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By E. R. Torak

Custom Coals, International has installed and is presently testing a 225 kg/hr. (500 lb/hr.) micronized-magnetite, fine-coal cleaning circuit at PETC's Process Research Facility (PRF). The cost-shared project was awarded as part of the Coal Preparation Program's High Efficiency Preparation Subprogram. The project includes design, construction and testing of a fully-integrated, bench-scale circuit, complete with feed coal classification to remove the minus 30 micron slimes, dense-medium cycloning of the 300 by 30 micron feed coal using three different size micronized-magnetite mediums, and medium recovery circuits using drain and rinse screens and various stages and types of magnetic separators. This paper describes the project circuit and goals, including a description of the current project status and the sources of coal and magnetite which are being tested.

Jan 1, 1996

By A. Singh, C. Da Corte

"South Africa possess the biggest fluorspar reserves in the world followed closely by China. In light of the current commodity downturn this paper explores the use of Dense Media Separation (DMS) as a coarse pre-concentration method for two fluorspar deposits located in South Africa in which the dominant gangue is carbonate present in the form of dolomite and calcite. Heavy Liquid Separation indicated that conventional pre-concentration of the drill core samples from both deposits would result in unacceptably high fluorite CaF2 losses. At a maximum CaF2 loss to floats of 5% the benefit of DMS would be economically marginal and difficult to justify as a conventional pre-concentrator. In light of cashflow constraints, a twin flowsheet was proposed for the sole purposes of upfront cash generation in which the majority (67-77%) of the CaF2 would report to a high grade flotation plant in 38-41% of the mass whilst the rejects would be stockpiled for flotation at a later stage. Considering the proposed twin flowsheet approach the high grade product split was achieved using DMS and this paper documents the challenges encountered and results achieved. INTRODUCTION Fluorspar is the commercial term for the mineral fluorite (calcium fluoride, CaF2). Worldwide production of fluorspar is dominated by four countries namely China, Mexico, Mongolia and South Africa. Although South Africa is the fourth largest producer, it has the largest fluorspar reserves closely followed by China (U.S. Geological Survey, 2017a). Fluorspar is broadly categorized into two grades namely acid grade also referred to as acidspar (>97% CaF2); and sub-acid grade (ceramic and metallurgical grade) commonly referred to as metspar (=97% CaF2). Acid grade fluorspar is used for the production of hydrofluoric acid (HF) which in turn is used for the manufacture of fluorocarbons and semi-conductors in the electronics industry; metal processing; the production of insecticides, herbicides and cleaning detergents, and the manufacture of uranium tetrafluoride used to concentrate the uranium isotope 235 for use as a nuclear fuel (British Geological Survey 2010; Miller 2001). Ceramic grade fluorspar (85-95% CaF2) is used in the ceramic industry as a flux and opacifier in the production of glass and enamels. Ceramic grade fluorspar is also used to make coatings for welding rods and as a flux in the steel industry. Metallurgical grade fluorspar (60-85% CaF2) is primarily used in the steel industry as flux to reduce the melting temperature and remove impurities in steel making. Similarly metallurgical grade fluorspar is also used as flux in cement production to reduce energy consumption (British Geological Survey 2010; Miller 2001)."

Jan 1, 2018

By J. C. Stankus

In this paper, an innovative concept in longwall tailgate support is discussed. This new concept utilizes a new high capacity roof truss system in lieu of conventional wooden crib block. The first field test was conducted at Bailey Mine and was very successful. Similar tests have been installed in other mines and seams. An extensive instrumentation plan was designed and implemented in the truss test area. The test data has shown that the dynamic roof truss system effectively controls the various abutment pressures caused by longwall mining thus maintaining a stable tailgate entry.

