Validation of Petroleum Hydrocarbon Stratified Remediation Subsoil Criteria

Bonnie Drozdowski
GL 09-9188-50

The concept of stratified remediation for petroleum hydrocarbons (PHCs) refers to the application of alternative remediation standards for varying soil depths at upstream oil and gas facilities in Alberta. The surface soil criteria apply from the soil surface down through the soil profile to a depth of either 1.5 m or 3 m depending on the area of consideration. The subsoil criteria which are less stringent can be used below the 1.5 m or 3 m depth. There is a need to validate the current Alberta Environment subsoil guidelines (Alberta Environment, 2010) by providing empirical evidence that regional deep rooted crops are not affected by critical PHC concentrations in subsoil under drought conditions when the plants are forced to extract moisture from depths below 1.5 m. A soil column study, funded by the Petroleum Technology Alliance of Canada (PTAC) was established in 2011 to validate these guidelines and to determine the phytotoxic effects of PHC contaminated subsoil on deep rooted crops. The objective of the study is to provide empirical evidence to show that there are no phytotoxic effects on canola and alfalfa grown in fine and coarse textured subsoil contaminated with F2 and F3 hydrocarbons at levels at or above Alberta Tier 1 critical concentrations over four growing seasons in the greenhouse.

Canola and alfalfa from the first growing season were harvested in November and December of 2011, respectively. One way ANOVA were conducted on the total canola and alfalfa biomass separately, comparisons were not made between the fine and coarse textured subsoils. The biomass data from the first growing season indicated no significance differences in either crop biomass yield between the control and the F2 treatment in both fine and coarse textured subsoil. We also did not find any significant differences in the mean crop biomass between the control and F3 treatment in the coarse texture soil, however we did find significant differences in both canola and alfalfa biomass between the control and F3 treatment in the fine textured subsoil.

Canola plants were re-seeded after harvest, similar to the first growing season each pot will be thinned to five plants. Both the growth of canola and alfalfa will be monitored until the 2nd harvest in April 2012. Data from the first two growing season will be compiled and presented at the annual PTAC forum. Two more growing seasons will follow subsequently, the final report to PTAC will be submitted in December 2012 and data from this study will be presented at the PTAC annual forum in March 2013.

Policy Issue

Additional Science for the Refinement of Regulatory Guidelines/Directives/Policies/Criteria. The degree of conservatism current in some regulatory guidelines can be linked to some unnecessary remedial efforts throughout the petroleum industry. The development of accepted scientific studies to reduce these conservatisms would ultimately lead to a reduction in perceived waste going to landfill and a reduction in remedial costs.

Knowledge Gap
Plant species sensitivity to petroleum hydrocarbons. Field Studies / Data Collection that addresses Plant species sensitivity to petroleum hydrocarbons at depths below 1.5m.