Is the construction worker protected by the Tier I Look Up Table?

Yes. Assuming surface soil contact by all potential receptors, the construction worker is a less sensitive receptor than either the residential or commercial receptor in the Tier I Look Up Table.


Technical FAQs

1. How do I use the TPH values in the Tier I Look Up Table when comparing them to the TPH reports received from the laboratory? Answer

The Modified TPH values in the Look Up Table have different values in each of the three columns sub-titled gasoline, diesel/#2 fuel oil and #6 oil (heavy oil). Modified TPH is Total TPH minus the BTEX compounds.

Use the column that describes the type of petroleum source that has created the contaminated site. For example, if the source is gasoline, the lab report is compared to the Modified TPH criteria under the gasoline column. The Look Up Table value in the gasoline column is the not the allowable level of C6-C10 hydrocarbon as reported by a laboratory. The Look Up Table value is to be compared to the total petroleum hydrocarbon measured at the site less the concentration of the BTEX parameters.

If two products have spilled and mixed (i.e. gasoline and diesel) use the lowest value under either the gasoline or diesel columns. If two contaminants are present on the same site but clearly separated, they may be treated as two different source areas using the appropriate column criteria.

2. Can I use the Tier I Look Up Table criteria with off-site impacts? (For example if I have on-site Commercial receptors and off-site residential receptors.) Answer

Yes, but subject to the following conditions:

  • The site and any adjacent property are consistent with the default conditions for the Tier I Look Up Table. The defaults are found in the Atlantic PIRI Reference Documentation on the web site.
  • Use the correct Tier I criteria for the receptor that may be at risk. (If the adjacent off-site receptor is Residential, the hydrocarbon concentrations in soil and groundwater at the property boundary must meet the Tier I Residential criteria.)
  • Ensure that the off-site criteria will also be met in the future. This can be done by either presenting monitoring data showing steady state conditions or by groundwater modeling. Steady state means that the observed concentrations within the plume remain constant or decrease with the passage of time.
3. Are Tier I Look Up Table criteria applicable to sites with basements? Answer

Tier I Look Up Table criteria were calculated based on slab on grade construction assuming one meter of clean surface soils below the slab overlying the impacted sub-surface soils.

The RBCA model developers assumed that a source would not be located beneath a building (i.e., tank installation) and that contaminant migration from the source tank would migrate below the building in a manner which results in a clean 0 to 1.0 meter soil zone below the existing slab on grade structure. The Atlantic RBCA model does not consider advection when calculating indoor air impacts.

Tier I criteria may be used for residential furnace oil contamination (#2 fuel oil) in typical cases. The Atlantic PIRI Committee considered several furnace oil tank release scenarios using Tier II assessment where the product is near the basement wall and floor (next to approximately 30% of the wall/floor area). The Tier II scenario calculations assumed impacted soil and groundwater within 10 cm of the basement floor and walls and produced higher remedial criteria than the Tier I Look Up Table.

As such, use of the Tier 1 criteria at sites is reasonable for many sites with basements, however, the Site Professional is responsible for comparing the site to the other Atlantic PIRI default conditions before using the Look Up Table. This specifically includes the condition of the floor and walls for cracks and dirt floor sections, including sumps with open bottoms.

How are basements considered at Tier II?

If a basement exists, the site-specific depth to contaminated soil or groundwater should be calculated from the basement floor, not the ground surface.

If you conduct Tier II calculations on a building with a basement you should consider the buried sections of walls that can transmit vapours to the interior. This can be done by considering the sum of the basement wall and floor area in contact with soil as the modified floor area and recalculate a new Building Volume / Area Ratio (Screen 8.4). When calculating the building volume, only the basement height should be used since complete mixing of basement air and first floor air is unlikely. Ensure that the Building Volume / Area figure is placed in the correct exposure box for your site (Residential or Commercial).

4. How can I justify use of the Tier I Look Up Tables if the groundwater table at my site is less than the 3.0 metres below ground surface (BGS) used by Atlantic PIRI as the default condition? Answer

In general, if site conditions do not match the Tier I default parameter assumptions, Tier II should be used. Nevertheless, Tier I subsurface soil criteria are conservative for groundwater depths less than 3 m below the building floor slab due to conservative modelling assumptions. If the groundwater is within 1 m of the slab, Tier II should be used to develop groundwater SSTLs.

5. What is the difference between silt/clay and sand/gravel in the Tier I Look Up Table? Answer

A coarse grained soil (sand/gravel) is defined as material having greater than 50% (by dry weight) particles equal to or larger than 75 microns (200 mesh) in diameter. Materials with less than 50% sand-sized particles are considered fine-grained soil (silt/clay). If no seive data is available, then the lowest applicable number should apply until a seive test is performed.

6. Is the construction worker protected by the Tier I Look Up Table? Answer

Yes. Assuming surface soil contact by all potential receptors, the construction worker is a less sensitive receptor than either the residential or commercial receptor in the Tier I Look Up Table.

