Comment #1 This draft…

Comment #1 This draft guidance document does not consider the most recent literature and research differentiating the attenuation response of petroleum hydrocarbon vapours in the subsurface as compared with historical databases based on chlorinated contaminant vapours migrating in subsurface soils. This is a critical omission which dates the document and decreases its value, because numerous studies (references below) document the effects of attenuation, and the significant impact that the vertical length of the pathway between the source and the receptors of concern in a building has on potential vapour intrusion risk. This must be taken into account in such a guidance document. Therefore, the document requires significant updating. Davis, R.V. 2009. “Bioattenuation of petroleum hydrocarbon vapors in the subsurface: Update on recent studies and proposed screening criteria for the vapor-intrusion pathway”. Lavis, Matthew A., Ian Hers, Robin V. Davis, Jackie Wright, and George E. DeVaull. 2013. “Vapor Intrusion Screening at Petroleum UST Sites”. Groundwater Monitoring & Remediation. Volume 33, Spring 2013, Issue 2, pages 53–67. Peargin, T., and R. Kolhatkar. 2011. “Empirical data supporting groundwater benzene concentration exclusion criteria for petroleum vapor intrusion investigations”. International Symposium on Bioremediation and Sustainable Environmental Technologies, Reno, Nevada. US EPA. 2013. “Evaluation of empirical data and modeling studies 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. Wright, J. 2011. “Establishing exclusion criteria from empirical data for assessing petroleum hydrocarbon vapour intrusion”. Program and Proceedings of the 4th International Contaminated Site Remediation Conference - 2011 Clean UP, 142–143, September 11–15, 2011. Comment #2 The guidance document is in many ways not aligned with Ontario Regulation 153, in that the guidance seems to imply that additional vapour intrusion investigations may be required, even if a site has soil and groundwater concentrations below the applicable generic standards. This makes this document confusing and difficult to interpret in the context of implementing O.Reg.153. The guidance should support the regulation, not create new requirements. This document as written would create significant confusion in the professional community. It needs to be aligned closely with and support implementation of the regulation. Below are some examples of apparent discrepancies (or items that may require clarification) between the draft guidance document and O.Reg.153: Section 5.3.2 - rather than indicating a SV probe install depth of 0.5 to 1 m above the water table, the O. Reg.153 requirement could be incorporated stating sample depth to with 0.5 m of the capillary fringe top. Text box on p.5-10 of the draft guidance indicates that minimum sampling depth is 1 m below ground surface. The O. Reg.153 indicates 1.5 m. This depth conflict is also present in Section 5.3.4 of the draft guidance. Section 5.3.3 of the draft guidance, paragraph 2, indicates that depending on the results of the initial soil vapour sampling event, one sampling event may be sufficient. The O.Reg.153 states at least two sampling events separated by at least 3 months is required. Section 5.4.1 – although the guidance regarding long screens in fractured media makes sense, the O.Reg.153 limits screens to 0.5 m. Section 5.4.1 – second last paragraph “If multiple probes are installed in a single borehole…” The O.Reg.153 does not allow for multiple probes within a single borehole.

[Original Comment ID: 160846]