NWT RESEARCH DATABASE

Regions: Inuvialuit Settlement Region, Gwich'in Settlement Area

Tags: hydrology, permafrost degradation, biogeochemistry, mud sumps, ecological risks

Objective(s): To describe permafrost conditions and assess environmental risk at several drilling waste sumps in the Mackenzie Delta region, NWT.

Project Description: This licence has been issued for the scientific research application No. 5833. This research aims to describe permafrost conditions and assess environmental risk at several drilling waste sumps in the Mackenzie Delta region, NWT. The objectives of this project are: 1) Assess the vulnerability of drilling mud sumps in the Mackenzie Delta region under varying site conditions and different climate change scenarios. 2) Determine the impact of hazardous industrial substances contained in drilling mud sumps on microbial community composition, major soil functions and key aquatic bioindicator species that characterize an intact permafrost ecosystem. 3) Understand the resilience of thawing permafrost ecosystems to contaminants (self-healing capacity). 4) Assess contaminant mobilization by thawing permafrost that controls contaminant concentration and residence time. 5) Deliver an environmental risk assessment for drilling mud sumps with the aim to support the development of mitigation strategies in collaboration with local stakeholders. Summer leg (01.08.2024-08.09.2024) Planned field work includes visiting 8 mud sumps near the Inuvik-Tuktoyaktuk Highway on foot. The plan is to conduct a series of measurements and sampling to better understand the thaw susceptibility of the mud sumps and the ecosystem condition in the immediate and broader vicinity of the drilling sumps. Specifically, we plan to conduct geophysical surveys (Electrical Resistivity Tomography, Ground Penetrating Radar), topographic surveys (terrestrial and drone), vegetation mapping, collect soil samples and perform penetration tests around the drilled mud sumps. For the geophysical surveys electrodes for repeated geophysical measurements and some temperature and moisture sensors will be installed and left temporarily at the sites. All installations will be removed before the end of the project (December 2026). The penetration tests are performed using the lightweight PANDA system (https://www.sol-solution.com/en/products/equipment/panda/) in order to gain an understanding of the mechanical soil properties. They are conducted by pushing a small diameter (< 1 cm) rod into the soil with a hammer, measuring the induced and resulting forces. Penetration tests are generally known for their minimally-invasive nature and should not pose any ecological risks. The plan is to perform 9 penetration tests per site; 8 around the sump (4 located directly at the corners, 4 located a distance of the sump width away from the sump corners) and one additional penetration test in the middle of the sump. In order to calibrate the penetration test results we also plan on taking drilled core samples at eight locations around the sump, coinciding with the penetration test locations, and in the middle of the sump cap if permissible. The drilling will be conducted with a lightweight coring system which is powered by a small diesel engine and operated manually by one or two people. From each of the 8 boreholes we plan to take 3 core samples, one from the active layer and two from the permafrost. The drilling depth is unlikely to exceed 3 m due to fine-grained material, however this could extend through the sump cap into some drilling waste. In each of the boreholes temperature sensors will be installed. To gain an understanding of the sump geometry, GPR surveys are planned. 10 transects shall be measured, 4 around and 6 on top of the mud sumps. A 300 MHz shielded antenna mounted on wheels will be used for this. Furthermore 2 diagonal ERT and seismic transects are planned using 48 electrodes / geophones, respectively. The electrodes and geophones will penetrate the soil to a depth of not more than 10 cm and will be spaced approximately 1-2 meters from each other. The electrical current is provided by a battery, while the seismic source is given by a manually operated sledgehammer making contact with a metal plate on the ground. The aforementioned non-invasive methods (GPR, ERT, seismic) all complement each other and are an important step to determine the mud sump geometry. In addition we plan on conducting a drone survey. The drone is to be equipped with a multispectral camera and shall perform laser scanning in order to generate a digital terrain model of each site. In order to assess the soil morphology, major chemical and physical soil parameters, microbial community composition and specific processes of carbon/nutrient cycling depending on permafrost degradation and possible mud sump contamination, at each of the 7 mud sumps three soil profiles of ca. 80 x 40 cm will be dug down to the permafrost. Soil samples from the surface of the permafrost will be collected by hammering a steel core into the soil. In order to minimize disturbance of the vegetation, soil work will be performed on wooden boards and the excavated sods and soil material will be placed on tarps. After collection of the soil samples, the pit will be refilled by horizon and finally the sod incl. vegetation will be replaced on top of the soil. Furthermore, sediment and water samples in creeks as well as in ponds and lakes surrounding the drilling mud sumps will be collected. Approximately 15 water bodies will be sampled in 2024, including limnological surveys (water column profiling, water sampling, bathymetric profiling) and surface sediment sampling using an Ekman grab (~5 samples per waterbody). Sediment cores will be recovered using a UWITEC piston corer (~8 sediment cores, up to 1m long). These samples will be analyzed in the laboratory for microbial and chemical composition in order to identify present and past impact of thaw sumps on key terrestrial and aquatic functions. We will focus on potential contaminants such as salts and hydrocarbons to determine if mud sumps are leaking. We will also take surface samples from the mud sump cap to investigate vertical movement of contaminants (salt and hydrocarbons). In addition, the plan is to conduct hydrologic field measurements (discharge measurements, infiltration experiments) with a focus on determining soil hydrologic conductivity. We will install sensors for soil temperature and moisture in the active (seasonally thawed) soil layer along with data loggers to obtain a time series of key hydro-thermal variables. Winter leg (15.11.2024-15.12.2024) Planned fieldwork includes visits to a set of 8 sump sites proximal to the Inuvik-Tuktoyaktuk Highway by foot or snowmachine. Work conducted at the sumps include topographic surveying, conduction of geophysical surveys of the shallow subsurface (e.g. geoelectric tomography) to measure the frost state of the sump during early freezeback. Measurement of distributed snow depth and physical properties of the early snow cover will be performed. This also includes snow, soil, and surface temperature measurements. Spring leg (01.03.2025-31.03.2025) The field work in spring will be a repetition of the winter leg in order to repeat the work at the 8 sump sites (see map) proximal to the Inuvik-Tuktoyaktuk Highway by foot or snowmachine. It is the aim to gain detailed insights into the freezeback behavior of the mud sumps using time lapse ERT geophysical surveys. Of particular interest is also the development of the snow cover (snow depth and physical properties). As an amendment to the soil samples taken during the summer leg, cores of frozen soil (8 mud sumps x 3 locations per site) will be taken with a Sipri corer. In order to communicate the project and its results, the research team will stay in contact with the HTC and local partners by sending out informative letters to the HTCs. Communication will range from simple reporting of results to collaborative, reciprocal knowledge-sharing. There may be an opportunity to combine winter fieldwork at a site with an environmental monitoring workshop, similar to monitoring workshops hosted by the ILA in early winter for the past few years. This integration with a workshop could help demonstrate monitoring approaches, including geophysical surveys, that may be of interest to the ILA for developing its monitoring capacity. The researchers have visited the communities (Aklavik, Tuktoyaktuk, and Inuvuk in February and July to discuss, prepare and inform about this project (dialogue with communities below). The team also introduced our project at the ILA’s April 2023 environmental monitoring workshop in Inuvik, and to the Inuvialuit Settlement Region Sump Technical Working Group. In addition, results will be shared when we visit the communities again in the year after the field work. Due to the long lasting activities of the Alfred Wegener Institute, results will be reported after this project ends. It will include: meetings, presentations in the community and schools, written field reports, copies of publications or theses, co-authored publications and websites. The fieldwork for this study will be conducted from: August 01 - September 14, 2024 November 15 - December 21, 2024