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Conestoga Rovers & Associates (CRA) reviewed the Ministry of the Environment’s (MOE’s) Draft Technical Guidance: Soil Vapour Intrusion Assessment (Technical Guidance) posted on the Environmental Registry under EBR Registry Number: 011 2912. CRA reviewed the Technical Guidance to ensure that the approaches and methodologies advocated in the document are consistent with the current state of the science regarding vapour intrusion and human health risk assessment. The Technical Guidance pertains to soil vapour behavior, assessment, and monitoring, and aims to provide a basic understanding of soil vapour intrusion and approaches required to identify and evaluate the vapor intrusion exposure pathway for sites with subsurface contamination. The purpose of the Technical Guidance is to assist proponents characterize and monitor volatile compounds present in the subsurface relative to soil vapour intrusion. The Technical Guidance is intended to assist qualified professionals in conducting risk assessments to identify sites, or contaminant levels, for which contaminant exposures through the vapour intrusion pathway may result in human health risks/hazards above acceptable levels. CRA has conducted numerous risk assessments within Ontario as well as throughout Canada, the United States, and the United Kingdom. In doing so, CRA has gained detailed knowledge of risk assessment guidance and approaches published by a broad range of regulatory jurisdictions. As a result, CRA has a thorough understanding of the current state of the science regarding soil vapour intrusion assessment and risk assessment practices, human health toxicology, and geoscientific principles. CRA is well positioned to provide comments on whether the proposed soil vapour intrusion assessment is based on best industry practices and defensible risk assessment. From this perspective, CRA has reviewed the technical basis for the soil vapour intrusion (VI) assessment presented in the Technical Guidance to ensure that the proposed methodologies are consistent with the current state of the science regarding vapour intrusion and risk assessment. Comments are provided below where CRA has identified that this is not the case. Comments are also provided in some cases where the proposed methodologies appear to be based on overly conservative, or unrealistic, approaches that are viewed as a hindrance to the continued redevelopment of Brownfield sites within Ontario. General comments are provided first related to the document as a whole, followed by specific comments regarding details contained in various sections of the document. GENERAL REVIEW COMMENTS 1. The Technical Guidance makes few distinctions between the approaches taken between Petroleum Vapour Intrusion (PVI) sites and Chlorinated Vapour Intrusion (CVI) sites. Based on the rapid aerobic biodegradation rates for petroleum hydrocarbons and associated compounds, the potential for CVI to be an issue at a site is much higher than for PVI. This Technical Guidance should recognize that PVI and CVI are sufficiently different to warrant different approaches, since screening and evaluation approaches for PVI using the same criteria/methodology as for CVI is overly conservative. 2. Throughout the Technical Guidance, statements indicate that even if the soil concentrations meet the risk based S-IA component values, as per the Rationale for the Development of Soil and Ground Water Standards for Use at Contaminated Sites in Ontario, dated April 15, 2011 (MOE, 2011), soil vapour sampling should be conducted. This recommendation is based on the limitations associated with the use of soil data to evaluate the vapour intrusion pathway. These references should be removed from the document as they directly contradict the Ontario Regulation 153/04 (O. Reg. 153/04). In accordance with O. Reg. 153/04, if the maximum soil and groundwater concentrations for all applicable contaminants of concern (COCs) meet their respective risk based component values (S-IA and GW2) no further evaluation of the vapour intrusion (VI) pathway is required. In this case, a Record of Site Condition (RSC) can be filed without performing a risk assessment or additional sampling to evaluate the VI pathway. Current wording in the Technical Guidance suggests that even if the S-IA and GW2 risk based component values are met, soil vapour sampling is recommended to further evaluate the VI pathway. The Technical Guidance should be consistent with O. Reg. 153/04. Sections of the Technical Guidance that contain statements related to this issue are identified in the specific comments provided below. 3. The Technical Guidance makes numerous generic statements inferring continual future monitoring requirements that would result in a proponent monitoring soil vapour quality beyond the imminent future with no defined end point. This is an unrealistic approach that will impede the continued reuse of Brownfield sites within Ontario in a timely manner. Statements of this nature should be removed to ensure that the approach advocated in the document will permit proponents to achieve site closure. Sections of the Technical Guidance that contain statements related to this issue are identified below in the specific comments provided below. 