Assessment of the Significance of Contaminants and Sources

7. Assessment of the significance of contaminants and sources

Please note that it is acceptable for the facility to account for every source and every contaminant in its ESDM report. However, the facility may also choose to assess the significance of sources and contaminants and eliminate those that are determined to be negligible from further analysis. This approach may allow a facility to focus on a more detailed analysis of emissions and POI concentrations of the significant contaminants and sources.

Where the facility opts to focus on the significant sources and contaminants, the ESDM report must provide an explanation of how it was determined that a contaminant is discharged in a negligible amount. The results of this assessment may be summarized in a Sources and Contaminants Identification Table.

Note that although a facility may emit a contaminant in a significant amount, there may be some sources that emit this contaminant in a negligible amount. Section 8 of the Regulation sets out requirements for assessing negligible sources of contaminant(s).

Section 26 of the Regulation sets out the requirements for documenting assessments of significant sources in an ESDM report. The ESDM report must include an indication of whether a source of contaminant was considered when using an approved dispersion model (see s. 26 (1) 3 ii, and s. 8).

In addition, paragraph 4 of subsection 26 (1), of the Regulation requires that the ESDM report must also include a list of contaminants that are emitted in significant (or non-negligible) amounts. For clarity, contaminants determined to be emitted in negligible amounts do not need to be included in this list (s. 8).

The ESDM report must include an explanation of how it was determined that contaminants and sources were considered negligible (s.26 (1) 3 iii A and 5). The ESDM report also must include information related to significant contaminants and sources to be included (e.g. in the description of operating conditions, the explanation and assessment of emissions, the Source Summary Table, the site plan, the identification of the approved dispersion model and the Emission Summary Table).

In summary, the combination of section 8 and paragraphs 3 through 9 and paragraph 11 of subsection 26 (1):

• allow for the exclusion of negligible contaminants and sources from both the use of the models and certain portions of the ESDM report (note however that paragraph 2 of subsection 26 (1), requires all sources and contaminants to be listed); and
• require an explanation of how it was determined that a contaminant is emitted in a negligible amount or a source of contaminant discharges a negligible amount of the contaminant.
• in an effort to ensure that ESDM reports are comprehensive enough to identify any exceedences of POI Limits, the ministry may, as a result of site-specific considerations and consistent with subsection 8 (2) of the Regulation, require the inclusion of sources that were originally considered negligible.

Chapter 6 Initial Identification Of Sources And Contaminants provides guidance on the initial listing of all sources and contaminants. The rationale for excluding insignificant sources and contaminants emitted in negligible amounts must be included in the ESDM report (e.g., in an appendix to the report). The following three options have been developed to provide guidance in assessing the significance of sources and contaminants and thereby eliminating negligible sources and contaminants from further analysis:

1. Screening-out contaminants that are emitted in negligible amounts (refer to Chapter 7.1 Screening-Out Contaminants that are Emitted in Negligible Amounts)
2. Screening-out sources that emit contaminants in negligible amounts (refer to Chapter 7.2 Screening-Out Sources that Emit Contaminants in Negligible Amounts)
3. Generalized guidance to identifying insignificant or significant sources and contaminants (refer to Chapter 7.3 General Guidance to Identifying Insignificant or Significant Sources and Contaminants)

In addition, fugitive dust emissions from on-site road-ways and storage piles may be excluded from use with the approved dispersion models under the special circumstances set out in Chapter 7.4 Fugitive Dust Emissions.

7.1 Screening-Out contaminants that are emitted in negligible amounts

The significant contaminants for some types of sources can be readily defined. One method of identifying significant contaminants is to use emission thresholds (see Chapter 7.1.2 Identifying Significant Contaminants Using an Emission Threshold). Appendix B and Table B-1: Guidance for Screening-Out with Dispersion Factors provide guidance on using dispersion factors to screen-out contaminants. Another method of identifying significant contaminants is to use the ministry’s list of de minimus concentrations for contaminants that do not have ministry POI Limits. Appendix B Supporting Information for the Assessment of the Significance of Contaminants and Sources provides guidance on how to apply the de minimus values in Table B-2B List of Contaminants Excluded from de minimus level.

7.1.1 Combustion of natural gas and propane

The significant contaminant from the combustion of natural gas and propane is typically nitrogen oxides. Other contaminants, for this type of source, are generally emitted in negligible amounts.

7.1.2 Identifying significant contaminants using an emission threshold

In most cases, contaminants that are emitted from a specific facility may be identified as negligible when they are below emission thresholds that are developed using the following formula:

Emission Threshold (g/s) = 0.5 × Ministry POI Limit (µg/m³)

Dispersion Factor (µg/m³ per g/s emission)

Aggregate facility-wide emissions of a contaminant that are less than the calculated site-specific Emission Threshold may be considered negligible.