Jan 1, 1995

By C. Pace, D. Darlington, A. Montera, C. Lingren

"A phosphate beneficiation plant in Utah is using isotope-based Prompt Gamma Neutron Activation Analysis (PGNAA) technology to analyze the entire slurry streams of the incoming feed and final product in order to adjust the flotation circuits in near real time and optimize the plant output. The plant has gained greatly improved visibility/control and has reduced product variability for improved profitability and product quality. This paper takes a look at the economics as well as application details and the difference this technology provides in a phosphate application. SIMPLOT PHOSPHATES INTRODUCTION Simplot’s Vernal, Utah Phosphate Mine and Mill are located in the northeast corner of the state in the Uinta Mountains along US Highway 191, eleven miles north of the town of Vernal. The phosphoric acid and fertilizer plant fed by the Vernal mine is located 94 miles Northeast of Simplot Phosphates in Rock Springs, WY.At the Vernal plant, loader and shovel mining to 85 Ton capacity trucks is done at an annual rate of 3.8 Million tons of ore. Run of mine ore is crushed in a mineral sizer to minus 14 inch diameter at the rate 11,500 tons a day and transported to the SAG Mill’s 130,000 ton surge stockpile by overland belt. ORE RESERVES The ore is a Phosphoria Formation of sedimentary rock type dating to the Permian Age. The ore body rests over a 25 mile area on Weber Sandstone from the Pennsylvania and Permian geologic period. Layers of Phosphate Rock can vary in thickness from 0.3 up to 2.1 feet, alternating with layers of Mudstone. The eastern edge of the ore’s body Panel “G” runs 16 feet deep with a feed grade of 21.5% P205 with lower MgO diluents of less than 2.79%."

Jan 1, 2016

By Guy Bridges, Elton Ko, Cheng Ting Ning, Owen Ng, Giovanni Chang, Robert Anderson

"PROJECT OVERVIEWThe Liantang/Heung Yuen Wai Boundary Control Point (BCP) and Associated Works will be the seventhland crossing between Shenzhen and the Hong Kong Special Administrative Region (HKSAR) of China.The project includes site formation of about 23 hectares of land for the development of the BCP and anapproximately 11-kilometre (km) long dual two-lane trunk road (the “Connecting Road”), connecting theBCP with the existing Fanling Highway. The route alignment is within a relatively rural area of HongKong, with very limited similar infrastructure works carried out nearby. It passes beneath bothmountainous terrain, and alluvial plains, and falls within an area of several major regional faults andassociated metamorphism, resulting in a complex variety of ground conditions.ALIGNMENTThe Civil Engineering and Development Department of the Government of the Hong Kong SpecialAdministrative Region carried out extensive public engagement in selecting the alignment of theConnecting Road. Over 70 consultation forums with public bodies, including the District Councils, RuralCommittees, local representatives, etc. were held during the alignment design process. In order toalleviate the concerns of various nearby villages, and to minimize land clearance and environmentalproblems, the original alignment of 10 km long (3.5 km of tunnels and 6.5 km of viaducts) was revised toits final alignment of 11 km long which comprises 5.7 km of tunnels, 4.3 km of viaducts and 1.0 km of atgrade roads.The finally adopted alignment commences at the southern end with an interchange with the existingFanling Highway, part of Route 9, which is a dual three lane expressway currently being widened to dual4 lane. Alongside the expressway is the main rail connection to the mainland of China, and theinterchange viaducts connecting to the southern portal of the Lung Shan tunnel must cross over thisrailway. The southern portal is located in the foothills of Lung Shan, and the 4.8km long tunnel is alignedin a north-northeasterly direction. The southern half passes under mountainous terrain of Lung Shan,and then crosses a valley containing the Kwan Tei river. The northern section comprises low hillsseparated by an alluvial plain and Tan Chuk Hang village area. At the northern end, the tunnel turns tothe north-west to connect with Sha Tau Kok road, an existing single carriageway road, with a newroundabout interchange. Mid-way along this tunnel there will be a ventilation building, connected to the main tunnel by a 330m long ventilation adit. To the north-western side of this interchange is the900m long Cheung Shan tunnel, and after this the remaining 4.3km of the highway connecting with theBoundary Control Point is to be constructed as an elevated viaduct. The alignment is shown in Figure 1."

