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7 Effects on Vegetation As a result of oil and gas exploration and development, vegetation on Alaska's North Slope has been affected by diesel fuel, oil, and saltwater spills; by disturbances related to roads and gravel pads; and by damage attributable to seis- mic exploration (Forbes et al. 2001, Jorgenson and Joyce 1994, McKendrick 2000b, Walker 1996~. These direct physi- cal effects can reduce the insulating quality of the vegetation and cause additional disruption of the surface ("thermo- karst") by thawing the underlying ice-rich permafrost (Chap- ter 6~. Because most industrial activity has been concentrated on the Arctic Coastal Plain, data about the accumulation of effects on vegetation come primarily from that region. How- ever, as industrial activity spreads south into the foothills of the Brooks Range, it will affect vegetation types not previ- ously influenced. In addition to summarizing those specific classes of effects, this chapter examines areas of special bi- otic importance and the challenges that attend removal of facilities and rehabilitation of gravel areas, including regula- tory issues. SPILLS AND CONTAMINANTS Oil spills on the North Slope have been smaller than have been spills in other oil-producing regions of the world. 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) (McKendrick 2000b, Appendix F). For comparison, the 1994 Usinsk oil spill in Russia covered about 70 km2 (27 mi2) of terrain and released some amount between 93 and 114,000 metric tons (102 and 126,000 tons) of oil, causing an estimated $15.5 million in damage to aquatic resources in three large rivers, destroying 200,000 m3 (262,000 yd3) of forest, and sparking large polluting fires (Vilchek and Tishkov 1997~. Spills of that magnitude have been avoided in Alaska because of the system of monitoring and check valves in all pipelines. To date, most North Slope contaminant spills have occurred on gravel pads, which have 76 minimized the extent of the effects. Contaminant spills on tundra, however, can cause significant damage to vegeta- tion. The effects of spills vary by the season, the vegetation, and the substance spilled. A winter spill on frozen tundra is easier to clean up than is a spill in warmer periods because the contaminants can be removed as frozen material from the surface (McKendrick 2000b). As would be expected, some plants are more sensitive than others: The most sensi- tive vegetation is found in dry areas, and some plants, such as Dryas and Sphagnum, are particularly sensitive. Three substances are spilled most frequently: oil as it is drilled or transported for processing, diesel fuel stored for or in use by oil and gas exploration and development equip- ment, and saline water (seawater used in oil recovery opera- tions or for testing pipelines or saltwater produced as a by- product of oil extraction). The damage can persist: Diesel fuel can remain in tundra soils for more than 20 years with little recovery of plants in affected areas (Walker et al.1978~. Saltwater spills, although uncommon, are especially problematic. Salts are not biodegradable and they are toxic to many plant species (Simmons et al. 1983~; Dryas and de- ciduous shrubs that grow in wet ground, including dwarf willows (Salix spp.), are the most sensitive; sedges that grow in wet places (Eriophorum and Carex) are the most resilient to saltwater. The standard response to saline water spills is to flush the spill site with freshwater, which reduces effects and promotes more rapid recovery. Colonization by salt- tolerant species, such as Dupontia grass, eventually occurs (Jorgenson and Joyce 1994), but recovery of the most sensi- tive plants can take several years. The extent of a seawater spill is difficult to detect at the time of the spill without chemical testing of the soils. Old reserve-pit fluids also contain salts (French 1985~. The toxicity of the fluid varies seasonally and from one pit to another (Myers and Barker 1984), but it tends to de- crease as pits age because of dilution by snowmelt waters. The plant species most affected by reserve-pit fluids are

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EFFECTS ON VEGETATION the same as those affected by saltwater spills (Myers and Barker 1984, Simmons et al.1983~. Recent grind-and-inject techniques have largely eliminated new contamination by reserve-pit fluids. Soil salinity also contributes to the diffi- culty 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 concentra- tions about 12 1/m2 can result in the death of most plant species (Walker et al. 1978~. Several common species of deciduous shrubs (Salix spp.) and sedges (Carex spp. and Eriophorum spp.) and a few aquatic mosses (e.g., Scorpi- dium scorpioides) are more resistant. Recovery in areas where the soils are saturated with oil to a depth of more than 10 cm (4 in.) is very poor after 12 years (Walker et al.1978~. Long-term recovery from light to moderate oil spills is usu- ally better because the toxic components break down over time. Oil spilled on wet tundra kills the moss layers and aboveground parts of vascular plants, and sometimes kills all macroflora in the affected area (McKendrick and Mitchell 1978~. Because tundra acts like a sponge, spreading is lim- ited and generally only small areas are affected (BLM/MMS 1998~. But those effects can be severe, and recovery from tundra spills can take 10 years or more (McKendrick 1987~. In general, spills that saturate the tundra produce severe, long-lasting effects, and recovery is slow. Walker (1996) reported that recovery from diesel fuel spills also proceeds slowly. Twenty-eight years after a spill at Fish Creek, little vegetation recovery was evident and the fuel was still present in the soil. Places where crude oil and crankcase oil had spilled showed better results after 28 years, except in the areas of heaviest effect. In experimental spills (Walker et al. 1978) of crude oil and diesel fuel, tundra plant communities on diesel fuel plots showed no recovery after 1 year. There was some recovery of sedges and willows after 1 year on the crude oil plots. However, mosses, lichens, and most dicots showed almost no recovery. Walker and colleagues (1978) suggested that vegetation spill-sensitivity maps can be de- veloped. Natural seeps also can affect vegetation; sedges seem to be among the most tolerant plants (McCown et al. 1973~. Many bioremediation techniques have been used within the oil fields (Jorgenson and Joyce 1994~: Microbial degra- dation has been enhanced by fertilizer treatment, aeration, and hydrologic manipulation (Jorgenson et al. 1991~. Burn- ing of spilled oil and thermal remediation also are used (Jorgenson and Joyce 1994~. The oil industry has developed technology to prevent, clean up, and rehabilitate most terres- trial contaminant spills, but techniques for optimizing the microbial degradation of hydrocarbons in tundra soils still needs development. Although the effects of contaminant spills could accumulate if the size and frequency of spills 77 were to increase, their effects have not accumulated to date on North Slope vegetation. Oil and saltwater spills are de- scribed in detail in appendixes F and G. Most of the literature on the response of tundra vegeta- tion to contaminant spills has been from short-term observa- tions, 1-3 years. Longer term studies are needed to deter- mine the recovery potential of various plant communities and for use in developing maps that will show areas of sen- sitivity to spills and those in which there would be a good possibility of recovery from a spill. ROADS AND GRAVEL PADS There is an extensive, increasing network of roads and gravel pads on the North Slope (Figures 4-3 through 4-6~. The effects of gravel pads on vegetation are usually local- ized, but roads (especially old roads and those more heavily traveled) have a variety of sometimes far-reaching effects on plants and animals and can cause broad changes to ecosys- tem structure and functioning. Roads directly cover and kill tundra vegetation, but their effects extend beyond their foot- prints. Roads can displace wildlife, impede wildlife move- ment, and increase human access to an area. They are visu- ally conspicuous, change hydrological patterns, and assist in the dispersal of nonnative plants (Ercelawn 1999~. Road- related changes that are unique to cold regions include alter- ations of snow distribution patterns and creation of ther- mokarst (irregular depressions caused by melting and heaving of frozen ground) (Walker et al. 1987a). The Prudhoe Bay region has a variety of road types. Roads to remote drill sites are rarely traveled; roads that link oil-field structures are heavily used. As would be expected, wide, more heavily traveled roads cause more severe indi- rect effects: heavy road dust, hydrology changes and flood- ing, altered snow distribution, thermokarst, increased acces- sibility to associated off-road-vehicle trails, and greater opportunity for invasion by nonnative plant species. Hunt- ers, tourists, and other users cause additional effects in a broad area along the Dalton Highway corridor. The effects of dense networks of roads and gravel pads are complex- several roads can influence the same piece of ground. Road- side structures, such as pipelines, power lines, power plants, and industrial centers, can make large areas of land unavail- able or undesirable to wildlife, subsistence hunters, and wil- derness travelers. Old Roacis, Exploration Trails, and Drill Sites When exploration of the North Slope began, knowledge about of the effects of exploration and construction tech- niques on permafrost was limited. From early exploration through the 1950s, trails often were cut directly into frozen ground. Large tractors and tracked vehicles traveled over thawed ground in the summer, often leaving deep ruts, and sometimes road builders removed the vegetation mat com-

