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By D. H. Rousell

"Rocks of the Whitewater Group (Aphebian age) oc ithin the Sudbury Basin and consist of three formations rre, from oldest to youngest: Onaping, heterolithic breccias lus an igneous-textured component; Onwatin, argillite and siltstone; and Chelmsford, greywacke with minor argillite with siltstone. Mineralization in these rocks is as follows:1) Sulphides are disseminated throughout the Onaping Formation. Pyrrhotite, the major sulphide mineral, occurs mainly as fragments; other sulphides are chalcopyrite, sphalerite, galena, pyrite and marcasite.2) Zn, Pb, Cu, Ag and A u mineralization in the Vermilion member, a carbonate-chert unit near the base of the Onwatin Formation (Vermilion and Errington mines).3) Pyrite and minor base metals in the Onwatin Formation .4) Mineralized quartz veins, located at or near the base of the Onaping Formation, include such deposits as Moore Lake (Pb, Zn and Ag), Foisey (Zn, Pb), Papineau (Cu, Au and Co) and Proulx (Pb, Zn, and Cu). Quartz-carbonate veins in a meta-gabbro sill contain Cu, Zn, As and Au. Material from quartz veins from two former ""gold mines"" (Gordon Lake and Creighton) yielded no Au values.5) Anthraxolite veins in the Onwatin Formation .The mineral occurrences can be explained in term of either the volcanic theory or meteorite-impact theory of basin formation. According to the latter theory, the sulphide fragments in the Onaping Formation may have been formed by the brecciation of sulphide-rich pods located in the upper mantle and at the base of the transient crater; some of the sulphides may have been derived from target rocks of the Huronian Supergroup. The Vermillion-Errington deposits may represent sedimentary exhalative deposits of the Remac type; mineral-rich brines, trapped at the base of the transient crater, rose upward and precipitated the mineralized carbonate-chert under reducing conditions. These conditions continued throughout the deposition of the upper Onwatin Formation but pyrite was the only sulphide that formed.The quartz veins were emplaced during the time of basin deformation. Metamorphism remobilized and concentrated carbonaceous material in the Onwatin Formation 10 form the anthraxolite veins."

Jan 1, 1984

By O. Benavente, M. C. Hernández

Selenium is obtained mainly from copper anode slimes, which is a by-product of the copper electrorefining process. Selenium is present in copper anode slimes as silver and copper selenides. Traditionally, selenium has been obtained by pyrometallurgical processes; however, hydrometallurgy has now been incorporated either full or partial to the conventional process. Some hydrometallurgical processes are been developed and used at laboratory level an industrial scale. This document describes theoretical background and results of characterization and dissolution of selenium from a decopperized anode slimes in an alkaline oxidizing system. The results have indicated that the oxidizing leaching process reaches a practically complete dissolution of selenium (up to 90 %); the undissolved portion is due to the generation of a AgCl around the particle surfaces that delays the progression of the reaction. The results indicated that 90% of selenium extraction can be obtained by dissolution under moderate conditions of pH, temperature and reagent concentration in oxidizing medium. INTRODUCTION Selenium is distributed in the earth's crust in most rocks and soils. Selenium is essential, as it has wide range of applications in the medical and food industries as well as, used in semiconductor, sensors and photochemical devices. Selenium is rarely found in the native state, 90% of selenium is obtained from copper anode slimes, which is a byproduct of the copper electrorefining process (Lu, Chang, Yang, & Xie, 2015; Xiao et al., 2017; Yang et al., 2018). In anode slimes, selenium is present as an intermetallic compound, as Ag-Cu selenides. Currently, selenium is recovered from the anode slimes via hydrometallurgical and pyrometallurgical processes (Lu et al., 2015). The traditional pyrometallurgical method recovers selenium effectively, but faces difficulty as a result of increased energy costs and strict environmental regulations associated with the process (Li, Yang, Jin, Chen, & Tong, 2017). Therefore, hydrometallurgical processes are proposed in oxidizing medium such as nitric acid, alkaline leaching with sodium nitrate, wet chlorination and pressure leaching, amongst others (Hait, Jana, & Sanyal, 2012; Kim & Wang, 2010; Xiao et al., 2017; Yang et al., 2018).