Jan 1, 2016

By K. N. Santini

The evaporite deposit at Searles Lake consists of alternating brine-saturated saline beds and saline-bearing mud beds. Three major subsurface brine-saturated saline horizons have been identified by private companies and the U.S. Geological Survey. They have been termed, from bottom to top, the Mixed Layer, Lower Salt, and Upper Salt. The important water-soluble components (Na, K, Mg, CO3, HCO3 , SO4, Cl, and B407) are either in brines or have combined to form the following minerals: halite, hanksite, trona, nahcolite, burkeite, borax, thenardite, northupite, sulfohalite, glaserite, etc. Kerr-McGee Chemical Corp., the current operator at the lake, selectively pumps interstitial brines from each of the major horizons to feed its three chemical plants. As the pumping continues, brines are continuously replenished within the deposit by dissolution of the minerals through natural recharge or artificial fluid injection (solution mining). The brines are processed to produce a variety of chemical products, which include sodium carbonate and sulfate, potassium chloride and sulfate, sodium borate, and boric acid. The Anaconda Minerals Co. has been evalua¬ting potential domestic trona acquisition since 1981. We have evaluated various properties in the Green River, Wyoming trona district, and Owens Lake and Searles Lake in southern California. In 1983, we purchased with our joint-venture partner, Leslie Salt Co., the southern portion of Searles Lake from Occidental Petroleum Corp. Since mid-1983, Anaconda has been conduct¬ing a small exploration-drilling program at the property. The initial core holes were drilled along and adjacent to the existing access road. In 1984 we used an all-terrain drill rig to gain access to drill sites on the playa where no roads exist. The use of this equipment proved to be highly successful. The drill program consists of coring to an average depth of 450 feet and collecting brine samples from potentially commercial horizons. The brine samples are collected by setting a packer and swabbing the hole. The core is logged and split lengthwise; one-half is submitted to our Tucson Geoanalytical Laboratory for semi-quantitative mineralogy by X-ray diffraction and the following suite of chemical analyses: Na, K, Mg, C03, HCO3, SO4, Cl, B407, Li, H20 insolubles, and acid insolubles. Additional test work for selected core samples will include effective porosity and horizontal permeability determinations. The brine samples are subjected to the same suite of chemical analyses (minus insolubles) as the core samples. In addition, specific gravity is also determined. Both cross sections and isopach maps are being constructed. The hydrological characteristics of the potentially commercial horizons are also being investigated.

Jan 1, 1987

International Minerals & Chemical Corp.'s New Wales operation near Mulberry, FL, is reportedly the world's largest concentrated phosphate chemical fertilizer and phosphate-based animal feed ingredients complex. Its latest expansion represents a $191-million investment. Two Northwest draglines were put to work at the operation early last year and, according to a company spokesman, total production from the units have more than doubled that from older rigs. This article describes how the draglines are used and provides details on the New Wales operation. The principle product at New Wales is phosphoric acid, produced by reacting ground phosphate rock with sulfuric acid in large concrete attack tanks. For each ton of phosphoric acid produced, New Wales must dispose of about 4.5 t (5 st) of waste gypsum. New Wales stores the gypsum on-site, and uses durable Northwest draglines to help handle the material. Two Units Maintain the Gypsum Stack After the gypsum is separated from the phosphoric acid through 23-m-diam (75-ft-diam) vacuum filters, it is mixed with water from a 121-hm2 (300-acre) recirculating cooling pond and, in slurry form, is pumped to the top of a 121-hm2 (300-acre) gypsum stack located adjacent to the cooling pond. The slurry contains mostly gypsum (CaSO4), with small traces of silica and other elements. The water at this point is corrosive, containing from 1-2% phosphoric acid. Its pH usually ranges from 1.5-2.0. Water drains from the gypsum stack into the cooling pond. Only about 15% of the pond's water, however, comes from the gypsum stack; the balance is from various sources throughout the complex and is held in the pond to cool before being returned for reuse in the plant. About 97% of New Wales' water needs come from this recycling program. The gypsum remains on the stack, inert, ready for future processing if it becomes economically feasible. Throughout the handling process, Northwest draglines work around the stacks' rim, continually directing the waste flow and digging out dried solids to heighten the perimeter dike to provide more storage volume. When wet, gypsum is extremely soft. When dry, it compacts well and provides footing with enough bearing capacity to support the machines. Processing at New Wales started in 1975 and the gypsum storage area has already been built up 12 m (40 ft) above grade. A total of 14.8 km3 (12,000 acre-ft) of solids are now stored. The draglines dredge material from near the perimeter dikes and place it to build parallel berms. This

