The Arctic Gold and Silver Mine Site located on Montana Mountain near Carcross, Yukon (the Site) operated during the late 1960's. After mining operation was ceased in 1969, there remained potential environmental issues with regards to the tailings that had accumulated at the Site during mine operation. A potential environmental issue associated with these tailings is the possibility that Acid Rock Drainage (ARD) could occur. To ensure that ARD reactions do not occur in the future at the site, the federal government (with assistance from consultants) developed a reclamation plan for the tailings at this site. A silty clay material was used to cover the tailings to prevent oxygen and water from entering and reacting with the iron-sulphides to produce ARD. EBA Engineering Consultants Ltd., the Carcross Tagish First Nation and partners, on behalf of Mining Environment Research Group and Indian and Northern Affairs Canada, conducted a study to evaluate the performance of the silty clay cover over a tailings impoundment at the Site between September 2000 and January 2001. Data-gathering equipment was installed at the Site. Three rounds of testing and monitoring at the site were completed to gather data regarding the thickness, oxygen concentrations, temperatures and moisture levels within the tailings and the cover. This report presents the conclusions and recommendations of the study:: - Observations show that the cover system was installed properly and according to the design - Preliminary data show that the cover is working to reduce the amount of moisture and oxygen entering the tailings - It would be valuable to collect more data at the Site to observe trends and see how well the cover systems will work over time in a northern climate.

Geophysical measurements and related field data were collected by the U.S. Geological Survey (USGS) at the Alaska Peatland Experiment (APEX) site in Interior Alaska from 2018 to 2020 to characterize subsurface thermal and hydrologic conditions along a permafrost thaw gradient. The APEX site is managed by the Bonanza Creek LTER (Long Term Ecological Research). In April 2018, seven boreholes were emplaced to depths of 2.3-2.5 meters (m) to allow for repeat logging with downhole nuclear magnetic resonance (NMR) to quantify the spatial and temporal variations in unfrozen water content within active-layer and permafrost soils. NMR data were collected on ten separate occasions between April 2018 and October 2020. In June 2018, soil temperature and moisture sensors were installed at select locations and depths across the study site to record point-scale temperature and moisture conditions in 30 minute intervals. In August 2018, electrical resistivity tomography (ERT) data were collected along four 82 m-long transects. Models of electrical resistivity produced from these data revealed the spatial variability in soil lithology and thermal state (frozen vs. thawed) to depths up to 10-15 m below the surface. Lastly, manual permafrost-probe measurements of thaw depths were collected at each instrument location during summer site visits for comparison to the geophysical data.

Geophysical measurements and related field data were collected by the U.S. Geological Survey (USGS) at the Alaska Peatland Experiment (APEX) site in Interior Alaska from 2018 to 2020 to characterize subsurface thermal and hydrologic conditions along a permafrost thaw gradient. The APEX site is managed by the Bonanza Creek LTER (Long Term Ecological Research). In April 2018, seven boreholes were emplaced to depths of 2.3-2.5 meters (m) to allow for repeat logging with downhole nuclear magnetic resonance (NMR) to quantify the spatial and temporal variations in unfrozen water content within active-layer and permafrost soils. NMR data were collected on ten separate occasions between April 2018 and October 2020. In June 2018, soil temperature and moisture sensors were installed at select locations and depths across the study site to record point-scale temperature and moisture conditions in 30 minute intervals. In August 2018, electrical resistivity tomography (ERT) data were collected along four 82 m-long transects. Models of electrical resistivity produced from these data revealed the spatial variability in soil lithology and thermal state (frozen vs. thawed) to depths up to 10-15 m below the surface. Lastly, manual permafrost-probe measurements of thaw depths were collected at each instrument location during summer site visits for comparison to the geophysical data.

