Contaminants, Land and Soil Assessments

Contamination, Land and Soil Assessments

Overview

The scope of this assessment includes a preliminary review of historical land uses within the main works area which have contamination potential, an inspection of contamination sources within the project area, and an assessment of the impacts that may result arise as a result of contamination. Further mitigation or required assessments will also be outlined.

This will be examined through toxicological reports into previously contaminated sites, and boring into the ground beneath the Main Works site to identify rock types that could contaminate the area if disturbed.

These surveys were conducted under the Commonwealth Environmental Protection and Biodiversity Act, the Contaminated Land Management Act, the Protection of the Environment Operations Act, and the Environmentally Hazardous Chemicals Act.

Contamination assessment areas include:

The proposed tunnel alignment and underground power station, and associated subsurface infrastructure, including portals, access tunnels, ventilation shafts, and adits
Temporary surface construction areas including construction and laydown areas, and accommodation camps
Access roads and the cable yard
Temporary and permanent excavated rock disposal locations

There are two primary rock types that could cause contamination within the site, being Naturally Occurring Asbestos (NOA) and Potentially Acid Forming rock (PAF).

NOA includes rock such as Actinolite, amosite, anthophyllite, chrysotile, crocidolite, and tremolite. These rock types may have small fibres of asbestos that can be released into the air if the rock is fractured. A high potential for NOA is reported in rocks underlying the site, and was recorded during surveys in the Gooandra volcanics, the Boggy Plain Suite, and the Shaw Hill gabbro.
PAF are rocks that generate acid when exposed to oxygen and water in the air. They are usually composed of sulphide materials, most commonly iron sulphide. The excavation and breakage of rocks as a result of tunneling, construction, and placement has the potential to create Acid Mine Drainage (AMD) that could leach into the nearby soil and groundwater, negatively affecting the local environment. Such rocks were similarly found beneath the Main Works site.

Additionally, surveys were undertaken to establish potential historical contamination, particularly in the Lobs Hole region. Lobs Hole was formerly home to a copper mining and processing operation. In surveys conducted near the mining site, elevated levels of copper, lead, mercury, nickel, and zinc were recorded, and near the former tailings ponds area elevated levels of arsenic, copper, mercury, and nickel were recorded. Additionally, the nearby Yarrangobilly river reported having elevated levels of copper and nickel in the sediment, and elevated levels of total copper, dissolved copper and zinc concentrations in the water.

Other previous land use activities may have also potentially contaminated the site, including vegetation clearing, historic settlements, and agriculture.

Jump to impacts, mitigation, or critique

The soil and land assessments classify and map soil types within the Main Works area, to identify soil management measures, and to identify any soils that may require mitigation measures if disturbed.

Soils were primarily identified through desktop analysis, and utilising previous surveys in the area; additional field surveys were not taken as there was no available approval pathway to undertake soil sampling within the area. The assessment states that “The level of information contained in this report is considered appropriate for the EIS with relatively little value to be added with an EIS field soil survey program, recognising that targeted site-specific soils assessment will be undertaken as required prior to construction to determine management measures.”

This assessment was conducted under primarily state-based soil assessment guidelines, including the Land and Soil Capability Assessment Scheme.

The dominant soil types within the site are Kurosols, with Tenosols and Rudosols being the next most dominant. These soil types are largely associated with steep, stony topography and exposed ridges of higher altitude. Alluvial Rudosols are also found along waterways, and Organosols can be found in valley floors where organic matter and water accumulates. Most of the soils found within the Main Works area show only low to moderate levels of fertility and display low to moderate water infiltration rates.

Lob's Hole Mine c.1900.

The mountain that can be visible in the background of the first image.

Lob's Hole Mine c.1900.

1/2

Map depicting the various soil types within the Main Works area, with Kurosols being depicted by the the tan-brown colour.

1/6

Maps produced by EMM demonstrating where contamination could arise within each section of the Main Works.

Contamination Impacts

If NOA rocks are disturbed during excavation or boring, the inhalation of mobilised asbestos fibres presents a potential human health risk.

Additionally, the excavation of PAF rock and potential generation of acid leachate could negatively impact the local environment. If acid leachate or contaminated sediment is not monitored appropriately, it may also be transported via the movement of water downstream, impacting the wider catchment and downstream water bodies.