4. The Technical Guidance is intended to reflect the current state of the science regarding VI; however, the Technical Guidance neglects to include recently published studies that address the attenuation of petroleum hydrocarbon vapours in the subsurface (Lahvis et al., 2013; USEPA, 2013a), and other volatile compound vapours in the subsurface (USEPA, 2013b). Lahvis et al. (2013) and USEPA (2013a) are peer reviewed studies that examined hundreds of petroleum impacted sites spanning a range of environmental conditions, geographic regions, and time. While most of the sites included in the study were associated with releases from underground storage tank (UST) systems many of their findings are applicable to non-UST related releases. The general conclusions of these two reports are summarized below: a) Dissolved-phase petroleum hydrocarbon sources are unlikely to cause a PVI risk unless groundwater comes in direct contact with the building foundation b) Source type (dissolved phase or light non-aqueous phase liquid [LNAPL]) and vertical distance from the source to the building are critical factors that determine if PVI is a potential risk c) Of the UST-related releases, there is negligible PVI risk from a LNAPL source located deeper than 4.1 to 4.6 metres (m) below a building. For non-UST releases, such as fuel terminal, refinery, and petrochemical sites, there is negligible PVI risk from a LNAPL source deeper than 5.5 to 6.1 m below a building. It is recommended that the MOE revise the Technical Guidance to incorporate the key PVI concepts, such as those identified above, from the recently published literature on PVI and CVI. Incorporation of the source to building separation distance principals summarized above would help eliminate unnecessary VI characterization at petroleum impacted sites. 5. Since the document is intended to be “Technical Guidance”, the main text of the document should be shortened to provide more concise summary of key concepts and recommended approaches. A shortened document would be more useful to practitioners with appropriate backup information provided in appendices or in existing published references.  SPECIFIC REVIEW COMMENTS 1. P. ii, List of abbreviations and acronyms – The listed carbon ranges for the petroleum hydrocarbon concentrations are inconsistent with CCME. The correct ranges are F2 (>C10 C16), F3 (>C16 C34) and F4 (>C34 C50). 2. P. 1-6, Section 1.3.2, paragraph #3, line 4 – Please correct the spelling of “redevelepment” 3. P. 2-3, Section 2.1.1, Figure 1 – In the flowchart for VI presented in Figure 1, the note at the bottom of the figure indicates that “additional assessment may be warranted when within 10X of standards of screening levels”. In accordance with O. Reg. 153/04, if the maximum soil and groundwater concentrations for all applicable COCs meet their respective risk based component values (S-IA and GW2), no further evaluation of the VI pathway is required. A RSC can be filed without performing a risk assessment or additional sampling to evaluate the VI pathway. The presented flowchart should be revised to be consistent with O. Reg. 153/04. This comment should also be addressed in the following locations: • P. 2-4, Section 2.1.2.1, paragraph 1, last sentence • P. 4-6, Section, 4.2.5, 2nd sentence • P. 4-10, Section 4.3.1, paragraph 6, point #1 4. P. 2-4, Section 2.1.2.1, paragraph 1, line 4 – An outdated reference (MOE, 2009a) is provided in relation to the risk based MOE component values. This should be updated with the appropriate current reference. This comment should also be addressed in the following locations: • P. 2-4, Section 2.1.2.1, paragraph 1, line 8 • P. 2-6, Section 2.2, paragraph 3, line 7 • P. 4-7, Section 4.2.5, last line • P. AII-1, Appendix II, USEPA (2002) Draft Vapour Intrusion Guidance, paragraph 3, line #1 5. P. 2.5, Section 2.1.3, last paragraph, final sentence – This sentence states that even if the screening level assessment finds concentrations at the site are below derived screening levels (SLs) additional monitoring may be required to “assess whether conditions assumed for the screening level assessment continue to apply, or if verification of estimates based on indoor air concentrations are required”. This type of ambiguous language should be removed from the document, since it has the potential to lead to continual monitoring with no defined end point. This comment should also be addressed in the following locations: • p. 2.5, Section 2.1.4, last paragraph, first sentence. • P. 4-33, Section 4.4.3, paragraph #2, first sentence 6. P. 2-6, Section 2.2, paragraph 4, first sentence – The Technical Guidance recommends that soil vapour characterization be carried out whenever there is soil contamination within the unsaturated zone. In accordance with O. Reg. 153/04, if the maximum soil concentrations for all applicable COCs meet their risk based component values (S-IA) no further evaluation of the VI pathway is required. This section should be revised to be consistent with O. Reg. 153/04. 7. P. 2-6, Section 2.2, paragraph 4, last sentence – This sentence should be modified to include sub-slab soil vapour sampling. It is standard industry practice to complete sub-slab vapour sampling to evaluate potential risks related to VI prior to conducting indoor air sampling. 