Hail Creek Mine

In January 2018, Erizon was approach by Rio Tinto to undertake 32.8-hectares of revegetation works for early rehabilitation and soil stabilisation. The project would take place at one of their prominent coal mines, located at Hail Creek, 120 Kilometres from Mackay in Central Queensland. The project involved delivering a high-quality, successful solution by utilising expert personnel, specialist equipment and a wealth of experience in working within mine site regulations.

Upon inspection of the site, Erizon put forward a framework that articulated Rio Tinto’s industry commitment to establish a safe and sustainable area that underpinned the future of the local ecosystem.

An essential obligation in commencing the rehabilitation works consisted of the examination of the overburden area and batter structures, in conjunction with independent soil testing. The investigation also utilised 3D multispectral drone mapping of the site, which provided a high degree of area-specific data, including land characteristics, positioning, Normalised Difference Red Edge Index (NDRI) and Normalised Difference Vegetation Index (NDVI).

This site evaluation prompted a proposal suggesting a tailored amelioration and fertiliser program where soil conditioners and probiotics at the time of seeding would be essential in achieving the long-term establishment of vegetation growth. The suggested mulch application would assist in the erosion protection during high-intensity rainfall of the batters until visible signs of growth would appear and naturally protect the substrate.

The proposed recommended solution was put forward as a two-part application process to meet the client’s goals and objectives for the site:

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

The tailored product solution had been scientifically developed to cater to the requirements of the site by providing soil stabilisation designed to underpin healthy vegetation for early rehabilitation. This solution would be applied in a two-part application process by Erizon’s purpose-built HydroTrucks, which are designed to hydraulically disperse product evenly onto the substrate area.

Part 1: Amelioration and Fertiliser Program
The first application process would consist of a seed mixture of pasture grasses and native trees, which would be accompanied by the amelioration and fertiliser solution.

Based on the soil construct and scientific analysis of the substrate, the soil profile would require various adjustments - suggested additives included: trace elements, soil conditioners, and probiotics.

The soil amendments strategy was designed to help influence and support microbial activity for optimal nutrients, growth, and development of vegetation.

Part 2: Hydromulching BFM
Hydromulching BFM solution consists of a cellulose-binding agent and a long length mulch with interlocking organic fibres designed to permeate into the soil surface, while ensuring consistent infiltration of water and airflow. The mulch provides extensive coverage, acting as a safeguard for the seed by helping it to retain moisture for faster germination and growth while protecting the soil and seed placement from erosion caused by wind and rain.

The solution is specifically designed to mould to the contours of the surface substrate, including high gradient batters such as those found at Hail Creek. The two-part product recommendation took into consideration the erosion control effectiveness, ability to facilitate growth and the functional longevity for successful rehabilitation of the area to the standard of Government legislation.

Equipment:
The primary equipment used on this project were Erizon’s fully mine compliant HydroTrucks - their pure design, power, and speed eliminated the need to work on steep slopes and can provide fast and adequate coverage. The purpose-built trucks have built-in agitators within the holding tanks that consistently mix the product to ensure that an even application is hydraulically applied at a distance of 100m and boasts the ability to cover 50,000+ square meters per day.

After extensive analysis and the implementation of safety and contingency procedures; works commenced with an initial 3D drone survey designed to map the area to a high degree of accuracy. This procedure provided significant data that assisted in determining the application area and rates for solution coverage.

The first step of the application process involved the implementation of the amelioration and fertiliser program, where a combination of water, seed and organic matter was hydraulically applied onto the surface substrate to ensure effective seed-to-soil contact.

The second stage of the project required a higher than usual application of the Hydromulching BFM solution over the project area. The matrix of the product fibres protects seed placement from environmental factors such as water or wind. The recommended solution was made based on its scientific construct and non-toxic, environmentally sustainable nature; in conjunction with its ability to establish vegetation and sustain erosion protection until signs of growth.

The two-step application process was successfully applied to the 32.8-hectare site area, over the course of 12 days, from start to finish.

Erizon’s company safety policy, ‘Vision Zero’ played a crucial role in identifying potential contingencies that posed challenges to the project. These have been designed in consideration of the safety, quality, and environmental management system procedures, and intended as a mediation strategy to combat workplace injuries and eliminate hazards.

The primary challenges that posed some concern for the Hail Creek project included the following:

Location
• Due to the scope of the site, there were some challenges associated with the access points to manoeuvre the HydroTruck equipment around the uneven substrate and high gradient batters. In reaction to these challenges, Erizon’s team were compliant 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 heat. 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 employee’s welfare by ensuring that everyone was hydrated and maintained scheduled breaks.

• Rain and wind also posed a risk to the application process; therefore, scheduled applications were executed to align with environmental conditions. This strategy helped facilitate the successful implementation of the hydromulching solution.

This tailored solution of Hydromulching was carried out in the wet season of January 2018 and took approximately two weeks to establish vegetation. The development and restoration of the plant cover underpinned the establishment of a biodiverse root system embedded into the surrounding soil particles. The healthy growth provided substantial ground surface protection, which created a mechanical barrier from the impacts of rain and erosion.

Post Application 
Delivery Performance 
• In February of 2018, approximately 2.5 weeks post-application, the Bower Basin of Queensland experienced severe storms with rain battering the surrounding region. A total of 183.4mm of rain fell on the area, with the most extensive rainfall, recorded at 57.8mm. Erizon can report that despite the high velocity of rainfall on the 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, where the team met with key Rio Tinto personnel. A final verification check was then conducted via visual inspection and drone monitoring to ensure that the project outcome aligned with 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 established in the stipulated time frame.