New technologies: how to assess environmental effwts Although the example given here pertains to coal mining, the method could cover a whole gamut of projects
Patrick J. Sullivan Ball State Unioersity Muncie, Ind. 47306 Milton L. Lavin Jet Propulsion La bora tory California Institute of Technology Pasadena, Calif: 91 103
Every new technology has the potential for creating unforeseen environmental problems. Consequently, a major objective in designing new technology should be identification of such possible adverse effects. This would allow redesign or modification of the technology, if economically feasible, to eliminate its environmental hazards. This concept is a fundamental component of the Advanced Coal Extraction Systems Definition Project that is funded by the Department of Energy and performed by the Jet Propulsion Laboratory, California Institute of Technology ( I ) . Although developed to evaluate deep coal mining technology, this method can be applied to many developing technologies.’ To demonstrate the major elements of the method, a contemporary roomand-pillar mining system (RP) was compared with a new hydraulic borehole mining system (HBM), which has the potential to overcome many traditional mining problems. The HBM is a modified room-and-pillar scheme that reaches the seam from the surface through a cased borehole, breaks the coal into manageable pieces with a hydraulic jet, and then lifts the slurried coal up the borehole to a separation facility. Though not ideally suited to the mining of flat-line seams, HBM can be applied to this mining structure to produce, in effect, a remotely operated R P system. Thus, an analysis of 262
Environmental Science & Technology
this HBM application yields a baseline comparison with the R P system. This comparison has four distinct steps: definition of the engineering characteristics of each mining system; characterization of the coal region where the mining systems will be used; assessment of each system at an early (conceptual design) stage of development; and assessment at a more advanced (preliminary design) stage of development. Before an environmental assessment can begin, each technology must be defined precisely in terms of its engineering characteristics. Figures 1 and 2 illustrate the R P and HBM systems and the engineering data required to assess each system at both conceptual and preliminary design stages. The sites must be described in sufficient detail to identify the significant opportunities and constraints for a given technology. However, the site characterization must also be fairly generic to allow flexibility of evaluation. An early environmental evaluation should avoid overly rigid constraints and so encourage the development of a promising technology. Characterization of a selected coal region, for example, requires a different level of detail for each design stage. In other words, there is no need to collect site-specific data when information on hardware performance is still imprecise. At the conceptual design stage, the evaluation requires only an overview of the basic physical and biological characteristics of the region. At the preliminary design stage, however, characterization usually requires fairly specific information on one or more representative sites, spanning the range of mining and reclamation variables. Thus, with an increase in engineering information
from conceptual to preliminary design stages, siting characteristics also change from regional to site-specific. The Central Appalachian bituminous subregion (2) will be used for the analysis of RP and HBM. Within this subregion, we chose a site in Clay County, Ky., because it broadly represents reclamation problems likely to be encountered and because a large amount of information on Clay County was available from the Lands Unsuitable for Mining Project, Kentucky Department of Natural Resources. The regional environmental characteristics required at both the conceptual and preliminary design stages are summarized in Table 1. Conceptual design stage An assessment of the potential environmental effects of each system at the conceptual design stage (“conceptual assessment”) is critical to the continued development of the hardware or to its planned modes of application. The conceptual assessment is based on the following assumptions: All technologies can, at the conceptual design stage, be defined in terms of their component generic processes. (For example, coal mining technologies can be defined by the processes of site and seam access, coal extraction, coal haulage, and the like.) Each generic process has known potential environmental impacts. (For instance, vertical boreholes created by the HBM can be assumed to have potential effects of aquifer contamination and groundwater alteration similar to those of any well-drilling operation.) For coal mining technologies, it was determined that a checklist format was best for identifying impacts at an early stage. Checklist users must describe mining activities and the salient engi-
0013-936X/81/0915-0262$01.25/0 @ 1981 American Chemical Society
Volume 15. Number 3. March 1981 263
neering characteristics of a new system. fill the checklist out, and identify potential environmental effects. A checklist analysis of the two systems is summarized in Figure 3. This illustrates a simple correspondence between mining activities in a selected region and negative impacts that may occur for each resource. To present some detail, however, several major impacts identified for each system by the checklist analysis are summarized. Note that only major differences in potential environmental effects are listed. (For instance, im-
pacts of access roads are omitted because they are required by both.) There are significant differences between the potential environmental impacts of the two mining systems. At this level of analysis, it is clear that in this application the HBM has few environmental advantages over the conventional RP system. In fact, the HBM causes several major adverse impacts that the RP system does not. Most of these impacts are caused by boreholes, HBM surface activities, and the use of water as a working fluid. However, to illustrate the remainder
of the method, it will be assumed that the HBM was found environmentally acceptable in the conceptual assessment. Preliminary design stage At the preliminary design stage, the additional engineering information available allows potential impacts to be more accurately assessed. When a technology is implemented, there are two basic types of impacts: utilization and alteration. Each technology requires a specific amount of natural resources in order to perform its basic
. .. .
