Hydromulching Case Study – Sibelco BBR Clay Mine Rehabilitation
Sibelco engaged Spray Grass Australia (SGA) in June 2017 to develop a mine rehabilitation program for their BBR Clay Mine, located in Gulgong New South Wales.
The Gulgong district has traditionally been a major producer of high-quality kaolin clays. Upon closure of the BBR Clay Mine in 2007, Sibelco had attempted to rehabilitate the mine site in autumn of 2018, however, reactivated mine operations for a short period.
During the previous rehabilitation attempt, the reclaimed area was ploughed and direct-seeded with fertiliser and eight seed mixes. The program resulted in the germination of three seed varieties including fescue, cocksfoot and a small amount of native cover crop. Due to the lack of vegetation cover and consistent erosion onsite, the rehabilitation project was deemed a failure.
In reaction to this problem, Sibelco relied on the expertise and recommendations of SGA to ensure that the following objectives would successfully meet their requirements:
- Deliver intermediate stabilisation of batter surface
- Generate a high strike seeds rate
- Establish a long-term rehabilitation solution
- Develop a hydromulching solution suited for overland flow and embankments
During the initial site investigation on the 10th August 2017, SGA met with Sibelco personnel to discuss the project objectives and expectations. During the visit a 3-dimensional drone survey was conducted to map out the project area, followed by a substrate assessment. Soil samples from the site were later taken from the landfill mound, including the transfer station batter, south-west and the north-east corner of the mine for an independent analysis.
Laboratory results indicated that the soil was lacking in the microbial and nutrient characteristics for development and support. These findings prompted an amendment and customised program recommending the following product solutions:
- EnviroLoc – Hydromulching BFM
- High carbon humate soil conditioner
- Ag calcium boost
- Fertiliser and amendments solution
- Native seed blend
The tailored program would consist of a two-part application process designed to stabilise the substrate for healthy vegetation growth while taking into considerations the client’s requirements, site characteristics and challenges.
Part 1:Amelioration and Fertiliser Program
The initial product application would incorporate a mixture of seeds accompanied by a tailored fertiliser and amelioration solution. The native seeds would provide essential covercrop for effective erosion control from weather events likely to cause increased water flow over uneven terrain areas.
The tailored soil modifications would need to be applied with the seeds to amend the unbalanced soil profile. The product adjustments included the implementation of trace elements, soil conditioners, and probiotics for influenced microbial activity, environmental conditions and vegetation development.
Part 2: Enviro Loc – Hydromulching BFM
The Hydromulching component entailed interlocking fibrous mulch combined with a cellulose-binding agent, designed to enable optimal water and airflow infiltration. The much would act as a safeguard for seed and soil protection by moulding to the contours of the substrate, including elevated batters. This strategy would enable faster germination and effective erosion control.
The equipment used on this project included one of SGA’s fully mine compliant HydroTrucks – chosen for its sophisticated design, control, and pace eliminating the need to work on steep slopes and can provide fast and adequate delivery. The HydroTrucks in-built agitators offer a consistent product mix for an even hydraulic application.
The attached cannons and hoses provide the flexibility to adjust the application of the hydromulching solution to the specific conditions required of the site, including enhancing quality, safety and productivity. These attachments can apply product up to 400m and boast the ability to cover 50,000+ square meters per day.
SGA undertook revegetation works to 11.2 hectares of land located at Sibelco’s clay mine, under the direction of site management. SGA met with onsite personnel to discuss the proceedings of the project; this included a final operational check and the implementation of safety and contingency procedures. During the initial inspection of the site, a 3-dimensional drone survey of the mapped area confirmed the site-specific requirements such as the measurements of the area and product coverage rates. The following process consisted of a systematic approach to deliver the tailored solution over a two-phase process.
The application process involved the implementation of a tailored amelioration and fertiliser program consisting of seed, water and organic materials. This tailored mix was hydraulically applied at a lowered rate to reduce the intrusive force of the species and avoid competition with the native seedlings.
The project required a second pass of the site with the application of the tailored Hydromulching BFM solution, chosen for its scientific construct and environmentally sustainable nature. The customised solution would enable seed germination and maximum erosion protection during the interim between the application period and of signs of vegetation growth.
The two-step application process measured a three day period, where technicians were able to successfully implement the customised program over the 11.2-hectare area.
The BBR Clay Mine rehabilitation project was initially pushed back a week due to heavy rain which compromised the subsoil. Given the moisture present within the substrate, technicians were required to wait for the soil to stabilised before mobilising on site.
When the team were able to attend the site, they were fortunate to maintain an uninterrupted schedule, which contributed to the ease and effectiveness of the product application.
The client inspected the area after the project and was pleased with the prompt application and ability for SGA technicians to meet the project requirements. Active communication played a constructive role in achieving healthy vegetation coverage and erosion protection. The client and SGA personnel were pleased with the outcome of the project.