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By J. D. Miller, P. L. Sibrell

The nature of surface sites for the adsorption of gold from alkaline cyanide solutions has been investigated using samples of synthetic, highly-oriented pyrolytic graphite (HOPG). This HOPG material offers an idealized graphite structure enabling the independent study of the graphitic basal-plane sites and the edges, or defect sites, of the graphitic planes. Radiochemical and X-ray photoelectron spectroscopic experiments independently demonstrated that gold adsorption was much higher on the edges (defects) of the graphite planes than on the planes themselves. These results suggest that site-specific adsorption is prevalent in the adsorption of gold by graphitic carbons (including activated carbon, carbon black and graphite) and that most of the favored sites are at edge defects in the graphite crystal structure.

Jan 1, 1993

By G. Konstantopoulou

Environmental degradation due to abandoned quarries is an international problem, more intense when these sites are found in urban or suburban zones, in environmentally sensitive areas or are visible from sites of special interest. Rehabilitation solutions applied worldwide, range from simple relief restoration and planting to more sophisticated site exploitation in order to serve specific social needs. The elaboration of rational rehabilitation plans for every site presupposes deep knowledge and comparative evaluation of all the parameters of the problem. In this paper, a methodological approach of rehabilitation solutions for abandoned quarry sites is elaborated, based on domestic and international experience and practice. Solutions are grouped in eight main categories. In every category the framework of prerequisites and confinements (environmental, technical, social, economic, legal) for their application in Greek quarry site is investigated. A comparative assessment of alternative restoration solutions is introduced, using tools supplied by environmental economics, cost-benefit analysis, G.I.S. and multi-criteria analysis and follows in two stages: 1) Establishment of a set of criteria aiming at a priority list for a number of quarry sites located in a geographical or administrative district. 2) Assessment of alternative solutions for every single quarry from the previous priority list for the selection of the most adequate using technical, economical, social and environmental criteria.

Jan 1, 2008

By Allan M. Hale

Taconite tailings reclamation, especially the stabilization of tailings ponds, .dams, and slopes, can be effectively accomplished through the use of appropriate vegetation. Utilizing vegetation provides both aesthetic and ecological enhancement of a site while at the same time protecting tailings structures against wind and water erosion. Generally, the methods and techniques for establishing vegetation are well known; however, there are many site-specific factors that can alter a particular reclamation approach. Those factors include slope gradient, tailings material size, solar exposure, and physical and chemical properties of tailings. In addition to the site-specific factors, variations in climate, geography, and physiography of a region can have a pervasive influence on the success or failure of a revegetation program. Both the site-specific and regional factors control reclamation planning in such areas as plant variety selection, methods and times of plants establishment, maintenance techniques, and subsequent monitoring methods. As a result of this multifactor relationship, it is important to establish a data base that identifies both the site-specific and location conditions in order to tailor the reclamation plan to the specific area. When an appropriate data base has been collected, detailing the various site-specific and regional factors that will influence a revegetation program (in the absence of previous testing), it is very beneficial to apply experimental techniques to develop the reclamation plan for a specific site. The reclamation plan for a specific site may include several techniques adapted for the differences found within the specific site as the result of topographic or other influences. Considering this, the Reserve Mining Company and Dames & Moore undertook to develop a successful reclamation plan based on a detailed test plot program conducted at the Mile Post 7 location.