TABLE 1
Site and regional characteristics a
*
R.au,.d
Topography
C a u Q l U a l mlgl
>
~
~~~
The lardforms are a combination of ridgetops (20%). sideslopes (60%).
Ridaes and SidesloDes are preiominantly icfested while the valley bdtoms are devoted primarily to agriCUIWE and wban develop ’ ment.
The mine area is located on the westem border of the Appalachian plateeu.
~
. -
and toeslopes (20%) that blend Into a complex configuration of concave and convex slocms. Over 70% of the reOion has a s l w oradlent of 3550%. Near the ridgelops. the slope g&Ienl decre&slo a range of 12-20%. With the IoesloDe. the oradient ranaes from 2-6%. The maximum elevation (1686 R above s e i level) occirs in the eastern pcflion of the mine area and decreases to 1185 tt above sea level to ths west. Local relief averages 300-500 R(7). in the mountain physiographic region. Over 80% of the land is covered by nahral ve@alion. The mine m is bounded to the west and sovlhwesl with broad valley flood plains which are covered with grass, herbaceous plants, and culllvated crops. On the gentle slopes above ttw flood plain and within the narrow upland stream valleys, land uses are a mixture of res&ntial (no cllles), pasture, and cropland (20%). The remainder of the
typically 300-500 fi from
rkl@op to the fiislcoal bed greater than SO-in. thick. WitMn the overburden there
fer yields range 50gpm. There are many nnial streams in the
From the data presemed b Goose Creek can be ass
264
mm
Numerous ridges (slopes 20%) that are broad at the summit and aentlv slooina
valley floorq Land use
R.WN*
Environmental Science 8 Technology
mission. This leads to primary impacts caused by the direct utilization of a resource (for instance, consumption and subsequent contamination of water used as a working fluid in cutting coal). Secondary impacts often occur because of alteration or contamination of other resources (for example, contamination of surface water by acidic water pumped out of a mine to prevent flooding). Underground coal mining systems have three major utilization impacts: total area disturbed (subsidence or surface modification), total water resources withdrawn from other uses, and the overall energy efficiency of the process. The major alteration impact is the degradation of water quality by sedimentation and acidic contamination. The two mining systems will now be assessed in terms of these four major impacts. Total area disturbed Room-and-pillar. The R P mining system can be used only in the Jellico coal zone. Given the engineering data in Figure 2, and assuming that 57% of the coal can be removed (the remainder is left as pillars supporting the roof), 6503 tons of coal can be extracted per acre. To meet a projected mine capability of 633 600 tons/y, the RP system will disturb 98 acres of land each year. The mining plan for the site provides for pillars large enough to prevent near-term surface subsidence. Nonetheless, the land above the mine workings will be regarded by most regulatory agencies (and developers) as suitable only for restricted uses. Hydraulic borehole mine. The HBM can operate in both the Amburgy and Jellico coal zones. The engineering data in Figure I and the geometry of an extraction cavity (Figure 4) indicate that each borehole will produce 525 tons of coal. With the same production level as the RP mine, the HBM system will disturb 93 acres/y to produce 633 600 tons. Although the HBM disturbs less land directly above the extracted coal zones, this acreage is distiibuted over a wider area than that required by the RP mining system (Figure 5 ) . Because the borehole miner is crawler-mounted and equipped with leveling jacks, it does not require an earthen pad for operation. Thus, it is well suited for the more gentle ridge tops of the regions. Water resources Room-and-pillar, At least 30 gal/ min (gpm) will be required for sustained mining operations (24 h/d). It is clear from data on the available