Notes for Development of Emission Thresholds:

1. The averaging period for the Emission Threshold calculation must be consistent. The averaging period for the ministry POI Limit and the dispersion factor must be the same (see following example of developing site-specific emission thresholds).
2. The appropriate ministry POI Limit can be obtained from the ministry list of point of impingement standards and guidelines, available from the ministry website^{footnote 9[9]}.
3. Where a contaminant has more than one ministry POI Limit, multiple emission thresholds must be calculated. The emission threshold(s) can be converted to the appropriate averaging period (e.g., mass per 24-hour period for a ministry POI Limit with a 24-hour averaging period and mass per 1 hour period for a ministry POI limit with a 1 hour averaging period, such as nitrogen oxides).
4. See Appendix B, Table B-1 Guidance for Screening-Out with Dispersion Factors for factors that are dependent upon distance from the source to the closest POI (use the source that has a POI closest to it, for multiple sources of a contaminant) and have been developed, on a maximum 1-hour average basis, by the ministry using a conservative set of assumptions. These factors can be converted to other averaging periods (to remain consistent with the averaging period for the ministry POI Limit) using the formula set out in section 17 of the Regulation or the equivalent formula set out below in Table 7-1 Averaging Period Conversion Factor (F).
5. µg/m³ means micrograms per cubic metre.

In most cases, Emission Thresholds for contaminants without ministry POI Limits may be developed using ministry recommendations for de minimus POI concentrations (24-hour average basis) that are set out in Appendix B (see Table B-2A: Contaminants Not Listed in the ministry Document, “Summary of Standards and Guidelines to Support Ontario Regulation 419/05: Air Pollution – Local Air Quality” (PIBS # 6569e) that Can Be Considered Insignificant in a Specific Situation and Table B-2B: List of Contaminants Excluded from de minimus level) of this Procedure Document. These de minimus concentrations are only applicable to contaminants that are not included in the list of ministry POI Limits or Jurisdictional Screening Level (JSL) List - A Screening Tool for Ontario Regulation 419: Air Pollution – Local Air Quality” (PIBS # 6547e) (see Chapter 12.2 Contaminants without Ministry POI Limits). The appropriate use of other dispersion modelling screening tools, such as screen3 in screening-mode, as described in the ministry document, “Air Dispersion Modelling Guideline for Ontario” (as amended from time to time) may also be used to assist in the development of Emission Thresholds.

Examples of Developing Site-Specific Emission Thresholds:

Contaminant is Xylenes (CAS # 1330-20-7) and Shortest Distance from a Number of Sources to the Property-Line (in an area classified as urban) is 50 metres

1. The standard in Schedule 3 of the Regulation for Xylenes is 730 µg/m³ (24-hour average).

2. The 1-hour average Dispersion Factor from Appendix B for 50 metres (interpolated) = 5450 µg/m³ per g/s.

3. Dispersion Factor Converted to 24-hour average is 5450 × (1 ⁄ 24)^0.28
   = 2238 µg/m³ per g/s.
4. Site-Specific Emission Threshold for Xylenes:
   = 0.5 × (730 ⁄ 2238) = 0.16 g/s or 14 kilograms per 24-hour period.

Therefore, in this situation, if facility-wide emissions of Xylenes are less than 14 kilograms in a 24-hour period they can, in most cases, be considered negligible.

7.1.3 Sub-speciation of contaminants

There are some ministry POI Limits (e.g., mineral spirits^{footnote 10[10]}) that represent a group of contaminants. In these cases, sub-speciation into the individual components is generally not required unless the mixture contains contaminants with specific ministry POI limits.

In addition, there may be situations where air emissions may be comprised of a complex mixture of a relatively large number of contaminants. For example, volatile organic compound emissions are comprised of a multi-component spectrum of compounds that make up raw materials at a facility. In this or a similar type of situation, it is reasonable to focus on those substances that have already been identified through other air emission reporting processes such as the federal National Pollutant Release Inventory. These emission reports are submitted through Environment Canada’s Single Window Reporting System.

For clarity, speciation of VOCs in a maximum ground level concentration (MGLC) acceptability request is necessary.

7.2 Screening-out sources that emit contaminants in negligible amounts

Although a facility may emit a contaminant in a significant amount, there may be some sources that emit this contaminant in a negligible amount. The following Chapters provide guidance to screen-out sources of contaminants emitted in negligible amounts.

7.2.1 Specific examples of sources that emit contaminants in negligible amounts

Appendix B, Tables B-3A and B-3B list examples of sources that may emit contaminants in negligible amounts. In general, sources in Table B-3A Specific Examples of Sources that Likely Emit Contaminants in Negligible Amounts may be considered to likely emit contaminants in negligible amounts, however an additional explanation may be required on a case by case basis to justify these sources as negligible. Sources in Table B-3B: Examples of Sources that may Emit Contaminants in Negligible Amounts are examples of sources that may emit contaminants in negligible amounts but an additional rationale is needed.