Jan 1, 1980

By Van E. Housman, Stephen D. Hoffman

The Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), also known as "Superfund", requires a listing of sites that have known releases or threatened releases of hazardous substances, pollutants, or contaminants throughout the U.S. When EPA determines that a significant threat exists, it places the worst contaminated sites on the National Priorities List (NPL). CERCLA provides EPA broad authority to clean up hazardous sites that threaten human health and the environment. There are currently 52 sites on the NPL that were placed on the list because of high human health or environmental risk as a result of non-coal mineral extraction, beneficiation, or processing operations. This list covers mining sectors from aluminum to zinc. While some of these sites were abandoned, many are still operating. (There are additional mine sites that have been recently proposed to be included on the NPL that are not included in this paper.) EPA is continuing to develop a mining program to address human health and environmental threats from active non-coal mines. EPA has performed a comprehensive study to assess the waste management practices at all of the 52 mine sites on the NPL. In addition, EPA is continuing to collect information on the specific mining sectors (i.e., gold, copper) that represent many of the NPL mine sites. One of the goals of this effort is to attempt to identify the types of mining practices that lead to human health and environmental problems at the NPL mine site. EPA estimates that there are currently 500 to 1,000 active mines (not including placer operations). While some mining NPL sites began operations before the turn of the century, only a handful of the NPL mines entirely ceased operations prior to 1970. Of the 52 NPL sites studied by EPA, 12 are currently active. By definition, these mines represent current mining practices. Approximately 17 additional NPL mines that ceased operations between 1970 and 1990 represent some degree of current mining practices. Therefore, at best, less than half on the 52 NPL mine sites can be said to definitely represent past mining practices. Although some mining waste management practices have changed over time, the basic technology for extraction and beneficiation of mineral ores have remained fairly constant over the last fifty years. While the use of acid to leach copper dumps, the use of cyanide to leach gold in heaps, and the spread of solvent extraction techniques has changed some aspects of mining, the basic operation of removing ore from the ground and concentrating it through beneficiation has remained fundamentally the same as when most of the non-active

Jan 1, 1992

Previous models describing the aggregation of polymer coated particles fail to take into account the fact that there are a limited number of sites onto which a polymer segment can adsorb, called ?active? sites. Thus, the collision efficiency is a factor not only of the fractional surface coverage, but also of the number of active sites. In this study, a physical model of the flocculation system was devised in which the number of these sites could be varied, in order to study the effect on particle aggregation.

Jan 1, 1987

By A. McCombs

Previous models describing the aggregation of polymer-coated particles fail to take into account the fact that there are a limited number of sites onto which a polymer segment can adsorb, called "active" sites. Thus, the collision efficiency is a factor not only of the fractional surface coverage, but also of the number of active sites. In this study, a physical model of the flocculation system was devised in which the number of these sites could be varied, in order to study the effect on particle aggregation.

Jan 1, 1988

By K. Cothern, S. Novack, D. A. Johnson, R. Borden, S. Pavlou

A procedure is presented for ranking hazardous waste sites for remedial decisions, and an example with application to mining waste sites is discussed. Typical contaminant concentrations are calculated from field data. Exposure indices that compare these measured concentrations with allowable limits are then computed. The limits are selected to protect both the health of humans (for both carcinogen and noncarcinogen effects) and the health of key organisms in the ecological food web. The additive exposure index for a site, defined as the sum of all contaminant-specific exposure indices, is then used in ranking the sites and assigning each a priority for remedial action. One key source of uncertainty in the process is the estimation of a typical site concentration from data that include values reported as "below certified reporting limit" (BCRL). This uncertainty is compounded in the additive exposure index and therefore may have a substantial effect on the assignment of remediation priority. A general approach is presented for incorporating consideration of BCRL data into uncertainty evaluation when assigning remediation priority designators to hazardous waste sites.