FIGURE 3
Checklist summary of potential negative impacts for the room-and-pillar and hydraulic borehole mining systems ~~
Resource
Type Of impact
Mining adivltiesl8iIe characterialw
Erosion
ia Road conmctimn l b inherent rite-emiy potential 1c Extent of mad netwon i d Overburdenremoval Sulface spoil storage l g Wide-area leveling l h Limited ieve'. ti Highwali m~ if
Topographic alteration
Land
2a Undergroundextracltm
SUbaidence
Water quality
Water
wndwater llteration
I
I Availability I
Ecoloav
I
I
4b t ~ u ~ i i ~ kafi lshafls y
4c casing and oesling of sha; 4d Need m pvmp wi working Sa Adequacy Of on-rile wurc 5b On-site water storage
7b Vetlelation removal df-rile
water resources that there is sufficient water for this system from either surface or groundwater sources. Hydraulic borehole miner. In order to achieve the same production as the R P mine, the HBM must drill 1206 boreholes per year. According to the engineering data in Figure I , 260 hours are needed for one borehole miner to extract all the coal from one cavity. Thus, 20 borehole miners will be required to produce 633 600 tons of
I
coal per year. Assuming that the cutting and pumping water is recycled, each miner will use 168 gpm (Figure I). This translates into a total of 3360 gpm for full production. In light of the local water resources, the HBM cannot maintain full production without water storage facilities to provide backup support to the slurry transport and recycling system. There appear to be adequate water resources to maintain full production. Volume 15, Number 3. March 1981
265
FIGURE 4
FIGURE 5
Extraction cavity characteristics of the hydraulic borehole miner
A compmison ofexbaction -*
Area of hexagon surrounding each = s2,3)1 borehole (land use) 2
-
Extrachon efflClenCy 01 a = ij hexagonal dose-packed grld 2\ 3
($y
-iooo~
Ratio of cavity diameter to borehole spacing (dis)
Borehole miner area is approximately 40 acres Contour elevation Map area (approximately 900 acres) corresponds to room-and-pillar extraction
.This area IO fmm me ~ o n h w equalter ~f of me @le Quadrangle. KY. (73)
Energy resources Room-and-pillar. Given the energy requirements for coal extraction as summarized in Figure 2, the RP system will utilize 5 X IO" Btu/y. Assuming that the coal being mined has an average of 13 000 Btu/lb, 1.64 X IOI3 Btu will be extracted. Consequently, 3% of the energy extracted will be consumed in the mining operation. Hydraulic borehole miner. The borehole miner requires energy for drilling, cutting the coal, and pumping the coal out of the extraction cavity. All of these operations are performed by machines that consume fuel oil. Given a consumption rate of 5.47 X IO-2 gal of fuel/hp-h, and 1.4 X IO5 Btu/gal (Figure I), the HBM will require 4.53 X I 0 6 gal of fuel, or 6 X IO" Btu/y. Thus, 3.7%of the energy extracted will be utilized in the mining operation.
nation of topography and soil characteristics found a t the HBM mine site. Because this calculation is very lengthy, it will not be shown here ( 4 ) . However, the data indicate that the HBM will produce 150-300 tons of sediment per year, which is approximately three to five times greater than the amount of sediment produced by the RP system during active mining. This calculation does not take into acwunt sediment yiela from reclaimed slopes or off-road track damage of the HBM miner. Because the HBM utilizes a large number of slurry lines, there is the potential for increasing water pollution problems if a line should break. If the overburden a t the mine site contains acid-producing materials without a significant alkaline component (such as iron sulfide with no associated carbonate), acid drainage could result from the introduction of mining water.
