NWT RESEARCH DATABASE

Tags: environmental assessment, site remediation, soil, hydrology, groundwater, pollution

Objective(s): To further determine the current environmental and physical conditions at several petroleum hydrocarbon spill sites along the Canol Trail, and address the gaps identified from the 2012 sampling program.

Project Description: The purpose of the Supplemental Environmental Site Assessments is to further determine the current environmental and physical conditions at several petroleum hydrocarbon spill sites along the Canol Trail, and address the gaps identified from the 2012 sampling program. Key findings from these select sites will be synthesized to identify the scope and nature of the spills, potential trends regarding contaminant fate and transport, and development of conceptual models that may be applicable at remaining spill sites. From this will anticipate that this project can reduce potential future data gaps and allow development of the appropriate remediation strategies and costs. This will include the identification and quantification of environmental impacts to soil, and groundwater at the sites. The long-term program objective is to reduce the liability of the Canol Trail by developing and implementing a remediation and/or risk management plan to mitigate existing or potential risk to human health and the environment from the Trail. Borehole Drilling The proposed field program at the sites will involve the use of both a portable auger drill (Beaver hydraulic auger with hammer drill sampler) and a portable Ponjar hammer drill. The site is at the boundary of continuous/discontinuous permafrost, and therefore the thermally active zone in surficial soils may be expected to be in the depth range of 1 to 2 metres below ground surface. In permafrost terrain, contaminant migration is a near-surface phenomenon and soil sampling is expected to focus on shallow soils. Select boreholes will be completed as groundwater monitoring wells. The wells will be constructed of PVC comprised with a 1.5m slotted screen, riser with a small riser stickup. Site derived aggregate will be used as well gravel to minimize the amount of sand shipped to the sites. Bentonite clay will be used to plug the riser interval of the well. Each well will be purged and allowed to stabilize prior to groundwater sampling. Soil and Sediment Sampling Soil and Sediment sampling will be used to aid with the interpretation of site petroleum hydrocarbon and PAH impacts. Soils and sediment will be sampled either directly from the drill-rig auger, split spoon samplers, or core tubes. Field Volatile Organic Carbon (VOC) vapor monitoring will be completed for each soil sample. Subsurface materials will be inspected, described and photographed. Groundwater Sampling Groundwater monitoring wells will be developed and purged prior to sampling to remove drilling induced fines and stagnant water. Chemical parameters such as pH, temperature, and turbidity will be measured with hand held meters prior to sampling each monitoring well. Groundwater samples will be removed using bailers or other low-flow sampling devices (e.g., peristaltic pump) and stored in laboratory supplied bottles. Samples will be stored on ice and transported to Norman Wells to a receiving laboratory depot. Slug Tests Slug testing will be completed to assess the hydraulic properties of the shallow aquifers at the sites. Testing will include installation of an inert slug (e.g., sand-filled bailer) into the well and monitoring the change in hydraulic head over time with a down-hole water level measuring instrument. The slug will be removed and the test completed again to measure the change in head again until the well has reached a static equilibrium level. Test data will be modeled to estimate hydrogeological properties such as hydraulic conductivity, storativity, and transmissivity. The project is working towards remediation of the Canol Trail which will have social benefits for wildlife and users of the trail, as well as environmental benefits. The results of this study will be incorporated into Aboriginal Affairs and Northern Development Canada (AANDC) consultation process with local community groups. A summary and copy of the final report will be sent to the Aurora Research Institute upon completion of the report. The fieldwork for this study will be conducted from July 1, 2013 to August 30, 2013.