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By Björn Johansson

"SUMMARY Every tunnel designer has to consider the power of water ingress when designing a new tunnel. Either you choose solutions with simple methods to divert the ingress water or a robust system with the intention that it will give gain on low maintenance costs and a long lifetime. This article describes a new method to divert ingress water in a robust way and more economical than traditional concrete lined tunnels. This system is based on a bolt grid suspending a water tight membrane, which is reinforced and covered with sprayed concrete. The method has been in limited use in Sweden since 2005 and with continuous improvement, still going on, it is now applied for the large project “Stockholm Bypass”, a 21km long highway project. TUNNEL MAINTENANCE RELATED TO WATER INGRESS The Swedish Transport Administration maintain approximately 190 various tunnels that is constructed by a number of different methods, (Swedish Transport Adm 2015). Commonly the ground conditions are good and fairly low ground support is needed. Contrary water and winter conditions can be sever, which gives high impact onto the tunnel design and in particular methods to protect against “frost and water ingress”. During a tunnels lifetime it is common that maintenance related to water ingress occurs several times and sometimes frequent occasions every year. Such maintenance costs and consequences of lost open time for the tunnel can rapidly become higher than the initial cost of the tunnel. Thereby it is obvious that spending time during design to evaluate requirements for a suitable system against water ingress is preferred. Icicles Icicles are formed when water is below freezing degrees and drips or run from an ingress point. At very cold conditions also water flows running at high velocity freeze into ice and a rapid growth can appear. If the integrity of the tunnel traffic area is interfered by icicles they urgently have to be removed before they cause an accident. Typically the tunnel or a part of the tunnel must be closed to do such maintenance. TUNNELS FROST AND WATER INGRESS PROTECTION IN SWEDEN In Sweden methods to perform “frost and water ingress protection” are primary developed for drill and blast tunnels as it is most common tunneling method. The foundation Swedish Rock Engineering Research has done a comprehensive report SveBeFo Rapport 77 that describes water and frost prevention in Swedish tunnels up to year 2005. Below is only slight description of those various methods. Lately some more attention is paid to concrete lined tunnels made by TBM since TBMs successfully built water tight tunnels in City Tunnel (Malmö) and Hallandsås Project. When environmental demands require maintained ground water levels, water tight tunnels made by pressurized concrete lining becomes more economical and on the same time also becomes protected from icicles and water drips."

Jan 1, 2016

By M. Baumann

Operating and maintaining the heavy equipment used in open-pit mining operations is an ongoing challenge for mines. Typical operations employ a combination of shovels, wheel loaders, and haul trucks to excavate and transport the material for further processing. As this is the first point of contact for the material after blasting, it is often a bottleneck of all downstream processes, thus, equipment uptime and efficiency is crucial. Automated systems for bucket tooth monitoring, payload measurement, proximity detection, and rock fragmentation analysis will be examined. The impact of these systems on operation safety, efficiency, and reliability, in real-world scenarios will be investigated. The process of managing all the above fleet of equipment in a mine can be streamlined by connecting the equipment monitoring systems to a central server. Using the central server, the distribution of this information can be automated to ensure that the right people see the data in a timely manner, improving both proactive and reactive responses to threats to safety and productivity.