Jan 1, 2019

By Greg M. Hollyer

The search for minerals in the future will be dominated by deeper exploration and the need to accurately target ?blind? deposits as more and more of the ?easy? near surface targets are exhausted. In this context, key technologies are emerging for deep exploration both in grassroots and minesite exploration, including the Titan 24 Deep Penetrating geophysical technology. Introduced in 2001, this technology has grown rapidly into an accepted approach for exploration in a variety of geologic environments, including brownfield environments where discovering additional reserves would most quickly benefit companies. Titan 24 belongs to a new class of sophisticated Distributed Acquisition Systems (DAS) which record high-volume, high-quality data simultaneously at multiple receiver stations. This data is then processed digitally, modeled using specialized inverse modeling software, and interpreted according to geologic and other parameters. The result is a robust, high-quality, high-volume data sets which provide a basis for improved imaging to depth. In this paper, the Titan 24 distributed technology is discussed. Illustrations of the vast improvement to overall exploration are showcased through results in several case studies. These include examples from two gold deposits, a porphyry deposit and a minesite. These examples show the range of applicability of the technology and the ability to effectively image mineralization, lithology, structure and alteration to depth as an aid to understanding prospective mineral deposits and targeting drills more accurately.

May 1, 2008

By P. A. Gonzalez Contreras

Scorodite is considered as a secondary mineral formed from the product of weathering of primary minerals by chemical or biological reactions. In the case of biological scorodite formation, microorganisms mimic and accelerate what in nature takes a very long time, i.e. biocrystallisation. The goal of the biological scorodite formation is to form very stable arsenic crystals suitable for long-term and safe disposal. The biological formation of scorodite is a novel combination of biological oxidation, biocrystallisation, and proper bioreactor design to achieve the biological formation of scorodite crystals in one step. We have explored simultaneous biological arsenic and iron oxidation at 30ºC and at 70ºC leading to arsenic-jarosite phases and scorodite, respectively. As biologically formed scorodite crystals are very stable (TCLP < 1 mg/L As (V)), the risk of arsenic toxicity is minimized when leaching takes place. This process is suitable for arsenic concentrations above 0.5 g/l As achieving up to 20 mg/l As in the effluent. This biological scorodite formation system is a selfsufficient bio-oxidation system and therefore many new applications can be explored such as reprocessing of arsenic trioxide, orpiment or calcium arsenate to scorodite crystals for a stable and safe disposal.

Jan 1, 2014

Agenda ? Where?s Victor ? What work was done to get approval to spend $982m ? a brief history ? Some project facts ? The triple bottom-line accomplishments to date ? Construction A Brief History of Victor ? 1960?s ? first sampling in area ? 1980?s ? stream samples and Victor kimberlite discovered ? 1990?s ? test / bulk samples ? 1999 / 2000 ? large bulk samples ? 2000 / 2003 ? technical evaluation through to Feasibility Study, permitting process

May 1, 2006

By J. N. Hilton, D. Moffett, E. Barnes

"A recent pilot-plant program carried out at Rio Algom&apos;s Quirke uranium mine at Elliot Lake, Ontario is described. The goal of the research was the production of tailings basin effluents which were low in total radium-226. The process tested involved precipitation of radium with barium chloride and sedimentation in plastic-lined settling ponds. Adjustment of the tailings basin overflow from its normal value of pH 9.5 by addition of sulphuric acid to about pH 7.5 was found to give approximately a five-fold improvement in total radium-226 removal. A five-month demonstration test resulted in an effluent with a mean total radium-226 activity of44 pCi/L after 2.5 days settling time and 29 pCi/L after 5 days. The results from the demonstration program are used to propose a schedule of achievable total radium-226 activities where precipitation and sedimentation are employed. The maximum suggested values for 5 days nominal settling time are: 30 pCi/L in an annual mean, 45 pCi/L in a monthly mean. 60pCiIL in a weekly mean and 80 pCi/L in any single grab sample.IntroductionRadium-226 has been removed from effluents at the Elliot Lake uranium mines since the introduction of the first barium chloride treatment system in 1965. Current practice, which has changed little over the years, consists of radium-barium sulphate precipitation by the addition of a low do se of barium chloride to the clear overflow from the tailings basin(l·2l. Provision is made for the precipitate to settle in large natural or constructed ponds and lagoons. The residence time in these ponds, which depends on the site, ranges from 3 to 35 days, with varying degrees of efficiency being achieved."

