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TAB #2: Site Assessment Procedures

DESCRIPTION:

Contaminated sites

Contaminated sites may include production areas, landfills, dumps, waste storage and treatment sites, mine tailings sites, spill sites, chemical waste handling and storage sites, and airport fire fighting training areas (FFTAs). These sites may be located in residential, commercial, industrial, rural, urban, or wilderness areas.

Until site assessment activities take place, one can not say with certainty that a site is or is not contaminated. This TAB is intended to provide an overview of the site assessment process to help determine if, and to what extent, a site is contaminated. It is recommended that any activities associated with site assessment and site remediation be conducted in accordance with the CCME Interim Canadian Environmental Quality Criteria for Contaminated Sites, as well as other federal and provincial regulations, guidelines, and codes of practice.

Many of the following procedures will require in-depth analysis and the careful use of assessment techniques. A high degree of expertise is required, and it is therefore recommended that the site assessment work be contracted out. Also, an integral part of the site assessment process involves a detailed quality assurance and quality control program.

This TAB includes a Flowchart, outlining the site assessment process. Each step in the site assessment process is then discussed in detail.

Future Technical Assistance Bulletins will elaborate on specific activities discussed in this TAB.

Site assessment process diagram

STEP #1: PRELIMINARY SITE ASSESSMENT

The purpose of a preliminary site assessment is to gather available data to assist in the evaluation of a site for contamination. It should be determined during the preliminary site assessment whether or not the site requires immediate interim actions to ensure that human health and safety are protected and to prevent the spread of contamination in the environment. This should also be evaluated throughout the entire site assessment process, as indicated on the flow chart.

Information required for the preliminary site assessment are as follows:

(1a) Physical Site Characteristics

The geology, hydrology, soil characteristics, and ecological processes of the site should be determined. Much of this information is gathered during subsurface investigations (Step #3). However, during the preliminary site assessment phase, some information can be obtained by consulting the following sources:

• Published reports (e.g. geological reports, groundwater reports, soil surveys, rainfall data).
• Topographical, geological, soil, and flood plain maps.
• Previous and Visual site investigations.
• Discussion with informed people.
• Existing scientific literature.
• Air photos.
• Conservation authorities.
• Naturalist clubs (plant and animal surveys).
• Environmentally Sensitive Area (ESA) reports.

A current and historical description of the site and its facilities should be developed (refer to Table 1).

Table 1: Facility Information

(1c) Contaminant Characteristics

Review and identification of the potential contaminants that may be contained in, or released to the environment is necessary (refer to Table 2).

Table 2: Contaminant Information

Prior to the following steps, a sampling protocol and a Quality Assurance/Quality Control (QA/QC) program should be developed to ensure that the data obtained are accurate and representative of actual conditions. QA/QC should be ensured by adhering to prescribed protocols, the calibration of field instruments, proper sampling and collection techniques, and by providing records of responsibility, non-conformity events, corrective measures, and data deficiencies. Refer to TAB #4 and TAB #5 for more information on developing a sampling protocol and a QA/QC program.

STEP #2: FIELD INVESTIGATION - SITE SCREENING METHODS

The purpose of field investigations is to define and delineate the contaminants present and the general extent and location of contamination.

Geophysical methods and soil vapour surveys are used to identify the "hot spots" of a site. They act as siting tools to optimize the locations of wells and boreholes over large study areas so that data can be collected efficiently and rapidly during subsurface investigations.

(2a) Geophysical Methods

Identification of the potential applications of various geophysical methods (refer to Table 3).

Table 3. Potential Application of Geophysical Methods

Note:
PM - Primary Method
SM - Secondary Metho

(2b) Soil Vapour Surveys

Soil vapour surveys are capable of qualitatively identifying areas that contain volatile and semi-volatile organic compounds. Although there are several types of soil vapour surveys, the Jar Headspace Test is commonly used. For a detailed description of this technique, refer to TAB #1.