Another impact noted by the contamination report was the potential of contamination through:

improper waste disposal
potential leaks and spills of hydrocarbons or lubricant from machinery
heavy metals from treatment plants

Impacts on soil

Ongoing erosion is noted by the assessment as a threat being caused by human activities, including development and the creation of roads, horse-riding, and walking tracks.
Further erosion is caused by non-native hoofed mammals, including feral pigs, deer, horses, and goats, who eat and trample sensitive vegetation, causing a decrease in available root systems to hold the soil together. Of note is also the fact that the Main Works occurs in an alpine environment, where freeze-thaw cycles can exacerbate the rate of erosion.
Soil contamination, though the mixing of soil with petrol, oil, herbicides, or other chemicals may occur during transport, excavation, or storage.

Degradation of soils can involve the loss of nutrients, aeration, water content, microbiota, or organic matter, reducing its overall fertility. This may hinder rehabilitation and re-vegetation outcomes. Due to the time taken to form certain soil types and the restricted growing season of alpine and sub-alpine vegetation, the degradation of Alpine Humus soils (Tenosols) and bog and fen peats (Organosols) are of particular concern.
As some vegetation types rely on those soils to grow, and they are in limited abundance, degradation of these soils, in particular, could threaten whole ecosystems. These soils are also of concern because they are slow to form and difficult to rehabilitate. Structural decline and compaction of soils may also be caused by the movement of heavy vehicles and machinery.
Clearing of land may also cause localised hydrology changes, as also covered in the Aquatic Ecology. This may increase the likelihood of landslips, causing the movement of fertile topsoil into local water sources.
Changing salinity is also of concern. Although the risk that salt levels could be increased by works has been noted to be small, as the level of salt present within the soil is naturally low even small changes to salinity could impact soil productivity.
General loss of soil is also noted to be a primary impact of this project. Soil will need to be removed and stored during this project, however, some level of soil is always lost during transport and handling, or through contamination, and the mixing of topsoils, subsoils, rocks, and other materials, which can fundamentally change its properties.
Finally, the importation of construction materials may introduce salt, pollutants, foreign microbes, weeds, or diseases into the soil.

Mitigating contamination

Mitigating impacts to soils

Mitigation strategies include the assessment and monitoring of:

Excavated areas and construction surface disturbance area
Contaminated soil and water during construction
PAF and NOA rocks
Waste management and transport
Virgin Excavated Natural Material (VENM)

Additionally, if sites within the Main Works area are deemed to contain “soil, surface water, or groundwater contamination that poses an unacceptable risk to human or ecological receptors caused by the project”, immediate remediation strategies will be undertaken.

Finally, a NSW Environmental Protection Agency-accredited site auditor will assess all contamination reports, and will evaluate the suitability of sites prior to development, to prevent potential contamination. During the operational phases of Snowy 2.0, an Operational Environmental Management Plan will be created to manage environmental impacts as they arise.

Critique

In summary, both assessments were highly detailed in recording and quantifying potential sources of contamination and soil types.

In particular, the Soil and Landscape Assessment extensively described threats to soil and impacts on the environment in great detail and addressed all threats with specific recommendations to address each.

However, the Contamination assessment was lacking in that regard. While it briefly touched ion impacts, it did not cover the impacts of what would happen if contamination leached into the environment; for example, increased heavy metals caused by machinery may impact the health and reproductive success of fauna, or the potential for contaminants to be absorbed into plant tissues and bioaccumulate up the food chain.

Extensive mitigation measures have been proposed for each potential threat to soil quality or loss, particularly in relation to the prevention of contamination and the protection of valuable topsoils. These include:

Using sods temporarily to stabilise the soil during rehabilitation
Avoiding the unnecessary disturbance of sensitive soils, such as Alpine hummus soils and peat bogs, through foot traffic and vehicle movement.
Calculating the volume of soil required for rehabilitation works prior to excavation to avoid unnecessary disturbance.
The appointment of a contracted Site Environmental Advisor to determine topsoil and subsoil stripping depths, and convey they accurately to earth-moving operators, to avoid contamination and unnecessary disturbance.

Management to minimise the structural decline of soil, including suitable storage
Preventing the use of fertilisers to reduce unintended ecological impacts
Only using fertilisers outside of the Kosciusko National Park if soil rehabilitation is required before rehabilitation works begin
The preparation of Erosion and Sediment Control Plans (ESCPs) for areas of concern, particularly where there is an increased risk of erosion, such as where there are soils that are particularly prone to dispersal or steeper slopes
The staggering of construction to limit the total area at risk of erosion at once, and installation of erosion control technologies
The recommendation to only undertake soil movement works when soils are not saturated with water or when rainfall is predicted, to reduce erosion risk.

Damage caused by feral horses to fragile ecosystems and waterways.

In-situ Naturally Occurring Asbestos.

Contaminants:

Soil and Land Assessment:

Impacts

Mitigation

Critique