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Leaving no mark on the NPR-A tundra BLM investigation shows that ice roads have short-term impacts on tussock vegetation but leave no long term effects on the tundra Alan Bailey Petroleum News
The use of winter ice roads has become the method of choice for industry to move drilling rigs and other heavy loads across the delicate tundra of Alaska’s North Slope. But what impact do these roads actually have on the Arctic vegetation and the underlying permafrost?
To answer that question, U.S. Bureau of Land Management researchers have been investigating the condition of the tundra along routes used by ice roads in the National Petroleum Reserve-Alaska, Scott Guyer, a BLM natural resource specialist, told the United States and Canada Northern Oil and Gas Forum in Anchorage on Oct. 28.
Construction Oil companies build ice roads early in the winter for use during the winter exploration and construction season. Road construction starts once there is sufficient frost and snow for a Rolligon low-impact vehicle to pack the snow down along the ice-road route, Guyer said. If there is insufficient snow to build the ice-road base, the road constructors use snow or ice chips from lakes, he said. Once the road base is formed, Rolligons spray water along the road route, to form the road as a layer of ice 12 inches to 14 inches thick.
Ice pads used to support tons of equipment at locations such as drilling sites are built in the same way as ice roads, but have a more substantial ice sheet that is typically about two feet thick, Guyer said.
After the ice roads and pads melt, they leave no lasting trace on the tundra. Or so people think.
The prevailing concept is that a single-season ice road causes no damage to the tundra, so that no environmental recovery process is necessary, Guyer said.
To test this hypothesis, the BLM team used remote sensing imagery to identify the precise locations of two NPR-A ice roads, one of which had been constructed in 1978 and the other of which dated from 2002. In the case of the 1978 ice road, the team was able to obtain some 1979 National Aeronautical and Space Administration color infrared photographs, in which the ice road trace could clearly be seen.
The team visited the road sites during the summer, observing the state of the tundra and measuring parameters such as the severity of any vegetation damage and the depth to the permafrost, both on the ice road track and on the neighboring tundra.
Visible track At the location of the 2002 road, variations in the color and texture of the tundra made the track that the road had followed very clear. And there was evidence of some damage to vegetation, especially in the drier tundra that consists of tussocks of vegetation. It appeared that the Rolligons had flattened the tops of some of the tussocks as they travelled along the road route spraying water.
“Quite a few of the tussocks have been affected,” Guyer said. “Some of the shrubs have been affected. Some of the willows have re-sprouted after being under ice during winter time.”
On the other hand, wetter areas of sedge tundra appeared unaffected by the ice road, and there was no observable impact of the ice road on lakes or the wetlands associated with lakes.
No trace By contrast, the team could find no trace remaining of the 1978 ice road. That particular road was constructed in February 1978 along a 37.5-mile route and was subsequently used for the transportation of 132,000 tons of gravel over a 38-day period, Guyer said.
But, despite that heavy usage, the vegetation that had been under the road appeared to have made a complete recovery.
“All the shrubs have responded,” Guyer said. And all of the other plants, with one minor exception, have recovered, he said.
The team did not find any ice-road impact on the permafrost along either ice-road route — there was no evidence of either permafrost thawing or variations in the depth to the permafrost as a result of ice-road construction and use, Guyer said.
The team also visited the site of the ice pad used for the drilling of the Puviaq well in 2003. Unfortunately, strong winds prevented the team from making measurements at that site, although informal observation suggested that the tundra had responded to the ice pad in a similar manner to the response observed for ice roads, Guyer said.
Short-term impact So, it appears that ice roads and pads do have observable impacts on the tundra in the short term, but no lasting effects.
The observable trace of a road route after the ice road has melted results in part from the fact that the ice of the road lasts longer than the ice and snow on the surrounding land during the spring melt, Guyer said. That delays the start of growth of the vegetation on the road track during the short Arctic summer, he said.
In addition, dry upland plants such as shrubs and cotton grass become encased in ice under the ice road. The solid ice freezes the plant tissue and inhibits the plants’ normal exchange of gases.
Wetland plants such as sedges, on the other hand, are normally encased in ice during the winter, so these plants are largely unaffected by ice road construction.
The good news, however, is that in no instance does the damage to the vegetation appear to have been sufficiently intense to prevent an eventual full recovery.
“We concluded that the environmental effects from ice-road construction completely recover over a 24-year period,” Guyer said.
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