In rapidly expanding cities, the demand for construction materials is already intense and will only increase. Despite some recycling of materials in major projects, the need for more extraction is expected to quickly exhaust existing quarries. Many new quarries will be needed – ideally, as close as possible to the location of demand, because transport is a major contributor to the cost of the materials as well as to greenhouse gas emissions. Proximity is a critical factor in keeping construction costs under control as well as minimising the substantial carbon emissions of haulage.
However, vacant land close to population centres is valuable and its uses are highly contested, which makes it difficult to site quarries near population centres. Extractive industries in such locations will also need to navigate increasingly stringent planning requirements and community expectations, particularly regarding noise, dust, visual impacts and environmental consequences for fauna, flora and water.
Demonstrating excellence in water management throughout the life of the quarry (and beyond) is one step in the right direction towards greater sustainability, smoother approvals and increased community acceptance – and it doesn’t necessarily have to come at a greater cost.
It is, however, an intricate challenge requiring expertise across a wide range of disciplines to create holistic, coordinated and sustainable water solutions. Finding a sustainable approach that minimises adverse impacts and maximises benefits will depend on understanding and responding creatively to water quantity and quality management, biodiversity and ecosystem support and social amenity, as well as to commercial or economic drivers.
When these water management considerations are worked through with a range of experts and stakeholders, it is possible that commercial operations can proceed safely within a sensitive environment and potentially achieve results that improve pre-existing natural conditions.
Water quantity is a major issue for quarries, such as how to handle large volumes of rainfall, stormwater or groundwater to avoid pit or downstream flooding and adverse impacts to nearby wells, or how to provide adequate water supply for onsite use or to maintain downstream surface water flows. This requires an in-depth understanding of the hydrologic conditions within the broader catchment and the project site, and insights into how future industry and development in the catchment might alter the catchment hydrology. It also requires designing for flexibility to handle current and future hydrologic conditions as they vary due to a changing climate.
The combination of climate change and expanding urbanisation and industry creates a complex landscape for managing water. Climate impacts in a local area may take the form of reduced rainfall and dry conditions or, conversely, increased frequency and intensity of large downpours – or even a seasonally varying combination of both.
In terms of surface water management, it is advisable to build climate resilience into the design solution by providing a design to contain peak flows that are greater than the design flows based on the current annual exceedance probability. Principles of sustainable drainage will greatly improve management of water quantity, such as incorporating features to slow and reduce runoff (e.g. swales and detention ponds).
A water balance model can be prepared to assess all sources of water coming into and going out of the quarry. This should be done for the pre- and post-development site. If the post-development model shows water shortages, consideration should be given to water harvesting and groundwater development options.
Beyond the modelling, it’s essential that there is ongoing monitoring of water quantity and quality, both upstream and downstream, and that quarry water demand is measured.
A closed-loop system is the ideal, if it can be achieved. This is where sustainable drainage and water harvesting can really come into play, such as by harvesting water runoff from all hardstand and roofed areas, storing it in a tank and reusing it on the site.
A critical concern for water management around any industrial site is water quality. Ideally, the water that leaves the site, as well as the water that remains on site at decommissioning, should meet appropriate regulatory requirements and be of a quality that is similar to or better than before the development of the site. For a quarry operation, this is a challenge – how can the inevitable dust and dirt be filtered from the water flowing from the site?
Slowing runoff and providing natural filtration will help to preserve or improve water quality. When the flow of water across a site is slowed, sediments and pollutants can settle out before the water leaves the site and flows back into natural waterways. Detention basins and wide shallow channels will slow the water’s passage.
Vegetation is a key component in the filtration process, so incorporating native planting into any water management plan will help to improve water quality by removing contaminants.
Again, monitoring will be critical to ensuring ongoing water quality, so there should be water quality monitoring in upstream and downstream watercourses and in groundwater around the site as well as upstream and downstream.
Biodiversity and ecosystem support
The approach to managing water at and around a quarry site can play a valuable role in supporting the health and diversity of local ecosystems.
The first step is to ensure that the siting of the quarry avoids, as far as possible, any significant impacts on watercourses or native vegetation of high ecological value. If a watercourse needs to be diverted to prevent water entering the active quarrying area, it is important to attempt to preserve existing habitats and, if necessary, to develop new habitats for fish and other aquatic fauna.
As the site is progressively decommissioned, the incorporation of water features and thoughtful landscaping with native vegetation can support ecosystems by improving existing habitat or providing new habitat for native fauna, such as birds, insects, frogs and fish. Native vegetation will encourage birds and insects, and aquatic features can provide habitat for frogs and fish. Frogs and fish can be further encouraged by including features such as shallow and deep sections of water, cascading rock-formed riffles to support fish movements upstream and downstream, and slow-flowing areas to allow fish to rest. Enhancing the riparian vegetation and managing weeds along water features and watercourses will also greatly enhance the overall environmental outcomes.
Developers of new quarries may find it challenging to gain the acceptance of the local community, but a social license is essential to the success of the project. Demonstrating ecological stewardship through sustainable management of water resources and biologically diverse aquatic and riparian communities will contribute to community acceptance, as will openness and transparency in community consultation throughout the lifecycle of the project.
Ideally, the community should be included in planning for the site’s future beyond the quarry’s active commercial life. There are many creative ways in which decommissioned quarries are being rehabilitated for enhanced social amenity. They can sometimes become well-landscaped public recreational spaces incorporating ecologically sensitive native plantings and water features such as ponds, lakes and streams. Such approaches will be welcomed by local communities and are also likely to increase the commercial value of the site.
When the extractive industry embraces and invests in excellence in water management throughout a quarry’s lifecycle, both the industry and the environment will benefit, as will communities. A quarry project that succeeds in balancing commercial, environmental and social goals can leave a valuable legacy of affordable materials made available locally, thereby avoiding emissions associated with transportation. Such a project also supports sustainable, liveable and resilient urban spaces accentuated by riparian amenity zones for the benefit of both people and nature.