This has seen investigations being undertaken to identify approved disposal sites, cost collecting, managing and transporting the drill slurry as well as ways in which the material can be recycled to benefit the environment.
A critical factor when costing and managing Trenchless Technology projects is to consider what to do with the drill slurry produced by HDD operations. Over the years the HDD drill slurry waste has not been seen as an important part of the trenchless project with all drill slurry being disposed by the contractor with little or no input from the client. In the past the drill slurry has been seen as an unwanted quantity and presents more of a problem than a benefit to the contractor. In the past drill slurry has been disposed of in a variety of ways including paddocks, down drains, private farm land, along roads and even left onsite.
Having adequate equipment like purpose built vacuum tankers and correct site preparation for collection of the drill slurry is vital if the product is to be properly disposed of. Ensuring the drill slurry isn’t contaminated through man-made or natural subsoils may allow for an array of additional benefits to be explored.
Bettergrow investigates
One Sydney-based company who has investigated the benefits with recycling drill slurry is Bettergrow. The Bettergrow business was established in 1988 and specialises in resource recovery solutions for beneficial reuse of sands, soils, as well as green waste and food waste.
In April 2007, with the assistance from the Department of Climate Change (Environment Protection Agency, New South Wales) and local council, Bettergrow established a purpose built recycling facility at Vineyard, New South Wales to receive and control drill slurry from HDD activities and hydro excavation. In February 2010, due to its successful Sydney operation, Bettergrow undertook a duplication of its Vineyard site and established a drill slurry disposal depot at its landfill site in Swanbank, Queensland.
Currently the HDD contractor or client can either transport the drill slurry using his own vacuum tanker, direct to a Bettergrow facility or leave the collection, vacuum tanker and transport management to Bettergrow. Once the drill slurry is collected at one of the Bettergrow facilities they utilise an array of resources to produce various soil conditioning products which include NaturaliserTM and MinemixTM.
Naturaliser is the aqueous phase produced at Bettergrow following screening, treatment and dewatering. To improve the quality of this resource, Bettergrow add proprietary admixtures to then be able to use the drill slurry as a bulk liquid conditioner for sandy, weathered agricultural soils.
Another use of Naturaliser is an aid for retention of soil water within the plant rooting zone in the domestic landscape and indoor plant trade.
Minemix is derived from the solid phase from blending the drill slurry treatment with selected stabilised organics and/or bottom ash. The solid phase consists of ground rock mineral material, extracted clay and bentonite clay. These blends are distributed as top soil replacement materials for denuded land such as quarry restoration.
To ensure a high standard of quality is maintained, Bettergrow follows a rigorous Quality Assurance procedure to ensure all materials delivered are within the required specifications expected by Bettergrow and the Department of Environment and Climate Change.
Bettergrow also undertake onsite audits through specialised industry professionals such as Trenchless Advisor Pty Ltd to ensure contractors are maintaining a clean and proper work site along with using appropriate drilling additives.