Jan 1, 1981

By R. Lovat, J. A. Hunter

"The design, development, and verification of the Lovat 7.6metre diameter full-face tunnel-boring machine is reviewed. Programmatic and technical challenges are outlined with a review of the specifications and the design to meet these requirements. Subsystem designs are presented for the waste material removal, ventilation, cutter head, structural support, advance technique, water removal, and interfaces with the Donkin-Morien Mine. The techniques used to verify that the design meets the requirements is by testing in the Lovat factory and in the field. Certification of the machine for use in a methane environment is discussed.IntroductionStudies have concluded that the average annual worldwide tunnel construction is 500 kilometres at an estimated average co st of $3,400 U.S . per linear metre. The total market value of the tunnelling industry is estimated as approximately $1.7 billion U.S. per annum. Of this, the current market for tunnelboring machine excavation is approximately $270 million U.S. per annum worldwide with a further potential of $250 million if more contractors are convinced that Tunnel-Boring Machines (TBM) are more suitable than conventional techniques. The worldwide civil tunnelling market has the potential to double each year in the next 5 to 15 years. Growth has been identified in the energy and mineral resources sectors of the economies of many nations and a significant volume of machine tunnelling studies and trials are presently underway for the extraction of coal, uranium , heavy oil or oil sand fuels, metallic and non-metallic industrial minerals and base metal or rare earth ores. Further tunnel projects for regional transportation, waterpower, irrigation , high density urban transportation, storm water sewers and water supply purposes are continually being implemented with new concepts like military security facilities and underground storage schemes being considered.Lo vat Tunnel Equipment of Rexdale, Ontario, the only Canadian manufacturer of TBMs was incorporated in 1973 to manufacture so ft ground tunnel-boring machines to satisfy this growing market demand. Lovat has produced an average of 5 machines per annum during the period 1972 - 1982 and has established an international reputation for competitive costs, quality of construction, after-sales service, and reliability. As of June 1982 Lovat TBM&apos;s have been used to tunnel over 240 km in projects throughout the world."

Jan 1, 1984

By Jerry M. Whiting, Neil J. Duncan

"Does Canada need a mining industry? Isn&apos;t it a chronically depressed collection of businesses that pollute the air and water and tear up the countryside? Wouldn&apos;t it be better if Canada&apos;s investors devoted their attention to high-technology endeavours, tourism, and other relatively pleasant tasks?Probably the answer to whether Canada needs a mining industry in the 21st century is to look at the real mining industry that is in operation today. The facts indicate that mining is a very important contributor to Canada. It has certainly encountered some challenging times during periods of recession, and it face s severe and continuing problems of cost and competition in world markets. However, uneconomic mines have been closed, others suspended, and productivity has risen dramatically with employment at 77 000, down from 101 000 in 1981. The country&apos;s metal and non-metal mines, metallurgical plants and semi-fabricated metals industries employed an estimated 378000 workers in 1986, and paid wages than any other sector of the Canadian economy. This effort resulted in the production of 60 different metals, non-metals and structural minerals valued at $13.5 billion.The trade aspects of the mining industry are of paramount importance. If there is a reason for this situation to change during the next century. it eludes the authors. Canada has the well-developed expertise to discover, evaluate, develop, operate and profit from existing and new businesses based in an enormous area endowed with a nearly unbelievable variety of mineral resources. Many countries throughout the world must rely on producers like Canada, if they are to maintain and/or improve their standard of living."

Jan 1, 1988

By T. G. Joseph

The chicken and egg scenario where adverse truck motions cause ground deterioration and poor ground profiles that in turn cause adverse truck motions is a downward deterioration spiral that dominates in our industry. If we can remove one action, the reaction must stop and vice-versa. A simple &apos;truck to excavator&apos; load data analysis and wireless communication system is outlined in this paper; that will provide visual assistance to the excavator operator in achieving improved load placement and balance in a truck body. In turn this will reduce the subsequent hauler duty cycle adverse motions and g levels that contribute to structural fatigue, higher tkph, reduced tire life and ongoing maintenance of haul roads

Nov 1, 2011

By John W. Korczak

The use of geological and grade block models has been standard practice in mine design for many years now, with a wide range of software available for creation and analysis. Although geotechnical parameters are of vital importance to mine planning there is very little in the way of commercially available systems for integrating geotechnical data into the mine planning and design process. Sirovision is a new technology developed by the CSIRO (Commonwealth Scientific and Industrial Research Organization) in Australia for automated, safe and accurate 3D mapping of geological and geotechnical features. Datamine has integrated this capability into its product range so that Sirovision has become an integral part of the day-to-day mapping, mine geology and geological / geotechnical modeling in both open pit and underground mine environments. This is the first integrated underground application of Sirovision from Datamine collaboration with Xstrata Nickel at the Nickel Rim South Project. This paper discusses the role of Sirovision in collecting the raw data required for geological and geotechnical analysis and the interpretation in a quick, safe, auditable and reproducible manner.

