In this page we take you through the whole Level 1 ERA
process for XYZ Enterprises including problem identification, conceptualising a
model of the site, a site investigation, receptor characterisation, exposure
assessment, toxicity assessment, risk characterisation, and
environmental risk management decisions. (Note: this is a long page).
For further details on the theory or background
relevant to the particular stage in the ERA framework, click on the
graphical icon beside the heading.
7B Anywhere Drive has been identified as a site requiring an
Problem Identification should take stock of the problem
and determine what should be assessed. The site should be characterised, current
and historic land uses should be determined, both at and around the site, and
the contaminants of concern should be identified. Potential receptors should be
defined and potential pathways identified.
The objectives for the ERA (including what information needs
to be collected, analysed, or assessed) should be set and documented at this
Based on the information obtained from the preliminary site
characterisation, an initial conceptual model for the site
can be developed. This may be a simple site sketch, but it should identify
possible contaminant sources, pathways and potential receptors. It is also
useful to tabulate the preliminary findings.
FINDINGS: PROBLEM IDENTIFICATION
XYZ Enterprises, Allsorts
Currently used as an industrial
facility for the finishing of steel products and storage/sale of scrap
metal. Around 60% of the site in bare soil, 20% with gravel chip surface
cover, and 20% of the site with a concrete slab/building cover.
Based on the Certificate of
Title and aerial photos, the land was originally pasture, and then
developed by a sawmilling company as a timber processing yard. Building
consents indicate that the site underwent upgrades. The date of timber
treatment plant installation is uncertain but possibly from the early
1970s. The use of boron is uncertain but use of PCP is unlikely as a
nearby site owned by the same company apparently undertook this task (see
records for STU Ltd). Unconfirmed reports of a boiler and possibly an
underground petrol storage tank (UST) at the site. Unconfirmed reports of
waste dumping on the bank of the river.
Copper, chromium, arsenic, boron,
Petroleum hydrocarbons, BTEX,
Metals (zinc, chrome, lead, others?).
Air dust from wind action, traffic on site
Groundwater leaching through soil profile,
leaking from petrol UST
Surface water stormwater runoff to river &
drain, groundwater infiltration;
Leachate from dump,
Direct contact with dump materials.
River/drain biota, river/drain
sediment, intertidal biota, riparian/ wetland biota, downstream river
users, down-gradient groundwater users, upwind properties/residents, soil
At this point it is usually necessary to undertake some form
of site investigation. In this example the site investigation involves some
further inspection of the site and sampling and analysis of soils, sediment and
surface water for contaminants of concern.
It is good practice to outline your site investigation in a
site investigation plan so that you have a clear idea of what you want to
investigate and how you want to go about your investigation before you start.
Many of the NZ guidance documents, reviewed
as part of this project, have full discussions on site investigation methods. Some
provide guidance on the number of samples that may be needed to provide a sound
statistical basis from which to assess the extent of contamination. Australian
Standard AS4482.1 1997 also provides details of these.
An example of a brief site investigation plan for on-site soil
contamination for XYZ Enterprises is presented below.
XYZ Enterprises, Allsorts Industrial Park
To establish the presence/absence of Copper Chrome Arsenic Boron and
trace metals contamination in soils at the site.
To undertake a site inspection to confirm the presence and location of
underground storage tanks, waste dump, boiler ash previously identified.
Copper, chromium, arsenic, boron ICPMS Timber Treatment Suite.
On-site soils, off-site soil as control site
7 on-site soil samples (n=21) & 1 off-site soil (background) (n=3)
at 3 depths 0.2m, 0.5m, & 1.0m.
On-site soil samples will be taken in a rough grid pattern; off-site
soil (background) will be taken from the adjacent northwest farm paddock
from at least 50m distance from the site boundary.
Chain of custody documentation for samples; photographs of the sample
locations and other points of interest; update site layout map showing
Sample results to determine the existence of on-site CCA/B & trace
Confirmation of location of UST dump site & boiler ash.
1: Possible excavation of test pits for dump site.
2: Test pits for UST &.Boiler ash.
What are the potential receptors that might be affected by the contaminants
In a level 1 assessment it is normally a straightforward
procedure to identify and characterise on-site human receptors. While this
process is not necessarily straightforward for ecological receptors, it is often
sufficient to only broadly identify them. Relevant ecological benchmark criteria
generally ensure the protection of sensitive species. However, despite this
level of assurance, it is worth thinking about the range of ecological receptors
that could be exposed to your contaminant of concern at an early stage in the
risk assessment process.
