Rio Tinto Mine- Hail Creek Mine Site Rehabilitation Project

Project Overview

In January 2018, Erizon was approached by Rio Tinto to perform revegetation and soil stabilisation on 32.8 hectares of land at one of their prominent coal mines at Hail Creek, 120 Kilometres from Mackay in Central Queensland. Upon site inspection, Erizon put forward a framework that was aligned with Rio Tinto’s industry commitment to establish a safe and sustainable area.

To ensure the best chance of success, the Erizon team conducted an extensive soil analysis of the overburden and batter structures. The results of the soil testing highlighted the specific amendments required to create an ideal environment for vegetation growth. Using 3D multispectral drone mapping, key area-specific data was also collected, including land characteristics, positioning, Normalised Difference Red Edge Index (NDRI), and Normalised Difference Vegetation Index (NDVI).

Based on the insights gained from the site evaluation, Erizon recommended a tailored amelioration and fertiliser program, where soil conditioners and probiotics were added to promote vegetation growth. The suggested mulch application was intended to protect the batters from erosion during high-intensity rainfall until sufficient vegetation had grown to naturally protect the substrate.

The recommended solution was implemented as a two-phase process:

• Application of trace elements, soil conditioners and probiotics
• Application of EnviroLoc – Hydromulching Bonded Fibre Matrix (BFM) with a native seed blend

Our familiarity with mine site regulations, specialist equipment, and expert personnel, enabled us to deliver a successful solution.

Solution

EnviroLoc has been scientifically developed to provide soil stabilisation for healthy vegetation growth. We tailored the application to meet site-specific requirements, with the two-phase process involving:

Part 1: Amelioration and Fertiliser Program
The first phase consisted of applying a seed mixture of pasture grasses and native trees, combined with the amelioration and fertiliser solution.

Based on the results of the soil analysis, we recommended adding trace elements, soil conditioners, and probiotics to improve the soil profile. These additives supported microbial activity and increased nutrients that promote vegetation growth.

Part 2: Hydromulching BFM

EnviroLoc Hydromulching BFM solution consists of a cellulose-binding agent and mulch with interlocking organic fibres. This hydromulching solution is designed to maintain consistent water infiltration and adequate airflow.

The mulch provided extensive coverage and safeguarded the seed against erosion caused by wind and rain. Because it improves moisture retention, EnviroLoc also promotes faster germination.

When designing the program, Erizon considered factors such as erosion control effectiveness, ability to facilitate growth, and the functional longevity for successful rehalitation.

Equipment:
The primary equipment used for this project wasErizon’s fully mine-compliant HydroRigs that are able to provide fast coverage and eliminate the need for workers to physically work on steep slopes. These purpose-built HydroRigs have built-in agitators within the holding tanks to consistently mix the hydromulching slurry to ensure even application, and can spray up to a distance of 100m.

With this, the two-step application process was successfully implemented to the 32.8 hectare site area over the course of just 12 days from start to finish.

Challenges

Erizon’s ‘Vision Zero’ policy intended to prevent workplace injuries and eliminate hazards played a crucial role in identifying potential contingencies that posed challenges to the project. The primary challenges that posed some concern for the Hail Creek project included the following:

• Location
  There were some challenges associated with the access points to manoeuvre the HydroRig equipment around the uneven substrate and high gradient batters. Erizon’s team complied with mine safety regulations, along with comprehensive contingency plans and documentation, including the appropriate JSA, JSEA, SWMS, SWP, and PARA.

Weather Conditions

• This project took place in the middle of summer with high humidity and temperatures of around 45°C. These environmental conditions prompted a fatigue and heat management plan, which implemented continuous weather monitoring to ensure that appropriate application schedules were in place. Performance measures were also in place to gauge the health and safety of employees, ensuring that everyone was hydrated and maintained scheduled breaks.
• Rain and wind also posed a risk to the application process; therefore, applications were scheduled to align with environmental conditions.

Results

This tailored solution was executed in the wet season of January 2018 and took approximately two weeks to establish vegetation. The healthy vegetation growth and restoration of the plant cover created a mechanical barrier that provided substantial ground surface protection against the erosive impacts of rain and strong winds.

Post Application
Delivery Performance

• In February of 2018, approximately 2.5 weeks post-application, the Bowen Basin of Queensland experienced severe storms with rain battering the surrounding region. A total of 183.4mm of rain fell on the area. Despite the high velocity of rainfall overthe application area, the hydromulching solution held up and provided superior erosion performance.

Monitoring & Verification

• Erizon examined the Hail Creek Mine site revegetation project area, approximately four months post-application. A final verification check was also conducted via visual inspection and drone monitoring to ensure that the project outcome met the agreed specifications.

The Inspection & Test Plan was finalised and given to Human Capital Management for the final sign-off. As a result, both Erizon and Rio Tinto were extremely pleased with the growth that had been established within the stipulated time frame.