Jan 8, 1982

By Alan T. Nelson, Ronald D. Mariani

The Tilden concentrator was originally constructed in 1974 for the processing of low grade hematite. Flotation is a key concentrating process in the operation, and therefore flotation optimization has been a major concern since the plant startup. This paper will discuss some of the modifications made in the process to achieve optimization. The conversion that now enables the plant to process magnetite as well as hematite also will be discussed. INTRODUCTION The Tilden Mine, located in Ishpeming, Michigan, is managed by Cleveland-Cliffs Iron Company and is owned by Cleveland-Cliffs and two Canadian steel makers. It was constructed and started production in 1974 and expanded in 1979 for processing a low grade, fine-grained hematite iron formation for which there was previously no technology available. Several papers have been written describing the unique character of the concentrating operation. The hematite plant consists of 12 grinding and concentrating lines, which utilize two stages of autogenous grinding with crushing of an intermediate sized product. The ground product is deslimed in a highly dispersed alkaline environment to reject silica. Corn starch, the flocculant, has a high affinity for iron at the operating pH range of 10.5 to 11.0. The ore is upgraded from 35% to 45% iron in the desliming step. The deslime thickener underflow is the feed to flotation. Each flotation line consists of a bank of 10 rougher cells, followed by four scavenging banks incorporating 5, 4, 3, and 3 cells each. The Wemco flotation cells are each 14.1 cubic meters (500 cubic feet) in volume. A total of 12 flotation lines are available. [ ] A reverse flotation process is employed, using a straight-chain, 8 to 10 carbon primary ether amine silica collector. At the levels used in the circuit, the amine also serves as a frother. A final concentrate is produced in the rougher cells. The concentrates from the four scavenging steps are combined and recirculated to the feed end of the roughers, with the fourth scavenger froth being discarded as a final tailing. Upgrading to about 65% iron is achieved, with control of the circuit based on final concentrate silica grade. Starch is again used, this time as a depressant for iron. During the years of operation, several key areas of the flotation process have been targeted for optimization. The most significant improvements have been realized in the following areas: *Grade Control Automation *Control of Water System Chemistry *Flotation Spray Water This paper will focus on these areas, but other minor improvements also will be briefly discussed.

Jan 1, 1993

By L. G. Hendrickson

Direct-reduction processes for converting iron ores to metallic iron in the solid state have been available for some time; and whenever scrap becomes expensive, there is a new wave of interest in these processes. It is well established that direct reduction, coupled with electric-furnace steelmaking, is a technically viable method for making steel and in some circumstances is economically competitive with the conventional blast-furnace--basic-oxygen-process (BOP) route to steel. This raises a number of interesting questions, several of which could be of great interest to the coal and ore mining industries. For example, what are the quality requirements of the raw materials for direct-reduction--electric-furnace steelmaking? Would they be different from the present requirements for blast-furnace--BOP steelmaking? Other questions relate to how much steel will be made by the direct-reduction route in the future. The quality questions can be discussed with a fair degree of certainty, but a prediction of the amount of steel that will be produced by the direct-reduction--electric-furnace route is beyond the scope of this paper. However, an attempt will be made to identify some of the factors that will influence whether there is a swing to direct reduction and the rate at which it may occur.

