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By N. Sahin, M. Can, Z. Ekmekçi, Y. Öztürk, Ö. Biçak, I. B. Çelik, B. Kocabiyik

"In this paper, a case study from Çayeli Bakir Isletmeleri A.S. (Rize, Turkey) about the selective flotation of copper minerals from sphalerite is discussed. Çayeli Cu-Zn Sulfide Ore contains different ore types, such as yellow ore, clastic ore, bornite-clastic ore, bornite-yellow ore, and black ore. For some of these ore types, selective flotation of copper and zinc is very difficult presumably due to presence of secondary copper minerals such as bornite, chalcocite and covellite, and also surface oxidation. These factors affect Cu-Zn selectivity due to activation of sphalerite particles in the ore during the process. The main objective of this work was to improve Cu-Zn selectivity by optimization of the pulp chemistry for different ore types of Çayeli ore. After preliminary flotation tests investigating effects of different chemical conditions, a plant survey was performed to determine the plant performance and sources of the problems when problematic bornite-clastic ore is treated in the plant. Various chemical conditions are tested in the laboratory scale test for better depression of sphalerite in copper flotation circuit. Combination of Na2S+ZnSO4+MBS was found to be the most effective depressant scheme. INTRODUCTION Ore variability is one of the most important factors affecting performance of a process plant both in short and long term planning. The geometallurgical modelling becomes a common tool to determine ore variability problems and develop the most efficient solution during life of mine (1, 2). Flowsheet design and equipment selection and sizing are usually done based on the results of ore variability test works. However, in some cases ore variability may not be foreseen during the design stage and therefore the solutions should be developed based on the existing flowsheet and equipment in the plant. In this situation, ore characterisation, problem statement and diagnostic testing should be applied step by step. The problem could be due to changing feed grade, mineralogical characteristics, grindability and surface characteristics when flotation is involved. The variability in feed grade with fixed mineralogy can be handled with relatively simple modifications (i.e. adjusting throughput or equipment capacity) in the plant. Variability in ore mineralogy is the most complex and difficult problem to tackle. Because, mineralogical variations could bring variations in mineral composition, texture and liberation. These variations can potentially lead to the variations in grindability of the ore and flotation behaviour. Variations in grindability are usually managed by optimization of operational parameters in grinding circuit, as it would be costly to replace the existing equipment in the circuit (3). The variations in flotation behaviour are mainly due to variations in mineral types and distribution, texture and surface oxidation. One or all of these factors could be observed in a flotation operation. Therefore, a comprehensive investigation both in plant and lab scale should be conducted for definition of source of the problem. The testwork to solve the problem and retrieve the performance is planned and conducted depending on the source of the problem (4, 5)."

Jan 1, 2017

By Garry W. Warren

The electrochemical oxidation of chalcopyrite in the absence of-a chemical oxidant was studied in ammonia/ammonium sulfate solutions by anodically polarizing electrodes prepared from massive chalcopyrite. The effects of pH, cupric and ammonia ion concentration were systematically evaluated. Kinetic parameters were obtained from the anodic charge-transfer regions of the anodic polarization curves. Increasing ammonia and hydroxyl ion concentrations increased the rate of oxidation. A mechanism is proposed which explains the first order dependence of (NH3) and (OR) associated with a single electron transfer process. An empirical relationship which accurately describes the dependence of the rest potential (i.e. zero current potential) on solution composition is also given.