Feb 23, 2014

By R. E. Vivas, J. Garcia

"INTRODUCTION Freeport-McMoRan is a leading international natural resources company that operates large, long-lived, geographically diverse assets with significant proven and probable reserves of copper, gold, molybdenum, cobalt, oil and natural gas. Freeport-McMoRan is the world’s largest publicly traded copper producer and largest producer of molybdenum. The Sierrita mine is an open pit truck and shovel operation from which copper and molybdenum are produced. An important key to Sierrita’s success lies in their ability to realize their plans in the field. In certain circumstances, the mine plans are not achieved, and the operation fails to meet its targets which is an issue revealed in reconciliation reports. This technical session discusses the methodologies and procedures used at Sierrita to monitor the implementation of the mine plans, measure the performance of the operation and reduce the variance between plan and actual. Ensuring the operation stays on target is vital so mine productivity and profitability can attain its maximum potential. PROJECT OVERVIEW The Sierrita mining complex is located in Pima County, approximately 20 miles southwest of Tucson, Arizona as shown in Figure 1. The first mining claims at Sierrita date back to the late 1800s while underground mining activities started in the early 1900s. However, open pit development of Sierrita began more than 50 years ago to become the modern mining complex it is today. In 2009, Freeport-McMoRan purchased the adjacent Twin Buttes copper mine, providing significant synergies in the Sierrita minerals district. This venture included the potential for expanded mining activities, operations growth for mining copper and molybdenum, and reclamation activity. It should be noted that in addition to copper and molybdenum, the Sierrita mine produces rhenium which is a rare and highly value metal. The ore deposit contains oxide and sulfide mineralization. The oxide ore is delivered to the leach process while the sulfide ore is routed to the crusher and mill circuit 4,700 jobs on Arizona’s economy Freeport-McMoRan partners with the communities near Sierrita to provide programs that contribute to their sustainability"

Jan 1, 2015

By C. J. Bise, P. Bucks

Central Appalachian coal reserves are a valuable natural resource in high demand, both domestically and internationally, justifying efforts to increase percentage recovery through pillaring. Unfortunately, the challenge associated with pillar extraction introduces additional safety risks during the activity. Although pillaring developed prior to mechanized mining, current technology and mining practices have made this form of mining highly modernized. However, current fatality trends suggest that work still needs to be done to control the residual risk that is not controlled by modern practices, such as those having a personnel-performance-based component. This paper investigates the application of modern coal pillaring techniques and will present a risk-management-based strategy that targets personnel-performance-based risk, in order to improve the ability of safety engineers, managers and trainers to provide training programs addressing the needs of pillaring sections.

Jan 1, 2012

By Karel Rössler, Petr Vítek

"The Ejpovice tunnels in Czech Republic were built by EPBM in soft Clyashale, and in weathered profile with low soil overburden. The segmented liner at the cross-passage openings required support, which would not interfere with the EPBM clearance envelope during the scheduled pull back of the EPBM through both tunnel tubes. For that reason support frames or radial bolting could not be used. Steel rods inserted into the neighboring segments during the ring assembly, and later grouted were tested and realized as an innovative solution. The paper presents practical experience gained with the segmented liner support during cross-passages construction. INTRODUCTION An innovative solution using the grouted dowels was developed and realized for sixteen cross-passage openings of the twin Ejpovice Tunnels, whose construction was part of the railway track Rokycany – Plzen modernization. The following paper described practical experience gained with the innovative support of cross-passage openings, which was realized by short steel dowels grouted within the segments of the EPBM segmented liner. The paper is a continuation of the paper published in WTC 2015, which described the design aspects of the grouted dowels support, while the following paper concentrated on the production, and the performance of the dowel support observed during the breakout for the cross-passages openings. The connection by grouted dowels was patented by Metrostav, a.s. Company THE EJPOVICE TUNNELS CONSTRUCTION The Ejpovice tunnels construction started in 2013. The start of the high speed train operation through the tunnels was planned for 2018. The project was funded by the state government with the support of European Union funds of up to 70%.The tunnels were excavated with one EPBM (Earth Pressure Balanced Machine) with the external diameter of 9.89 m. The segmental liner inner diameter was 8.7 m, and thickness of 0.4 m. First, the South tunnel tube was excavated from the East portal, then the EPBM was pulled back through the South tunnel, and the excavation was started from the same portal for the North tube. After the South tube was freed from the EPBM excavation operations the cross-passage construction started. Due to the short time schedule, in the North tube the cross-passage construction started while the tunnel was still under construction. Therefore, the cross-passage construction was performed concurrently with the segments transportation, and with the EPBM pull-back through the tunnel. There were 8 cross-passages along the tunnels with a maximum distance of about 500 m, Fig.1."