Jan 1, 1992

By A. D. Davis, C. J. Webb, C. S. Johnson

The Belle Eldridge Mine is an inactive lead-zinc mine in Spruce Gulch south of Deadwood, South Dakota. Acidic mine drainage (AMD) produced at the site drains into Spruce Creek, a tributary of Whitewood Creek. The site is on U.S. Bureau of Land Management (BLM) property. Extensive fieldwork was done at the Belle Eldridge Mine through the cooperation of the BLM and the South Dakota School of Mines and Technology. The site was extensively mapped to identify physical and environmental hazards such as tailings, waste rock, collapsed buildings, adits and workings. An exhaustive search of the historical records of the Belle Eldridge Mine was conducted. Maps of the under-ground workings of the Belle Eldridge dating from the 1930’s and 1940’s were found. The maps were used to correlate currently collapsed features to old adits and tunnels. Using hand corers and a portable drill rig, waste rock, tailings and soil core samples were collected and depth to bedrock was determined and the total volume of waste and tailings pile were determined. Related work examined the hydrology of the site. The site is very complex hydrogeologically. Numerous underground and surface workings and tunnels add to the complexity. Several seeps are located at the site, one of which is producing AMD. Recharge to the site was studied, and a 100-year flood plain map was produced.

Jan 1, 2000

By Keith G. Wallace

In 1982 the U.S. Congress passed the Nuclear Waste Policy Act (NWPA) to provide for the development of an underground repository for spent nuclear fuel. This development will be managed by the United States Department of Energy. In 1986, the President selected three areas for site characterization to determine their suitability for the development of an underground repository; those sites were: 1) A site in volcanic tuff located at Yucca Mountain in Nevada, 2) a site in bedded salt located in Deaf Smith County in Texas, and 3) a site in basalt located in Hanford, Washington. At present conceptual repository designs are being developed for each site. A key element of a repository design is the underground ventilation system required to support construction, nuclear waste emplacement, and potential waste retrieval. This paper describes the preliminary ventilation system designed for the repository in tuff. The concept provides separate ventilation systems for the construction and waste emplacement activities. The paper further describes the means by which acceptable environmental conditions will be re-established to allow re-entry into previously closed rooms for the purpose of inspection, maintenance or retrieval.

Jan 1, 1987

By K. G. Wallace

In 1982, the US Congress passed the Nuclear Waste Policy Act (NWPA) to provide for the development of an underground repository for spent nuclear fuel. This development will be managed by the US Department of Energy. In 1986, the President selected three areas for site characterization to determine their suitability for the development of an underground repository. Those sites were: (1) a site in volcanic tuff located at Yucca Mountain in Nevada, (2) a site in bedded salt located in Deaf Smith County in Texas, and (3) a site in basalt located in Hanford, WA. At present, conceptual repository designs are being developed for each site. A key element of a repository design is the underground ventilation system required to support construction, nuclear waste emplacement, and potential waste retrieval. This paper describes the preliminary ventilation system designed for the repository in tuff. The concept provides separate ventilation systems for the construction and waste emplacement activities. The paper further describes the means by which acceptable environmental conditions will be reestablished to allow reentry into previously closed rooms for the purpose of inspection, maintenance, or retrieval.