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78 pletely, causing deep thermokarst (Bliss and Wein 1972, Chapin and Chapin 1980, Hernandez 1973~. Trails com- monly became wetter than the natural habitat and were colo- nized by species more adapted to wet sites. Higher biomass and changes in nutrient concentrations occurred in the trails (Chapin and Shaver 1981~. At times, subsidence and erosion created trails as deep as 5 m (16 ft) (Lawson et al. 1978~. Some old trails and seismic surveys made by government contractors in the 1940s are still clearly visible because they are deeply rutted, often flooded, and filled with vegetation that is quite different from the surrounding tundra (Hok 1969, 1971; Lawson et al. 1978~. In the 1960s, peat roads were built by scooping the ac- tive layer from two sides of an area and piling it in the center to form an elevated surface. This method also resulted in severe thermokarst. By the 1970s, gravel had replaced peat in road construction. Now in many cases, ice is used. There has been a parallel evolution in the techniques used to build drill sites. Many of the early exploration wells were drilled without gravel pads. In some cases the drilling wastes were deposited directly on the tundra. As environ- mental awareness increased, drilling wastes were contained in reserve pits, which often leaked. The continuing effects of those old reserve pits on the arctic vegetation pose special challenges for rehabilitation. Moclern Roacis and Gravel Pacis The currently preferred method for road and site de- velopment is to build a thick gravel pad, often more than 2 m (6.5 ft) thick, to insulate the underlying permafrost. Sometimes polyethylene insulation is placed below the pads to reduce the amount of gravel needed. If a pad is temporary, a thinner layer of gravel or sand is used. Thick gravel pads that protect the permafrost cause other envi- ronmental effects: They create dry elevated areas that are difficult to rehabilitate after a pad is abandoned, they re- quire gravel mines whose sites also must be rehabilitated, they block natural drainage channels, and they alter snow- drift 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. 1997, Brown and Berg 1980, Klinger et al. 1983b, McKendrick 2002, Pamplin 1979, Walker 1996, Walker et al. 1987a). Roacl Dust Dust is an inevitable by-product of the use of gravel roads on the North Slope (Figure 7-1~. Dust loads are highest along the Spine Road and, until 2002, when it was chip- sealed, the Dalton Highway, where traffic is heavier and faster than on other area roads. One study showed that as much as 25 cm (10 in.) of dust had been deposited in some areas along the Spine Road (McKendrick 2000b). Earlier CUMULATIVE EFFECTS OF ALASKA NORTH SLOPE OIL AND GAS studies reported that all vegetation was eliminated within 5 m (16 ft) of the most heavily traveled roads at Prudhoe Bay. Mosses were eliminated to about 20 m (66 ft) (Auerbach et al. 1997, Everett 1980, Walker and Everett 1987~. Dustfall 1,000 m (3,280 ft) from the road was several times higher along the Spine Road than at the other sites because of the heavier traffic (Everett 1980~. In acidic tundra regions, the normally high buffering capacity of the tundra was neutral- ized by the heavy dustfall. At an acidic tundra area in the foothills, the pH in roadside areas has shifted from acidic to alkaline (pH 4.0 to pH 7.3) (Auerbach et al. 1997~. Several road-related phenomena interact to increase the depth of the tundra's active layer. The elimination of the moss carpet reduces insulation, and deep snow drifts accu- mulate near the roads, increasing the wintertime soil surface temperature. Despite the deeper snow associated with el- evated roads, the snow melts earlier because the darker, dust- covered snow surfaces absorb more heat. Ponds near roads also absorb more heat. All of these factors combine to warm the soil, deepen the thaw, and produce thermokarst adjacent to roads. The earlier snowmelt near roads also can open these areas to wildlife several days or weeks before adjacent snow- covered tundra areas become accessible (Walker and Everett 1987~. Tracts of dust-killed vegetation have expanded from those observed in 1980s, and thermokarst, which was spread- ing rapidly during the 1980s (Walker et al. 1986b, 1987b), continues to spread along ice-wedge polygon troughs. Changes along the roads have not been documented consis- tently, and detailed long-term studies are needed. Paved roads produce far less dust, and chip-seal treatments (an ap- plication of asphalt followed with an aggregate rock cover) have reduced dust along the Dalton Highway and some other roads. Roacisicle Floocling Flooding, another major effect, is generally confined to wet and aquatic tundra vegetation. Most road-related flood- ing occurs where roads cross low-lying, drained thaw-lake basins. Drainage patterns on the flat tundra are complex, and there are many unconnected drainage systems. In areas where there is an intersecting web of roads, such as around the Prudhoe Bay development, flooded areas are more com- mon and often difficult to drain (Figure 7-2~. The road to West Dock, constructed in 1980-1981, is 7 km (4 mi) long, crosses four drained lake basins, and caused flooding to about 131 ha (324 acres) of tundra (Klinger et al. 1983a). It is difficult to position culverts along such roads because the routes of melt water drainage often are not detectable at the time of road construction. Even if culverts are located appro- priately, they generally are frozen at the time of the spring melt. In deeply flooded basins, elevated microsites, which are important nesting areas for some bird species, are sub- merged and thus unavailable during the nesting season (Walker 1997~.

