCH/CASE STUDIES
(Updated 02/18/99)
OUTLINE
ACID MINE DRAINAGE
DISPOSAL OF FLUIDIZED BED COMBUSTION ASH IN AN UNDERGROUND MINE TO CONTROL ACID MINE
DRAINAGE AND SUBSIDENCE
Head W.J. et al. 1994-1998.
EVALUATION OF TECHNIQUES FOR THE DISPOSAL OF FLY ASH FROM THE CONEMAUGH GENERATING
STATION INTO AN UNDERGROUND MINE FOR IN-SITU TREATMENT OF ACID MINE DRAINAGE.
Michaud, L.H. 1996.
LABORATORY STUDIES ON THE CODISPOSAL OF FLUIDIZED-BED COMBUSTION RESIDUE AND COAL
SLURRY SOLID.
Dreher, Gary B., et al. 1996.
AGRICULTURE
INVESTIGATIONS OF A BRINE DISTURBED LAND: A PROPOSED RECLAMATION STATEGY
Pyle, Terri Ann. 1996.
SYNTHETIC SOILS FROM INDUSTRIAL AND MUNICIPAL WASTES--PHASE II AND III
Drake, L. and M. Maxwell. 1994-96.
BENEFICIAL USE
COAL ASH: INNOVATIVE APPLICATIONS OF COAL COMBUSTION PRODUCTS (CCPs)
Dienhart, G.J., B.R. Stewart, and S.S. Tyson. (eds). 1998
UNDERGROUND MINING
FLUID PLACEMENT OF FIXATED SCRUBBER SLUDGE IN ABANDONED DEEP MINES TO ABATE SURFACE
SUBSIDENCE AND REDUCE ACID MINE DRAINAGE
GAI Consultants, Inc., et al. 1996.
STABILIZATION OF UNDERGROUND MINE VOIDS BY FILING WITH COAL CONVERSION RESIDUALS.
Butler, Ray D. , et al. 1995.
ABSTRACT AND LOCATION
Butler, Ray D. , et al. 1995. Stabilization of Underground Mine Voids by
Filling with Coal Conversion Residuals. Energy & Environmental Research Center,
University of North Dakota, 43 pp.
Coal mining from the early part of this century left numerous abandoned underground mines
in North Dakota with surface subsidence problems. One mine reclamation project to mitigate
subsidence that is currently receiving attention involves injecting fly ash grout as a
flowable fill into a groundwater-saturated haul tunnel beneath a state highway near
Wilton, ND. This study presents the preliminary findings.
Flowable fill (480 yd3) consisting entirely of fly ash and 16% water was
gravity fed from cement trucks into injection wells to fill the tunnel cavity. A
high-lime, cementitious fly ash produced locally from combustion of low sodium lignite was
used.
The initial impact on groundwater in the cavity area involved elevation of pH, dissolved
solids, and sulfate. After 10 days, the effects of the injection slug dissipated to near
preinjection levels as monitored by five wells around the filled cavity. Six months later,
sulfate and dissolved solids were several hundred mg/L above background and pH was normal.
Resource Conservation and Recovery Act (RCRA) and other trace metals were not leached.
Tests of cores taken at 6 months indicated permeabilities of 1E-5 cm/s and average
compressive strengths ranging from 96 to 485 psi, suggesting certain parts of the fill
lacked the expected intensity of cementitious reactions. Mineral analyses confirmed
calcium based cement phases were not well developed, possibly because groundwater pH or
sulfate composition buffered cementitious reactions.
Ordering Info:
Interlibrary Loan Request: Debbie McGinnis, Office of Surface Mining, 1999
Broadway, Suite 3320, Denver, CO 80202-5733. (303) 844-1436; fax (303) 844-1545; email: dmcginni@osmre.gov.
Dienhart, G.J., B.R. Stewart, and S.S. Tyson. (eds). 1998. Coal Ash:
Innovative Applications of Coal Combustion By-Products (CCPs).
A pictoral documentation of advances in the field of beneficial use of CCPs and the
role of the American Coal Ash Association. It summarizes with numerous color photos
applications of CCPs for the purposes of: (1) Concrete Product Applicatons; (2)
Geotechnical Applicatons; (3) Manufactured Products; (4) Agricultural Applications; (5)
Environmental Applications; and (6) International Projects. It describes the
American Coal Ash Association and the CCP industry and their activities, and provides of a
well illustrated technical summary of the methods of generation and characteristics of
CCPs.
