Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:3:p6
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 3 (pt 6/8)
Character Range: 111305–114403

erodible soil, potentially adverse ecological effects may occur some distance from the contaminant source area. The potential for off-site environmental impacts should be considered in the development of the conceptual site model. Methods for determining leachability are discussed in Schedule B3.

It is common for established industrial areas to contain higher levels of soil contamination (such as metals) than surrounding areas.  Receptors and soils immediately adjoining older industrial zones may be affected by the accumulation of soil contaminants caused by migration through subsurface contaminant movement and erosion of contaminated soils.

For example, a site with lead (Pb), zinc (Zn) and petroleum hydrocarbon concentrations in soil below EILs and ESLs for commercial/industrial land use (where a 60% or 65% species protection level would apply) would be acceptable for the site use. However, if the site adjoined an area of ecological significance, such as a protected wetland, the site assessment should also consider the possibility that contamination may migrate off-site and impact the wetland where 99% species protection limits would apply.

In other cases sites may have aged metals and metalloid contaminants with stable, cohesive soils and low in situ leachability and pose a low risk to the ecosystem.

3.5              Considerations for groundwater assessment
When groundwater from a monitoring well contains levels of contaminants above the appropriate investigation levels (Tier 1 assessment), then further investigation (Tier 2 assessment) is required. This may take the form of consideration of site-specific conditions and circumstances which may result in modification of the generic Tier 1 criteria. If no modification of the Tier 1 criteria is applicable, the assessment proceeds directly to Tier 3 where groundwater concentrations at the point of exposure (point of use) are compared with the generic GILs or site-specific response levels. If this indicates that the investigation levels are exceeded at the point of use, or in the discharge environment of the groundwater, then an appropriate response is required. The relevant guideline documents should be consulted for informed interpretation and application of GILs and modified GILs.

Groundwater protection may be a particular concern where contamination occurs in sandy soils containing naturally low levels of organic matter, clay and trace elements. In most situations, soil contaminants at levels below appropriate EILs or HILs do not pose a threat to local groundwater sources. However, possible impacts on groundwater should always be considered particularly for sites impacted by petroleum hydrocarbons and halogenated solvents. In some cases the soil may not reveal contaminants of concern while groundwater is affected.

It should be noted that some jurisdictions may have groundwater protection policies that require action even where levels do not exceed the AWQG values at the point of use.

3.6              Aesthetic considerations

    3.6.1          Introduction
Aesthetic issues generally