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EFFECTS ON VEGETATION (a) (b) 79 FIGURE 7-1 (a) Trucks raising dust plumes along the Dalton Highway. Truck speeds often exceed 60 mph, and winds can distribute the dust to distances of more than 1 km from the road (Everett 1980). Chip sealing, which is now being done, reduces dust along the Dalton Highway. (b) Environment along the Prudhoe Bay Spine Road. Barren areas are caused by thick dust, and ponded areas are caused by thermokarst. This was formerly an area of low-centered polygons that was converted to high-centered polygons by erosion of the polygon troughs. SOURCE: Walker 1996. Reprinted with permission, copyright 1996, Springer-Verlag.

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80 CUMULATIVE EFFECTS OF ALASKA NORTH SLOPE OIL AND GAS FIGURE 7-2 One of the four lake basins along the Waterflood road at Prudhoe Bay. The photo was taken in early summer before ice in the culverts thawed. By late summer the large oval impoundment drained, but the vegetation changed over a period of 3 years. Notice the lack of elevated microsites for bird nests in the flooded areas compared with the other side of the road. Also note the other impoundment along the road (arrow), which does not drain all summer. SOURCE: Walker 1996. Reprinted with permission, copyright 1996, Springer-Verlag. Invasion of Nonnative and Native Species Nonnative species have sometimes been introduced in seed mixtures and mulches during rehabilitation efforts (Johnson 1981, Kubanis 1980~. Surveys along the Dalton Highway during the late 1970s showed that 13 plant species had been introduced, and 9 of them were reproducing (Kubanis 1980~. However, none of those species has been documented as successfully invading native-plant commu- nities. Climate change could cause more species to invade the North Slope. Current rehabilitation research focuses on natural revegetation with minimal application of nonnative seed mixes (Jorgenson et al. 1997~. Vegetation patterns also can be altered when native species that grow naturally in other areas move into disturbed sites (e.g., dusted areas, seis- mic trails, snow pads) (Emers et al. 1995, Johnson 1981, McKendrick 2000b). The grass Arctagrostis latifolia often invades those areas, but other species do as well depending on the severity of the disturbance. Coastal and dune plant species can colonize severely dusted areas well inland (McKendrick 2000b). Overall, invasion by nonnative spe- cies has not been an important problem. Estimates of Indirect Effects Few detailed analyses of the growth of the oil-field infrastructure assess indirect effects such as dust, flooding, and thermokarst. Nor do they address the various types of habitat lost to direct and indirect effects. Such analyses re- quire 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. Figure 7-3 illustrates one section (Walker et al. 1987b). Although there are no data to delineate the extent of the indirect physical effects of the North Slope's road network, historical mapping studies from the 1980s showed that wide margins on both sides of roads were affected by dust, thermokarst, intermittent flooding, gravel spray, vehicle trails, and trash (Walker et al.1987b). The width of the mar- gins varied according to the amount of traffic and the terrain type. Very flat portions of the oil field with many drained thaw lake basins and many roads had extensive areas of road-

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EFFECTS ON VEGETATION ~ Wet sedge ttmdla ~ Dry tundras d) 5~}0 40~) 30~} it, 200 10~) (~l el roads ~ Const' ction-'nduced ~ Gravel and construction an~ads thermo~arst deltas FIQodect areas ~ Whicle tracks ~ B=e'~ - JUSt kitiec! tu'~d'-a Ql drained water~ody ~ :~k 1968 ~ 972 81 A! I, flooding) , . fk ;~ ..... i - i 1976 1980 1984 FIGURE 7-3 Geobotanical and historical disturbance mapping. The area shown is among the most heavily developed portions of the oil field. (a) Vegetation map shows the terrain as of 1949, before development. Soils and landforms also were mapped. (b) Infrastructure as of 1970, with a few roads and drill sites. Some flooding (violet) and roadside disturbances (red) are evident. (c) Infrastructure as of 1983. SOURCE: Walker 1996. Adapted from Walker et al. 1987b. Numerous large pads include the processing facility at GC-1 (center) BP base operations camp (lower right), a construction camp (northwest of GC-1), and several production pads. The roads and pads inhibit drainage, and there is extensive flooding in the drained thaw effects in lake basins. (d) Progression of direct (solid lines) and two indirect effects (dashed lines). The area of indirect effects in this portion of the oil field was nearly triple the area of the direct effects. SOURCE: Alaska Geobotany Center, University of Alaska Fairbanks, 2002; adapted from Walker et al. 1987b. side flooding that greatly exceeds the gravel-covered areas terrain of the roads and pads (Figure 7-3~. Effects of ground excavations were most widespread in floodplains, whereas effects of dust and thermokarst were most extensive on upland areas. In a very wet area of a heavily affected portion of the oil field, the ratio of indirect effects (roadside flooding, dust, debris, thermokarst) to the area of the gravel road was 8.6:1. In dry areas of the same heavily developed portion of the field, the ratio was 2.4: 1, and the mean for all mapped areas (mostly in heavily devel- oped portions of the field) was 6:1 (data derived from Walker et al. 1986b). Walker and colleagues (1987b) focused on some of the most severely affected areas of the oil field areas that were developed first but that no longer represent development practices (Robertson 1989~. Their study is, however, an im- portant reference for changes within the oldest, main part of the oil field. Their methods could be used again to examine more recent changes and used elsewhere to assess effects in areas where newer technology has been used. SEISMIC EXPLORATION Some seismic trails from the 1940s are still visible on the North Slope. There are no maps that show all of the early trails, so an estimate of their total length cannot be calcu- lated. Many studies of the effects of off-road vehicles have noted critical factors that determine the amount of damage to the tundra (Abele et al. 1978, 1984; Radforth 1972, Walker et al. 1977): ground pressure total weight of each vehicle number of passes by the vehicles type of vegetation The development of new methods for seismic exploration might reduce damage by reducing the weight, tracks, or the number of vehicles used. Nearly all of our knowledge about long-term recovery from seismic exploration comes from a single U.S. Fish and Wildlife Service (FWS) study of a2-D (two-dimensional) seismic survey in the Arctic National Wildlife Refuge in 1984-1985 (Emers and Jorgenson 1997~. Although technol- ogy changes since then limit the applicability of its results, the study does provide valuable information on different types of effects and on the recovery rates of tundra. According to Emers and Jorgenson (1997), the 1984- 1985 seismic exploration consisted of more than 2,000 km (1,200 mi) of seismic lines, arranged in 5 x 20 km (3 x 12 mi) line spacings. Another 2,000 km of trails was associated with moving the support camps. Most seismic lines consisted of a multitude of trails caused by multiple passes by a variety of vehicles (Figure 7-4~. Camp-move trails caused more damage than the seismic lines did, however, particularly when the snow cover was insufficient to protect the ground and the tractors scraped the tundra as their treads sliced through the vegetative mat. Effects were estimated from an aerial photo survey that examined a random sample of 20% of the trails a year after disturbance. About 14% of the trails showed no detectable disturbance; 57% had low disturbance; 27% had moderate disturbance; and 2% had high disturbance (Reynolds and Felix 1989~. Eight years after the exploration, only about 4% of the seismic and receiver line trails were still disturbed, but camp-move trails showed more disturbance about 15% were disturbed, including 4% that showed medium distur-