8. P. 2-7, Section 2.2, last paragraph – This paragraph indicates that the Technical Guidance “does not provide all the information and evaluation required under the RSC regulation”. The Technical Guidance should fully document what is expected in a soil vapour assessment to obtain a RSC and prevent the misuse of MOE and proponent resources through additional rounds of unnecessary review. It is recommended that all of the information and evaluation required by the MOE to evaluate the soil vapour component of a RSC application be included within the Technical Guidance. The information may be summarized in tables such as those provided in O. Reg. 153/04 that summarize mandatory requirements for risk assessment reports, Phase One Environmental Site Assessments (ESAs), and Phase Two ESAs. 9. P. 3-4, Section 3.3, Figure 2 – Please label all arrows on the figure, or provide an appropriate legend. It is unclear what each arrow is intended to represent. 10. P. 3-4, Section 3.3.1, paragraph #1, line 7 – The text “isbiologically” should be "is biologically". 11. P. 4-2, Section 2.1, paragraph #2 – The Technical Guidance indicates that the presented site screening process is consistent with recent developments in science for soil VI assessment. However, this is not the case for PVI. The Technical Guidance needs to be updated to include recent scientific literature (Lahvis et al., 2013; USEPA, 2013a) and regulatory policy applied in regulatory jurisdictions throughout North America for petroleum impacted sites (see general comment #4). 12. P. 4-3, Section 4.2.1, paragraph 1, first sentence – The Technical Guidance indicates that the minimum requirements for site characterization are described in O. Reg. 153/04. However, O. Reg. 153/04 only applies if a RSC is being sought for a site, which is only mandatory if the property is going to be used for a more sensitive land use in the future. This sentence should be re-phrased. This comment should also be addressed in the following location: • P. 7-3, Chapter 7, paragraph 7 13. P. 4-5, Section 4.2.4 – It is recommended that the Comparison to the Generic Site Condition Standards (SCS) (Section 4.2.5) be moved before Section 4.2.4. In accordance with O. Reg. 153/04, if the maximum soil and groundwater concentrations for all applicable COCs meet their respective risk based component values (S-IA and GW2) no further evaluation of the VI pathway is required. Evaluation of buildings in close proximity to a contamination source is only required when there are exceedances of the component values. 14. P. 4-6, Section 4.2.4, paragraph 2, Lateral exclusion – The Technical Guidance proposes a lateral exclusion distance of 15 m for biodegradable chemicals, presumably based on the scientific literature referenced in the preceding paragraph. This lateral exclusion distance should be updated based on the current PVI literature for petroleum impacted sites (USEPA, 2013a; Lahvis et al., 2013). 15. P. 4-7, Section 4.2.5.1, Earthen basements – If impacts are within 5 m (vertically) of an earthen basement, the Technical Guidance indicates that this scenario should be precluded from the vapour screening process. However, this may be overly conservative for PVI based on the recent scientific literature (Lahvis et al., 2013; USEPA, 2013a). For instance, Lahvis et al (2013) and USEPA (2013a) reported that greater than 95% of benzene concentrations are below risk based concentrations at any distance above a dissolved petroleum hydrocarbon source. For LNAPL, the required vertical screening distance was greater than or equal to 4 m. This section should be updated to reflect the recent scientific literature regarding PVI. 16. P. 4-9, Section 4.3.1, paragraph 4 – The multiple lines-of-evidence approach that involves testing of soil, groundwater, soil vapour, and in some cases indoor air, is recommended within the Technical Guidance. However, in accordance with O. Reg. 153/04, if none of the identified site COCs in soil or groundwater exceed their respective risk based component values for VI (S-IA and GW2, respectively) and there are no precluding conditions, there is no need for additional evaluation of the VI pathway through soil vapour or indoor air measurements. This recommendation should be removed from the Technical Guidance. 17. P. 4-10, Section 4.3.1, Table 1, Soil – The table indicates that soil data can be “used to identify a potential concern, but not relied upon to screen out”. This contradicts O. Reg. 153/04 which indicates that if the maximum soil concentrations for all applicable contaminants of concern meet their risk based component values (S-IA) further evaluation of the VI pathway is not required. This section should be revised to be consistent with O. Reg. 153/04. This comment should also be addressed in the following location: • P. 4-12, Section 4.3.1, Soil Data, 2nd paragraph, last sentence 18. P. 4-13, Section 4.3.1, Groundwater Data, 3rd paragraph, last sentence – The Technical Guidance recommends that groundwater characterization programs include investigation of vertical concentration variability. Groundwater characterization above the vertical delineation requirements specified in O. Reg. 153/04 may not be warranted for petroleum hydrocarbons and other volatile compounds since it is the dissolved concentrations within the upper groundwater unit that could potentially impact the indoor air quality. USEPA (2013a) found that there was no apparent correlation between benzene groundwater