Detailed Site Investigation (DSI)
or Phase 2 Environmental Site Assessment
If a Preliminary Site Investigation (PSI) or other assessment identifies a risk of contamination and the available information is insufficient to enable site management strategies to be devised, a Detailed Site Investigation, or DSI, may need to be conducted.
The DSI is the site sampling, or Phase 2 investigation stage. It sets out to delineate the vertical and lateral extent of site contamination - usually with the site’s proposed land use in mind; or to inform upon appropriate site remediation or management strategies.
Soil is always tested and groundwater and/or surface water is tested where the past use of the site means there is a risk of contamination; the soil is contaminated with compounds that can contaminate groundwater; or, if a surrounding site is known to be, or is potentially contaminated, and there is a risk of the contamination migrating to your site.
The site is generally investigated in accordance with the requirements found in AS4482. These may be reduced due to the scope of a particular project, but sampling plans must be driven by clear Data Quality Objectives. The concentrations of chemicals are compared to criteria in the National Environment Protection Council’s “National Environment Protection (Assessment of Site Contamination) Measure (NEPM)” as amended in 2013.
There are many technical considerations in making a proper assessment of the site contamination and doing so requires a suitably qualified specialist such as Atma Environmental. This will include evaluation of the contaminant type(s) and distribution, source-receptor pathways, data completeness, etc.
It is imperative that your consultant has a solid understanding of what underpins the NEPM guidelines. Preference should be given to consultants who are members of the Australian Contaminated Land Consultants Association (ACLCA), such as Atma.
If the soil is being tested with removal offsite in mind then the contaminant concentrations need to be assessed against the requirements stated in Environmental Protection Authority Victoria Publication IWRG621 “Soil Hazard Categorisation and Management”, or similar guidance for other states in Australia.
Where a properly planned and executed DSI demonstrates that the site is not contaminated, then no further works are required. If it demonstrates that the site is contaminated, further investigation to inform decontamination requirements or to clarify potential human health risks may be required.
Atma Environmental’s team of highly qualified contaminated land specialists can manage any of your site investigation requirements, including:
- Ground gases (e.g. methane) and vapours;
- Waste categorisation.
- Service stations;
- Greenfield sites;
- Educational facilities;
- Childcare centres;
- Council sites;
- Defence sites;
- Dry cleaners;
- Agricultural sites and sheep dips;
For more information on environmental site investigation, download our report, “What you Need to Know About Contaminated Land”, which provides a overview of what is involved in determining the contamination status of land you may be purchasing or developing, or call Atma Environmental now on +61-3-9429 6955.