Jan 1, 1978

By Thomas Schwind, Benedikt Grau, Angelos Gakis

"In Crossrail’s Farringdon station, compensation grouting was successfully utilized to mitigate the surface settlements induced by the tunneling works. The main focus of this study was the platform tunnels, which were approximately 300m long each and were enlarged to platform size using sequential excavation method (SEM) from the existing TBM running tunnels, initially supported using sprayed concrete linings. The rear grouting injections were carried out at a typical distance of minimum 5m above the completed, fully strengthened shotcrete lining hence inducing some additional stresses. In-tunnel monitoring using surveying targets was performed systematically to ensure that no excessive distortion of the initial shotcrete lining occurred. 3D finite element analyses were utilized to back calculate the actual “effective” pressure that was imposed on the completed shotcrete rings against the additional measured in-tunnel displacements due to the compensation grouting episodes. Additionally an assessment of the theoretical, “maximum” allowable grouting pressures that would lead to overstressing of the lining is presented. INTRODUCTION As part of the back analysis performed for the SEM tunnels in Farringdon station, an investigation of the effect of compensation grouting on the two constructed platform tunnels was undertaken. The platform tunnels were 10.6m high by 11.4m wide and approximately 300m long each. They were enlarged to their final shape from the existing TBM tunnels using SCL methods. This study utilized 2D and 3D finite element (FE) analyses in order to back calculate the observed tunnel crown displacement, assessing the equivalent grouting pressures during the rear injection episodes of the concurrent grouting operations. The results provide a useful reference for the order of magnitude of the grouting pressure load cases that can be applied in the numerical simulation of similar cases. Part of the results presented in this paper, were derived by the second author as part of his Master of Science thesis in Technical University of Graz."

Jan 1, 2016

By M. S. Klima

Coal gasification solid residue (slag) contains unconverted carbon (char), which is considered an impurity for utilization applications of slag. Under this study, table concentration was used to process approximately 24,000 pounds of a nominal-3.4 mm gasifier slag (-85% ash) to separate high (-100%) ash slag from low (-50%) ash char. The results indicated a nearly ideal separation of the slag from the char for sizes coarser than about 1 mm. An overall slag yield of 71 % was obtained. The slag was sufficiently clean to be used as feed material for the production of expanded lightweight aggregate. The recovered char had an ash content of about 47% and was a nominal -1mm in size.

Jan 1, 1997

Recent expansion programs have made the Yunkang underground coal mine the number one producer in Shenxi Province. The mine is the newest in the Datong Coal Administration, currently rated at around 3 Mt/a of coal. Located in the Wa Chushi mountain range about 23 km north of the city of Datong, the mine has undergone a series of expansion phases since startup in 1973. Initial design capacity was 1.5 Mt/a and ultimately, production will be brought to an estimated 7.0 Mt/a by 1985, according to mine superintendent Li Jia-zhi. How Coal Occurs The coal, Jurassic in age, occurs in three economically identifiable seams designated No. 2, 3, and 7. Seams are 100-250 m below the surface. Reserves from this economic zone were not quantified, but Superintendent Li indicated that there was enough mapped out to sustain the expanded production rate for over 20 years. Below the Jurassic coal is another possible economic zone, a Permocarboniferous coal lying 400-600 m below the surface. Little development drilling has been conducted to ascertain its potential. The Jurassic beds are relatively flat and coal quality is reportedly one of the best in China. Heat content of the coal runs around 33.5 MJ/kg and the ash content is less than 10%. In some areas, it is less than 7%. Coal preparation is simple and involves a washing and screening separation into four principal size fractions. Washed coal is stored in one of six storage silos, each with 4000-t capacity. Mining the No. 2 Seam Since startup, primary production has been derived from the No. 2 seam. The coal is relatively hard and is topped by a hard cement-like conglomerate. These factors, coupled with an average thickness between 4 to 6 m, precluded the use of conventional longwall techniques, according to mine engineers. The solution was development of a room-and-pillar tech-

Jan 3, 1980

By V. Rajaram

The Parachute Creek Member of the Green River Formation in the Piceance Basin, Colorado, contains vast reserves of oil shale, nahcolite, dawsonite, and other accessory minerals. The dry alkali process of sulfur dioxide removal using nahcolite (naturally occurring sodium bicarbonate) has great potential. A room and pillar mining scheme has been designed to extract a nahcolite zone occurring at a depth of 472 m, from the lease application area of the Yankee Gulch Joint Venture. Geotechnical parameters affecting mine design will be discussed. A preliminary development plan for mining at the rate of 1000 t/d will be described in detail.