STEP #3: COMPREHENSIVE SUB-SURFACE INVESTIGATION

From the information gathered in Step #2, a sampling and analytical program should be established. Traditional methods such as test pits, soil boring programs, and well drilling programs are the most commonly used approaches for obtaining site-specific data for analysis.

• Are used as site-screening tools, and are created and investigated prior to borehole programs and well construction.
• Permit direct observations of in-situ conditions, and are most useful in investigations of free product and residual soil contamination.
• Provide a rapid and cost effective method of sampling, and allow visual characterization of soils to practical depths.

• Boreholes are best suited for collecting undisturbed soil samples to perform permeability testing.
• Best suited for collecting undisturbed soil samples to perform permeability testing.
• Continuous coring technique and split spoon boring are commonly utilized methods to gather core samples.
• Often samples from different depths are needed for analysis.

(3c) Monitoring Wells

• Monitoring Wells are used to develop a three dimensional hydrogeological model. From the model, groundwater conditions are interpreted.
• A Minimum of 3 wells are needed to estimate groundwater flow direction.
• One borehole should be constructed upstream from contamination, to be used for baseline data.
• Slug tests can be used in the complete well to determine the permeability of the aquifer in the immediate vicinity of the well screen.

TABLES 4, 5, 6, 7 and 8 outline the information that may be collected in Step #3, the purpose of the collection, and the various collection methods.

STEP #4: ANALYSIS OF FIELD SAMPLES

• Toxicity and levels of hazardous substances present in relevant media (e.g. air, ground-water, soil, surface water, sediment, biota).
• Environmental fate and transport mechanisms within specific environmental media such as physical, chemical, and biological degradation processes and hydrogeological conditions.
• Potential human and environmental receptors.
• Potential exposure routes and extent of actual or expected exposure.
• Extent of expected impact or threat, and the likelihood of such impact or threat occurring.
• Level(s) of uncertainty associated with the above items.

Parameters of the analysis are dependent upon the type of contamination that has occurred. The CCME Interim Canadian Environmental Quality Criteria for Contaminated Sites document should be used to determine the contaminant levels and analytical parameters to be tested. For additional parameters, refer to provincial regulations and policies (such as Ontario's Land Use Guidelines and Alberta MUST), and to U.S. EPA (614) guidelines.

From the above information, the following type of remedial investigation can be determined.

STEP #5: REMEDIAL INVESTIGATION

The remedial investigation consists of developing a baseline environmental risk assessmentin order to determine if remedial action is necessary. If remedial action is necessary, a remedial investigation (RI) report should be developed. This RI report should form a base of information that is capable of supporting and substantiating the selection, undertaking, and maintenance of a remedial action program. Remember to take into account the CCME remediation criteria as a basis for establishing remediation objectives.

Canadian Council of Ministers of the Environment (1991). National Guidelines for Decommissioning Industrial Sites.

Environment Canada (1984). Manual for Spills of Hazardous Materials. (To obtain a copy, contact the Canada Communication Group at (819) 956-4802).

Maine Department of Environmental Protection (1989). Groundwater Sampling Manual for Underground Petroleum Storage Sites.

Ontario, Ministry of the Environment (MOE) (1997). Guideline for Use at Contaminated Sites in Ontario.

United States Environmental Protection Agency (1982). Currently Available Geophysical Methods for Use in Hazardous Waste Site Investigations.

United States Environmental Protection Agency (1988). Guidelines for Conducting Remedial Investigations and Feasibility Studies Under CERCLA.

This document is available for download as an Adobe Acrobat file (.pdf). If you do not have the Adobe Acrobat Reader, you can use the link below to obtain it, at no cost, from Adobe's Web site.Get Acrobat Reader.

• Environment Canada
  Ontario Region - Environmental Protection Branch
  Environmental Contaminants &
  Nuclear Programs Division
  4905 Dufferin Street
  Downsview, ON M3H 5T4
  Telephone: (416) 739-4826
  Fax: (416) 739-4405
  Our TABs can be found on the Internet at:
  http://www.on.ec.gc.ca/pollution/ecnpd/

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