Jan 1, 1978

By R. Bishop, J. Baggett, J. Monsalve, J. Hole, N. Ripepi, A. Abassi

This work focuses on the operational and safety issues associated with karst voids in large opening underground mines. Issues include water inrush, structural instability, and engineering uncertainty in these environments. Coupled with the fracturing prevalent in folded sedimentary rocks, karsts are complex and challenging ground control risks. Traditional methods of predicting karst locations, such as probe drilling, are impeded by the inconsistent spatial distribution and variable sizes of the features. Ground penetrating radar (GPR) is a geophysical technique that transmits radio waves into a medium and subsequently detects reflected waves via a receiver. The travel time and energy of received signals are then processed and interpreted. The difference in material properties between limestone and open karsts causes strong reflections. GPR is frequently used as a geophysical surveying technique in several industries, however there is a lack of published research on underground mining GPR applications. The purpose of this work is to prove the viability of GPR in underground stone mines for karst detection, and to discuss the importance of karst detection ahead of mining. INTRODUCTION The Mine Safety and Health Administration (MSHA) currently lists 116 active underground stone mines in the United States, the vast majority of which extract limestone for crushed stone products. These limestone mines have the potential to encounter karst voids at some point in their operation, as most karstic regions of the United States develop in limestone rock masses (Kuniansky, Weary, & Kaufmann, 2016). Karsts, the cavities formed by the dissolution of carbonate rock, have long plagued the mining and tunneling industries, as well as been a hindrance on the Earth’s surface, producing sinkholes and ruining otherwise valuable land for construction and public use. The impact of karsts on the Gavarres tunnel in Spain is well documented by Alija et al; constant instability conditions, material spills into the tunnel, and unexpected cavities seriously delayed the project deadlines and “were not foreseen in the design” (Alija, Torrijo, & Qunita-Ferreira, 2013). At the water supply project in Sohngua River, China, Bin et al detail the presence of both water and sediment filled karsts which are sources of disastrous conditions at this tunnel (Bin, et al., 2017). A hydrological tunnel in Lebanon encountered numerous massive karsts in the tunneling path which required remediation via friction anchors, rockbolts, welded wire fabric, channel steel arch segments, invert steel beams, and shotcrete (Leech, Jaoude, & Ghanem, 2008). From a design standpoint, rock mass classification schemes, such as the RMR from Bieniawski and the Q-system from Barton, are not able to represent the true nature of a karstified carbonate rock mass, and therefore complex case-by-case analyses of underground conditions are necessary (Andriani & Parise, 2017).

Jan 1, 2019

Factors which cause thiourea consumption in gold-leaching systems include adsorption by gangue mineral particles, complexation with base metal ions, thermal degradation, and oxidation by air/ferric iron. Of these factors oxidation by ferric iron is the most significant factor. Of course, ferric sulfate is desired as an oxidant for the gold leaching reaction, but an excess of ferric sulfate leads to high thiourea consumption. In this regard, the rate of gold leaching by thiourea must be balanced against the rate of thiourea decomposition. It is important to note that the thiourea decomposition reaction in ferric sulfate solution is relatively slow in pure solutions and has been found to be first order with respect to both thiourea concentration and total ferric iron concentration. However, when mineral particles from gold-bearing ores or concentrates are present, the decomposition rate can become quite significant. As might be expected, the catalytic activity of mineral surfaces varies with particle composition and size. Experimental results are discussed with respect to the consumption of thiourea.

Jan 1, 1997

By Hesam Dehghani, Farid Alimohammadnia, Nima Babanouri, Mokhtar Kalhori

In open-pit mining, blasting pattern design is performed to achieve a desired degree of fragmentation for loading, hauling, and crushing operations. Inappropriate fragmentation of rock will result in numerous problems such as incurring extra costs for secondary blasting, production interruption, etc. Wetness of the blast holes is one of the most important factors, which can cause the inappropriate rock fragmentation. Lowering ambient temperature in the vicinity of the explosion, the presence of water in the hole adversely affects the quality of the explosive while dissipating part of the explosion energy, ending up with inappropriate fragmentation problems. In the present research, in order to study blast-induced fragmentation conditions in Baba-Ali Iron Ore Mine, three scenarios were considered: explosion of ammonium nitrate with fuel oil (ANFO) in dry hole, explosion of ANFO in wet hole, and explosion of the emulsion in wet hole. For this purpose LS-DYNA, a numerical simulation code was used. Results of the present research showed that, compared to the explosion of ANFO in wet hole, the explosion of the emulsion produced more uniform distribution of fragment size, while the explosion of ANFO in dry hole resulted in fewer large fragments.

By S. Chatterjee

Mining represents the first industry in the United States to have federally mandated training for its workers. Although the topics to be covered are specified in 30 CFR 48, course content is left to the discretion of the individual mine operators. Unfortunately, certain topics to be covered, such as prevention of accidents, are usually mine specific, making it very difficult to use the same course content in every mine. Further, training requirements may change from one mine to another, due to changes in the demographic characteristics of the workers, or changes in job and organizational characteristics. Therefore, if the intention of safety training is to modify the behavior of workers, it is expected that there should be some changes in the content of safety training programs in order to address the specific requirements of individual mines, or at least mines of similar worker and job characteristics. This study has been directed towards the development of a systems-based procedure for conducting a needs analysis. A special effort was made to understand the psychology of worker behavior by analyzing worker reactions to various organizational and job characteristics.