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82 CUMULATIVE EFFECTS OF ALASKA NORTH SLOPE OIL AND GAS (b) FIGURE 7-4 (a) Trailers on skids make up Camp 794 on the tundra of the National Petroleum Reserve-Alaska. Photograph by Erik Hill, courtesy of the Anchorage Daily News. Reprinted with permission. (b) Tractors towing camp trailers during a camp move in the Arctic National Wildlife Refuge, 1984. SOURCE: Jorgenson et al. 1996. bance and 1% that showed high disturbance (Emers et al. 1995). Figure 7-5 shows examples of damage caused by seis- mic-exploration vehicles. Effects are rated on a 4-point scale with O indicating no damage and 3 indicating extensive dis- turbance of vegetation. Although the typical effects of individual seismic trails in the Arctic National Wildlife Refuge generally were mi- nor, they were extensive and varied greatly with vegetation type, terrain, vehicle type, operator vigilance, and amount of snow cover. Minor effects and rapid recovery occurred in flat areas of wet tundra, which are common on the Arctic Coastal Plain. Damage was greater in areas with more microrelief and in areas with taller shrubs that were not cov- ered by snow, which is more common in hilly portions of the North Slope. Tussock tundra and frost-boil tundra were par- ticularly susceptible because of higher microrelief. The greatest damage occurred where the vegetative mat was destroyed and the underlying soil was exposed. This was infrequent and usually resulted from tracked vehicles or sleds on skids cutting into hummocks or other raised areas or from Caterpillar operators making a tight turn or dropping a blade too deeply into the snow. High disturbance also oc- curred where vehicles became mired in deep snow and their

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EFFECTS ON VEGETATION 2 - Moderate 83 No effect to slight scuffing of higher microsites. Trail goes through photo from foreground to background, passing between the two wooden stakes in the distance. Note slight color difference in tussocks on trail (light brown color rather than grays, due to scuffing of tops of tussocks. Less than 25% decrease in vegetation or shrub cover; less than 5% soil exposed. Comparison of standing litter and slight scuffing in wet graminoid and moist sedge-shrub tundra. Tussocks or hummocks scuffed. Trail evident only with tracks on Dryas terrace sites. All of the foreground and much of the background of this photo show tussocks disturbed by dispersed vehicle traffic. Note the flattened, brown-topped tussocks compared to the tussocks with level O disturbance pictured above. Vegetation or shrub cover decrease 25-50%, exposed soil 5-15%. Compression of mosses and standing litter in wet graminoid and moist sedge-shrub tundra; may have increase in aquatic sedges. Tussocks or hummocks crushed but show regrowth. Portions of trail may appear wetter than surrounding area. Some disruption of vegetative mat within tracks of riparian shrublands and Dryas terrace. May be some change in vegetative composition. Note the two vehicle tracks going from foreground to background. Tussocks in the tracks are crushed. Over 50% decrease in vegetation cover or shrub cover; over 15% soil exposed. Obvious track depression in wet graminoid and moist- shrub tundra; standing water is apparent on trail that is not present in adjacent areas in wet years; moist sedge-shrub tundra changing to wet graminoid. Crushed tussock or hummocks nearly continuous; general depression of the trail is evident; change in vegetation composition. In riparian shrub and Dryas terrace vegetative mat and ground cover substantially disrupted. Note the exposed soil and crushed tussocks on the trail. FIGURE 7-5 Examples of seismic-exploration disturbance on tussock tundra vegetation in the Arctic National Wildlife Refuge, summer 1985. SOURCE: Jorgenson et al. 1996.

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84 operators tried to extricate the equipment instead of being pulled out (Shultz 2001~. The most common sites of high disturbance were in areas with low snow cover and where vegetation is easily disturbed river terrace plant communi- ties or plant communities on stabilized sand dunes. The plant species that are most sensitive to disturbance and that have poor potential for recovery are among the most common. Cottongrass tussocks (Eriophorum vaginatum) are susceptible and often are crushed or cut open by the grouser bars on tracked vehicles, as are evergreen shrubs (Rhodo- dendron decumbens, Vaccinium vitis-idaea, Dryas in- tegrifolia), some deciduous shrubs (Betula nana, Arctosta- phylos rubra, Salix phlebophylla, S. reticulata), some mosses (particularly Sphagnum and Tomentypnum nitens), and all lichens (Felix et al. 1992~. Some affected species, such as Labrador tea (Rhododendron decumbens) and low-bush cranberry (Viburnum vitis idaea), are used extensively by the Inupiat, who have concerns about the effects of seismic trails on their subsistence harvests. The physiological rea- sons for the sensitivity of certain species are not known. In 1998, 14 years after the original survey, 7% of the plots assessed on the ground were still disturbed, and 15% showed disturbance that was visible from the air (J. Jor- genson, FWS, personal communication, 2001~. The active layer was deeper on about 50% of the disturbed plots than it was in adjacent control areas after 10 years (1984-1994~. By 1998, differences in thaw were still noticeable on many of the trails. Based on the current recovery rates, the long-term trends each disturbance category can be illustrated (Figure 7-6~. Overall, the vegetation recovery reaches a plateau after about 8 years. Some trails are likely to be visible from the air for decades after that (Jorgenson, unpublished material, 2001) (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 three- dimensional (3-D) seismic methods. One study of the Colville River delta detected the trails left from repeated 2-D exploration in 1992, 1993, and 1995 and from 3-D work in 1996, but it reported generally minor disturbance (Jorgenson and Roth 2001~. High disturbance occurred on only 1% of the sites surveyed, mostly dry dune areas. Maps of those survey lines show the much higher density of trails associ- ated with the 3-D operations, which can be spaced as close as 200 m (660 ft), or rarely even closer. It was difficult to quantify the numerous random stray trails that were not part of the seismic lines or camp-move trails (for example, see Figure 7-7a). Some areas were surveyed several times by different companies, resulting in a maze of seismic trails, camp trails, and ice roads, which are difficult to separate or identify by type and year of ongin. Some repetition is caused by the need for new or better seismic information, but it also occurs because the data are proprietary and companies will not share information that might help competitors, thus set- ting the stage for each to gather data and conduct analyses independently. The Importance of Snow Cover The Alaska Department of Natural Resources (DNR) is- sues tundra travel permits for seismic crews based on their examination of several sites each December and January. The permits allow tundra travel for seismic camps when there is an average minimum of 15 cm (6 in.) of snow and 30 cm (12 in.) of frozen soil, which is determined by the number of times a hammer must strike a stake to drive it into the soil. Conditions are monitored throughout the winter. DNR closes tundra travel in April or May, again depending on conditions. / - /1 / Disturbance Level 7 .,.~ 0 2 Years since disturbance FIGURE 7-6 Recovery after seismic disturbance. SOURCES: Data from Felix et al. 1992; Emers et al. 1995; FWS, unpublished, 2002.

