IMPACT OF ROAD CONSTRUCTION ON PERMAFROST AND GROUNDWATER HYDROLOGY IN THE GATES OF THE ARCTIC NATIONAL PARK, ALASKA

The Alaska Industrial Development and Export Authority was approved to build a new road from the Dalton Highway to the Ambler Mining District in central Alaska. The road alignment will be approximately 340 km long and built on sensitive permafrost environments just south of the Brooks Range. Road materials have different thermal and hydrogeologic properties than the organic material and silty soil that currently comprise much of the land surface and shallow subsurface. This study attempts to address questions of how this new road may affect permafrost thaw, active layer thickness, and groundwater flow in areas along the road alignment.

The Nutuvukti Lake watershed in Gates of the Arctic National Park was identified as the study area. Data from 25 soil cores were taken from the road corridor in summer 2014 with depths ranging between approximately 1.0 to 4.6 meters. A hobo logger in the study area provides hourly temperature data at the surface and 1.5 meters depth from August 2014 to July 2016. Daily mean surface temperature ranged between -15.4°C and 22.3°C.

Various surface conditions and soil hydrothermal properties are considered in preliminary modeling of the thermal and hydrological processes of the study site. A sinusoidal daily mean temperature variation was applied at the land surface, and thermal properties of the soil layers are based on soil core data and previous literature. Results are compared using hydrologic and thermal properties before and after a simulated road placed on top of the existing ground. Preliminary estimates suggest that the active layer may change by tens of centimeters under the new road. As active layer thickness directly impacts shallow subsurface hydrology, model results help to assess how hydrology may be altered by the new road.