Jan 1, 2016

By Eric Hansen, Todd Wanless, Chris Mueller, Shannon Dunne, Scott Elmer

Between 2010 and 2018, Houston added more than 1 Million residents; the third largest rate of growth in the nation. With growth, the region faces new challenges with water supply, capacity of its wastewater system, and regional drainage. While tunnel construction has been limited in Houston since the Clean Water Program of 1990s, it is about to see a resurgence to improve water supply reliability and to reduce flood risks and sanitary sewer overflows. This paper examines the challenges with “going deep” below the built urban environment and related to high ground water; stiff, fissured clays; flowing silts and sands; faults; hazardous materials; and abandoned well fields.

Jun 13, 2021

By J. Boisvert, E. Daniels, C. Deutsch

"INTRODUCTION Conventional mine planning is performed on a single resource model at a selective mining unit (SMU) scale deemed appropriate for the deposit and mining method. Estimation methods such as kriging and inverse distance, commonly used to construct a single model, are susceptible to histogram smoothing (Rossi & Deutsch, 2014). This can be mitigated by limiting the number of composites per estimate, therefore correctly reproducing the distribution of estimates (Boisvert & Deutsch, 2012). Search limiting techniques remedy histogram smoothing at the cost of introducing a problematic conditional bias (Isaaks, 1999) and introduces even greater spatial smoothing. Localization is an alternative, offering histogram reproduction through post processing of more robust probabilistic modeling techniques. A single localized model at the SMU scale is desirable. The correct histogram can be reproduced and a single model allows for the use of conventional mine planning and resource evaluation techniques. Despite the advertized benefits of localization, the necessary reliance on a larger panel scale as a middle step in the localization process yields unsightly “edge-effect” artifacts (Boisvert & Deutsch, 2012). Two approaches to artifact reduction are presented here. The first is a straight forward optimization approach designed to minimize an objective function that penalizes artifacts including panel edge discontinuities to generate a model free of panel edge-effects. The second approach redefines a panel in a less conventional fashion as a randomly chosen set of SMUs throughout the domain. This method produces a model void of any regular panel shape resulting in an artifact free model. Artifact reduction minimizes the obvious “edge-effect” issues of localization but local precision issues described by Boisvert & Deutsch (2012) persist. Localization is not a replacement for quantified uncertainty for comprehensive risk analysis and resource evaluation. LOCALIZATION Initially developed with Uniform Conditioning in mind, localization collapses a distribution of local uncertainty at a panel scale to an SMU scale model for mine planning (Abzalov, 2006). This process has been extended to Indicator Kriging (Hardke, 2011), Sequential Gaussian Simulation (Boisvert & Deutsch, 2012) and MultiGaussian Kriging (Daniels and Deutsch, 2014). The localization process is performed in a similar fashion regardless of which technique is chosen to create the prior model of uncertainty. Methodology There are three scales of importance considered in the localization process. The point scale, otherwise known as the data scale, is the smallest and is the scale at which experimental data is collected. The SMU or block scale is the familiar scale at which mine planning and resource evaluation takes place. Lastly, the panel scale is larger and contains a number of SMUs. Each of the three scales is illustrated in Figure 1."

Jan 1, 2015

By J. Mattern

Performance monitoring, operational practices and ongoing collection of geologic data in open pit slopes all provide valuable information for quantifying potential steepening of subsequent slopes. Mining at the Goldstrike open pit has been ongoing since the early 1980’s, with its share of slope instabilities. In areas where slopes have remained stable, consideration has been made for potential slope steepening of final walls. With the proper available equipment, steepening of bench face angles via pre-split blasting is not an uncommon method for steepening of inter-ramp slope angles. As an alternative at Goldstrike, the commonly used Modified Ritchie Criteria for empirical catch bench width has been adjusted resulting in quantified, rock specific formulas for bench width and rock fall berm placement. The result is an inter-ramp slope angle increase of 2 degrees on a 300m high slope, without the necessary purchases and procedural changes that would be required for pre-split drilling and blasting. The result has shown significant net benefits through reduction in mined waste tons and an increase in gold reserves. Location The Goldstrike open pit is located on the Carlin Trend gold belt in northeastern Nevada USA (Figure 1). The mine has produced over 43 million ounces (1.2M kg) of gold during the past 30 years. Engineering Geology Stratigraphy Figure 2 is a stratigraphic section of the rocks in the Goldstrike open pit. Quaternary alluvium and Miocene materials typically are poorly indurated stiff soils and are not present in all locations. Bedrock units consist of siltstones, mudstones, sandstones and cherts. From top down the major units exposed in the open pit are the Vinini Formation, the Rodeo Creek Unit, and the Popovich Formation. In general, rock mass strength increases with depth.