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EFFECTS ON VEGETATION The only published study of seismic disturbance in rela- tion to snow cover suggests that measurable, low-level dis- turbance occurs at depths of as much as 45 cm (18 in.) in tussock tundra, and 72 cm (28 in.) in sedge-shrub tundra (Felix and Raynolds 1989b). Moderate disturbance occurs at snow depths to 25 cm (10 in.) in tussock tundra and 35 cm (14 in.) in moist sedge-shrub tundra. Knowledge of the distribution and ecological signifi- cance of snow in arctic ecosystems has grown considerably in the past 20 years (e.g., Jones et al. 2001, Liston 1999, Olsson et al. 2002, Sturm et al. 2001~. The structure of the snowpack is critical to maintaining the relatively warm win- ter microclimate at the base of the snowpack (Pomeroy and Brun 2001~. The subnivian layer, the highly porous granu- lated layer of snow at the base of the snowpack, acts as insu- lation and is important to many wintertime processes, such as soil microbial activity and wintertime carbon dioxide flux (Oechel et al. 1997), and to the movement of small mam- mals (Aitchison 2001~. Plants are sensitive to the thermal conditions at the base of the snowpack (Walker et al.2001a). Ice roads and pads and vehicle trails alter snowpack struc- ture and can physically disturb vegetation and soils if the snowpack is thin. 85 FIGURE 7-7 Aerial views of seismic trails. (a) Intersecting seis- mic-exploration and camp-move trails, Arctic Foothills. The heavi- est trail (center) near Kavik in the tussock tundra is a camp-move trail. The intersecting trails (left) are seismic lines. Also shown here are numerous stray trails that are not part of the camp-move or seismic trails. Tan colors show damaged cottongrass tussocks (Eriophorum vaginatum) and dead dwarf shrubs. SOURCE: Jorgenson, unpublished material, 2001. (b) Heavily impacted tun- dra in hill slope with frost boils, sedge-dwarf-shrub tundra, and high microrelief. SOURCE: Jorgenson, unpublished material, 2001. Trails in (a) and (b) were made in winter 2001 and photographed in summer 2001. (c) Camp-move trail from 1985 exploration in the Arctic National Wildlife Refuge, photographed in 1994. This trail remained visible because of trail subsidence, a decrease in shrub and mosses, and an increase in standing dead sedge leaves. SOURCE: Jorgenson et al. 1996. Small amounts of snow in northern Alaska are a par- ticular problem for wintertime exploration activities. Near the coast, the average April wind-packed snow depth is 30 cm (12 ink. The snowpack normally builds up to about 20 cm (8 in.) within 10-20 days after freezeup and then in- creases slowly through the rest of the winter (Dingman et al. 1980~. Several factors affect the local and regional distribu- tion and characteristics of snow, including increasing snow- fall from east to west and from north to south across the North Slope, gradients of wind across the North Slope, and differences in snow cover associated with topography. The use of average snowpack and frost thickness by regulatory agencies to determine when to open and close the tundra travel season does not consider such differences. If snow cover increases in the future, as some climate- change models predict, the effects of seismic trails could be reduced. Snow cover also affects the depth of frost penetra- tion. Generally, snow insulates the tundra, so if the snow- pack accumulates earlier or to greater depths, the timing of the opening of the seismic season could be affected. Less snow would shorten the seismic season. Earlier warming in spring could mean the cessation of seismic activities earlier in the year. The length of the season for off-road tundra travel

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86 CUMULATIVE EFFECTS OF ALASKA NORTH SLOPE OIL AND GAS .~c 1.. FIGURE 7-8 Opening and closing dates of North Slope off-road traffic. SOURCE: ADNR. has decreased (Figure 7-8), mainly the result of later open- ing dates for the season rather than earlier closing dates. A more complete understanding of just how much snow and frost penetration are needed to adequately protect the tundra from seismic operations is needed. Potential Accumulation of Effects of Seismic Trails According to the best estimate of the Committee on Cumulative Environmental Effects of Oil and Gas Activities on Alaska's North Slope, 32,000 line miles of seismic trails, receiver trails, and camp-move trails were made between 1990 and 2001, and if current trends continue, another 27,000 line miles will be surveyed in the next 10 years. A large percentage of the trails should recover within relatively short periods. Data from the Arctic National Wildlife Refuge showed that after 8 years only about 3% of the seismic and receiver line trails and 10% of camp-move trails were still disturbed (Emers et al. 1995~. Based on these recovery rates and modern ratios of trails in each disturbance category, the committee projected the total seismic line miles in each disturbance category into the future (Figure 7-9~. This figure projects cumulative line miles of trails for the next 12 years in each of four distur- bance levels illustrated in Figure 7-5, and it assumes the same rates of recovery that occurred in the Arctic National Wild- life Refuge. According to this model, about 17,500 miles will recover fully (Level 0, although parts could be faintly visible from the air). About 6,200 miles will have Level 1 disturbance, 3,600 miles will have Level 2 disturbance, and about 300 miles will show Level 3 disturbance. Although there are no comparable data for modern seis- mic methods, the Arctic National Wildlife Refuge data pro- vide some useful insights. First, after about 6 years, the re- covery of old trails in disturbance categories 1 and 2 about balance the addition of new trails. As long as the rate at which new trails are added remains constant, the recovery of old trails generally keeps pace, and the total footprint of seis- mic trails on the landscape at any one time will remain about the same. The sum of trails in disturbance categories 1, 2, and 3 currently is about 10,000 line miles (Figure 7-9), so the posited relationship is valid only if the improved tech- nology does not result in a decrease in the degree and amount of tundra disturbance. However, newer technologies appear to cause less long-term damage. There is a small increment of trails in disturbance category 3 that do not recover, and the total line miles in this category continues to climb slowly. Because of the large number of seismic line miles created each year, even very small percentages of trails in category 3 can accumulate to large totals over many years. If this trend were to continue to 2025, then another 29,900 line miles will have been surveyed. If 1 % of the trails are in category 3, this would add nearly 300 line miles of degraded land to the North Slope. Trails in this category can deteriorate over time and become worse as permafrost subsidence and erosion occur.