Ordering Info: American Coal Ash Association, 2760 Eisenhower Ave., Suite 304,
Alexandria, VA 22134-4553; (703) 317-2400, FAX (703) 317-2409; Website
www.acaa-usa.org/pubs/publist.htm
Interlibrary Loan Request: Debbie McGinnis, Office of Surface Mining, 1999
Broadway, Suite 3320, Denver, CO 80202-5733. (303) 844-1436; fax (303) 844-1545; email: dmcginni@osmre.gov.
Drake, L. and M. Maxwell. 1994-96. Synthetic Soils from
Industrial and Municipal Wastes--Phase II and III.
The objective of this project is to evaluate the possibility of creating synthetic
soils entirely from industrial and municipal wastes, which could be used for reclamation
of orphan surface mines. It offers the possibility that one environmental liability (bulk
waste) could be used to solve another environmental problem (orphan mines).
Contact: National Mine Land Reclamation Center, West Virginia University, P.O.
Box 6064, Morgantown, WV 26506; (304) 293-2867
Interlibrary Loan Request: Debbie McGinnis, Office of Surface Mining, 1999
Broadway, Denver, CO 80202-5733, (303) 844-1436, FAX (303) 844-1545
Dreher, Gary B., et al. 1996. Laboratory Studies on the Codisposal of
Fluidized-Bed Combustion Residue and Coal Slurry Solid. Illinois State Geological Survey,
Champaign, Illinois. 28 pp.
The oxidation of pyrite in coal slurry solid, or tailings, from a coal preparation plant
produces acidic leachate in the coal slurry impoundment. If left untreated, the acidic
leachate may result in local environmental deterioration. The acidic solution could
enhance the solubility and mobility of potential groundwater contaminants. If an alkaline
material is added to the coal slurry solid, it either prevents or slows pyrite oxidation,
or neutralizes the acid produced during the oxidation, and generally decreases the
solubility of heavy metals. Therefore, the likelihood of groundwater contamination is
diminished. Such codisposal of coal slurry solids with an alkaline material might allow
revegetation of coal slurry solids without the soil cover presently required by regulatory
agencies.
In this research we investigated the interaction of water with mixtures of fluidized-bed
combustion (FBC) residues or agricultural limestone (aglime) and coal slurry solid (CSS)
under laboratory conditions. We compared the concentrations of various trace elements in
leachates and extracts from the unmixed FBC and CSS materials and from mixtures of FBC
residues and CSS materials with the Illinois standards for concentrations of trace
elements in general-use water. We also used scanning electron microscopy to study
particles of FBC fly and bottom ash.
The major minerals in the unleached CSS were clay minerals and quartz (SiO2).
Also present were minor amounts of pyrite (FeS2) and calcite (Ca CO3).
The major minerals in the unleached FBC residues were lime (CaO) and anhydrite(CaSO4).
When mixed with water, the lime was hydrated to portlandite [Ca(OH)2], which
was converted to calcite during exposure to atmospheric carbon dioxide.
The major ions in the leachates and extracts from the FBC residue-CSS mixtures were
calcium (Ca2+), sodium (Na+), sulfate (SO42-),
and chloride (Cl-). The pH of the solutions from the FBC residues initially
appeared to be controlled by the equilibrium between calcite, gypsum, and sulfuric acid.
The alkaline species in the FBC residue effectively neutralized any acid produced by the
oxidation of pyrite in the CSS.
Constituents that were often observed in the leachates and extracts at concentrations
greater than the respective concentrations for Illinois general use water quality were
boron (B), chloride (Cl-), fluoride (F-), iron (Fe), Mercury (Hg)
manganese (Mn), nickel (Ni), selenium (Se), and sulfate (SO42-).
Boron, chloride, cobalt, fluoride, manganese, and nickel were often present in leachates
and extracts at concentrations that could be toxic to some plants.
Scanning electron microscopy revealed that some particles of ash were enlarged during the
FBC process by accretion of molten ash constituents, and that portions of some limestone
particles were inhibited in their reaction with sulfur dioxide (SO2) in the FBC
process, apparently due to the presence of magnesium (Mg).
Ordering Info:
Interlibrary Loan Request: Debbie McGinnis, Office of Surface Mining, 1999
Broadway, Suite 3320, Denver, CO 80202-5733. (303) 844-1436; fax (303) 844-1545; email: dmcginni@osmre.gov.