concentrations from a dissolved source and deep soil vapour probes (within 0.9 m). A weak relationship based on visual observations was noted for LNAPL source data (USEPA, 2013a). Therefore, additional vertical delineation of groundwater impacts will not provide any additional insight to predict future VI potential for petroleum hydrocarbons and other volatile compounds. This comment should also be addressed in the following location: • P. 4-11, Section 4.3.1, paragraph 6, point #3 19. P. 4-24, Section 4.3.2.5, Table 3, Note #1 – The Technical Guidance indicates that bioattenuation adjustment factors (BAFs) for the biodegradation of petroleum hydrocarbons can only be applied if biodegradation is supported through oxygen profiles. This discussion needs to be updated based on the current literature for PVI. USEPA (2013a) investigated the relationship between co-located oxygen and total petroleum hydrocarbon vapour concentrations. Oxygen was not found to be limited for dissolved source sites due to the low oxygen demand associated with the vapour flux. For LNAPL, relatively low oxygen concentrations (less than 4%) were noted when TPH vapour concentrations exceed 1 x 106 µg/m3 or 1 mg/L. Therefore, measuring oxygen profiles for petroleum impacted sites, particularly with dissolved sources, is an unnecessary expenditure of proponent resources. Furthermore, there is an abundance of literature regarding petroleum hydrocarbon degradation rates in the vadose and saturated zones. As result, unless there are precluding conditions at a site, there is no basis to measure site specific oxygen profiles. This requirement should be removed from the document for the application of the BAFs. This comment should also be addressed in the following locations: • P. 4-10, Section 4.3.1, paragraph 6, point #3 • P. 4-23, Section 4.3.2.5, paragraph 4, sentence #3 • P. 5-13, Section 5.3.4 20. P. 4-25, section 4.3.2.7, paragraph 3 – The Technical Guidance recommends comparing the predicted indoor air concentration derived using soil, groundwater, and soil vapour data. However, differences in indoor air concentrations predicted from various media are to be expected due to the differing levels of conservatism associated with the input parameters that are used to predict indoor air concentrations. This factor should also be discussed within this paragraph. This comment should also be addressed in the following location: • P. 6-27, Section 6.5.3.7, pargraph 1, line 10 21. P. 4-25, section 4.3.2.7, last paragraph – The Technical Guidance recommends that a multiple lines-of-evidence approach should be followed instead of a “bright line” approach to determine if further action is required. However, in order to continue the reuse of Brownfield sites within Ontario and successfully file for a RSC, a “bright line” approach must be used. In accordance with O. Reg. 153/04, if the maximum concentrations meet the screening level criteria, even marginally, no further action should be required. This comment should also be addressed in the following location: • P. 4-26, Section 4.3.2.7, Table 4 22. P. 4-26, Section 4.3.2.7, Table 4, Note 1 – This note indicates that an indoor air testing program should generally include subslab soil vapour. Typically sub-slab sampling is performed prior to indoor air testing. If sub-slab soil vapour concentrations indicate that there is no VI risk, then an indoor air program should not be required. Sub-slab soil vapour sampling should be removed from the indoor air testing program, or identified as optional. In addition, Note 1 makes reference to a Section 4.3.2.8, that does not exist in the document. This comment should also be addressed in the following locations: • P. 4-26, Section 4.4, paragraph 1, last sentence • P. 4-31, Section 4.4.2.1, paragraph 1, second sentence 23. P. 4-27, Section 4.4, last paragraph, last sentence – The Technical Guidance indicates that in order to achieve site closure following a detailed VI assessment, indoor air and sub-slab vapour testing will typically be required. If soil vapour concentrations obtained from soil vapour probes installed near the source or outside the footprint of the building meet the SLs, there is no reason to conduct further investigative activities. General statements such as this should be removed from the document as they infer continual monitoring and site assessment with no defined end point. 24. P. 4-32, Section 4.4.2.2 – Although the document includes a discussion of background issues that may be encountered during indoor air sampling programs, there is no discussion regarding the comparison of the indoor and outdoor air concentrations. Indoor air concentrations should first be compared to outdoor ambient air quality within the vicinity of the building. Discussion regarding this comparison should be included within this section. This comment should also be addressed in the following location: • P. 6-25, Section 6.5.3.1, Constituent Ratios 25. P. 4-32, Section 4.4.2.2, paragraph #2, last sentence – The wording of this sentence is awkward and requires revision. 