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EFFECTS ON VEGETATION 20000 - 18000 - 16000 - 14000 - 12000 - 1 0000 - 8000 - 6000 4000 2000 o 87 1 Low 2 Moderate - - - 3 High 1990 1991 1992 1993 1994 1995 1996 Year 1997 1998 1999 2000 2001 FIGURE 7-9 Hypothetical cumulative line miles of trails during 12 years and totals in the four disturbance levels based on the following: (1) Total seismic line miles equivalent to that during 1990-2001. (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. 1995~. (3) The recovery rate in each disturbance category is the same as that in the Arctic National Wildlife Refuge studies. SOURCE: Alaska Geobotany Center, University of Alaska Fairbanks, 2002. The model used here is based on information from stud- ies that measured recovery rates on the ground. It does not address the question of how much remains visible from the air. About 15% of the trails created in the Arctic National Wildlife Refuge between 1984 and 1985 are still visible from the air (J. Jorgenson, FWS, unpublished material, 2001~. Those trails affect the visual quality of large landscapes and are a cause for particular concern in pristine areas, such as the Arctic National Wildlife Refuge, especially given that most North Slope travel is by small aircraft. There have been no studies to document recovery rates of trails visible from the air. Some seismic trails have caused significant changes to plant communities (Emers and Jorgenson 1997, Emers et al. 1995~. Although most trails recover to resemble the original plant community within about 8 years, heavily damaged ar- eas do not. The long-term consequences of the changes are unknown, but possibilities include the establishment of weedy species and the subsidence of trails because of thermokarst. Invasive grasses have colonized some highly disturbed trails, making them more visible from the air (Emers et al. 1995~. An average of about 1,300 line miles of seismic trails is added each year. The total area likely to be affected an- nually can be estimated by multiplying by the width of trails on average, 30 m (100 ft) and adding the areas of the associated camp-move trails. This was done for the en- vironmental impact statement for the northeastern portion of the National Petroleum Reserve-Alaska, in association with the first lease sale. Assuming the same ratio of 2-D to 3-D exploration for the entire North Slope, the predicted 13,000 line miles over 10 years would translate to a total affected area of 1,114-3,421 km2 (430-1,321 mid. This estimate does not include areas affected by receiver lines perpendicular to main lines or to the many stray vehicle trails on the tundra. The estimate also does not include the areas between the trails, which often are visually affected, especially in areas of 3-D seismic exploration, nor does it include recovery that would occur within the 10-year pe- riod. It also does not address the fact that a good portion of the seismic line kilometers will occur in areas already sur- veyed using older seismic technologies. And it does not take recent technological improvements into account. But the estimate does give some impression of the extent of the areas that are likely to suffer effects caused by seismic ac- tivities in the near future, although the degree of effect is difficult to judge given that effects are less if the tundra is adequately protected by snow. In the future, seismic-exploration is expected to increase in the foothills region, where effects are likely to be different from those documented on the coastal plain. Research will be needed to identify and monitor those effects. The com-

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88 mittee is not aware of data that can be used to assess the ecological significance of the persistence of disturbed linear segments of tundra. Ice Roads and Pads ice roads, airstrips, and drilling pads have been built in recent years to reduce costs and environmental effects of gravel construction (Hazen 1997, Johnson and Collins 1980~. Extended-season ice pads have many environmental and eco- nomic advantages for exploration (Hazen et al.1994, Stanley and Hazen 1996~. Those ice pads are covered with reusable insulated panels that help preserve the ice in the summer, allowing drilling to resume nearly two months earlier the next season. There have been some studies of the short-term ecosystem effects of ice roads (Johnson 1981, Johnson and Collins 1980, Walker et al.1987a), but there have been no long-term studies. Most of the effects of ice roads involve the direct physical dis- turbance of vegetation, the effects of debris from the road, and the destruction of the subnivian layer (Walker et al.1987a). The biotic effects of ice roads are substantially less than those of gravel roads and pads but more severe than those of seismic trails. Studies of vegetation recovery at an extended-season ice drilling pad showed a 34% decrease in vascular plant cover 2 years after the pad melted; the effect was greatest on raised microsites (Noel and Pollard 1996~. Climate warming could restrict the use of ice roads and pads in the future. AIR QUALITY The effects of air quality on vegetation near industrial facilities on the North Slope appear minimal: for example, concentrations of NOX and SO2 from 1989 tol994 were be- low those generally expected to be harmful to plants (Kohut et al. 1994~. High concentrations of NOX occurred only dur- ing a small percentage of monitored hours. The NOX and SO2 monitoring revealed no effects on vegetation that could be attributed to pollution. The researchers (Kohut et al.1994) recommended continued monitoring at 2-year intervals to ensure that any changes in vegetation could be detected rela- tively quickly. This monitoring is not being conducted (S. Taylor, BP [retired], personal communication, 2001~. Lichens are known to be vulnerable to SO2, and concen- trations as low as 12 ,ug/m3 for short periods can depress photosynthesis in several species, with damage occurring at 60 ,ug/m3 (BLM/MMS 1998~. (The National Ambient Air Quality Standards maximum 3-fur limit for SO2 is 1,300 ,ug/m3.) Sensitivity of lichens to sulfates is greater under the moist and humid conditions that are common on the North Slope. Air monitoring that was conducted from 1989 to 1994 showed maximum 3-fur concentrations of SO2 above 12,ug/ m3 at 11 of the 12 sites monitored; 1 site exhibited concen- trations greater than 100,ug/m3 (USACE 1999, Table 5.4-5~. Thus, even though air quality meets National Ambient Air CUMULATIVE EFFECTS OF ALASKA NORTH SLOPE OIL AND GAS Quality Standards, it is not clear that those standards are suf- ficient to protect arctic vegetation. Similarly, although most monitored concentrations of ozone were reported by Kohut and colleagues (1994) 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 deposi- tion of contaminants on snowpack on the moss, Hylcomium splendens, at Prudhoe Bay and in the Arctic National Wild- life Refuge (FWS 1995a). The report documented enrich- ment of nutrients and several trace elements in the Prudhoe Bay snowpack compared with sites in the Arctic National Wildlife Refuge. "Significant inputs of major and trace ele- ments, including heavy metals [were found] at Prudhoe Bay at two sites, one near drilling operations and the central pro- cessing facility, and the other near the North Slope Borough solid waste incineration facility." Effects appear to be local, however (FWS 1995a). AREAS OF SPECIAL IMPORTANCE Several features of the North Slope vegetation deserve special mention because they are important focal points for wildlife activity; nonacidic tundra, bird mounds, pingos, river corridors, salt marshes, and small groves of trees near spnngs. Nonacidic Tundra Regions Most North Slope oil and gas development has occurred on nonacidic tundra. Because it grows on mineral-rich soils, this tundra is especially important to wildlife. It is home to many plants and animals, including four major caribou herds, three of which calve in areas of coastal nonacidic tundra. The nonacidic soils of the region could contribute to this wildlife diversity (see Chapter 3 for additional discussion of soil pH). The digestible, nutrient-rich vegetation could be especially important for caribou and other herbivores. The warmer soils could provide habitat for burrowing mammals, such as voles (Microtus oeconomus), ground squirrels (Spermophilus parry)), and lemmings (Lemmus sibiricus), which in turn could provide favorable hunting grounds for a variety of predators. River Corridors River corridors are probably the most biologically di- verse and the most affected of the important terrain types in the Prudhoe Bay region. A diversity of plant communities occurs in association with waterways: ground squirrels, bears, and foxes use well-drained valley sites for their dens, and all predators find abundant prey along rivers. Riparian systems vary considerably. For example, riparian communi- ties are different in loess and sandy regions. Communities have more species in warmer portions of the North Slope.