For example soil biota may include plants, animals and fungi
that may all be affected to a greater or lesser degree by soil contamination. Of
the soil fauna, some may simply live in or on the soil, others may consume the
soil or organic litter on the ground surface, and each may be exposed to a
contaminant through a very different exposure pathway.
For the XYZ Enterprises site, possible receptors include:
On-site workers & site visitors
Off-site residents downwind
Groundwater users; and
River and estuary users (e.g contact and non-contact
recreation, fishers / mahinga kai) possibly affected through interaction
with water and/or consumption of wildlife. To confirm or otherwise at a
Soil Biota: The site has been
an industrial site since the 1960s. Soil biota assumed to be limited to common
robust species with little off-site migration. Overgrown grass and weeds are
present in places on-site and soil fauna and flora are of moderate concern as
Drain Biota: Limited
instream habitat, some weeds on bank, prolific algae. No fish or other fauna
observed. Sprayed regularly by council staff. Sediment in-fauna, if present
Riparian (riverbank) Biota:
The riverbanks are steep at this location. No apparent indigenous
species or other riparian habitat of note (e.g blackberry). No receptors of
Downwind Habitat: No apparent
habitat of note downwind. Mainly industrial properties. No receptors identified.
ABC River: ABC River as
main receptor of concern. Include migrating fish, resident fish/eels, aquatic
insects. Possible sediment in-fauna.
Wetland Biota: 450m
downstream of the site includes raupo, reeds, willows, sedges, and waterfowl
ducks, occasional seagulls, rare bittern (DOC records), frogs, aquatic insects,
eels. No receptors of immediate concern. Migration and/or feeding in and around
site may require confirmation at level 2/3 if drain or river biota affected.
Intertidal Biota: 1.5km
downstream of the site where river exists to sea via a channel. Narrow
intertidal area on both sides of the channel. No known shellfish beds or other
habitat of note. No receptors of immediate concern.
In summary, ecological receptors of immediate concern at XYZ
Wetland and intertidal biota are not identified as receptors
of concern at this stage. They may need to be revisited later if adverse impacts
are identified for aquatic biota in the ABC River (Risk Management Decision).
What concentrations of the contaminants of concern might the receptors be
At level 1 the assessment of exposure is incorporated into the
criteria against which you are assessing your contaminants of concern. These
criteria have been developed for one or several potential exposure pathways and
they may or may not be relevant to the conditions at your site.
For XYZ Enterprises four
small examples are provided to highlight how exposure may be assessed.
Looks at how risks may be assessed at a Level 1
assessment by considering the appropriate exposure pathways for likely
Provides a standard Level 1 assessment example for an area
suspected of metals contamination.
Looks at how off-site aquatic effects can be
identified and broadly scoped using on-site data.
Looks at how other factors may affect a risk
What might the contaminants of concern do to the receptors and at what
For a level 1 toxicity assessment the concentrations of contaminants of
concern are compared with relevant guideline or assessment criteria for
that contaminant. Again, the relevant guideline criteria tend to be
conservative (i.e. they represent the likely worst case situation and
therefore tend to be protective of most species). However, it is good
practice to be aware of any factors that may change how the contaminant
of concern affects your receptor.
For example, some metals exhibit variable toxicity to aquatic life
depending on the hardness of the receiving water. Others may exhibit
different toxicity at different oxidation states and some organic
compounds in aquatic environments can have increased toxic under
While these factors are generally well covered in the relevant guidance
documents (reviewed in this site), summary tables or checklists often do not contain this information.
A good summary is presented in the MfE/MoH Health and
Environmental Guidelines for selected Timber Treatment Chemicals
There are some instances where you may know very little about some of
the basic properties of a contaminant of concern. Good sources of
information on contaminants of concern can be found in various web-based
databases (reviewed in this site).
These include iris, toxnet (http://toxnet.nlm.nih.gov/), or
These databases can provide some of the basic information including its physical and
chemical properties, likely human health effects and ecological effects.
However, in many of these sites, the assessor could be presented with
numerous benchmark criteria developed for different agencies for
different purposes, some of which may not be suitable for use in all
For CCA and BTEX in soils we have compiled a list of some relevant
benchmark criteria with a commentary on their applicability to NZ
XYZ Enterprise example - continued
Surface water samples were analysed from the river and
drain at XYZ Enterprises and presented in the following table.
Average contaminant concentrations (n=3) from ABC river
upstream (1R) and downstream (2R), of XYZ Enterprises and from drain
upstream (1D) and downstream (2D) of XYZ Enterprises:
h: hardness dependent
Total copper is elevated in river water downstream of
the site and exceeds both chronic and acute criteria. The hardness of the
water was not measured and although it exceeds USEPA criteria (at hardness
of 100 mg/L) it is likely that water hardness in the ABC River could be
much lower (30 mg/L) resulting in a lowering of the relevant criteria.
