Natural Resources Extraction: Stressors and Impact Management - Sustainable Practices in Geoenvironmental Engineering - page 150

5.3.1 Mining-Related Industries
5.3.1.1 Pit Mining
The irst two categories mentioned in the previous section can be considered jointly as
mining-related industries . For these (mining-related) industries, there are typically three
types of interactive contact with the geoenvironment. There are at least two different types
of mining: (1) surface mining or open-pit mining and (2) underground mining. Mining sites
are characterized by piles of waste rock, huge pits, and AMD. Decommissioning proce-
dures often must include remediation and closure strategies—requirements that have not
been imposed in the past. Remediation through decontamination, isolation, or immobili-
zation may be required for contaminated areas. For closure of open pits, two simple strate-
gies that have been employed: (1) reiling of the pit with clean material for new land-use
options and (2) harmonizing with the surroundings. Before open-pit illing, consultation
is needed to ensure that the geological heritage is not destroyed. Maintaining formations
is essential for research and teaching purposes or education of the public. Waste storage in
these pits used to be a common practice. However, because the base of the quarries is often
relatively permeable, groundwater contamination from waste leachates can result. If the
pit is left for recreation or as a monument, slope stability must be ensured. Flooding of the
pit can be quite beneicial. Waring and Taylor (1999) have proposed this as a method that
is low cost and passive for preventing AMD by eliminating exposure of the sulide miner-
als to atmosphere and hence denying oxidation of these minerals. Reservoirs can be used
for ishing or wildlife or recreation or restoring biodiversity, and vegetation may also be
introduced. Mines could also be sealed against seepage of rainwater and snow, and drain-
age systems should be developed to divert water away from the tailings and thus reduce
AMD problems.
The issues of prime importance in respect to the geoenvironment and its sustainability
relate to (a) the actual mining operation itself and its impact on the suricial environment
and (b) the various waste products issued from mining and resource extraction opera-
tions. Most mining wastes are associated with recovery processes of host rock material
for production of natural resources such as metal and nonmetal ores and products. These
include aluminum, iron, copper, gold, lead, molybdenum, silver, tungsten, uranium, zinc,
coal, asbestos, gypsum, barite, syenite, potash mineral, salt mineral, bitumen (from oil
sands, “tight rocks,” shales, etc.) quartz, limestone, sand and gravel, and stone. In addition
to solid wastes generated during the mining process, liquid wastes in the form of tailings
and other process liquid waste streams associated with mining and milling operations
are obtained. These need to be considered as sources of stressors that could impact on the
geoenvironment. Speciic and detailed examples of various mining activities and mill-
ing processes can be found in mining-milling textbooks dedicated to the study of these
subjects.
5.3.1.2 Discharges from Beneiciation and Processing: Stressor Sources
Procedures and processes required to extract minerals from the ores obtained in mining
operations vary according to the kinds of minerals being extracted. These procedures and
processes fall under the category of beneiciation operations and mineral processing . These
operations are designed to physically separate the mineral of interest from the surround-
ing nonmineral elements commonly called gangue, and to use various means to recover
the mineral of interest. Operations included in beneiciation and mineral processing are
(a) ore preparation—crushing and grinding (commonly known as comminution ), washing;