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EFFECTS ON VEGETATION River corridors were among the first areas disturbed by oil and gas development because they are sources of gravel and routes for roads and buried pipelines. The lower portion of the floodplain of the Little Putuligayuk River (Figure 7- 10) has been intensively mined for gravel and used for waste disposal; in places, it is no longer recognizable as a flood- plain (Walker 1996~. Fluvial processes are slowed in the Arctic because the highest flows tend to occur when most of the floodplain is frozen. As a result, areas altered by gravel mining take much longer to recover than is the case in lower latitudes. Some components of river floodplains, such as higher terraces, are more sensitive to disturbance and also are slow to recover. Pingos and Bircl Mouncis Pingos, another important landform of the Arctic Coastal Plain ecosystem, attract numerous species of ani- mals, including arctic foxes (Alopex lagopus), arctic ground squirrels, caribou, grizzly bears (Ursus arctos), lemmings, raptors, buff-breasted sandpipers (Tryngite subruficollis), plovers, and ptarmigan (M.D. Walker 1990, Walker et al. 1991~. The pingos around Prudhoe Bay are apparently quite old, and they do not erode easily or collapse as do pingos composed of more fine-grained materials, such as those in the Mackenzie River delta (Mackay 1979, Walker et al. 89 1985~. They consequently have old, well-developed plant communities (M.D. Walker 1990, Walker et al. 1991~. Pin- gos attract people because some animal species, such as arc- tic foxes, are easily trapped at these sites, and pingos offer good vantage point for hunters and surveyors. 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. 1980~. They are thought to have accumulated organic matter over long periods from fertilization by birds and small mammals. Predatory birds use these higher sites to observe the surrounding terrain. Other animals, such as voles and lemmings, take advantage of the relatively dry habitats. The importance of bird mounds to coastal plain ecosystems has never been evaluated, but they support diverse plant com- munities. They are easily damaged by ice road construction and camp moves during seismic operations. Rare and Enclangerecl Plants Three North Slope plant species are considered endan- gered or threatened by the Nature Conservancy as listed in the Alaska Rare Plant Field Guide (Lipkin and Murray FIGURE 7-10 Floodplain of the Little Putuligayuk River. SOURCE: Alaska Geobotany Center, University of Alaska Fairbanks, 2002.

