There was a time not too long ago when most contaminated soil was simply dug up and hauled to landfills, or perhaps surrounded by slurry walls to prevent the spread of contaminants.
Over the last decade, the Environmental Protection Agency (EPA) and the Queensland Department of Environment and Resource Management (DERM) have focused on techniques designed to treat soil or render its contaminants to a harmless level.
Referred to as ?soil remediation techniques?, the number of these alternative treatment technologies continues to grow. Most, however can be classified into five general categories: biological, physical, immobilisation, chemical, and thermal.
?Every site varies considerably. It?s very different to general civil or construction excavation works,? explained Barry Finch, the director and owner of Earthbound Excavations, a company specialising in soil remediation.
A current project being undertaken by Barry and his team of six is a former caravan park. The site has underground fuel tanks which have leaked hydrocarbons into the soil.
For soil contaminated with hydrocarbons to be deposited in landfill, it must meet the minimum level of contamination as set by the DERM. If the levels exceed the minimum requirement, the material is ?farmed? to remove the contaminants.
?The material is first covered with lime, then fertiliser. It?s then blended, turned and aerated every fortnight,? explained Barry.
The microbial organisms within the material break down the contaminants to a harmless level enabling the material to be deposited safely into landfill. ?This process is utilised to remove contaminants that include, asbestos, arsenic, hydrocarbons or heavy metals (TPH) such as lead and mercury,? he said.
At the opposite end of the site are boat building sheds with slipways where the boats underwent repairs. The boats were sandblasted to remove old lead-based paint, which ran off into the water and sediment of the river bed.
?Retaining structures built from concrete enable excavation of the marine mud and prevent the contaminants going into the water with the tide,? said Barry.
Barry has spent the greater portion of his life working on and around heavy machinery. Leaving school at 14, he started work as a diesel mechanic before coming to Australia from England with his family in the mid-1960s.
He first became interested in the process of soil remediation in 1997 while working on the site of the 2000 Olympics at Homebush in Sydney?s west.
Formally, the site consisted of abattoirs and brickworks which required an extensive amount of remediation to be complete before construction of the stadium and athlete?s village could begin.
Ten lakes were built, all specially designed and holding up to 55 billion litres of water each. Large pipelines enabled the water to be pumped from one to another and up to the village to water parklands.
Contaminated land is listed on the Environmental Management Register (EMR). Backfilling cannot commence until after the contaminated soil is removed and the area is tested and passes inspection for minimum contaminant levels.
?This type of excavation is very precise, almost surgical, so patience is key,? said Barry. ?When excavating contaminated soils you may be removing as little as 200 millimetres at a time.?
Once a predetermined level has been achieved, further soil samples are taken and tested to determine if additional excavation is required.
Barry started Earthbound Excavations after working at Thiess Services with Steve Thorne, an accomplished environmental engineer whose studies have focused on remediation techniques. Barry and Steve have since joined forces to provide comprehensive contaminated land remediation and civil services.
Earthbound Excavations currently run two Volvo EC210C excavators. The first was purchased in December 2008 and the second the following April.
?The Volvos are fantastic machines, everything about them is first class – the economy, operator comfort and the well laid out interiors.
?Before purchasing the Volvos I did a lot of research on numerous machines and the Volvos came out on top. It was a decision driven not by price but the quality of the machine and ongoing services offered by CJD.
?The operators have commented on numerous occasions how smooth the Volvo machines are, not just with the operation of the controls but when moving over uneven ground and clearings, which is important in our line of work.?
CJD complete all the servicing requirements for Earthbound Excavations. ?The team are efficient and very helpful, parts are readily available and services are scheduled around our needs so we don?t lose days on site.
?CJD are very professional to deal with. They?re honest in their approach and extremely helpful and the service doesn?t stop once you have bought the machine. They are always on hand whenever we need them.?
Earthbound Excavations run its Volvo machines six days a week, with operators in the cab for up to 10 hours per shift.
?With the nature of our business, the operators need to be able to concentrate at all times. It?s not a bulk excavation process, so you can?t get into auto pilot mode. At the end of a day our operators exit the machine feeling as fresh as they got in.?
Prior to leaving an excavated site, Earthbound Excavations need to thoroughly clean all the machinery to prevent transferring contaminants to a new site.
?Remediation is an in-depth process not constrained to just the removal of contaminated soils but complete rehabilitation of the land, and our Volvo equipment is instrumental to us achieving this,? Barry concluded.
Source: CJD Equipment