In 2004 and 2005, methods for restoring the damage done to the permafrost layer of an exploration trail was investigated using natural and bioengineered techniques rather than mechanical means. The impacted trail was created in November 2002 and is located off Kilometer 159 of the Dempster Highway. The methods included backfilling the impacted areas with adjacent vegetated material and transplanting plugs or islands of vegetation from donor areas in the immediate vicinity. Hand collections of seeds of various species growing on site were dispersed over some of the mitigated areas. Live willow staking was conducted at a stream crossing. The exploration track was 1.2 km in length. Approximately half of the access trail required remediation of some form, the remainder having minimal or no disturbance. The techniques of using native material to backfill the impacted areas, and willow staking to channelize the stream flow at the lower crossing has been effective in controlling erosion and restoring the site. The hand-spread grass and sedge seeds hastened colonization on the applied areas. Although these techniques are labor intensive they definitely are effective and inexpensive, especially on a small scale. The trail appears to be largely restored by July 2009 with some sections of the trail virtually indiscernible from the surrounding environment. It is doubtful that had the application of gravels and peat moss using dump trucks (the initial recommendation) been undertaken in 2004, the final result would not have been as successful.

This dataset provides field observations of thaw depth and dominant vegetation types, a LiDAR-derived elevation map, and permafrost distribution and probability maps for an area on the coastal plain of the Yukon-Kuskokwim Delta (YKD), in western Alaska, USA. Field data were collected during July 8-17, 2016 to parameterize and to validate the derived permafrost maps. The YKD is in the sporadic to isolated permafrost zone where permafrost forms extensive elevated plateaus on abandoned floodplains. The region is extremely flat and vulnerable to eustatic sea-level rise and inland storm surges. These high-resolution permafrost maps support landscape change analyses and assessments of the impacts of climate change on permafrost in this region of high biological productivity, critical wildlife habitats, and subsistence-based human economy.

This release contains Active Layer Thickness (ALT) and Organic Layer Thickness (OLT) measurements measured along transects in Alaska, 2015. Site condition information in terms of wildfire burns is also included.

This release contains Active Layer Thickness (ALT) and Organic Layer Thickness (OLT) measurements measured along transects in Alaska, 2015. Site condition information in terms of wildfire burns is also included.

Geophysical measurements were collected by the U.S. Geological Survey (USGS) at five sites in Interior Alaska in September 2021 for the purposes of imaging permafrost structure and quantifying variations in subsurface moisture content in relation to thaw features. Electrical resistivity tomography (ERT) measurements were made along transects 110 - 222 m in length to quantify subsurface permafrost characteristics. ERT transects were collected across a fireline boundary within the Bonanza Creek Long Term Ecological Research (LTER) site where repeat measurements have been made since 2014; across and adjacent to two thermokarst lakes, Vault Lake and Goldstream Lake; and along two profiles at the North Star golf course in Fairbanks, Alaska. Models of electrical resistivity produced from these data revealed the distribution of frozen and thawed soil to depths of 10-40 m below the surface. Manual permafrost-probe measurements of thaw depths were collected at set intervals along each ERT transect used for comparison to the geophysical measurements, except at the North Star golf course where shallow permafrost was absent.

Geophysical measurements were collected by the U.S. Geological Survey (USGS) at five sites in Interior Alaska in September 2021 for the purposes of imaging permafrost structure and quantifying variations in subsurface moisture content in relation to thaw features. Electrical resistivity tomography (ERT) measurements were made along transects 110 - 222 m in length to quantify subsurface permafrost characteristics. ERT transects were collected across a fireline boundary within the Bonanza Creek Long Term Ecological Research (LTER) site where repeat measurements have been made since 2014; across and adjacent to two thermokarst lakes, Vault Lake and Goldstream Lake; and along two profiles at the North Star golf course in Fairbanks, Alaska. Models of electrical resistivity produced from these data revealed the distribution of frozen and thawed soil to depths of 10-40 m below the surface. Manual permafrost-probe measurements of thaw depths were collected at set intervals along each ERT transect used for comparison to the geophysical measurements, except at the North Star golf course where shallow permafrost was absent.