7. Can the Atlantic RBCA software be used for contaminants other than petroleum hydrocarbons? Answer

At present, Version 2 of the Atlantic RBCA software is sanctioned for use only with TPH and BTEX. The physical/chemical properties and toxicological data has been reviewed and updated for these compounds. Although the current release of the software contains similar data for many other compounds, these data have not been reviewed to ensure that they are up-to-date and appropriate for use in Canada. As a result, the Atlantic RBCA software model cannot be generally sanctioned for use with chemicals other than TPH and BTEX.

However, the concepts of risk assessment and management apply to non-petroleum contaminants under the Atlantic RBCA process adopted by the Atlantic Provinces. Site Professionals calculate such risks for a Tier 3 assessment.

8. Does the Atlantic RBCA software calculate cumulative risks? Answer

The use of cumulative risks in developing remediation objectives for contaminated sites is appropriate for chemicals that have the same biological end-points. The current Atlantic RBCA model uses cumulative risks for dealing with TPH and BTEX. However, for chemicals that have differing biological end-points, the summation of exposures or risks is not toxicologically sound and has little practical meaning.

The User Guidance manual outlines how cumulative risks are considered in the RBCA process. It also clearly indicates that the use of the Atlantic RBCA model for compounds other than BTEX and TPH can only be done in consultation with local regulators. Such consultation would also likely require input from a toxicologist or similar professional who can properly address the issues relating to interactive effects between chemicals.

The Site Professional must also consider the potential for cumulative risks from exposure to the same chemical through multiple pathways (e.g., indoor air and potable water). At many sites, one exposure pathway will be the critical pathway; however, the Site Professional should consider all possible exposure pathways in the site assessment process. Version 2 of Atlantic RBCA contains a Cumulative Risk Worksheet to facilitate this type of evaluation.


General FAQs

1. What is Risk Based Corrective Action (RBCA)? Answer

RBCA (pronounced “Rebecca”) refers to a new philosophy for managing contaminant release sites. With this new approach, the amount of environmental management required to ensure protection of human health and the environment is based on a scientific assessment of the risks posed by the contaminants, both now and in the future.
Environmental management always considers the risks of contaminants on a site. RBCA also considers the likelihood that people or environmental resources could be harmed by the contaminant. It achieves this by looking at the characteristics of the site, such as the type of soil, the location of water on the site and how the land is likely to be used in coming years.

RBCA clean-up goals are based on reducing risks to low, acceptable levels. This may be achieved by reduction of contaminant concentrations and it may also involve reducing the potential for exposure. An industrial site destined for redevelopment as a playground would require more stringent environmental management than if it were continuing in industrial use, where children do not play and workers protect themselves from exposure to substances.

At some sites it is not possible or practical to remove substances due to technological, physical or financial constraints. The risk-based approach allows the risks associated with leaving substances in place to be estimated. This information is then used to design appropriate risk management solutions to manage contaminants onsite and eliminate risks or reduce them to appropriate levels.

Previously, an industrial site would have to be cleaned to very low, background-level criteria by reducing the amount of contamination present. This would be true even if the land was remaining in industrial use. To confuse matters more, different jurisdictions could set different criteria for the clean up.

RBCA sets the stage for effective and efficient clean-ups. The advantages of using RBCA include that it:

  • Permits rapid response to critical levels of contamination
  • Documents the substances at a site, their location and their extent on- and offsite
  • Estimates the size and likelihood of risks and hazards to human and non-human receptors
  • Documents and evaluates the effectiveness of measures proposed to manage contamination in place
  • Targets cleanup levels are based on current and future use
  • Provides options in appropriate remedial measures
  • Allows property owners to allocate environmental resources more effectively
  • Offers consistency in determining clean-up levels within and between jurisdictions
  • Results in fewer sites being fenced off and abandoned
2. When we hear about petroleum contamination, what exactly does that mean? Answer

Petroleum products include gasoline and furnace oil. Our society has used these products for almost a century and spills and fuel from leaking storage tanks have contaminated many properties.

Petroleum contamination is a concern because it is persistent in soils, where it moves and degrades very slowly. Spilled petroleum products can seep into streams and dispersing into groundwater reservoirs, seriously degrading water supplies. Petroleum impacted soils release harmful vapours that have the potential for adverse effect to both human health and the environment. when the soil is disturbed.

The effects on human health include everything from minor physical symptoms to life threatening diseases such as cancer. Children are often most at risk from exposure to contaminated soil, air and water.

Petroleum products can also have a serious adverse effect upon the environment. Sites where spills have occurred can release substances that can kill fish, impair the reproduction of birds, and contaminate the food web, resulting in both short term and long term damage to an ecosystem.

3. How is an Atlantic RBCA clean up carried out? Answer

When a spill occurs or contamination is discovered, the provincial Department of Environment is advised and an investigation is initiated. No matter how big or small the contamination seems to be, a sequence of basic activities are performed for all human health and ecological risk/exposure assessments, which include:

  • a visual site assessment and document review to look for any causes for concern
  • identifying chemicals of concern
  • identifying possible receptors – adults, children, animals and plants
  • identifying pathways that could result in exposure to the chemicals of concern, through air, water, contact with the soil or breathing of dust
  • risk and sensitivity/uncertainty quantification, and
  • development of a remedial action plan to manage risks
  • implementation of the remedial action plan

There are up to six steps involved in an Atlantic RBCA cleanup:

Step 1: Initial Notification

When contamination is discovered, a Department inspector investigates as part of the notification process. The investigation identifies who is responsible for the property, identifies contaminants and includes a preliminary assessment of risk. The Inspector can order immediate, limited clean up action, or the Inspector can advise the property owner to hire a professional to do a more thorough site evaluation.