Jan 1, 2019

By S. C. Suboleski, R. Zhao

A Simulation/Animation Model (SAM) with several unique features has been developed for continuous mining in room-and-pillar production systems. Initial cut data are generated by the program based on a short list of general section parameters, and is graphically displayed on the screen for checking and editing. This portion of the program includes several intelligent features. For example, a different cut sequence will be generated for uni-directional section ventilation than for bi-directional flow. Once the data are accepted, the entire simulation may be viewed in animation. Effectively, much of the data are checked visually by watching the actions of the mining equipment. Following the simulation, results are summarized as bar and pie charts, as well as printed output. In addition to the extensive use of graphics, the program contains several advances in simulation techniques as well.

Jan 1, 1993

By Ryan Marsters, Adam Pring, Robin Dornfest

Raw water supply in the central Rocky Mountains often relies on trans-basin conveyance. Many of these older diversions incorporate high-elevation, miles-long tunnels driven over a century ago in hard rock. Tunnels were excavated using conventional drill-and-blast mining and weak ground was supported by timber sets and other various means. Over time, timbers rot and fail, rock quality deteriorates, and the timbers are gradually replaced by more timber, steel patches and braces, formed concrete, rock bolts, split sets, shotcrete, and other means which are commonly applied over existing support, thereby reducing tunnel cross sections, obscuring previous support systems, and rarely addressing the failing rock itself, leading to further deterioration of both the rock and the existing support. Traditional investigation techniques to assess compromised areas are often unfeasible due to access, depth, rubble and voids behind weight-bearing existing supports, confined space, poor invert conditions, poor ventilation, and flowing water. This presentation will discuss design procedures for assessing obscured ground conditions, assigning support classes which accommodate for unknowns, and implementing contractual means to address inevitable surprises or quantity overruns. Case studies include raw water supply tunnels in the Rocky Mountain region constructed between early to mid-20th century.

Dec 1, 2022

By Joseph Clare

It’s not the 1960s anymore. Upgrading wastewater pipelines in the current era demands the latest trenchless technology to minimize impacts. King County Wastewater Treatment Division in Seattle, Washington is designing a nearly mile long Direct Pipe® influent sewer combined with microtunneling to replace a 1960s era trunk sewer constructed along and within Coal Creek and its natural area. Trenchless installation using Direct Pipe® and microtunneling was chosen due to reduce impacts to residential neighborhoods, natural creek environments, and the constraints of topography

Jun 13, 2021

By Bradley V. Nelson

A number of improvements in the ventilation system at the Henderson Mine have been made during the past several years. A key to these improvements was the installation of a computerized monitoring and control system. Employees can determine the status of any of hundreds of devices in seconds through the use of this monitoring system. Mine dewatering pumps, the water treatment system, the ore haulage system, electric power usage as well as other devices are controlled and/or monitored. Ventilation parameters which are monitored include air flow volumes and carbon monoxide as well as the status of main surface fans, mine doors, and ventilation raise doors. Main underground fans are also constantly monitored and can be controlled remotely. These underground fans can be programmed to automatically start and stop to follow work schedules, optimizing air quality while reducing power cost. Mine air heating costs have been reduced by replacing an electrical resistance heating system with a direct fired natural gas heating system at the portal of the ore haulage tunnel.