GAI Consultants, Inc., et al. 1996. Fluid Placement of Fixated
Scrubber Sludge in Abandoned Deep Mines to Abate Surface Subsidence and Reduce Acid Mine
Drainage. Electric Power Research Institute, Palo Alto, CalIAOrnia.
This project involved an investigation into injecting fixated scrubber sludge (FSS), into
abandoned underground coal mines to limit mine subsidence and reduce acid mine drainage.
The goals of the project were to develop an FSS grout which would travel at least 30 m
(100 ft) from an injection borehole and achieve an unconfined compressive strength of at
least 690 kPa (100 psi). Included were laboratory evaluations of various FSS mixes and
grout pumps, field evaluations of the injection procedures, grout movement and associated
ground water chemistry and laboratory evaluations of grout strengths and ground water/mine
pool chemistry.
The abandoned underground coal mine utilized for the project is located on Indianapolis
Power and Light Company property at their Petersburg Generating Station in southwestern
Indiana. Scrubber sludge at Petersburg is a mixture of scrubber sludge filter cake, Type F
fly ash and lime. This FSS is disposed on site as a residual waste at 70 to 80% solids
content (Cw) , fly ash (FA) to scrubber sludge (SS) filter cake ratios of
0.6-0.9 FA to 1.0 SS and quicklime of 0 to 3.5%.
To evaluate mix variables and mine effects on the grout, many mixture variations
incorporating the Petersburg FSS materials were investigated. The proportion of fly ash to
scrubber sludge (FA:SS) in the mixtures ranged from 0.7 to 1.3 with a solids content (Cw)
of 45 to 70% and a lime contents of 0 to 10%. The results showed that strength development
in the FSS was dependent upon the lime content being a minimum of 4% and variations in
FA:SS ratio and in solids content over 50% had little effect.
Various types of injection equipment were evaluated with a preference for
"off-the-shelf" equipment that was easily transported. Centrifugal and positive
displacement pumps were evaluated and a positive displacement pump was selected because of
the proposed high solids content (55-65%) of the FSS and the need for high pressures for
injection.
Thirty-five air rotary borings (15 cm [6 in] diameter), which had been cased to rock and
left open to mine level, were drilled for injection and/or monitoring of the mine
workings. Three 5 cm (2 in) ground water monitoring wells were also installed.
The field injection program lasted 40 working days and involved the injection of 12502 m3
(16,351 yd3) of FSS into three primary injection boreholes. Total FSS volumes
injected into each borehole varied from 3,290 m3 (4,300 yd3) to
almost 6,000 m3 (6,800 yd3) and based upon these volumes, areas of
the mine filled from one borehole all exceeded 0.4 ha (1 acre).
Ground water monitoring was conducted through 14 monitoring points. Sampling was conducted
nine times, four before, one during and four after injection, the last sampling bout nine
months after injection. The analytical parameters were a mixture of scrubber sludge and
coal mining indicator parameters. The results of ground water sampling indicate only
subtle or inconclusive changes in water quality. All ground water quality changes involved
FSS related parameters. There were no changes in heavy metal concentrations associated
with FSS injection.
The unconfined compressive strength of the injected FSS in the mine workings varied from
683 to 3,172 kPa (99 to 460 psi). Two low strength samples, with unconfined compressive
strengths of 117 and 241 kPa (17 and 35 psi), were obtained from the one borehole and are
believed to have resulted from a lime content below 4%during injection into that
particular area. Permeabilities varied from 1.4x10-7 cm/sec for a 2,413 kPa
(350 psi) sample to 3.4x10-5 cm/sec for the 241 kPa (35 psi) sample.
The results show that FSS is amenable to injection into underground mines using
conventional off-the-shelf equipment. One borehole can be used to stabilize 0.4 ha (1
acre). The injected FSS completely fills the mine voids, achieves strengths in excess of
690 kPa (100 psi) and has only minimal, if any, effect on ground water.
Ordering Info:
Interlibrary Loan Request: Debbie McGinnis, Office of Surface Mining, 1999
Broadway, Suite 3320, Denver, CO 80202-5733. (303) 844-1436; fax (303) 844-1545; email: dmcginni@osmre.gov.
Head, W.J. D.D. Gray, H.J. Siriwardane, W.A. Sack, P.F. Ziemkiewicz, M.A.
Burnett, and D.C. Black. 1994-98. Disposal of Fluidized Bed Combustion Ash
in an Underground Mine to Control Acid Mine Drainage and subsidence., 1995.