Step 2: Site Evaluation – Tier 1

A professional trained to use the Atlantic RBCA process evaluates the site for the property owner. Atlantic RBCA includes three tiers of site evaluation. At Tier 1, the sources of contamination transport pathways and exposure pathways are identified.

Using documents or the Atlantic RBCA software, measures of the levels of contaminants on the site are compared to risk-based screening levels (RBSLs) provided in an Atlantic RBCA generic look-up table. If the screening levels are not exceeded and the conditions on the site are not exceptional, no further action may be required.

Step 3: Remedial Action Plan or an Expanded Site Evaluation – Tiers 2 and 3

Where contaminant concentrations on a site are above the screening levels, the site professional prepares a remediation action plan to correct the situation and submits it to the Department of Environment.

An appropriate remedial action plan sometimes requires a Tier 2 evaluation, specific to conditions of the site, to correctly identify the best ways to manage and reduce the risks. This is often true at petroleum release sites. In a Tier 2 evaluation, the site professional collects detailed site data. The site-specific information is entered into the Atlantic RBCA software, which calculates Site-specific Target Levels (SSTLs).

Some sites with complex conditions or contaminants benefit from a more extensive evaluation. This is a Tier 3 approach which goes beyond the Atlantic RBCA software to include detailed site characterization, developm ent of site-specific numerical models and evaluations, and complex fate and transport models.

After the Tier 1, 2 or 3 site evaluation is completed, the site professional develops an appropriate remedial action plan to meet the risk management targets that have been identified and submits it to the Provincial Department of Environment.

Step 4: Review of the Remedial Action Plan

The Provincial Department of Environment reviews each remedial action plan to evaluate if it properly manages identified risks. Remedial action plans may require revisions, including returning to Step 3 to perform a more extensive site evaluation using the next higher Tier.

Once the Department accepts the remedial action plan, clean up work can begin.

Step 5: Remedial Action Plan Implementation

The property owner and site professional implement the remedial action plan to remove contamination, limit exposure pathways and institute controls on how the land is used. Testing after clean-up work is completed will confirms that target levels have been achieved.

Step 6: Compliance Monitoring and Site Maintenance

Once the property owner and site professional are satisfied that the objectives of the remedial action plan are achieved, they submit a Closure Report to the Department of Environment. The report details the final condition of the site, any land-use restrictions and any ongoing monitoring requirements. The Department of Environment acknowledges receipt of the Closure Report and confirms if further actions are required.

4. Who oversees the Atlantic RBCA program? Answer

Partnership is a key element in the success of Atlantic RBCA. A co-operative committee called Atlantic Partners in RBCA Implementation, (or Atlantic PIRI), developed Atlantic RBCA and continues to oversee its implementation across the region. The committee includes representatives from the petroleum industry, environmental consultant companies and government departments from the four Atlantic Provinces.

Atlantic PIRI encompasses the different mandates and objectives of each of the partners. The Provinces have a responsibility to prevent pollution and to regulate the clean up of contaminated sites. The petroleum industry views remediation of sites they own as a corporate necessity. Environmental consultants need to understand how and when to use Atlantic RBCA to serve their clients.

When Atlantic RBCA is applied to remediate a site, there is a working partnership between the property owner, the site professional, and the Provincial Regulator, which ensures environmental protection as well as cost-effective and efficient clean up.

In, addition to these partners, others have an interest in seeing contaminated sites managed effectively. Local governments are concerned about their potential liability when approving developments on contaminated land. Landowners and developers wish to redevelop contaminated sites and avoid long-term liability. Without a process they can have confidence in, bankers are reluctant to lend money for development of contaminated land, fearing they may have to pay for site cleanups if a loan defaults.

5. Does Atlantic RBCA represent an improvement in protecting the environment and human health? Answer

Yes. Atlantic RBCA increases the level of human health and environmental protection because it includes comprehensive analysis of risks that are related to the actual conditions on an individual site. The Atlantic RBCA software includes state-of-the-art analysis of the risks from petroleum products, taking into account the differing hazards associated with the different hydrocarbons. The software also estimates risks associated with other substances, such as the carcinogenic organic chemicals benzene and toluene which are commonly found in gasoline. This analysis produces more stringent clean up requirements when more risk is present.

As the risks are assessed, Atlantic RBCA requires the most protective values be applied. When a substance can present a risk to human health, the environmental management must ensure that health limit is not exceeded. Similarly, if a contaminant presents more risk to the environment than to human health, the environmental protection level will be applied. Even if no health or environmental risk remains, aesthetics such as a lingering odour or taste in water will be sufficient to require further management.