Jan 1, 1995

By M. Javier

"Mining makes civilization possible. It also creates socio-economic problems surrounded by sustainability controversies yet continues extraction without considering the balance and finitude of nature. Nature requires restoration of equilibrium if mining and life on earth are to continue. Mining is still practiced according to Agricola’s views and the consequences it has wrought on our planet demand we critically reexamine it from its very core, to its metrics, to its design, to its technology, to how it is taught, and to reconsider its raison d'être in 2017. This paper offers tools to new mining engineers that are required to transform and solve new challenges. The task before us is to formulate an updated core curriculum that meets the demands and realities of the 21st Century. Mining professionals must rethink and reteach how to redesign mines before shovel hits dirt, how to mine with restoration of nature figured in to the mining design. Mining needs a new extractive technology in order to transform the results of its well-known liabilities. Mining has evolved and its future must be different than its past. Our industry is capable of doing this but it needs to be shown the way. INTRODUCTION The statement that ‘mining makes civilization possible’ is of the utmost importance and has the most value to us. We can examine the past and present appropriately to see the future that we are building. Mining must be addressed in a different way that makes a positive difference and improves upon rather than continues to get the negative impacts of the past. See Fig 1. Mining creates disequilibrium in Nature by producing ore, waste, tailing, dilution of resources, toxic, and pollution to its ecosystems. What is next for mining on a limited planet? Delaying the transformation of mining is not an option to developing an updated and modern mining business-as-usual paradigm. It is hurting the essentials of living in a civilization; our livelihood is in danger to the point of unrest in nature as we generate a lot of eco-print by present mining practices. So, we are urged to eliminate this bottleneck in life by employing a different design. This way, we will have a vision on how to sustain our civilization. [1]. This new design, with input from current and future generations, will be our contribution to posterity."

Jan 1, 2018

By R. L. Grayson

An integrated approach to mine management is presented. A model for achieving the level of control of operations critical to surviving in the current market is outlined. The integrated Production and Cost Management System (PRaCaST) is designed to provide mine managers with a reliable, quantitative, decision-assisting system that can be used in formulating timely responses to complex fluctuations in operations. PRacaST consists of a productivity forecast model, sectional bills of materials containing current resources consumption factors, a linear programming scheduling model, and operations analyses that focus on production and cost performances. The system is applied to an underground coal mine.

Jan 1, 1988

By Janine L. Beazley, James H. Kyle

The effects of pH, pH modifier (lime or caustic soda) and cyanide on the pulp rheology of a number of ore types ranging from highly siliceous to highly kaolinitic has been investigated. All experiments were performed in fresh water at solids concentrations of 25 and 45% solids and in the pH range 6 to 11. The kaolinitic ores exhibited greater changes in rheology with pH and calcium ion concentration than did the siliceous ores.

Jan 1, 1989

By F. Schreiter

"One method to increase the exploitation rate of a mine is the use of backfill with residual materials in exploited areas. The backfilled material is meant to support both, the walls of galleries and pillars as well as the roof of mining openings. With increasing depth, the exploitation rate diminishes fast, thus the application of backfill in order to change the layout of the mine is crucial for economic success. In result of using backfill, it is possible to change the layout of the working area with a higher ratio to excavated areas and less area occupied by pillars. Thus it is possible to boost the output of a mine by using backfill. Setting the criteria for the selection of the best possible materials and whose improvement, it is useful to know about their qualities and handicaps. The Mining Department at TU Bergakademie Freiberg is analyzing the parameters of residues from different processing methods, accrued in plants of different potash mines and blending different residues for optimization of material attributes. These were significantly characterized by basically parameters like the size and the distribution of different diameters of the grain material. INTRODUCTION The chair for underground mining methods at TU Bergakademie Freiberg is tasked with the sufficient and sustainable supply of economics with raw materials. The steady high demand, the rising prices and the finiteness of the deposits are reasons for the need of an optimized economic utilization of natural deposits, a continuous improvement of mining technics and technology. From an ecological and economical position the best possible utilization of the resources has to be achieved. Many mining operations are by reasons of the deposit not able to haul valuable minerals only, they have to haul a mixture of valuable minerals and waste rock. This hauled combination is given into the processing plant for separation and enrichment of the valuable mineral. The residuals of the processing are commonly dumped to a waste rock pile. For minimizing the size of such a waste rock pile and also minimizing the ecological footprint of a mining operation the only way is minimizing the quantity of accruing waste rock material. Both, optimization of economic utilization and also minimization of waste rock dumps can be realized in one by backfill with processing waste rock material in mined out areas. Especially in mines, mined by room and pillar method, smaller dimension of the pillars are sufficient for safety and stability. By the way less valuable minerals have to be leaved back in the mine and the mine outcome is increasing."