Jan 1, 1988

By Warren D. MacEvoy

INTRODUCTION Good ventilation bulkheads (stoppings) can be obtained only by conscientiously adhering to four basic principles: carefully selecting the site for the bulkhead, adequately preparing the site, properly constructing and sealing the bulkhead, and checking the results with a smoke tube before leaving the area. If all these guidelines are followed during each ventilation project, a poor job will result only from the use of improper materials and cannot be blamed on carelessness or oversight. SITE SELECTION A perfectly constructed bulkhead in the wrong location can be completely worthless. Conceivably, a bulk-head in the wrong location could cause dangerous ventilation conditions that are difficult to identify and isolate. If the suggestions herein are followed, a considerable amount of work, time, and material may be saved. Perhaps the single most important step is always to select the exact site for a bulkhead before starting construction. Although the latitude in selecting a site may be limited by instructions or operating conditions, it is common to find poor bulkheads built within a few meters (feet) of a site that would have been far superior but was overlooked during the planning process. The ideal site for a bulkhead should have as many of the following features and conditions as possible: 1) To provide a solid bulkhead, the selected site should be in firm and unbroken ground. 2) To minimize the amount of work and material required and to minimize the danger of later damage to the bulkhead, the site should have as small a cross section as possible. 3) The bulkhead site should not be encumbered by interferences such as pipes, wires, ditches, wire roof supports, trash, muck piles, etc. 4) The walls and timbers of the site should be free from oil, grease, or tar that would inhibit adhesion of the sealant used on the bulkhead. 5) Unless special precautions are taken, the site should not have water seepage, standing water on the floor, or water-carrying ditches. 6) To expedite construction of the bulkhead, the site should have reasonable access to transportation, supplies, communication facilities, and compressed-air lines. 7) The site should have a reasonably level floor, allowing direction of the bulkhead door swing to be reversed at a later time if so desired. In a steeply sloping location, it may be possible to open the door in one direction only. SITE PREPARATION Once a suitable site has been selected for the bulk¬head, it must be prepared properly. All site preparation work should be completed before starting any construction work on the stopping itself. Unfavorable site conditions can be identified during the course of thepreliminary site preparation, saving time, effort, and materials that otherwise might be wasted. The follow¬ing preparation steps help assure the construction of a good stopping: 1) If wire mesh has been used at the site, a strip 457 mm (18 in.) wide should be cut and removed from the walls and roof at the selected location. 2) The exposed strip of rock should be barred down thoroughly to provide a smooth surface. 3) All obstructing materials should be removed, including old timbers, pipes, rockbolts, wires, etc. If a conduit must cross the bulkhead area, it should be located or relocated away from the floor, walls, and roof to allow a 6.28-rad (360°) seal around the juncture between the conduit and the bulkhead structure. 4) All loose muck should be cleaned from the site and a trench about 152 mm (6 in.) deep should be dug from wall to wall in the floor. The trench must be wide enough to accommodate the entire bulkhead, including the posts. 5) The rock surfaces of the walls and roof should be cleaned with a wire brush to remove as much loose surface material as possible. Thorough cleaning promotes adhesion of the bulkhead sealant to the surfaces of the walls and roof, thus promoting an airtight seal. 6) It is quite difficult to seal landing mats that cross a bulkhead. If such a crossing cannot be avoided, the bulkhead should be placed between the end and the first hole in the steel so at least one side of the bulk-head can be sealed easily and completely. That may have to be done prior to actual construction if the end is located on the opposite face from the seal coating of the bulkhead. BULKHEAD CONSTRUCTION The three principal considerations in bulkhead con¬struction are the type of bulkhead, materials to be used, and construction method to be employed. For many projects, the bulkheads are specified by the requesting agency, with no latitude for independent choice of the type, materials, or construction method. In such cases, any deviations from the specifications, for any reason, must be approved in advance by the proper department or by the project senior ventilation engineer. Types and Materials When a choice of type, materials, or method is allowed, consideration should be given to factors such as cost, required useful life, proximity to blasting concus¬sions, availability of materials, direction of permissible air leakage, and degree of airtightness required. Other factors to be considered include the amount of time available, accessibility of transportation, potential for interference with operations or production, ambient water conditions, availability of connections to com¬pressed-air lines, etc. Despite the multitude of factors to be considered, most stoppings can be analyzed easily and the proper choices can be made without much difficulty. The four common classes of bulkheads utilized in

Jan 1, 1982

By P. Arell, D. Folkes

This paper presents the basics of EPA’s Hazard Ranking System (HRS), which is used to evaluate sites for possible inclusion on the Superfund National Priorities List (NPL). The paper describes the surface water, ground water, air, and soil exposure pathways and how they are applied to mining sites. Key factors contributing to the site score include the likelihood of a release, waste characteristics, and the targets for each pathway. Waste volumes, definitions of landfills versus surface impoundments, and background concentrations are of particular importance to mining and smelting sites. Because of the presence of metals, large waste volumes, and observable releases, mining and smelting sites often receive high enough scores to be proposed for the NPL based on a single path-way. Neverthess, owners and operators can take steps to reduce the risk of being scored, and to reduce the potential for high scores.