The project will evaluate the technical, economic, and environmental feasibility of
filling abandoned underground mine voids with alkaline, advanced coal combustion wastes.
Success will be measured in terms of technical feasibility of the approach, cost,
environmental benefits, and environmental impacts. Phase I was the development of the
grout and predictive models. Phase II was model verification. The verification will allow
the technology to be adapted to different site conditions. Phase III will be a full scale
test at Anker's 11 acre Longridge mine site. The project has demonstrated that FBC ash can
be successfully disposed in underground mines. Additionally, the project is directed
towards showing that such disposal can lead to reduction or elimination of environmental
problems associated with underground mining such as acid mine drainage.
Contact: National Mine Land Reclamation Center, West Virginia University, P.O.
Box 6064, Morgantown, WV 26506; (304) 293-2867
Interlibrary Loan Request: Debbie McGinnis, Office of Surface Mining, 1999
Broadway, Denver, CO 80202-5733, (303) 844-1436, FAX (303) 844-1545
Michaud, L.H. 1996. Evaluation of Techniques for the Disposal
of Fly Ash into an Underground Mine for in-situ Treatment of Acid Mine Drainage.
The research refines the technology that can be used to prevent or reduce the formation
of AMD at the source in underground mines. The project examines behavior at field-scale
and seeks to apply sufficient control to the site to define the important factors
influencing behavior. The technology potentially provides a low/zero maintenance method of
treating existing AMD, while simultaneously developing a viable, low-cost, environmentally
sound use of waste products from coal-fired power-generating stations. The use of sludges
from the treatment of water at the generating station and from the chemical treatment of
AMD at the mine site as alkali activators in the fly ash cement may be investigated later
if the study is extended. Phase I defines the feasibility and anticipated benefits of a
field-scale in situ demonstration project involving fly ash grout injection to neutralize
AMD and determine any negative effects, including the possible leaching of trace metals.
Contact: National Mine Land Reclamation Center, West Virginia University, P.O.
Box 6064, Morgantown, WV 26506; (304) 293-2867
Interlibrary Loan Request: Debbie McGinnis, Office of Surface Mining, 1999
Broadway, Denver, CO 80202-5733, (303) 844-1436, FAX (303) 844-1545
Pyle, Terri Ann. 1996. Investigation of a Brine Disturbed Land: A
Proposed Reclamation Strategy. University of Oklahoma, Norman Oklahoma. 149 pp.
Salt-damaged soils resulting from oilfield activities are one of the most common
sources of non-point source pollution in the state of Oklahoma. The two primary effects of
brine on soil and soil fertility are: (1) the degradation of the physical structure of the
soil; and (2) the alteration of the normal osmotic gradient existing between the plant
roots and the soil.
It was the intent of this study to combine laboratory and field studies to determine the
impact brine has had on a specific site located in Clearview, Oklahoma. Batch studies were
also conducted to determine the recommended application rates for the proposed amendments.
The Clearview site was severely eroded and devoid of vegetation. Analysis of the soils
showed significant increases in concentrations of soluble salts typically found in brine.
Based on pH, electrical conductivity (EC), and exchangeable sodium percentage (ESP)
values, the soil was classified as a saline-sodic soil. The soil was determined to be a
clay loam with a clay content of 36% and was classified qualitatively using the pinhole
test as a slightly dispersive soil.
The water quality of two creeks that received the drainage water from this brine disturbed
land was impacted, especially during runoff events. It was found that the creeks were
receiving high concentrations of soluble salt and sediment loadings exiting the brine
disturbed land.
Based on the results of a batch study, the recommended application rates for the
reclamation of the Clearview Site consisted of the following: (a) 1 ton/A of fluidized bed
ash; (b) 9 tons/A of gypsum; (c) 1 ton /A of agricultural grade sulfur dust; and (d) 30
tons/A of broiler turkey litter. It is recommended that an effective drainage system be
established prior to the incorporation of the amendments. A salt-tolerant vegetation, such
as a Bermuda variety, is recommended for plant growth establishment.
Ordering Info:
Interlibrary Loan Request: Debbie McGinnis, Office of Surface Mining, 1999
Broadway, Suite 3320, Denver, CO 80202-5733. (303) 844-1436; fax (303) 844-1545; email: dmcginni@osmre.gov.
|
U.S.
Office of Surface Mining, Mid-Continent Region
Accessibility