The Tom Adit is an old mine shaft on the North Canol Highway right at the NWT border. Water leaking out of the adit (or shaft) is of concern due to contamination issues.
“The Tom Valley adit and associated workings were initiated in 1971 and formally closed in 1993. The exploration started with two portals, termed north and south, that meet approximately 40m from the outer face. The underground workings include one decline that is currently submerged, and two inclines that have groundwater drainage. These three branches begin approximately 500rn in from the portal opening. The west and east zone inclines are each approximately 1km in length while the decline appears to be slightly longer at 1.5km. In total the workings are 4km in length and underground exploration resulted in the removal of 145,100 tons of rock. The majority of this is stored below, and to either side of the north portal, in the waste rock dump.
The formal closure in 1993 satisfied reclamation requirements established by the Department of Indian and Northern Affairs. The south portal did not have any drainage and was simply backfilled. The north portal did have drainage and was backfilled in addition to the placement of pipes to facilitate continued drainage. In 1999 an inspection revealed that the north portal bulkhead was destroyed, likely from a blockage in the drainage pipes or an ice plug. In 2000, the area around the adit was cleared and a steel grill was installed 10m within the portal opening. The grill prevented access while continuing to allow the year-round adit drainage into Sekie Creek #2.
The Tom Valley property is currently held under a series of leases by the Hudson Bay Mining and Smelting Co., Limited (“HBMS”)."
HBMS has a Type B water licence (QZI5-060) regulating the adit discharge. This licence expires on December 31, 2020. It, and a variety of associated documents and reports, are available from the Yukon Water Board Waterline website. A copy of the license is available here. Here are the most recent water conditions - Report HBM 2016 WL - March 2017 (also from the Yukon Water Board website)
Historical Water Quality
To give a sense of how long the contamination has been going on, here is the Hudson Bay Report 1999 by Burns and de Graff.