Jan 1, 2004

By J. M. Dempsey, R. A. Litle

Asarco Incorporated’s Omaha, Nebraska refinery site and the City of Omaha’s downtown redevelopment projects are the perfect example of the marriage of the Brownfield and Sustainable Development strategies. Nebraska’s largest voluntary site remediation project created a focus point for redevelopment and has spurred over $1 billion in economic investment within a 1-mile radius of the site. Asarco was faced with options of very expensive and uncertain facility upgrades or a shutdown. Local leaders, Asarco, and regulators worked together to convert a controversial and complex site to a park-like redevelopment area with numerous long-term benefits to the City and the environment.

Jan 1, 2004

By A. C. Lyons

The presentation describes the history, preliminary report, site investigation, including examination of old records, design of tunnel including choice of levels, alternative linings and working sites, the preliminary contract involving shaft sinking on the site of the Tower Block; design modifications, the main contract, including shaft sinking, ground treatment, compressed air installation, machine tunnelling, tunnelling enlargements for chambers, waterproofing and equipment.

Jan 1, 1981

By A. D. Davis, C. J. Webb, C. S. Johnson, J. L. Porter

The abandoned Belle Eldridge Mine near Deadwood, South Dakota, is on land controlled by the U.S. Bureau of Land Management (BLM) property. The mine produced primarily lead and zinc during the first half of the twentieth century. The BLM has expressed concern about acidic drainage as well as elevated arsenic levels in tailings and waste rock at the site. The mine site was evaluated for remediation in 1998 and 1999. Recent reclamation and remediation work included substantial regrading of waste rock, removal of material where metal loading were of concern, and re-routing of drainage from an adit. Trenching at the site shoed a greater volume than originally calculated during site characterization. Material was removed to a repository that was constructed at a nearby drainage divide. Because of physical hazards, the BLM has decided to remove some historic structures. However, a search of mine records and an inventory of archival materials were complete to preserve the history of the site.

Jan 1, 2002

By L. H. Michaud

A mining company plans to extend its surface coal-mining operations in central Pennsylvania. Although the proposed site contains pyritic material, the results of the acid-base accountings for the site shows an overall Neutralization Potential to Maximum Potential Acidity Ratio (NP:MPA) of 4.26:1 for the entire site. The pyritic material is, however, associated with the lower of the three seams to be mined. If traditional dragline-mining methods are used, this would result in the acidic material being placed at the top of the spoil piles, exposing it to air and water, and therefore to the formation of acid mine drainage (AMD). Further concerns are associated with the fact that the alkaline material is not distributed evenly over the mine site. To prevent the formation of AMD, the company has proposed to mine the area using truck-shovel mining methods. This technique offers a more flexible alternative for cut sequencing and for the selective placement of waste material. Working with the Department of Mineral Engineering at The Pennsylvania State University, amine plan was developed for this site. This plan results in the layering of the alkaline and acidic spoil to achieve an overall net alkalinity in all spoil areas. Therefore, mining this site should not result in the formation of AMD.

