Soil Contamination

How Clean is that…Fill, Site, Waste?

In NSW the assessment of how “clean” is defined in relation to a site, to incoming fill or to soil to be disposed of, is regulated by different sections of the NSW Department of Environment and Conservation (DEC). The different sections apply different guidelines and standards. The following discussion excludes the consideration of soil containing asbestos.

Site

Sites are assessed against acceptance criteria for a range of possible contaminants. The criteria are usually applied in relation to the intended use of the site during a development planning process. The criteria are also sometimes applied in relation to the existing use of a site in cases where there is a concern about potential site contaminants and associated impact on health & safety.

To assess a site soil samples are collected and analysed for a range of substances. The selection of the range of substances for which the soil is to be analysed should be based on the history of the site and therefore the possible contaminants. The number of sampling points required depends on the size of the site, with a minimum of 5 sampling points, each point characteristically sampled at several depths. In addition to the basic samples, there must be blind and split replicates, blanks and rinsate samples analysed. The 95% Upper Confidence Level (95% UCL) of the average for the basic samples must be compared with the acceptance criterion. That is, if the site passes, then there is a 95% probability or better that the average concentrations of the contaminants are below the acceptance criteria. Therefore as long as there are no signifi cant hotspots it is possible for some results to be above the criteria.

Composited samples can be analysed for non volatiles thus reducing the cost, but the acceptance criterion is reduced by dividing it by the number of composited subsamples. Where contamination may be present compositing is not recommended, but it may save money when used as a screening tool where contamination is unlikely.

The acceptance criteria are divided into groups including:

• Single house residential with poultry and home grown produce contributing more than 10% of the fruit and vegetable intake. This criterion is applied to most single houses with yards even though poultry or home grown produce is not a realistic option.
• Residential, children’s day-care centres, preschools, primary schools with gardens and accessible soil where home grown produce contributes less than 10% and there is no poultry.
• Residential with minimal access to soil, including high-rise apartments and flats.
• Parks, secondary schools, recreational open space, playing fields.
• Commercial, industrial.
• Garden beds.

The criteria also contain requirements for odour and ascetic factors. At times even soil containing nothing other than broken pieces of brick may be considered unsuitable.

A typical program of site assessment and possible cleanup includes the conduct of a site history investigation, sampling, and if contaminated, preparation of a Remedial Action Plan (RAP), followed by remediation (usually consisting of excavating the contaminated soil and taking it to a disposal facility), and validation sampling and analysis. The whole program is written into what often becomes quite a large report which is frequently then submitted to independent audit.

The process can be time consuming and expensive.

Disposal of Waste Soil

When soil is removed from a site and taken to a disposal facility, because the facility is only licensed to accept certain classes of waste, the facility requires a Disposal Report. The Report must classify the waste into classes such as VENM (Virgin Excavated Natural Material), Inert Waste, Solid Waste, Industrial Waste, Hazardous Waste, Scheduled Waste.

To classify the waste soil material samples must in effect be analysed for concentration of potential contaminants, as well as leachability of those contaminants via the TCLP (Toxicity Characteristic Leaching

Procedure) test. This test consists of placing some soil into a container and dripping an acidic solution through it for a period of time to simulate conditions in a disposal facility. The leachate is analysed for contaminant concentration.

Certain types of waste can be disposed of without sampling and analysis. These include building and demolition waste and road base. These types are automatically classifi ed as Inert etc.

The criteria for what is an acceptable level of contaminants on a site and the criteria for disposal of waste including contaminated soil (Non Liquid Waste) are different from and independent of one another.

 

Fill and Crushed Concrete Material

Fill and crushed concrete imported on to a site should be tested against the site criteria. The guidelines require that the site which is the source of fill is visited and assessed visually. Its site history should be examined and care should be taken to ensure that the fill arriving onto the site is the same as the material examined and sampled at the source site.

Before accepting fill or crushed concrete GETEX advises that you check on the analysis, including the thoroughness of the analysis program, ensure the assessment included inspection of the source site and its history1, ensure the analysis certifi cate is for the same material as is being delivered to you.

Be careful moving untested soil around a site. If it later turns out to be contaminated the contamination can easily have been smeared around, resulting in increased clean up / remediation costs as well as extra validation costs

Disposal of Liquid Waste

Liquid waste is usually treated in a specially designed facility. Liquid waste is subject to licensing under the Waste Minimisation and Management Regulation.

Generally, other liquids are those which may be discharged to sewer in accordance with a discharge licence, or those that may be discharged directly into waters under the Protection of Environment Operations Act (POEO), or those which may be discharged into waters in accordance with a licence issued under that Act.

Sediment, Soil and Water Runoff Controls, Heath & Saftey and Environmental Considerations

Before starting work which involves disturbing soil ensure there are adequate controls in place to prevent sediment, soil, and uncontrolled water runoff or blow off. Arrange for proper truck clean down facilities to prevent soil from tracking out onto the road, arrange for collection, testing and disposal of possibly contaminated water, arrange for dust suppression. Consider whether any special occupational safety measures are needed such as personal protective equipment (PPE). Arrange for adequate personal washing facilities. Consider if the work may be unacceptably noisy, or if it might generate odours. Plan truck routes. Prepare Safe Work Method Statements.

Services

Consulting, management, monitoring and inspection services covering:

Hazardous Materials

• Lead, Silica, Dusts, Petroleum Products, Solvents, Gases
• Inspections/Registers
• Air Monitoring
• Management Plans

 

Occupational Hygiene Services

• Airborne Contaminant monitoring
• Workplace Assessments
• Risk/Hazard Analysis

 

Air & Water

• Quality Assessment & Monitoring
• Indoor/Commercial
• Environmental/Industrial

 

Download the Soil Contamination - How Clean is that…Fill, Site, Waste? Information Sheet (PDF)