May 1, 2009

By David R. Lentz

At True Hill in southwestern New Brunswick, low-grade porphyry-style Bi-8n-Mo greisen mineralization is associated with the cupola of an epizonal granite porphyry (granite) that also exhibits three episodes of brecciation. The first episode of brecciation is an in situ, 8 m to 10 m wide transitional zone of net-veined to coarse-grained "blocky" endogranitic mesobreccia that is chloritized and greisenized and hosts weak disseminated minerali.zation. In a zone closer to the host rockgranite contact, angular fine- to coarse-grained endogranitic mesobreccia with greisenized matrix is superimposed on the earlier transitional breccia. The latest episode is fault-controlled and consists of quartz- and chalcedony-hosted sub-angular to rounded fine-grained "pebble" mesobreccias that crosscut and brecciate the other breccia types, as well as the adjacent altered metasedimentary country rocks. The first two episodes of brecciation are magmatic-hydrothermal in origin related to hydrofracturing of the granite carapace and are accompanied by greisenization and mineralization, whereas the post-mineralization, silica-hosted, "pebble" mesobreccias related to hydromagmatic, low-temperature fluid circulation and/or boiling along faults near the contact. These magrnatichydrothermal and hydromagrnatic mesobreccias are similar to those associated with W-Mo-Bi porphyry-greisen mineralization at the Mount Pleasant deposit.

Jan 1, 1994

By M. Pierce

Empirical relations exist for the estimation of rock block strength at scales larger than standard core sizes. Two recently published relations account for the significant impact that microflaws (pores, open cracks, veins) and weathering/alteration can have on scale effect. These relations were used to estimate the rock block strength of heavily microfractured quartzite from the Bingham Canyon Mine. Predictions were compared to the results of Uniaxial Compressive Strength (UCS) tests conducted on cylindrical core samples of varying microfracture intensity and diameter. The comparison confirms the sensitivity to microfracturing suggested by existing relations and suggests that they would benefit from more detailed consideration of microfracture strength, density and persistence over a range of scales. The results of a numerical study illustrate how Synthetic Rock Mass (SRM) modeling techniques could be used to complement empirical data in the development of such relations.

May 1, 2009

CHALLENGES TO SCHEDULE/BUDGET Shortage of people (contractors, vendor support, engineering, staff) 2007 projects off the shelf Increase in metals prices Shortage of large tires Reserve increase Size of mine Unskilled labor force Community/government relations Limited access into valley English to Spanish SOLUTION Line 1 Line 2 concurrent construction, EPCM engineering review, advance scheduling Placed line 2 orders earlier Hedged currency, bulk orders Strategic alliances Flexible design Plan Deliveries Training, multiple contractors Engagement Built/upgraded roads Technical translators

May 1, 2010

By Georgia J. Lysay

Kemess South Mine ended operations in March 2011. Final reclamation works began during operations in 2008 in anticipation of closure. The focus of reclamation during mine operations was on the inactive areas of the tailings dam, waste rock dumps, and expended borrow areas. The general reclamation strategy for the Kemess Mine site marries long-term erosion control with successional reclamation principles. For disturbed areas, this requires application of growth media, proper preparation of surfaces, and introduction of native pioneer plant species to initiate successional processes of recovery. Tailings are retained behind an earthfill dam of approximately 140 m in height, with a crest length in excess of 1 km. Reclamation activities at the dam have included placement of growth media, specialized surface preparation and construction of diversion ditches. The final closure spillway is currently being constructed, with completion scheduled for summer 2011. The two main waste rock dumps contain segregated non-acid generating (NAG) waste rock and potentially acid generating (PAG) waste rock. Resloping of the NAG dump for long-term stability commenced in 2009, followed by placement of growth media and ground preparation. The PAG waste rock will be fully relocated into the expended open pit for final, permanent subaqueous disposal.