Water quality All deepmining systems disturb the surface because of their roads, buildings, refuse piles, and other aboveground facilities. Since the HBM requires some modification of the surface (for example, stripping the vegetation for construction of roads), it creates a greater erosion and sedimentation problem than does a conventional deep mine. A quantitative projection of sedimentation may be obtained by applying the Universal Soil Loss Equation (3) to the combi-
Comparing competing systems The potential impacts associated with the HBM make it an environmentally less desirable system to replace or compete with the RP in Central Appalachia. In addition, the cost of mitigating or controlling off-site impacts of the HBM (sediment control, water treatment, backfilling and revegetation, grouting boreholes, and the like) was found to be considerably greater than that for the RP system
266
Environmental Science & Technology
(5).
Because the HBM permits rapid' initial development of a property and eliminates the exposure of personnel to hazardous underground environments, it remains an attractive possibility for many mining situations. However, because of its lack of suitability and the potential environmental and reclamation costs associated with the HBM in Appalachia, three development options are available: The system could be redesigned to eliminate or reduce
potential impacts; the system could be evaluatedfor anothergeographicregion; or the suitability o f H B M could be assessed for mining other materials whose geologic Occurrence is judged to be less demanding in terms of irreversible impacts and mitigation meaFor instance. field Of a prototype HBM have been conducted in shallow, lenticular uranium deposits. This system has been proposed for the mining of oil sands
(6). Thus, by comparison of the two different underground mining systems, potential environmental effects can be identified during a technology's developmental stages. Additionally. impacts that are quantified can be expressedintermsof their cost of gation. For example. costs for water treatment, sediment-control structures, refuse storage, and revegetation can allbe calculated to a preliminary design stage. This allows Competing systems to be compared on the same basis,Such a comparison can be used as a guide for modification to reduce potential environmental effects. Note: The research described in this paper was carried out at the Jet Propulsion
Laboratory, California Institute of Technoiogy. and at Ball State University. Muncie, Ind. I t was sponsored by the Orriceof Mining, the u,s,Department
of Energy, through an agreement with NASA.
References ( I ) Goldsmith. Martin: Lavin. Milton L.
"Overall Requirements for an Advanced Underground Coal Ex!rrction System": Jet Propulsion Laboratory. California In~titule of Technology: 1980. JPL Publicutiun 8039. (2) Sobek. A. A,: Hcnning. R. J.:Smith. R. M.: Master. w. A."Asscssmcnt olReclamation Rescarch Topics in the Eastern Coal Provincc.': Land Rcclamatian Program. Areonne National Laboratory: 1980. (3) "Predicting Rainfdl Erasion Losscs": U.S. Dcpartmcnt of Agriculturc. US. GOvCrnmcnt printing officc: Washington, D.C.. 19x0. Agricultural Handbook Number 537. (4) Dutri. E.: Sullivan. P.: Hutchinsan. C.: Stcvenr. C. '.The Environmental Assessment or a contemporary C O ~ Mining I system-: The Jet Propulsion ~aboratory.Calilornia Institute of Technology: 1980. JPL Publication 80-99. (5) Sullivan. Patrick J.: Hutchinson. Charles F.: Makiharr. Jeannc: Evcnsixr. Juill. "A Methodology for the Environmental Assessmen1 Of Advanced coal Extraction SySlCmS": Jet Propulsion Laboratory. Calilornia Institute or xechnoiogy: 19x0.JPL Publication 79-82. (6) Savanick. G. "Borehole Mining-An Environmentally Compatible Mcthod of Mining Oil Sands": p a p prcscntcd a t an Open Industry BriefingonOil ShnleTechnology. held
at the US. Bureau of Mines Oil Shale Rc-