26. P. 5-3, Section 5.3.1, Overview of Sampling Strategy – The Technical Guidance should clearly outline the specific sequential approach to soil vapour sampling proposed within the document. For instance, if soil or groundwater concentrations exceed their respective risk based S-IA or GW2 component values, then characterization of soil vapour concentrations closest to the contamination source will be required. If warranted, based on exceedances of the SLs, characterization of soil vapour would continue closer toward the building concluding with sub slab soil vapour sampling. If exceedances are still noted, an indoor air sampling program will be required to evaluate this pathway. A flow chart (e.g., Figure 1) for the sampling strategy, including comparisons to the risk based component values or SLs at each step, would illustrate the sequential sampling approach clearly within the document. 27. P. 5-4, Section 5.3.2, Consideration for Sampling Locations, Deep (Near Source) Soil Vapour, paragraph #2 - The text indicates that to avoid the zone of excessive moisture, soil gas probes should generally be installed about 0.5 to 1 m above the water table. It is recommended that the document discuss how the water table level is to be identified. For example, groundwater levels measured in monitoring wells not screened in the upper most water bearing hydrogeologic unit can reflect the potentiometric surface of a lower confined system. Measured groundwater levels in this case could be well above the water table level, and result in the installation of very shallow soil gas probes located too far above the water table. The Technical Guidance should also provide procedures for the installation of shallow soil gas probes in cases where a very shallow groundwater table exists at a site. 28. P. 5.10, Section 5.3.2, Lateral Transects and Vertical Profiles – The lateral and vertical transects proposed here do not seem in line with the sequential sampling approach proposed in Section 2.2. Section 2.2 indicates that “the soil vapour assessment should generally begin with a characterization of soil vapour concentrations near to the contamination source and where warranted, continue closer toward the building”. If no exceedances of the SLs are noted in soil vapour data nearest to the contamination source (worst case scenario), there is no need to develop lateral transects and vertical profiles. The sequential sampling approach should be incorporated into this section of the Technical Guidance. This comment should also be addressed in the following location: • P. 4-14, Section 4.3.1, Soil Vapour Data, paragraph 4, first sentence 29. P. 5.10, Section 5.3.2, Lateral Transects and Vertical Profiles , paragraph 2, last sentence – The Technical Guidance states that more than three sampling locations may be required if the distance between the contamination source and the building is greater than 30 m. However, in the absence of precluding conditions at a site, the maximum distance between the contamination source and the building considered for petroleum impacts is 15 m. This section should be updated to include recent literature on lateral inclusion distances (e.g., USEPA, 2013a; Appendix A,). This may eliminate the need for lateral transects when dealing with petroleum impacted sites. 30. P. 5-43, Section 5.8.1, Bullet 4 –The Technical Guidance recommends comparing soil vapour with nearby groundwater concentration data. However, this may not be a useful exercise for petroleum impacted sites. USEPA (2013a) found that there was no apparent correlation between benzene groundwater concentrations, from a dissolved source, and deep soil vapour probes (within 0.9 m). A weak relationship based on visual observations was noted for LNAPL source data. Therefore, no valuable information may be obtained for petroleum impacted sites through this type of comparison. 31. Section 6.2.1, Table 10 – It would be helpful to include the number of samples used in the studies presented. Also, the table should be formatted to fit on to a standard letter size page (8¿ × 11) rather than a legal size page (8¿ × 14). 32. P. AIV-2, Appendix IV, Table of Health Based Indoor Air Target Levels - The Technical Guidance should provide the rationale for the presented O. Reg. 153/04 health based indoor air target levels. Updates to the toxicity reference values (e.g., trichloroethylene and tetrachloroethylene) used to develop the health based indoor air target levels should be addressed as well as mechanism to address future toxicity updates. The basis of the target level, as well as the maximum detection limits considered should be included. Several laboratories have documented difficulty in achieving the health based indoor air target levels and the corresponding soil vapour target levels based on these indoor air target levels. Therefore, a discussion regarding detection limits and these health based values needs to be incorporated into the document. REFERENCES Lahvis, M.A., Hers, I., Davis, R.V., Wright, J. and G.E. DeVaull. 2013. Vapor Intrusion Screening at Petroleum UST Sites. Groundwater Monitoring & Remediation. Volume 33, Issue 2, pages 53–67, Spring 2013. USEPA, 2013a. Evaluation of empirical data to support soil vapor intrusion screening criteria for petroleum hydrocarbon compounds, EPA 510-R-13-001. Washington, DC. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response. January. USEPA, 2013b. OSWER Final Guidance for Assessing and Mitigating the Vapor Intrusion Pathway from Subsurface Sources to Indoor Air (External Review Draft) U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response. April.

[Original Comment ID: 160859]