Jan 1, 2015

By Raymond Sandiford, Taehyun Moon

"In 2012, Superstorm Sandy (Sandy) caused extensive flooding in many of the tunnels in New York City. The inundation resulted in two distinct stress changes to the tunnel structures. The first stress change was water pressure on the inside face of the tunnel lining. The second condition related to the change in buoyancy of the tunnels. In areas where the tunnels were supported on rock and an adjoining area supported on soft soil, overstress issues arose. Numerical analyses were performed to assess the structural impacts of the tunnel water inundation; especially stress changes due to internal pressure as well as changes resulting from the buoyancy effects. The paper will discuss the assessment process and its results; it will demonstrate that the change in internal pressure were of little consequence, however the change in buoyancy resulted in significant increases in bolt stresses. INTRODUCTION Superstorm Sandy caused tens of billions of dollars in damage in the NYC metropolitan area. It also caused significant disruption to the transportation system by flooding most of the under river tunnels servicing Manhattan from the outer boroughs and New Jersey. The rehabilitation of the tunnels was of paramount importance to the restoration of the NY and NJ economies. With this rapid restoration, it was essential to determine whether the flooding of these tunnels caused damage to tunnel structures. A series of analyses were undertaken to ascertain whether the change in the stress conditions and buoyancy of the tunnels, due to the flooding, was significant enough to cause damage or over-stressing of the tunnel components. The effects of this unforeseen loading condition was a concern to the agencies operating these tunnels and were thus analyzed to ascertain if there were any adverse impacts. This was a concern because the majority of under river tunnels in NYC was built earlier in the century and constructed using bolted cast-iron lining segments. The cast iron, although quite strong in compression, is much less so in tension. Also, after nearly a century of use, the bolts connecting these segments together have under gone varying degrees of corrosion. The stress changes in both the liner segments and the supporting bolts were estimated for conservative ground support conditions to provide confidence that the flooding had not caused permanent damage."

Jan 1, 2016

By S. Bentley

"Everyone has a general idea what mixing means, but describing the mixing process is not so simple. The objective of any mixing process is to distribute and blend the materials with different characteristics, different quantities as evenly as possible resulting in a homogenous mixture. Introducing proportional movement with the optimal intensity into the materials achieves effective homogeneous mixing results. A simple one directional movement with inadequate acceleration of the materials would obviously not achieve the same mixing results. This would be more like stirring than mixing. The amount of relative movement that is introduced is a decisive factor. Circumstances for successful mixing involve distribution of all materials, and achieving the highest probability that all recipe particles located in a specific position at the beginning can be found at any random location in the mixing chamber at the end of the process. This is the only way to ensure that a consistent result is achieved every time mixing is repeated.THREE-PART CYCLE The mixing cycle occurs in three phases; charging the mixer, the mixing process, and discharging. The sequence in which the individual materials to be mixed are filled into the mixer can have a huge impact on the efficiency of the mixing cycle. The mixing cycle overlaps the charging process and the discharge cycle follows the mixing cycle. To achieve optimum results, effective discharging methods should be taken into consideration to avoid risks of segregation. Costs for energy and wear should be as low as possible and finally, it is very important that the mixing cycle takes place as quickly as possible. In concrete or paste backfill production, selecting the best mixing technology is crucial for both the quality of the final product to be blended and the efficiency of the production process. The optimum mixing system is one that rapidly disperses all ingredients evenly throughout the mixing trough and completely surrounds all the course or fine aggregate particles with the slurry cement particles. Specific for paste production it’s the mixers job to also break-down unconditioned tailings to achieve consistent paste viscosity or measured spread. Many paste and concrete formulas also involve small quantities of chemical additives which also must be evenly distributed effectively. The time required per mixing cycle as well as the costs of energy, wear and maintenance will determine the economy of the concrete production."