Jan 1, 1977

By A. W. Khair, S. S. Peng

Discussion by J. Parker Gentlemen; Rainy day in Upper Michigan, a good time to catch up on reading. Am doing that, and have a couple of questions concerning the K and P paper on roof problems and supports. I wonder if the authors can enlighten me. The compressive strength of the coal was reported as 4.4 MPa (633 psi) and compressive stresses measured in the coal seam were reported at around 27.6 and 48.2 MPa(4000 and 7000psi ). Can such a soft coal actually contain such a high level of stress? Can it be measured as if the material were elastic, or does the coal behave plastically? Can that stress level be confirmed with hydraulic load cells? And if the coal is so soft, and if it is plastic, why is the stress field not hydrostatic'? The intact roofrock appears to be unusually strong, with compressive strength reported at around 145 MPa (21,000 psi), and some failures were noted as soon as the rock was exposed. Were tests run to find out how that rock responded to the addition of moisture, from sprays or from humid air? Did moisture weaken the rock? Did it cause the rock to expand quickly, thus to induce internal compressive stress? How can the near-vertical cutters, as shown in the photographs, be attributed to primarily horizontal stresses? Did the cutters follow any particular pattern in the development panels, which might be related to a particular stress pattern? For example, did they always appear alongside the stiffest pillar? Or always along the northwest rib? Was there any evidence of the pillars and entries "rotating" under the influence of differential horizontal stresses? How much did the entries and pillars rotate as the longwall face approached and passed? After rooffalls, did the openings assume shapes which would indicate a preferred shape in that stressfield and geology? Did crosscuts always survive without damage, as shown in the sketch?

Jan 1, 1992

By Bauer, Steve, Colin Goodwin, Gerald, Randy Dempsey, Courtland

"The City of Ottawa’s Combined Sewage Storage Tunnel consists of two interconnected tunnels totaling 6.2 km with a diameter of 3m including access shafts and hydraulic structures which connect to the City’s most critical sewers. This tunnel will be built 15m to 30m below ground in the downtown core adjacent to, and crossing below, the Light Rail Tunnel, which introduces additional considerations in terms of sequencing and risk mitigation. The City embarked on a unique Procurement Process to address the risks involved with a large tunnel project and those associated with tunneling below downtown, underneath and adjacent to UNESCO World Heritage Sites, and connecting to live critical sewers. This paper describes the unique procurement approach employed and the contractual risk mitigation measures developed to provide the best value while minimizing risk. Specific features include Market Sounding, using a Fairness Commissioner, Contractor Prequalification and Risk Mitigation Measures in the Tender documents. INTRODUCTION This paper describes how the City of Ottawa (the City) and the project design team developed a strategic Procurement Process and Tender that incorporated industry best practices for technical and contractual risk management for the Combined Sewage Storage Tunnel (CSST) project. The process was unique in that, while it employed a systematic review of project risks, it also solicited input from industry, stakeholders and provincial and federal partners to develop the request for Tender for this traditional design-bid-build project. Key drivers for this approach were initiated from the City’s concerns for cost control, cost certainty and overall project risk mitigation. To address these concerns, the City implemented the risk review and mitigation process right from the project design team selection. It was critical that the project design team embraced this risk management philosophy and carried it through each phase of the project. This paper serves as an excellent resource for municipalities or other owners embarking on a similar tunnel project, on how to properly apply industry best practices and the benefits of using them."

