Revised as per information gathered on site. Small dozer (D3?) broke through a slough adjacent to a lake while clearing an access road (approximately 50m long) from the main winter road corridor to the lake for water truck access. Dozer had sunk into the slough to just above the tracks. Dozer was recovered with an excavator, flat deck semi and several other support vehicles from HRN in Norman Wells. Inspection of site before and after revealed no signs of spillage (nothing visible on the ground/snow, no sheen on water, no detectable smell). Recovery area was remediated prior to final departure of recovery equipment.