May 1, 2011

By Robert Marchand

_ North-western Quebec _ Bousquet mining district _ 21 M oz mining camp _ 100,000 t/yr (400 t/d) _ Shrinkage : 52 % _ Longhole : 40% _ Development : 8% _ 5 days/week _ 120 employees _Discovered in 1936. _12 changes of ownership. _Exploration & development : 1987 _Commercial production : 1990 _Shaft deepening : 1995 _Internal shaft : 1999

Oct 1, 2001

By J .. R. Brown, G. Deschenes

X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD) and Electron Probe Micro-Analysis (EPMA) were used to characterize chemically the gold complex adsorbed on activatedcarbon from a solution containing 102mglL Au and 0.5 giL thiourea. This paper also considers the gold chloride and the gold cyanide systems. The results indicate gold is adsorbed on activated carbon from the thiourea solution as the gold (I) thiourea complex, i.e. Au [CS (NH) 2];&apos; Other gold species such as metallic gold were not detected on the carbon support. These results also suggest the elution of the gold (I) thiourea complex can be performed with high recovery.

Jan 1, 1993

By H. Clare Horwood

"Two structures, a fracture zone and a shear zone, contained the two orebodies that yielded all the ore mined at the Gold Eagle mine. The orebodies are known as the Gold Eagle vein and the No. 1 shear zone. Both structures occur close to contacts between Timiskaming sediments, Algoman diorite, and later Algoman granite-granodiorite. The structures were produced by compressive forces from a south direction acting in the southern part of the McKenzie-Gold Eagle stock and in a cylindrically shaped inclusion of Timiskaming sediments.The mine, which exhausted its ore reserves and ceased operations in September of 1941, is on the east side of Mackenzie island, in the centre of Dome township in the Red Lake area.The Gold Eagle vein was located during the summer of 1933 by a surface exploration programme carried out under the direction of Alex Gillies. Sub-· sequent diamond drilling and underground exploration led to the installation of a mill, which came into production in October of 1937. The No. 1 shear zone was discovered and explored later from a drive on the 500-foot level. The mine produced a total of 40,204 oz. gold and 19,157 oz. silver from 223,628 tons of ore hoisted (180,095 tons milled) during its 4 years of mill operation.GENERAL GEOLOGYThe ore-bearing structures trend S.61°E. across Timiskaming greywacke, Algoman diorite, and later Algoman granite-granodiorite. The greywacke is a large, cylindrically shaped mass that is separated from the mai~ mass by the later intrusives. It is a massive, light-coloured, quartzose variety that has been recrystallized by the enclosing granite. The diorite and the granite-granodiorite are early and late components of the McKenzie-Gold Eagle stock. The diorite, which is a porphyritic rock containing large crystals of andesine-labradorite surrounded by hornblende, was injected early in the Algoman period. It was intruded and in large measure surrounded by the later granite-granodiorite. This rock varies from a granodiorite near the mine to a granite in the centre of the stock. All three intrusions are massive and homogeneous."

Jan 1, 1954

By Robert Cameron, Colin Ashton, John MacNeil, Leo Piciacchia

"The in pit dam construction and utilities relocation, known as the East Mine Corridor Relocation (EMCR) project, was developed to extend the life of the east side of the Base Mine pit by two veal&apos;s. This will result in the recovery of an additional 80 million barrels of oil and delay expenditures associated with the opening of the North Mine by two years. To accomplish this, a large in pit earth structure was required to provide a new embankment foundation for relocating a public highway, four powerlines, a natural gas back-up pipeline, a substation, and a conveyor train. This structure would also he required as a temporary dam 10 contain mature fine tails on the west side until mining is completed in the east mine corridor area, that will then be filled with fluid.The in pit dam, known as The Highway Berm, is 2.5 km long, 63 m high and has 42 million m3 of engineered soil added to the already existing end-dumped soil volumes. To complete the design and construction of a structure of this magnitude, in the very short time frame of two-and-a-half years, presented many new challenges. The main challenges faced were: designing while construction was ongoing; designing without the use of clay cores or sand filters; using relatively non-select overburden material; proper dewatering and base preparation; changing from construction of 50 m high spoil piles to a high specification construction operation; compacting lifts with heavy haulers; constructing during the winter; and monitoring movement of the structure with satellites."