Jan 1, 1994

By C. F. Johnson

Nearly all of the sulphur produced in the world today is converted to sulphuric acid and 49 % is used in the manufacture of fertilizers. In the last few years we have seen the beginning of another chapter in the volatile history of sulphur as the severe shortage of 1963:-67 has been transformed into present-day surplus. Prospects for further aggravation of this situation in the years ahead seem assured. In 1970, western world production showed a rate of increase of 4 -5%, which 1S somewhat less than that of 8% for the period 1963-1967. The rate of growth of consumption dropped considerably in 1968 when the demands of the fertilizer industry fell. During the same period of time, wide-spread demands have been set in motion for a clean environment which indicates that a fundamental change in sulphur supply, demand, and even sources, is likely to result from this upheaval. The sale of sulphur by Poland to the western world has increased and for 1970 was estimated at over one million metric tons. In the next few years, increase in Canadian sulphur supply will stern from two sources;

Jan 1, 1972

Coal has traditionally been an integral part of life in Kentucky. Coal mining produces a large part of revenue for the Commonwealth of Kentucky and provides a significant number of jobs to the residents of eastern (less in western) Kentucky. Recently, however, the coal industry of Kentucky has had to endure many hardships. The Clean Air Act set forth sulfur dioxide emission standards which have severely affected much of the coal mining industry in Kentucky, because much of the coal mined in Kentucky has a high sulfur content. In this paper, the background around the effects of Clean Air Act on the coal industry is introduced. The economic and social effects of the Clean Air Act on the Kentucky coal mining are addressed.

Jan 1, 1993

By Wilson Blake

The occurrence of rock bursts in some deep mines throughout the world constitutes a severe operational hazard. In addition to endangering the safety of the miners, the rock-burst problem is a major factor in mining economically in deep mines because of the loss of production and expense owing to cleanup and repairs following a burst. Developing means of controlling or eliminating rock bursts has been the subject of intensive research for over 50 years. While much has been learned about the effects of rock bursts, little is known about their basic causes; hence, control measures have been at best only partially effective--attested to by the number and severity of bursts that continue to occur throughout the world each year. In the Coeur d'Alene mining district of north Idaho, the rock-burst problem continues as the silver and lead veins persist at depth. These veins are presently being mined at greater than 7,000 feet below the surface and will be mined to some 10,000 feet in the future. The majority of rock bursts in this district occur in pillars. While pillar bursting has been essentially eliminated in some deep-mining districts by longwall techniques, modification or application of this technique to the thin, irregular, and near vertically dipping veins of the Coeur d'Alene district has not been found to be practical. The creation of pillars is a consequence of the horizontal cut and fill mining method used. Figure 1 shows a vertical longitudinal projection of the silver vein at the Galena mine, illustrating the mining method. Stoping progresses between raises and is carried upward between levels. A horizontal pillar is created as a stope approaches a mined-out level. Recent broad-band micro seismic monitoring of rock-burst-prone stopes by the Bureau of Mines has shown that potential burst zones could be delineated weeks in advance of a burst and that a definite sequence of events took place prior to the occurrence of a pillar burst (1). Hence, time was available for control measures to be effected when a stope pillar reached a critical burst geometry.