Jan 1, 1996

By J. Simmons, P. Ziemkiewicz

Acid-Base Accounting (ABA) is an analytical procedure that provides values to help assess the acid-producing and acid-neutralizing potential of overburden rocks prior to coal mining and other large-scale excavations. This procedure was developed by West Virginia University scientists during the 1960s. After the passage of laws requiring an assessment of surface mining on water quality, ABA became a preferred method to predict post-mining water quality,and permitting decisions for surface mines are largely based on thevalues determined by ABA. In order to predict the post-mining water quality, the amount of acid-producing rock is compared to the amount of acid-neutralizing rock, and a prediction of the water quality at the site (whether acid or alkaline) is obtained. We gathered geologic and geographic data for 56 mined sites in West Virginia, which allowed us to estimate total overburden amounts, and values for maximum potential acidity (MPA), neutralization potential (NP), net neutralization potential (NNP), and NP/MPA ratios for each site based on ABA. These values were correlated to post-mining water quality from springs or seeps on the mined property. Overburden mass was determined by three methods, with the method used by Pennsylvania researchers showing the most accurate results to actual overburden mass. A poor relationship existed between MPA and post-mining water quality, NP was intermediate, and NNP and the NP/MPA ratio showed the best prediction accuracy. In this study, NNP and the NP/MPA ratio gave identical water quality prediction results. Therefore using NP/MPA ratios, values were separated into categories: <1 should produce acid drainage, between 1 and 2 can produce either acid or alkaline water conditions, and >2 should produce alkaline water. On our 56 surface mined sites, NP/MPA ratios varied from 0.1 to 31, and six sites (11%) did not fit the expected pattern using this category approach. Two of eight sites with ratios <1 did not produce acid drainage as predicted (the drainage was neutral), and four of 40 sites with a ratio >2 produced acid drainage when they should not have. These latter four sites were either mined very slowly, had non-representative ABA data, received water from an adjacent underground mine, or had a surface mining practice that degraded the water. In general, an NP/MPA ratio of <1 produced acid or neutral drainage sites, between 1 and 2 produced mostly alkaline drainage sites, while NP/MPA ratios of >2 produced alkaline drainage with a few exceptions. ABA is a good tool to assess overburden quality before surface mining and to predict post-mining drainage quality after mining. The interpretation from ABA values was correct in 50 out of 52 cases (96%), excluding the four anomalous sites, which had acid water for reasons other than overburden quality.

Jan 1, 2003

By L. H. Michaud

An existing mining company plans to extend their surface coal mining operations in central Pennsylvania. Although the proposed site contains pyritic material, the results of the acid-base accounting for the site show an overall NP:MPA ratio of 4.26:1 for the entire site. The pyritic material is, however, associated with the lower of the three seams to? be mined. If traditional dragline mining methods were used, this would result in the acidic material being placed at the top of the spoil piles, exposing it to air and water, and therefore to the formation of Acid Mine Drainage (AMD). Further concerns are associated with the fact that the alkaline material is not distributed evenly over the mine site. In order to prevent the formation of AMD, the company has proposed to mine the area using Truck/Shovel mining methods. This technique offers a more flexible alternative for cut sequencing and for the selective placement of waste material. Working with the Department of Mineral Engineering at The Pennsylvania State University, a mine plan was developed for this site. This plan results in the layering of the alkaline and acidic spoil in order to achieve an overall net alkalinity in all spoil areas. Mining of this site should therefore not result in the formation of AMD.

Jan 1, 1994

By R. David Williams

Old mine workings are found throughout the Western United Sates on lands administered by the U.S. Bureau of Land Management (BLM), U.S. Forest Service (USFS) and private lands. Some of these mine workings date back to the late 1800s. There may be as many as 100,000 sites on lands administered by the U.S. Forest Service and Bureau of Land Management. The Bureau of Land Management has worked with the State of Montana and other agencies to identify and prioritize these sites on BLM administered lands. Following completion of the AML inventory work, the Bureau began an aggressive program to clean up priority sites. This presentation will highlight completed work as well as work in progress on several sites.

Jan 1, 2000

By P. Nelson, R. O’Connell, J. Rostami

Tunnel boring machine (TBM) system utilization is a critical factor for predicting machine performance. The process of estimating machine performance, including rate of penetration (ROP) and machine utilization (U) must incorporate an understanding of site geology, TBM specifications and site management. The study herein presents a preliminary analysis of the different activity time and downtime components from hard rock TBMs at two project sites to evaluate their impact on machine utilization. A comparison of crew experience, first between shifts and then between projects is included to analyze its effect on utilization and downtime. This work presents the sensitivity of the utilization factor to selected activities in the projects and the impact of geology and site set-up/logistics on machine performance.

Jun 13, 2021