Jan 1, 2016

By Richard M. Crowell, John W. Shield, Todd J. Harvey

Facing lower gold prices, gold mine operators throughout the world are seeking ways to reduce costs for treating refractory sulfide ores. Many gold mines, currently producing oxide ores, have underlying refractory sulfide deposits and the operators could extend the mine life by processing these sulfides. Fortunately, oxidation technologies for refractory ores need not be complex nor costly. GeoBiotics, Inc. has developed heap biooxidation technologies (GEOCOAT™) for treatment of refractory gold ores and concentrates. GEOCOATTM uses simple low cost unit operations common to heap leaching of gold and copper ores. The cost effectiveness and flexibility of GEOCOAT™ heap biooxidation allows mining companies to expand operations to include refract01y ore. In addition, GEOCOAT™ can be utilized to supplement or replace existing oxidation processes such as roasting, autoclaving, or agitated tank biooxidation, and to treat a lower resource grade than is currently economic. The GEOCOAT™ technology involves coating sulfide concentrates onto sized support rocks and biooxidizing the sulfides in a heap configuration. After biooxidation the concentrate is stripped from the support rock, neutralized and leached in conventional cyanidation facilities. Ashanti Goldfields Company Ltd. (AGC) produces over 885,000 ounces of gold per year from oxide and refractory ores at its Obuasi operations in Ghana. Refractory flotation concentrates are treated in roasters and in the world's largest stirred tank biooxidation facility. In August 1998, AGC and GeoBiotics jointly constructed and operated a field demonstration heap of the GEOCOATTM process at the Obuasi operations. The heap contained I 082 tonnes of support rock and 125 tonnes of concentrate. The heap was approximately 19 meters square at the base and 3.8 meters high, and ran for 88 days after which the concentrate was reclaimed. Average gold recovery after biooxidation was 91.5% with a NaCN consumption of 8.6 kg/t. Baseline gold recovery by direct cyanidation of the concentrate was 53.8%.

Jan 1, 1999

By Eero Pokki

The Päijänne Tunnel is being constructed to conduct raw water from Lake Päijänne to the Helsinki Metropolitan Area. The length of the tunnel will be 120 km and the cross-sectional area is 15.5 sq m. Excavation started in 1973 and will be completed in 1982. 94 km of the tunnel have been constructed from Lake Päijänne towards Helsinki. The construction has advanced according to plan, and due to Finland's hard bedrock there have not been any great surprises. When completed, the tunnel will meet the water requirements of the Helsinki Metropolitan Area for a long time in the future because, with a free fall of 36 m, 9.6 cu m/s of water can be conducted through the tunnel from Lake Päijänne to the Helsinki Area. With pumping it will be possible to obtain a flow of 15 cu m/s, although at first the discharge will only be 5 cu m/s. The tunnel was partly taken into service as early as March 1979 when it was possible to conduct water to the municipalities north of the Helsinki Area. It is already possible now to conduct water to Helsinki, too, but from the Korpimäki pumping station onwards it must be done through the River Vantaa, which is polluted. When the tunnel is completed in 1982, good quality water can be conducted from Lake Päijänne to the Helsinki Metropolitan Area through a continuous rock tunnel. The cost estimate in 1973 was $ 88 million while it is now $ 90 million notwithstanding high inflation. AREAS NEEDED FOR CONSTRUCTION The areas needed for construction were bought through voluntary deals. Areas of 4 - 5 hectares were bought along the tunnel line at about 5 km intervals. The excavation of access tunnels was started from these places, and the crushed rock from the main tunnel was also transported there. However, it was not necessary to buy the area

Jan 1, 1979

By Nancy L. Jackson, Leslie C. Thompson

Acid rock drainage is one of the most complex issues facing regulators and mining companies for management and remediation of mining wastes. All mining waste units, including open pits, underground workings, tailings, waste rock and leached spent ore have the potential to generate acidic leachate based on the acid generation or neutralization potential of the material. This paper uses a case study of the Walker Mine in northern California to give an overview of the available control and mitigation methods. Wetland design is emphasized as a low-cost alternative treatment option for wastewater remediation. The Walker Mine is located on the eastern flank of the Sierra Nevada, 20 miles north of Portola in Plumas County, California. The Walker Mine was an active copper mine between 1915 and 1941. During active mining, tailings were discharged into an area 1 mile west of the site at the confluence of Dolly Creek and Grizzly Creek. In addition, there were two main sources of metal-rich, acid waters impacting Dolly Creek: discharge from the mine tunnel portal, and seepage and surface runoff from waters contacting mine waste downslope from the portal area. A mine portal seal was installed in 1987 which prevented the majority of mine water drainage from further contaminating the area. Minor drainage from the portal and seeps discharge into a holding pond which overflows into Dolly Creek when elevation exceeds 6,200 feet. A site characterization study was performed to evaluate the potential water quality threat to Dolly Creek from mine tunnel discharge and waste rock seeps. Based on the results of this study several remedial options were investigated, both on a design and cost basis, to determine which abatement alternatives could be realistically implemented. The remedial options considered include both in situ containment (landfill, waste pile) or removal (backfilling into underground workings and/or sinkholes) of solid wastes. Waste water remedial options include long-term, seasonal treatment of the portal mine water, or long-term, passive treatment of portal discharge and waste pile leachate.