Jan 1, 1995

By Mehmet F. Taner

"The East Sullivan Stock (ESS) is a small, composite felsic alkaline pluton of presumedlate Archean age in the Val d’Or mining district. Three main facies have been distinguished: mon-zonite sensu stricto, porphyritic monzonite, and green trachytic porphyry. This monzonitic group ofrocks is of relatively homogeneous composition with high abundances of Na2O, K2O, Ba, Sr, Rb, Zr,Mo and LREE. The alkaline ESS is distinguished from other igneous units in the Val d’Or miningdistrict, such as the Bourlamaque Batholith, by relatively high concentrations of Ba, Sr, Rb, Mo, Cuand Au. The ESS hosts many base (Cu, Mo) and precious (Au) metal occurrences, including: (1)porphyry style Cu-Au-Mo disseminated sulfde deposits, (2) Cu-Au deposits in volcanic rocks near the ESS contact, and (3) pyritic gold mineralization in east-west trending shear zones. The ESS is well defined by concentrical zoning on the aeromagnetic vertical gradient color map, and displays four linear trends, which are assumed to be structural lineaments, at 035°-055°, 320°-300°, east-west, and north-south. The main mineral occurrences related to the stock display a preferred spatial association with the east-west linear magnetic trends.The ESS is preferentially located along a major structure and was emplaced late in the evolutionof the Abitibi subprovince like other felsic alkaline plutons. This stock is similar to late-tectonic min-eralized felsic alkaline intrusions of the Kirkland Lake and Larder Lake mining districts in Ontario, and to the Allard stock in the U.S.A. which is associated with gold and base metal mineralization. Similarities also exist with younger alkaline plutons associated with Cu-Mo-Au porphyry deposits in the Canadian Cordillera, which formed in tensional tectonic environments. The felsic alkaline magmamay have formed by partial melting of deeply buried supracrustal rocks, concomitant with the development of deep fractures such as the Cadillac Fault. In such an environment, hydrothermal solutions carrying remobilized metals from deep supracrustal rocks may have deposited gold and base metals in structural traps. Plutons similar to the ESS should be good targets for mineral exploration. Copyright © 1996 Canadian Institute of Mining, Metallurgy and Petroleum."

Jan 1, 1996

By Stephen C. Tadolini

"The use of a torque wrench to establish the amount of actual load developed on an expansion anchor bofting system dates back to work completed in the early 1950s. The advent of ultrasonic measurement systems and hydraulic torque wrenches has made it possible for the U.S. Bureau of Mines to perform torque-tension measurements in the laboratory and the field much more accurately. The results indicate that the amount of initial boft preload may be overestimated by amounts in excess of 45% of the expected load using torque wrenches. This inaccuracy is primarily due to the friction that occurs between the bearing plate and the head of the boft. These parameters become extremely important when the support system is being used to prevent joint members from slipping relative to each other or when the boft acts as a heavy spring to clamp two or more sections together. Methods to overcome the frictional losses are presented in conjunction with a laboratory method to determine the actual torque-tension ratios for expansion anchor and combination bolting systems.IntroductionMechanically anchored roof bolts have been widely used in the mining industry since their introduction in 1947. Estimates made in 1989 indicate that out of 85 million fixtures, approximately 49 million bolting fixtures still use applied tension to complete the reinforcement necessary to maintain stable openings. Nearly 85 million bolts are used yearly. The most widely used bolt is the resin-anchored headed rebar, followed by standard mechanical roof bolts, specialty bolts (mechanically anchored, resin enhanced fixtures) , and combination bolts . Po st-tensioned resin rebars, combination systems, and friction stabilizers make up the remaining 10% of the units used (Fig. I).For mechanical, combination, and tension rebar bolts, the bolt tension is the primary means of reinforcing the roof, but in many cases, because of poor installation procedures, the bolts are ineffective. Mine operators recognize the importance of proper installation procedures. Long-term bolt tension measurements are required in the Code of Federal Regulations (CFR)In each bolting cycle, the actual torque or tension of the first tensioned bolt installed with each drill head shall be measured immediately after it is installed. Thereafter, for each drill head used, at least one roof bolt out of every four installed shall be measured for actual torque or tension. If the actual torque or tension of any roof bolts measured is not within the range specified in the roof control plan, corrective action shall be taken."

Jan 1, 1991