7.2.2 Sources that are insignificant relative to total emissions

It may not be necessary to consider a source of contaminant that discharges a negligible amount of the relevant contaminant, having regard to the total amount of the contaminant that is discharged by all the sources of contaminant and to the nature of the contaminant (s. 8).

Sources that, in combination, represent less than 5% of total property-wide emissions of a contaminant can, in many cases, be considered negligible sources.

There are some exceptions to this general concept and as such, the ministry may require, on a case-by-case basis, the inclusion of sources that would typically be considered insignificant relative to property-wide emissions of the contaminant. For example, a source would be required to be included in the modelling of an ESDM report where it emits a relatively small amount of a contaminant, but is the main contributor to the POI concentration due to the close proximity of the source to the POI or poor atmospheric dispersion. Similarly, an otherwise negligible source may be required to be included in the modelling of the ESDM report where there is concern about the nature of the contaminant.

7.3 General guidance to identifying insignificant or significant sources and contaminants

Facility-specific assessments, within ESDM reports, of the significance of sources and contaminants can be developed and proposed but they should be submitted to the ministry for review prior to their inclusion in the ESDM report. Any facility-specific assessment is required to be consistent with the Regulation (in particular, section 8 and paragraphs 2 through 5 of subsection 26 (1)). Site-specific assessments of significance can be based on either qualitative or quantitative arguments or a combination of both.

Decisions that are made by the ministry on facility-specific proposals may be communicated to others, after being generalized and removing proprietary information or other confidential information under Freedom of Information and Protection of Privacy Act.

In addition, the ministry may, in cooperation with representatives of various industry sectors, develop sector-specific guidance to assist in identifying the significant sources that need to be included in an ESDM report. Sources not identified as significant could then be considered negligible.

7.4 Fugitive dust emissions

The operations of some sectors lend themselves to dust emissions from fugitive sources such as on-site roadways, storage piles and other fugitive sources. Emissions from these sources can be significant or of concern if the dust includes contaminants with health-based ministry POI Limits or if the emissions are likely to be relatively high. However, in some situations, fugitive dust emissions from on-site roadways, storage piles and other fugitive sources are insignificant or negligible. In many cases, the most appropriate manner in which to manage POI concentrations from these types of sources is through an effective best management practices plan. As a result, generally, fugitive dust emissions from on-site roadways, storage piles, and other fugitive sources may be excluded from the dispersion modelling assessment of compliance with ministry POI Limits, where:

1. the nature of the fugitive dust emissions is such that they are not likely to pose a health risk to humans; and
2. the emissions are relatively small or have been minimized through effective implementation of a fugitive dust control plan, consistent with best management practices.

If the emissions from fugitive sources contain significant quantities of any contaminants with health-based ministry POI limits, these must be included in the modelling. If the fugitive dust emissions include contaminants with no ministry POI limits, the contaminants must be included in the modelling of the ESDM report unless they are considered negligible.

7.4.1 Special Case: Consideration of a best management practices plan for fugitive dust

Fugitive particulate emissions from on-site roadways, storage piles (that are susceptible to wind erosion), and and other fugitive sources^{footnote 11[11]} be included in an ESDM report when the particulate contains significant quantities of contaminants that contribute to a ministry POI Limit that may cause a health effect (e.g., metals or other health-based ministry POI limits). As set out below, in certain circumstances particulate emissions from fugitive sources do not have to be included in the ESDM report if the facility has implemented a best management practices (BMP) plan for fugitive dust. For more information on BMPs, please refer to the ministry Technical Bulletin: Management Approaches For Industrial Fugitive Dust Sources, dated September 2016, as amended (which replaced Review Of Approaches To Manage Industrial Fugitive Dust Sources, dated January 2004).

Note: Stationary sources such as loading/unloading areas, material handling processes such as conveyor systems and related drop-points should be included in the modelling.

1. Sectors where metals in fugitive dust must be considered

It is anticipated that the fugitive dust from roadways, storage piles, and other fugitive sources emitted by facilities within the sectors listed in Table 7-2 Sectors Where Metal Content within Fugitive Particulate must be Considered may contain significant quantities of metals or other contaminants with health-based ministry POI limits or where no limit exists, may cause adverse health effects.

Table 7-2 Sectors Where Metal Content within Fugitive Particulate must be Considered contains two columns. The first column contains the NAICS Code and the second column contains the corresponding description.

Accordingly, metals (or other contaminants with health-based POI Limits) in fugitive emissions from on-site roadways, storage piles and other fugitive sources from facilities within these sectors must be included in the assessment of compliance when using an approved dispersion model. In addition, it is recommended that facilities in these sectors develop and implement a BMP plan to manage fugitive dust emissions.