Jan 1, 2015

By Carlton M. Ray, William P. Levy, Thomas Lindberg

"The District of Columbia Water and Sewer Authority (DC Water) is implementing its $2.6 billion DC Clean Rivers Project to reduce combined sewer overflows to the District’s receiving waterbodies and mitigate chronic sewer flooding in District neighborhoods. The First Street Tunnel project is a major component of the DC Clean Rivers Project, designed to mitigate sewer flooding and basement backups in the District’s historic and densely populated Bloomingdale neighborhood. Bloomingdale has been historically affected by sewer flooding and was severely impacted by four storms in the summer of 2012 that caused significant damage to homes, the environment and public property. As a result, DC Water accelerated the design and construction of the First Street Tunnel in order to mitigate the effect storms have on the undersized sewers serving the neighborhood. The infrastructure designed to mitigate flooding, including the tunnel, are located within the highly urbanized neighborhood – with some structures being less than ten feet from residents front door steps. The success of a large public works project of this magnitude and in this unique location depends on a well informed and supportive public. With the local community impacted by flooding but concerned about heavy construction impacts, this paper details the components of a successful public outreach plan and lessons learned throughout the design and construction process. Early identification of community mitigation, working cooperatively with stakeholders and frequent dissemination of accurate information required the project team to establish a culture of problem solving collaboration with the community. BACKGROUND Chronic Flooding in the Northeast Boundary Sewershed The Northeast Boundary sewershed, in which the Bloomingdale neighborhood is located, is served primarily by a combined sewer system and has a long history of chronic flooding problems during moderate to severe storm events. The sewer system that serves the Northeast Boundary drainage area was constructed by the Federal Government in the late 1800's when developed areas of the District terminated at what is now Florida Avenue. Since construction of the system, population within the sewershed area has grown at an exponential rate. In meeting the growing needs of the population, the District experienced development that transformed previously low-density rural areas into new communities. Impervious areas have increased drastically since the sewer system was constructed and consequently, the existing sewer system does not have the capacity to convey storms with return frequencies beyond the 2-year storm without flooding. As a result of the capacity limitations, many of the low-lying areas have become chronic flooding areas due to the surcharging of sewers."

Jan 1, 2016

By Dale A. Shay, Roy R. Cellan

The Santa Fe Mine, located in west central Nevada, began leaching ore in 1988 and completed ore processing in 1995. Homestake Mining Company has completed final reclamation of the site, including remediation of bare surface soils resulting from the oxidation of sulfide minerals and migration of acidity in the mine waste repositories. The need to remediate oxidized sulfides and mitigate resultant acidity at the Santa Fe Mine emphasizes the economic, reclamation, and environmental advantages for understanding and pre-planning for management of potential sulfide wastes during mine planning phases. The lack of pre-planning by mining companies for sulfide waste management was common in the 1980's due primarily to mining of reserves characterized largely as oxide deposits and to the common opinion that low moisture regimes in arid or semi- arid climates would not allow for significant acid generation. Since the 1980's, operational experience has shown that sulfide wastes, deposited randomly in waste dumps and without adequate planning for final reclamation success, can create final reclamation problems that are very costly to remediate. While mine waste characterization, waste management plan compilation, and in-pit selective waste handling procedures add operational costs, the reclamation experiences at the Santa Fe Mine are indicative that pre-planning and management is worthwhile both in actual overall cost efficiency and in successful reclamation of the mine site. The reclamation program at the Santa Fe Mine shows Homestake's continued commitment to the successful management and reclamation of their mine sites.

Jan 1, 2000