Ontario Regulation 153/04 Groundwater Standards

Evaluation Of Ontario Regulation 153/04 Groundwater Standards for F3 And F4 Petroleum Hydrocarbons

Petroleum hydrocarbons are common contaminants in the environment and as such, it is critical that the regulatory standards, and the values measured by the laboratory reflect the true risk of these contaminants in soil, groundwater and sediment systems. The standards first presented to the industry in 2009 represented years of work by the Ontario Ministry of Environment Conservation and Parks (MECP) to update the science supporting regulated values that best accomplish this goal. Although these standards were developed to support brownfield remediation and Record of Site Condition (RSC) filings in Ontario, they have become the default criteria applied to many other sites.

In the document “Soil, Ground and Sediment Standards for Use under Part XV.I of the Environmental Protection Act” (June 29, 2010), MECP set the groundwater standard for F3 (Cl6-C34) and F4 (C34-C50) hydrocarbons for all property uses and site conditions at 500 µg/L¹. MECP’s Rationale Document supporting the proposed standards for brownfield redevelopment in Ontario indicates that the chemical and physical properties for hydrocarbons used to derive this new standard were obtained from the TPH Working Group in Volume 3 – “Selection of Representative TPH Fractions Based on Fate and Transport Considerations”².

Heavier hydrocarbons will not dissolve in water and therefore, will not transport through groundwater systems in the dissolved phase. Alberta Environment and Parks (AEP) states in their 2008 standards: “Subsurface distribution in groundwater not required for F3 and F4 due to low aqueous solubility”³. If it is not possible to have significant amounts of dissolved F3 and F4 hydrocarbons in water, you would expect all laboratory results for F3/F4 hydrocarbons in groundwater to be “non-detect”, right?

As Qualified Persons (QPs) and laboratories have learned with low-level polycyclic aromatic hydrocarbon (PAH) analyses, the presence of sediment in groundwater samples can bias results high, often well beyond PAH solubility limits. Once a groundwater sample containing particulate material or sediment is submitted to the laboratory, it must be analyzed as a whole (i.e. water and sediment) since filtration will cause losses due to adsorption of the PAHs on the filter and container walls.

Bureau Veritas reviewed the solubility data provided in the TPH Working Group document (see Table 1). The data show that aromatic hydrocarbons are much more water-soluble than aliphatic hydrocarbons. Based on this information, only aromatic hydrocarbons could possibly be measured in the F3 range above the MECP required laboratory reporting limit of 500 µg/L. The data also suggest that it is not possible to have any measurable concentrations of dissolved aromatics or aliphatics in the F4 fraction.

Table 1: Hydrocarbon Solubility Data

With higher degrees of alkylation, aromatics become less water soluble. This suggests that unsubstituted aromatic hydrocarbons in the C16 to C21 range (e.g. non-alkylated PAHs) drive the water solubility limit of 650 ug/L listed by TPH Working Group. We understand that this 650 µg/L value was the basis for the 500 µg/L standard for F3 and F4 (aliphatic and aromatic) hydrocarbons.  It is noteworthy that MECP also regulates specific PAHs based on their individual chemical, physical and toxicological properties, and that the CCME hydrocarbon method⁴ allows for the subtraction of specific PAHs from the F3 and F4 fractions.  We also note that both the CCME and Ontario Analytical Protocols documents^5,6 specify that:

“The results of PHC analysis need not include either benzene/toluene/ethylbenzene/xylenes (BTEX) or polycyclic aromatic hydrocarbons (PAHs). If concentrations of BTEX and/or PAHs are determined, both corrected and uncorrected results must be reported as follows: 
• F1 and F1−BTEX 
• F2 and F2−napthalene 
• F3 and F3−PAH3 
• F4, F4−PAH3 and F4G”

As a validation, Bureau Veritas added 2 mL of commercially available motor oil to approximately 1 L of water. The mixture was shaken in a separatory funnel and allowed it to equilibrate.  After 48 hours, three 250 mL aliquots of water were removed from the bottom of the separatory funnel (note: These aliquots contain only dissolved hydrocarbons), and analyzed for F3 and F4 hydrocarbons. The experiment was performed in triplicate.  All results were < 100 µg/L for F3 and F4 hydrocarbons.

By reproducing a situation where free-phase product is present, we were unable to detect any dissolved hydrocarbons at 1/5th the 500 µg/L standard in the C16-C50 range. Although this was a simple test, it indicates that if you are measuring levels F3 and F4 hydrocarbons greater than 500 µg/L, it is likely the presence of sediment in your sample that is causing the exceedance. This underscores the importance of proper well development and use of technology such as low flow samplers to minimize the presence of sediment in groundwater samples, particularly in silty conditions.

References

[1] Ontario Ministry of Environment. Soil, Groundwater and Sediment Standards for Use under Part XV.I of the Environmental Protection Act. June 29. 2020.

[2] Guftason el al. Selection of Representative TPH Fractions Based on Fate and Transport Considerations - Volume 3. TPH Working Group. 1997

[3] Alberta Tier l Soil and Groundwater Remediation Guidelines. August 2008 pg C-50

[4] Canadian Council of Ministers of the Environment: “Reference Method for the Canada-Wide Standard for Petroleum Hydrocarbons in Soil – Tier I Method” 2001

[5] Canadian Council of Ministers of the Environment (CCME: “Guidance Manual for Environmental Characterization in Support of Environmental and Human Health Risk Assessment, Volume 4: Analytical Methods” (2016)

[6] Ontario Ministry of the Environment, Conservation and Parks: “Protocol for Analytical Methods Used in the Assessment of Properties under Part XV.1 of the Environmental Protection Act and Excess Soil Quality (ver.3.1)”, February 2021