Jan 1, 1971

By T. McCallum, C. Cooper, C. Lewis

"Following a successful solvent extraction (SX) pilot plant demonstration in 2016, CYANEX® 600 has been used commercially to recover molybdenum from concentrate leach liquor since March 2017. Consistent with the piloting results, the commercial plant has achieved expected molybdenum recovery, a significant reduction in base consumption, and a step-change improvement in physical performance. This paper highlights the optimization activities and plant performance from startup through normal operation. INTRODUCTION Historically, tertiary amines have been the most commonly used extractant for molybdenum and rhenium recovery. Tertiary amines utilize a protonation of the ligand combined with an anion exchange mechanism as proposed in equations (1-2). R3N + H+ ???R3NH + (1) 4R3NH+ + Mo8O264- ???(R3NH+)4Mo8O264- (2) In addition to the transfer of Mo and Re, the amine transfers acid and other anions to the strip liquor. The undesirable transfer of other species increases base consumption during stripping, impacting operating costs. Additionally, lower solubility of molybdenum-amine complexes create operational challenges, resulting in diminished physical performance. The presence of colloidal Si in concentrate leach liquors and the formation of Pickering Emulsions adds to the physical plant performance challenges with the amine extractant. CYANEX® 600, a phosphinic acid-based extractant, uses a cation exchange mechanism proposed by equation (3). 2(H2R2) + MoO22+ ??(HR2)2MoO2 + 2H+ (3) The cationic exchange mechanism eliminates chemical transfer of acid and other anionic impurities and avoids some of the physical challenges of the amine extractant (emulsion and 3rd phase formation). In addition, the reagent offers high selectivity for Mo over Re, which may be desirable in certain moly pressure oxidation (POX) flowsheets. Alkali base (ammonium hydroxide, sodium hydroxide, sodium carbonate, etc.) is used for molybdenum stripping. Therefore, reduction or elimination of chemical acid transfer from extract can significantly reduce base consumption in strip. Extensive laboratory and pilot plant testing was completed to evaluate the use of CYANEX® 600 for molybdenum recovery at Freeport-McMoRan’s Bagdad operation. The test work and pilot demonstration confirmed a reduction in base consumption along with improved selectivity. In addition, the evaluation highlighted a step-change improvement in physical performance over the incumbent amine extractant. The decision was made to convert the commercial operation to CYANEX® 600 in March 2017."

Jan 1, 2018

By Richard H. Oitto

With increased interest and urgency for coal mine safety and the passage of the Federal Coal Mine Health 'and Safety Act, the Bureau's research effort in roof control has been greatly expanded. One new project, the subject of this paper, concerns improving conventional roof bolting and has been involved with the effects of different variables on the performance of roof bolt expansion anchors. These include types of expansion anchor, rock type at the anchorage horizon, borehole roughness, rate of torquing a roof bolt to set the anchor, installed tension, bolt length, and relative humidity fluctuations. For this work, two types of experiments were carried out. One was concerned with tension loss in bolt-anchor assemblies and simulated anchor performance in a static roof. The other dealt with anchor slippage as tension was increased and simulated anchor performance in an active roof. Trials were made in the laboratory under controlled conditions so that factors suspected of affecting expansion anchor performance could be selectively studied. Because of the natural variability in rock and the fact that most expansion anchor components are essentially rough castings or forgings, the experiments were designed to permit using analysis of variance techniques for analyzing data. Thus, in this paper, "significant" means statistically significant.

Jan 1, 1972

By Jordan Hoover, Erika Moonin, Chuck George

"In response to a severe regional drought and in preparation for the further decline of water levels in Southern Nevada’s Lake Mead, the Southern Nevada Water Authority (SNWA) built a new intake system to ensure water supply to Las Vegas and its surrounding communities. In 2015, design began on the Low Lake Level Pumping Station (L3PS) that will move the water from this lower intake, ensuring operability of the water delivery system despite these declining lake levels. The L3PS Project includes a 159-meter-deep shaft, a large underground chamber, and 34-each 152-meter-deep, 2.4-meter-diameter drilled well shafts to be constructed in highly faulted and fractured ground. The Construction Manager at Risk (CMAR) delivery method was chosen to facilitate early contractor involvement in the design process to address the significant challenges and risks anticipated on this US$650 million Project. This paper describes the CMAR selection process; the CMAR involvement during design and benefits resulting from that involvement; and the unique collaborative effort among the owner, engineer, program manager and CMAR used to evaluate and select the best design approach, preferred underground construction methods, and coordinated geotechnical baseline report. PROJECT BACKGROUND AND NEED Seven of the United States’ western states rely heavily on the Colorado River and its tributaries for their water supply. The primary source of water for the Colorado River is winter snow that falls in the mountains ringing the Colorado River Basin. Flows in the Colorado River vary significantly from year to year, depending on the amount of snow and rain deposited in the basin. Beginning in the year 2000 and continuing to the present, snowfall has been well below documented historical averages and Colorado River flows have diminished."

