Federal Contaminated Site Risk Assessment In Canada Part I: Guidence on Human Health Preliminary Quantitive Risk Assessment (PQRA)

2. Scope Of Work / PQRA Report Content

The human health preliminary quantitative risk assessment (PQRA) report should include the chapters/sections listed below. It is important for risk communication purposes that each PQRA report be able to "stand alone". Therefore, all relevant equations, assumptions, models, etc., required for the PQRA must be presented in each report.

2.1 Executive Summary

A brief synopsis of the site, the definition of the problem, the results and conclusions of the PQRA, and any recommendations stemming from the analysis must be presented.

2.2 Introduction

This section should briefly identify the client department, the project manager/departmental contact, and the assessor undertaking the risk assessment.

2.3 Description of the Property/Site

A brief but complete description of the site should be provided, including all site characteristics that may be pertinent to the understanding and/or quantification of potential exposures and risks on-site. Subsections may include but not necessarily be limited to:

• site location;
• current site use;
• topography;
• geology;
• hydrogeology, including the use of groundwater as a source of drinking water;
• identification of current land uses and potential receptors on neighbouring properties;
• distance to the nearest community (village, town, city, etc.); if the site is within municipal boundaries, this should be mentioned;
• an estimate of the size of the population of the nearest community;
• proximity to local surface water;
• summary of on-site contamination, including identification and description of any plumes, dense non-aqueous phase liquid (DNAPL), light non-aqueous phase liquid (LNAPL), etc.;
• local or regional background concentrations of contaminants (as available and appropriate); and
• reference to appropriate reports that provide a detailed description of the property.

2.3.1 Concentrations of Contaminants in Environmental Media

The data on concentrations of contaminants measured on-site should be adequately summarized. At the least, for all sampled media (soil, groundwater, surface water, vegetation, etc.) the minimum, maximum, and arithmetic average concentrations should be reported, along with the number of samples analyzed. For soil samples, the depth at which samples were collected should be indicated. A map depicting sampling locations is often helpful in demonstrating or determining if the sampling plan has been adequate to reflect the distribution of contaminants across the property.

Direct pathways of exposure to soil contaminants (i.e., ingestion, dermal absorption, inhalation of suspended particulate matter) will relate predominantly to "surface" soil. The precise definition of surface soil will vary from site to site, depending on the depth of sample collection and may be represented by depths ranging from 5 cm to 1.5 m. The CCME (1996) defines surface soil from "grade" to 1.5 m below grade. Barring sampling from shallower depths, the CCME definition should be used to define surface versus subsurface soils.

The laboratory performing chemical analyses should be certified by the Canadian Association of Analytical Laboratories (CAAL) or similar organization. Further information on sample collection, analysis, and data management is offered by the CCME (1993a, 1993b).