Cumulative Environmental Effects of Oil and Gas Activities on Alaska's North Slope (2003) / Chapter Skim
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7. Effects on Vegetation
7. Effects on Vegetation
Pages 76-97
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From page 76... ...
The largest spill in the North Slope oil fields covered 1,700 m2 (18,300 ft2) of tundra, and no other spill has exceeded 500 m2 (5,400 ft2)
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From page 77... ...
Soil salinity also contributes to the difficulty of rehabilitating disturbed sites in some areas at Prudhoe Bay, where calcium carbonate concentrations are naturally high and summer precipitation is low (Jorgenson and Joyce 1994~. Studies of the effects of oil contamination of vegetation in the Prudhoe Bay region indicate that moderate concentrations about 12 1/m2 can result in the death of most plant species (Walker et al.
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From page 78... ...
Thick gravel pads that protect the permafrost cause other environmental effects: They create dry elevated areas that are difficult to rehabilitate after a pad is abandoned, they require gravel mines whose sites also must be rehabilitated, they block natural drainage channels, and they alter snowdrift patterns. The direct and indirect effects of the Dalton Highway, the Prudhoe Bay roads, and the Trans-Alaska Pipeline Corridor have been studied extensively (Auerbach et al.
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From page 79... ...
(b) Environment along the Prudhoe Bay Spine Road.
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From page 80... ...
Such analyses require a time-sequence of detailed photo-interpreted maps that show the ecological communities of a region before development and maps of the direct and indirect effects for several years during development. One such an analysis was performed for three heavily disturbed portions of the Prudhoe Bay oil field.
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From page 81... ...
study of a2-D (two-dimensional) seismic survey in the Arctic National Wildlife Refuge in 1984-1985 (Emers and Jorgenson 1997~.
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From page 82... ...
Effects are rated on a 4-point scale with O indicating no damage and 3 indicating extensive disturbance of vegetation. Although the typical effects of individual seismic trails in the Arctic National Wildlife Refuge generally were minor, they were extensive and varied greatly with vegetation type, terrain, vehicle type, operator vigilance, and amount of snow cover.
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From page 83... ...
FIGURE 7-5 Examples of seismic-exploration disturbance on tussock tundra vegetation in the Arctic National Wildlife Refuge, summer 1985. SOURCE: Jorgenson et al.
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From page 84... ...
(Figure 7-7~. 100 o it Q ._ ._ ._ o 90 80 70 60 50 40 30 20 10 O CUMULATIVE EFFECTS OF ALASKA NORTH SLOPE OIL AND GAS Few studies have examined the effects of current threedimensional (3-D)
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From page 85... ...
(c) Camp-move trail from 1985 exploration in the Arctic National Wildlife Refuge, photographed in 1994.
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From page 86... ...
This figure projects cumulative line miles of trails for the next 12 years in each of four disturbance levels illustrated in Figure 7-5, and it assumes the same rates of recovery that occurred in the Arctic National Wildlife Refuge. According to this model, about 17,500 miles will recover fully (Level 0, although parts could be faintly visible from the air)
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From page 87... ...
(2) The ratios of line miles in each disturbance category is the same as that resulting from the 1984-1985 seismic surveys in the Arctic National Wildlife Refuge (Emers et al.
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From page 88... ...
to be below those thought to injure temperate vegetation, little is known about the sensitivity of arctic vegetation to ozone. The FWS has studied the effects of atmospheric deposition of contaminants on snowpack on the moss, Hylcomium splendens, at Prudhoe Bay and in the Arctic National Wildlife Refuge (FWS 1995a)
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From page 89... ...
Most of the accessible pingos in the Prudhoe Bay region are littered with vehicle trails, trash, and debris from geodetic surveys; a few are scarred with bulldozer trenches formed during the search for gravel. Bird mounds, which usually are less than 1 m high, are scattered abundantly across the flat coastal plain (Walker et al.
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From page 90... ...
Numerous river bars and islands eliminated by mining have not been restored. The deeper gravel mines are not restored to their previous condiCUMULATIVE EFFECTS OF ALASKA NORTH SLOPE OIL AND GAS lion, but they are considered rehabilitated by Aeromap because they provide winter fish habitat even though they are strikingly different from the original habitat.
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From page 91... ...
A variety of rehabilitation strategies has been developed, including flooding of gravel mine sites to create overwintering habitat for fish; creation of wetlands in ponds perched on overburden stockpiles; revegetation of thick gravel fill and overburden to compensate for lost wildlife habitat; removal of gravel fill to help restore wet tundra habitats; restoration of tundra on less severely modified habitats; and remediation of areas contaminated by oil spills, seawater spills, and drilling mud (Jorgenson and Joyce 1994~. The oil industry is conducting experiments at several sites throughout the Prudhoe Bay oil field and at old well sites in the National Petroleum Reserve-Alaska.
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From page 92... ...
~.2 Current state lease terms specify removal of all machinery, equipment, tools, and materials within 1 year of the expiration of a lease; older lease terms for most Prudhoe Bay leases allow lessees to leave behind infrastructure with state permission (GAO 2002~. Older and newer leases alike leave decisions regarding the nature, ~ Lessees of land in the National Petroleum Reserve-Alaska are required by the lease terms to "reclaim the land as specified by lessor." The final environmental impact statement specifies no restoration requirements, and it explicitly leaves open the possibility that facilities may be left in place upon abandonment.
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From page 93... ...
So, for example, even if the state were to decide to impose stringent restoration requirements, the companies are not obligated to implement them on any abandoned sites within the Prudhoe Bay oil field until the entire unit has been closed. The Army Corps of Engineers, however, can require rehabilitation of individual pads within a lease or unit, although it has done so in only a few instances.
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From page 94... ...
The ADEC has not studied the extent of contamination in gravel roads and pads (ADEC, memo to NRC staff, 12/10/2001~. Economic Consiclerations There have been no comprehensive estimates of the cost of dismantling and removing the roughly $50 billion worth CUMULATIVE EFFECTS OF ALASKA NORTH SLOPE OIL AND GAS of infrastructure installed over the past three decades on the North Slope or of restoring the thousands of square kilometers of tundra habitat affected by development (GAO 2002~.
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From page 95... ...
· Roads have had effects as far-reaching and complex as any physical component of the North Slope oil fields. In addition to covering tundra with gravel, indirect effects on vegetation are caused by dust, roadside flooding, thermokarst, and roadside snow accumulation.
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From page 96... ...
The significance of ecological effects on vegetation of large areas of the North Slope is unclear. About 90% of trails from the 1984-1985 seismic exploration of the Arctic National Wildlife Refuge were not noticeable on the ground after 8 years of recovery.
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From page 97... ...
Some plant species are particularly sensitive to seismic trails, so the studies should consider effects at the plant-species level. · Monitoring of the long- and short-term effects of offroad ice roads and other off-road trails is needed.
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