Jan 1, 1993

By David A. Summers, Clark R. Barker

INTRODUCTION The use of high pressure water as a means of excavating valuable mineral from the earth dates back many hundreds of years, but is most familiar through its use in sluicing the gold bearing deposits of California and Alaska. Interestingly, that practice, which dates back from at least 1852, is now nearly defunct with only one known surviving hydraulicking operation.(l) In that particular development water under a relatively low, natural pressure head is carried to a nozzle and from the nozzle it is thrown a distance of perhaps 20 ft to wash the gold bearing material down into a channel from whence it's carried over some mineral collector, and the water is then recirculated. Development of this practice in coal mining began in Russia in 1915, and Dr. Muchnik established the criteria for hydraulic mining during the 1930's. The first water jet mine was established underground in 1939 and has been followed by several larger mines to the present day where there are at least 11 large mines producing about 10 million tons of coal per year in the Soviet Union.(2) Water jet mining has expanded from Russia through Japan, Germany, Poland, Czekoslovakia, and mainland China. The nearest location to the United States is currently at the Kaiser Mine in Sparwood, British Columbia, where a three-man crew has mined up to 3,400 tons of coal in a 6-hr shift. There are many advantages to this particular operation. It is one of the safest mining operations for coal in Canada and has won safety awards because of this. The process is relatively cheap since the cost of the equipment is much lower than that which would be required conventionally using either longwall or shortwall mining, and transportation is achieved by fluming the coal to a central station using a gravity feed and then pumping to the surface, (3) For this

Jan 1, 1976

By Gale F. Hoffnagle

INTRODUCTION On November 15, 1990, President Bush signed the Clean Air Act Amendments of 1990. These Amendments cover many aspects of air pollution control. The provisions which seek to control emissions of "air toxics" may, however, be the most far-reaching and will potentially have the greatest effect on American industry. The Administration has estimated that by the year 2005 industry will be spending $6.7 billion per year on air toxics control. Meanwhile, the Business Round Table has estimated that the price will be far higher, up to $62 billion per year, depending on how EPA and the States implement the program. BASIC REQUIREMENTS Any "major" source of emissions of 189 air toxics will be required to install "MACT." The translation of this statement requires some definitions: •MAJOR SOURCE - A facility (a contiguous property under single ownership and control) which has actual emissions of 10 tons or more per year of any single one of the air toxics or 25 tons per year of any combination of air toxics. •AIR TOXICS - Congress has provided a list of the 189 chemicals on this list. Those that may be important to the mining industry are shown on Table 1. This list can be changed by petition or by EPA. •MACT - Maximum Achievable Control Technology is to be defined by EPA for each industrial source category. EPA says there are about 400 categories. The Act defines MACT as: "the average emission limit achieved by the best performing 12% of the existing sources ... for categories with 30 sources or more" or, "the average emission limitation achieved by the best performing 5 sources in the category." TABLE 1 SELECTED AIR TOXICS FROM CLEAN AIR ACT LIST IMPORTANT TO MINING INDUSTRY Antimony Compounds Arsenic compounds (inorganic including arsenic)' Beryllium Compounds' Cadmium Compounds Chromium Compounds Colbalt Compounds Cyanide Compounds (dissociation compounds) Lead Compounds' Manganese Compounds Mercury Compounds' Fine Mineral Fibers Nickel Compounds Radionuclides (including radon)1 Selenium Compounds 1Previously listed under NESHAP 2The Administration may not list elemental lead as a hazardous air pollutant.

Jan 1, 1991