Jan 1, 2016

By T. S. Golosinski

Use of contractors to excavate, load and haul mined material is widespread in Australia. It is also becoming a common practice in many other countries. The paper reviews current practices in Australian contract mining. Various types of contracts are reviewed, including partnering arrangements and alliancing between the contractor and the mine owner. Applicability of various types of contracts to specific mining situations is discussed, as is their impact on overall mine performance

Jan 1, 1998

By N. Kuyucak

While Acid Rock Drainage (ARD) occurs naturally, its management poses challenges especially at the decommissioned sites. Two passive systems were designed and implemented at two different decommissioned mining sites in Canada in order to treat the seepage with ARD characteristics. One seep originating from a reclaimed tailings pond was neutral mine drainage (NMD) containing circumneutral pH and dissolved metals (e.g., nickel, zinc) in elevated concentrations. The other ARD from a tailings stack showed net acid drainage characteristics with low pH and higher metal concentrations than regulated limits. Due to the different ARD characteristics occurring at each site, different types of treatment systems were designed and implemented. Both sites experience extreme winter conditions. The NMD has been treated mainly by limestone drain and aerobic systems since 1997. The acid ARD has been treated by a system consisting of an anaerobic sulfate reducing bacteria (SRB) cell, an aerobic cell and a limestone filter since 2004. As this site has no access roads, space, or power, a significant capital cost as well as sludge disposal/storage requirements would have been required to institute a chemical (active) treatment system. Both systems have been successfully treating seepage and producing a water quality year round that could comply with regulated objectives.

Jan 1, 2010

By D. Williamson

In the post war years metals analysts and statisticians have generally tracked the demand for metals in line with changes in OECD industrial production (IP) growth rates because, undoubtedly, the correlation between IP growth and metal demand was reasonable. However the correlation was exaggerated. During times of expanding IP growth metal demand increased at a faster proportional rate than IP growth. This was probably due to industry restocking in anticipation of growing demand at the start of each economic cycle. Conversely, metal demand would slacken at a greater rate than would be suggested by negative IP growth as industry destocked in order to reduce costs. Nonetheless, overall, a reasonable correlation between IP growth, over the longer term, and metal demand could be painted. Yet, although this correlation has stood well since the last world war it has been based on the fact that the bulk of the world's IP growth stemmed from the industrialized countries of the western world, latterly including Japan. The so called "developing world" was of little consequence, whilst countries of the Soviet Union and Communist Bloc were deemed to be closed, self-contained entities which, for each metal, would either be net exporters or importers. These quantities would be used by analysts to calculate the overall supply/demand equation for the western world only and to deduce whether a commodity was in shortage or surplus. It is now believed that this method of projecting total world supply and demand for raw materials is outdated and takes little account of the worldwide political changes which have occurred since the collapse of communism and the revitalization of China, albeit under a notional communist government. It is no longer appropriate to assess global balances for raw materials on the basis of three economic blocs namely, western world, developing world and communist bloc. Rather, global balances need to be projected on a global basis. In this regard, since the collapse of communism and the removal of many other totalitarian regimes, capitalist forces are at work and are attempting to satisfy, with some considerable success, the expectations of the great mass of the world's poorer people. Such people, usually located in Asia, Africa and Latin America have aspired to the same standard of living as people living in western Europe, North America and Japan. Now, with free market forces at work their aspirations will start to be met. Consequently, the demand for metals and other raw materials will now rise at a much faster rate than at any other time in the world's history. Not only will the production of raw materials have to keep pace with rising IP in the developed world but will also have to keep pace with the demands associated with the rising expectations of rapidly increasing populations in the developing world, as well as from within the old communist bloc countries. This paper sets out to argue the case that metal demand could well increase at a rate faster than the world's mining companies, governments and financiers can deliver.

Jan 1, 1997

By D. M. Hausen

A quantitative x-ray diffraction method has been developed for the analysis of alteration minerals in wallrock. Alteration data are plotted and contoured (analogous to geochemical data). Alteration trends outlined by this technique correlate closely with geochemical anomalies, and in some cases attend well beyond the perimeter of anomalous base metal values. "Monomineralic contouring," applied originally to porphyry-type mineralization, has been extended to other types of mineralization, including volcanogenic massive sulfide deposits. Equipment and techniques used in the quantitative measurement of alteration mineralogy are discussed.

