‘Poor material’ of road blamed for equipment falling into Pontoon Lake

Reports newly published by a regulator go into more detail about how two pieces of heavy equipment fell into a Yellowknife-area lake just days apart.

A dump truck working on road construction fell into Pontoon Lake on August 11. An excavator fell into the same lake at virtually the same spot three days later.

KAG Canada, the parent company of contractor RTL Robinson Enterprises Ltd, filled out detailed reports for both incidents in August. Those have now been published to an NWT regulatory registry.

Summarizing the reports, the NWT government said it was satisfied that “no notable volume of fuel” was spilled in either incident, and that a sheen on the lake was the result of “grease applied to the equipment components.” Earlier, the GNWT said water tests showed no issue.

KAG’s reports provide the most information yet about the circumstances that led the truck and excavator to fall in.

The contractor was working to stabilize and widen Highway 4, which runs alongside Pontoon Lake, after the GNWT decided the road’s lack of stability in the area was a safety risk.

At 11:15am on August 11, that instability became abruptly apparent.

A dump truck was unloading rock – being used to widen the highway into the lake – when the driver “felt the truck leaning to the left” and realized it was sinking.

The ground beneath the truck gave way, “resulting in the earth sliding toward the lake, taking the truck with it,” KAG’s report states.

The truck settled in the lake on its driver’s side. The driver, uninjured, escaped through the passenger door.

The report stresses on multiple occasions that staff had not previously seen any indication that the ground was about to give way.

A cause of the incident is listed as: “Ground below rock roadway unknowingly changed.”

The truck was removed from the lake the next morning “without damage, injury or spill,” KAG states.

On August 14, at about 11:30am, the excavator hit the water.

According to KAG, trucks had returned to dumping rock at the lake side by this point. The excavator would move in behind them after each load to push any leftover rock over the bank toward the lake.

When the operator felt the machinery beginning to shift unexpectedly, they swung the machine’s boom and bucket out toward the lake and jammed it down into the rock “to try to hold the machine,” KAG writes.

In a “very slow-motion” chain of events, the operator had time to abandon the machine and flee up the bank as the road gave way, “taking hundreds of tons of rock with it” – and the excavator, which ended up in eight to 10 feet of water.

Nobody was hurt. Again, KAG says, there were “no environmental or wildlife impacts.”

The company ultimately blamed the highway’s initial build quality for the events of mid-August.

The ground below the road had not been prepared to modern standards, KAG’s second report concludes. “Poor material was used,” it continues, allowing the road to fail.

The second incident was enough for the GNWT to change course. A “re-evaluation of the project,” KAG writes, led the contractor to begin widening the road on the other side instead, away from the lake.