At this concentration, copper can be expected to be
acutely and chronically toxic to aquatic organisms. However, its toxicity
could be reduced if there is are elevated concentrations of dissolved
organic carbon (USEPA 1999). Water hardness and dissolved organic carbon
in particular will need to be measured to confirm this assessment.
Zinc is also elevated in the river water downstream of
the site and exceeds ANZECC guideline values for the protection of aquatic
ecosystems but not USEPA criteria. Further work would be required to
assess the toxicity of zinc once the water hardness has been established.
A level 1 assessment of XYZ enterprises site at 7B
Anywhere Drive has determined the following key points.
BTEX. Soils exceed benchmark value for benzene only.
pathway not complete. Likely secondary pathway (inhalation of
benzene outdoors) meets benchmark criteria.
Visitor / On-site worker
contact with sharp materials at dump site
physical exposure to on-site workers and site visitors accessing
site through broken fence.
Cu, Cr, As, Zn. Exceeds soil guidelines for Cu and Zn.
exposure through surface soils at concentrations exceeding
benchmark criteria for Cu and Zn in soil.
water ABC River: aquatic ecosystem
Cr, As, Zn
of aquatic species to Cu and Zn in surface water in ABC River in
concentrations exceeds benchmark criteria.
At a level 1 assessment the degree of risk is usually
expressed in qualitative terms. For example:
- The risk to on-site worker from exposure to petroleum
contaminants in the soil is likely to be low and within guideline
values for likely site activities;
- The physical risk to workers and visitors from
contact with sharp material at the dump site is likely to be moderate
as access to this area for site visitors is unrestricted and on-site
workers are often working on the site dumping or re-using scrap
- There is a potential risk to soil biota on-site and
to aquatic life from elevated concentrations of Cu and Zn.
- All other contaminants of concern are within
guideline values for the protection of soil-biota and aquatic species.
The uncertainties of the investigation also need to be
clearly outlined at this stage to provide a context to the Risk
Characterisation. For the XYZ Enterprises there are several areas of
- Recreational and cultural use of the ABC River has
not been assessed at this stage;
- The implications of exceedances of Cu and Zn on
wetland and intertidal receptors downstream of the site are not
- The toxicity of Cu in relationship to dissolved
organic carbon has not been established.
One area of uncertainty is the source of the Cu and Zn.
Previous examples routing soil contamination through to the ABC River
suggested that the source of the contaminant at the site is limited. You
may wish to check this to make sure that there are no other sources of Cu
and Zn nearby (e.g. stormwater coming from upstream of the site).
There are also a variety of assumptions that also need
to be recognised and documented. For example the migration of Cu and Zn
from the site to the ABC River via groundwater is considered to be
At this stage the assessor will need to make some
decisions regarding management actions at the ABC site. These decisions
may range from doing nothing, to undertaking a more detailed level of
investigation and risk assessment through to remedying any adverse
environmental effect that have been identified.
These decisions may be made by the site assessor, or
they may involve consultation with a number of other parties, including
the site owner, site users, regulatory agencies and/or those that could be
affected by off-site effects such as neighbouring landowners, Tangata
Whenua, or resource user groups.
For XYZ Enterprises, the following risk based decisions
- The dump site will be covered with a minimum
thickness of 0.5m of compacted soil and the fence repaired to prevent
- No further investigation or remedial work will be
undertaken for petroleum contamination identified at the site.
However, the presence of contaminants will be noted in site plans with
an annotation attached to the plan that restricts building on that
part of the site without further investigation or remediation.
- The potential for Cu and Zn to affect soil biota will
be further assessed.
- The potential impacts of Zn and Cu exceedances on
water quality in the ABC river will be assessed focussing on:
- the nature of Cu and Zn discharges from the site and
- factors that control toxicity of Cu and Zn to aquatic
- confirming the source of Cu and Zn;
- identifying specific receptors that are present in
the ABC River and assessing their sensitivity to Cu and Zn.
Assessing the potential for Cu and Zn to affect soil
biota iterates a level 1 assessment using more detailed soil sampling and
Assessing the potential impacts of Cu and Zn on aquatic
life in the ABC River is a level 2/3 assessment.
If you are unable to make a conclusive decision, the next step is a
Tier 2 assessment.
This is beyond the scope of introductory risk assessment.
However, some details for the XYZ example
at Tier 2 are provided.