Sufficient information must be provided to estimate the amount of metal content in the particulate. For example, speciation of metal content in fugitive emissions through site-specific analyses of road dust, storage piles or other fugitive sources would be useful to support emission estimates. If data quality of the emission estimates is not sufficient, a notice under s.11 of the Regulation may be considered. If any facility claims that roads or other fugitive dust sources are negligible, adequate sampling of the sources would be required to support this: a notice under section 8 of the Regulation may also be considered.

In addition to metals (or other contaminants with health-based POI Limits), fugitive particulate dust emissions from on-site roadways, storage piles and other fugitive sources from facilities within the sectors listed in Table 7-2 Sectors Where Metal Content within Fugitive Particulate must be Considered may also need to include an assessment SPM emissions unless the facility:

1. develops and implements a BMP plan and a copy of this plan is included as an Appendix to the ESDM report; and
2. retains a copy of the BMP plan and appropriate implementation records on-site for inspection by the ministry; and,
3. demonstrates that each contaminant that has a health-based ministry POI Limit (or that may cause health effects) has been adequately assessed in the ESDM report and any issues have been addressed.

BMPs should contain the best available controls for fugitive dust, and therefore best available control of all contaminants associated with the particulates from fugitive sources. For more information, please see the ministry Technical Bulletin: Approaches to Manage Industrial Fugitive Dust Sources (as amended). If an adequate BMP plan is implemented at a facility, fugitive dust emissions from roadways, storage piles or other fugitive sources may generally be considered to be a negligible source. Proponents may be asked to include sources of fugitive dust in the ESDM report if the BMP plan is not acceptable to the ministry or if sufficient information has not been provided on other contaminants of concern. The Director has the authority to require a person who discharges or causes or permits discharges of a contaminant to consider a source of contaminant as not being negligible (see subsection 8 (2) of the Regulation).

Note: BMP plans required by ECAs are reviewed by the district office and the Part II.1 Director. BMPs may also be part of an action plan as part of a site-specific standard request (part of SDB review).

2. Sectors where metals in fugitive dust is generally not anticipated

Fugitive dust emitted from facilities in the sectors listed in Table 7-3 Sectors where Metals in Fugitive Particulate is Generally Not Anticipated is generally not expected to contain significant quantities of metals or, other contaminants with health-based POI limits in the dust. Nevertheless, fugitive particulate from on-site roadways, storage piles and other fugitive sources from facilities within the sectors listed in Table 7-3 Sectors where Metals in Fugitive Particulate is Generally Not Anticipated must be included in the assessment of compliance with ministry POI Limits including SPM unless the facility:

1. develops and implements a BMP plan and a copy of this plan is included as an Appendix to the ESDM report; and
2. retains a copy of the BMP plan and appropriate implementation records on-site for inspection by the ministry; and,
3. demonstrates that each contaminant that has a health-based ministry POI Limit (or that may cause health effects) has been adequately assessed in the ESDM report and any issues have been addressed.

The BMP should contain the best available controls for fugitive dust, and therefore best available control of all contaminants associated with the particulates from fugitive sources. For more information, please see the ministry Technical Bulletin: Approaches to Manage Industrial Fugitive Dust Sources (as amended). If an adequate BMP plan is implemented at a facility, fugitive dust emissions from roadways, storage piles or other fugitive sources may generally be considered to be a negligible source. It should be noted that proponents may be asked to include sources of fugitive dust in the ESDM report if the BMP plan is not acceptable to the ministry. The Director has the authority to require a person who discharges or causes or permits discharges of a contaminant to consider a source of contaminant as not being negligible (see subsection 8 (2) of the Regulation).

The ministry Technical Bulletin: Approaches to Manage Industrial Fugitive Dust Sources (as amended) includes a review of approaches to manage industrial fugitive dust sources. The suggested approaches in the Technical Bulletin can be modified and customized based upon site-specific considerations including the proximity of receptors and based upon input by ministry staff.

This Table 7-3 Sectors where Metals in Fugitive Particulate is Generally Not Anticipated contains two columns. The first column contains the NAICS code and the second column contains the corresponding description.

7.4.2 When fugitive dust emissions are negligible

Fugitive dust emissions from roadways, storage piles, or other fugitive sources may generally be considered to be a negligible source for facilities in sectors that are not included in Tables 7-2 Sectors Where Metal Content Within Fugitive Particulate Must Be Considered and 7-3 Sectors where Metals in Fugitive Particulate is Generally Not Anticipated. However, if the emissions contain significant quantities of contaminants with health-based ministry POI limits, then these sources would not be considered negligible and should also be included in the modelling.