Jan 1, 1978

By R. P. Fischer

Traditionally, molybdenum and vanadium have been used chiefly as alloy metals in steel. They impart similar characteristics to most steels, and to some extent one can be substituted for the other. In the United States during the 1950's the production of steel increased about 5 percent, and the reported consumption of both of these alloy metals in steel increased some 40 percent. In Europe during the 1950's the production of steel in¬creased nearly 100 percent. Data on the actual consumption of these alloy metals in European steels are not available, but production and trade records show that the European supplies of molybdenum increased about 150 percent and those of vanadium about 350 percent during the 1950's. If most of the molybdenum supplies in Europe are being added to steel, as seems likely, then the European steel industry has nearly caught up with the United State in the rate of consumption of molybdenum in steel. The vanadium supplies, on the other hand, are puzzling--unless Europe is adding mach more vanadium to steel than is done in the United States, it seems reasonable to assume that other uses are consuming moderately large quantities of this metal or that appreciable amounts of it are being transshipped from Europe. To the extent that a changing volume of supply signifies a changing pattern of use, the increased demand for molybdenum and vanadium in Europe should be of interest to domestic producers and consumers of these metals.

Jan 1, 1964

By C. B. Queja

Flexible synthetic membrane liners have become a standard facet to copper and gold heap leach pad design. While gold heap leach operations have utilized most types of synthetic liners, copper leach operations have commonly only been lined with polyethylene. The objective of this study was to determine if there are any chemical reasons why other synthetic membrane types could not be used to line a copper heap leach facility. With engineered consideration, the flexible membrane liner under the ore pile serves two purposes. The first provides a near impermeable boundary which aides greatly in the collection of the metal laden process solution. The second advantage to the flexible membrane is the almost non-permeable barrier to benefit increased environmental awareness that has led to an increase in solution containment technology. The Environmental Protection Agency (EPA) has developed a compatibility test for solutions and membrane liners. The EPA Method 9090 is intended for use in determining the chemical effects of a solution on the physical properties of the flexible membrane liner material intended to contain them. Data from these tests would assist in deciding whether a given liner material is acceptable for the intended application.

Jan 1, 1995

By Seokwon Jeon, Ho-Young Jeong

"Various numerical methods have been tried to estimate the cutting forces of a TBM disc cutter. In this study, SPH/FEM coupled method was newly employed to improve the traditional FEM analysis. The disc cutter and rock were modeled by Lagrange and SPH codes, respectively. The numerical cutting test was carried out for representative Korean rocks with different cutting conditions. The results show that the cutting forces obtained from numerical simulation had a good agreement with those from LCM tests, and that applying SPH method to rock cutting model has advantages and improvement compared to traditional FEM method. Erosion criterion and erosion limit were not required to simulate the rock fragmentation process, and the cutting forces from the numerical simulation was more stable and accurate. The results indicate that the numerical simulation can be successfully used to estimate cutting performance of a TBM. 1. INTRODUCTION Various numerical studies have been carried out to accurately simulate the limitations of linear cutting machine (LCM) tests. Numerical modelling methods have advantages comparing with full scale tests in terms of cost and time involved. Many numerical methods have been used to simulate rock cutting process by different cutting tools and the studies are summarized in Table 1.In 2D simulations listed in Table 1, because they do not take account of rolling force and horizontal rolling mechanism of a disc cutter, indenter was selected as cutting tool in their modelling. For these reason, 2D modelling is not suitable for rock cutting modelling using a disc cutter. In contrast, 3D numerical models can take account of the indentation process by thrust force and penetration processes controlled by rolling force."

Jan 1, 2016

By Seung Han Kim, Andrew Yu, Carlos Jaramillo, Chu-Chieh Jay Lin

The Penstock Access Tunnel (PAT) concrete plug is a reinforced concrete plug separating the pressure tunnels from the personnel accessible tunnels and has leaked since the first filling at the Helms Pumped Storage Plant located in Fresno County, California. A grouting program was successfully implemented in 2009 to reduce the leakage from PAT concrete plug from over 1,000 gpm to 25 gpm. Recent observations indicated increasing water leakage through new pathways, leading to a decision to execute a high-pressure grouting and waterproof membrane installation program in 2017. The high-pressure grouting and membrane installation program was successfully executed in the areas adjacent to the PAT concrete plug where most of the inflows originated and the largest hydraulic gradients are suspected to present. It reduced the leakage from over 300 gpm of inflow to less than 20 gpm.

Jun 13, 2021