search Facility. Denver. Cola.. July 22. 1980. (7) Map Dava or the Big C m k 15-Minute USCS Quadranglc. prepared lor the Dcpartmcnl of Natural Resources. Kentucky. Environmental Systems Research Institute. 1980. (8) McDonald. Herman P.: Blevins. Robert L. "Reconnaissance Soil Survcy: Fourteen Counticr in ~~~t~~~ Kentucky"; U.S. D ~ . partment of Agriculture, Soil Conservation Seriice: 1965. Series 1962. No. I. (9) Ping. Russell G.: Sergeant. Richard E. Geologic Map ofthc Oglc Quadrnngle. Clay and Knox Counticr. Kentucky: US. Geological Survey: 1978. Map GQ-1484. ( I O ) Kilburn. Chabor:Price. W. E., Jr.: Mull. D. s. "AvailabililyolGround waterin~ ~ 1 1 , clay, Jackran. ~ n o x . ~ a u r c ~ ~. c s ~ i e . McCreary, Owrlcy. Rockcastle. and Whitley Counties. Kentucky": U.S. G ~ ~sur.I ~ vcy: 1962, Hydrologic Investigations Atlas
Kentucky. Progress Report. Series X": Kentucky Geological Survey. 1963. ( 1 2 ) Smith, R. M. -Land ~ ~ I\~~ i .l agnostic Atlas": Land Reclamation Progmm, Argonne National Laboratory: in prcparation. (13) Topographic MapoftheOglcQu~drangle (1:24 000): US. Geological Survey: 1954.
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Major impacts Room and plllar Coal refuse is stored aboveground. Thus, potential exlsts for structural failure of the refuse pile to produce sediment, or for contamination of surface and groundwater by acid drainage. The underground extraction of coal and subsequent subsidence (major or minor) will alter the natural groundwater flow above the mined-out seam, and may restrict future land use options. Flow of water Into the mine workings creates a potential acid drainage problem that is typically mitigated by treating the water after it is pumped from the mine. The long-term problem is handled by sealing the mine entrances. However; even though the best available technology is used, there is always a real possibility of seal failure and the massive release of potentially acidic waters.
Hydraulic borehole mlner Subsidence will be somewhat controlled by backfilling with refuse. Thus, problems associated with refuse storage will be reduced, and future land-use options may be preserved. However, impacts from the underground storage of refuse are not well defined. Mining from the surface has the potential for widespread disturbance of the ridges that characterize a region. In particular, the system will require a larger proportion of roads than would an underground mining operation. Thus, there is a greater chance for erosion and sedimentation. Multiple coal seams can be extracted so that more coal can be removed from the region. The numerws boreholes that will penetrate the strata above and below the coal bed will cause major disruptions of groundwater flow. The introduction of water as a working fluid will increase the chance of surface and groundwater pollution by acidic water if the geological materials contain acid-producing components. If the slurry recycling system ruptures, serious damage could result from the release of the slurry water.
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HA.38. ( 1 1 ) Kirkpatrick. G. A,: Price. W. E.. Jr.: ' Madison. R. A. .'water Resources or Eastern
Patrick J. Sullivan ( I . ) is an assistant projessor a/ Natural Resources in the Department a/ Natural Resources. Ball State University. Muncie. Ind. H e has previous experience as a senior environmental analyst-earth sciences with the Jet Propulsion laboratory, California Institute a/ Technology.Besides reaching at Ball State. he is currently conducting research on the reclamation andfinal use of sanitary landfills. I n addition to his academicyear at Ball State. Dr. Sullivan is also a visiting research scientist with the Argonne National LaboratoryfLand Reclamation Project where he is conducting research on the reclamation a/ prime /armland. Milton L Lavin ( r . ) is a member o j t h e technicalsta//o/the Jet Propulsion l a b oratory. California Institute a/ Technology, where he currently manages the Advanced Coal Extraction Systems Definition Project. The long-term goals o/this project are the development and demonstration ofmuch sa/er and more produrrive underground equipment /or several dif/erent mining situations. Prior to this assignment, Dr. lavin participated in a variety of user requirements studies./easibility studies, and system design studies. H e obtained an M.S. in aeronautical engineering/rom the Massachusetts Institute of Technology in 1961 and a Ph.D. in management from the same institution in 1969. Volume 15, Number 3.March 1981 267
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