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9o 19971: Erigeron muirii (Muir' s fleabane), Mertensia drummondii (Drummond's bluebell), and Poa hartzii var. alaskana (Hartz's bluegrass). All three occur in dry habitats associated with dry bluffs, flood plains, river terraces, sand dunes, rocky slopes, outcrops, fellfields, and mountain sum- mits. Those habitats are the primary sources of ballast and fill used for construction projects. FACILITY REMOVAL, REHABILITATION AND RESTORATION OF GRAVEL-COVERED AREAS Many industrial activities and their accompanying acci- dents and consequences spills or discharges of oil or other materials; tundra travel; the construction and operation of roads, airstrips, gravel islands, and pads; gravel mining; dust deposition, and impoundments disturb surface environ- ments (Walker 1996~. The extent to which effects accumu- late depends in part on whether efforts are made to amelio- rate them. The oil and gas industry generally defines rehabilitation as the conversion of a disturbed site into func- tional habitat for plants and animals without necessarily re- storing the original species and processes. Restoration means the replacement of lost habitat features, species, and pro- cesses that were present prior to disturbance (AOGA 2001~. As noted in Chapter 4, the committee commissioned an analysis of the history of the North Slope road and infra- structure network (also see Appendix E). The analysis in- cluded an estimate of the area affected by industrial develop- ment judged to be rehabilitated. Rehabilitated areas as defined by Aeromap, Inc., included areas that were no longer definable as clearly disturbed in aerial photographs or areas that now provide functional habitat but might be different from the original. In most cases, these areas were not re- stored to their former condition. Rehabilitation to some de- gree has occurred on only about 195 acres about 1% of gravel pads. The rehabilitated area includes the gravel mines of the Sagavanirktok and Kuparuk river floodplains rehabilitated by natural river action, engineered rehabilitation that oc- curred on abandoned exploration pads, and the flooding of the deep gravel mines in the oxbows of the Kuparuk River. According to the analysis, rehabilitation has occurred on about 11 ha (26 acres) of abandoned airstrips, 15 ha (37 acres) of offshore gravel pads, 29 ha (72 acres) of on-shore gravel pads, and 1,841 ha (4,549 acres) of gravel mines. Gravel has been removed from about 79 ha (195 acres); and the sites are in various stages of recovery. About 95% of the rehabilitation has occurred in gravel mine areas. Some of the shallow gravel mines in the floodplains of the Kuparuk and Sagavanirktok rivers have been allowed to recover by the natural action of the rivers. Before mining, floodplains consisted of a mosaic of barren active channels and barren and vegetated islands. Numerous river bars and islands eliminated by mining have not been restored. The deeper gravel mines are not restored to their previous condi- CUMULATIVE EFFECTS OF ALASKA NORTH SLOPE OIL AND GAS lion, but they are considered rehabilitated by Aeromap be- cause they provide winter fish habitat even though they are strikingly different from the original habitat. Although the size of the gravel footprint required to sup- port operations has been greatly reduced (Streever et al. in press), relatively little progress has been made on restoring existing sites affected by gravel fill. Only about 1% of the roughly 3,733 hectares (9,225 acres) of tundra habitat on the North Slope covered by gravel roads, pads, airstrips, and other facilities, has been rehabilitated, either naturally or from revegetation efforts. The factors that contribute to the low rate of site restoration include technical and natural con- straints imposed by the harsh environment of the North Slope; the lack of clear regulatory requirements governing the level and timing of restoration; uncertainty about whether currently unused sites will be required in the future; con- tamination and liability concerns; and the high cost of re- moving facilities and restoring sites in the region. Each of these issues is addressed below. Technical and Natural Constraints The North Slope presents special technical challenges to restoration and recovery. Extremely cold temperatures, meager precipitation (13-18 cm [5-7 in.] per year), and the short growing season lengthen recovery times substantially beyond those possible elsewhere in the United States. Natu- ral recovery of disturbed sites to original soil and plant con- ditions has been estimated to require 600-800 years for up- land mesic sites and 100-200 years for marsh sites (AOGA 2001~. Recovery of disturbed sites on the North Slope is com- plicated by the fact that any disturbance of the insulating vegetative mat can melt the underlying permafrost, a process that is extremely difficult to reverse and that can continue long after the initial disturbance ends. Finally, gravel pads and roads, which account for the vast majority of the directly affected habitat on the North Slope, retain moisture and nu- trients poorly and so slow recovery processes. Recovery times in the Arctic, as elsewhere, depend in part on the nature and extent of disturbance and the type of habitat affected. For example, wet sites tend to recover quickly from light oil spills; dry sites affected by diesel fuel spills recover exceedingly slowly, with little recovery occur- ring after several decades (Walker 1996~. Disturbed areas that would recover relatively quickly in more temperate cli- mates (such as those caused by Caterpillar tractor tracks) can persist for many decades because of melted permafrost. Restoration Research During the past few decades, considerable industry re- search has examined the feasibility of rehabilitating areas disturbed by oil-field activities (McKendrick 1997~. Until recently, that work has focused on revegetating sites with

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EFFECTS ON VEGETATION exotic grasses to avert erosion. More recent efforts have fo- cused on the use of native grasses and fortes and on the resto- ration of ecological processes and aesthetics, all of which are much more challenging goals (AOGA 2001~. A variety of rehabilitation strategies has been developed, including flooding of gravel mine sites to create overwinter- ing 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 drill- ing 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. Preliminary results indicate that, if cost is not a factor, a productive and diverse vegetative cover can be established even on sites with severe ecological limitations. Most of the studies suggest that natural re- colonization occurs relatively rapidly on thin fill and on or- ganic rich fill where moisture and nutrients are not severely limiting (Jorgenson 1997~. Low temperatures near the coast, however, reduce the number of species available and the rate at which recolonization occurs. A survey of 12 revegetated pads in the National Petroleum Reserve-Alaska showed that on average only 3 native species were found on pads at the cold coastal sites, lo were found on inland coastal plain pads, and 24 were found on relatively warm foothills sites (McKendrick 1987~. Fertilization and seeding with nonna- tive species appears to delay natural recolonization (Jorgen- son 1997~. More costly methods are required for rehabilitating the gravel roads, pads, and mine sites that dominate disturbed land (Jorgenson 1997~. Construction of berms and basins, application of topsoil, and use of various plant cultivation techniques are required on these sites. However, only a very limited amount of topsoil has been stockpiled for future use in the oil fields (Jorgenson 1997~. Sewage sludge is being considered as an alternative source of organic mate- rial. Native legumes with nitrogen-fixing ability could be essential for sustaining the long-term productivity of those sites. Removal of gravel fill has recently been done in wet- lands, and preliminary studies suggest that wetland mosa- ics of vegetation can be restored, although the method is expensive and finding acceptable locations for the fill can be difficult. Gravel extracted from 24 open-pit gravel mines, affects some 2,580 ha (6,364 acres) in various floodplains and del- tas on the North Slope (Table 4-4~. Rehabilitation typically involves converting mine sites to lakes, with a channel usu- ally cut between the pit and a stream or river so the site can be accessible to fish. Such sites create potential overwinter- ing habitat for fish, but they also result in the permanent loss of the original habitats. 91 Restoration Stanclarcis and Requirements Existing state and federal laws and regulations govern- ing surface restoration lack clear definitions and standards, and they overlap in potentially conflicting ways. The lack of definitions in the relevant statutes and regulations of clear restoration goals makes it difficult to plan and design resto- ration activities. The Federal 404 Program Section 404 of the Clean Water Act authorizes the U.S. Army Corps of Engineers to issue permits for the discharge of any type of fill material into waters of the United States, including wetlands. Because virtually all of the Arctic Coastal Plain is in wetlands, permanent facilities (roads, pads) require Section 404 permits, as do causeways, gravel islands, gravel mines, pipeline burial routes, and other con- struction activities, regardless of location on state, federal, or privately held land. Until 1979, however, the corps did not exercise its Sec- tion 404 authority on the North Slope, and it estimates that about half of the area covered by gravel was filled without permits (T. Carpenter, USACE, memo to NRC staff, 12/4/ 2001~. The corps now lacks jurisdiction over those "unper- mitted" sites, and no detailed mapping or inventory of them exists (T. Carpenter, USACE, memo to NRC staff, 12/4/ 2001; USACE, personal communication,12/12/2001~. Since 1979, 1,179 permits have been issued on the North Slope (USAGE, personal communication, 12/12/2001; D. Hobble, USACE, unpublished material, 4/2/2001~; 3 have been de- nied (GAO 2002~. The corps has no estimate of the total area affected by its Section 404 permits (USAGE, personal com- munication, 12/12/2001~. Restoration is not mandatory even for gravel roads, pads, and other facilities constructed under Section 404 per- mits. Restoration upon abandonment is governed by General Condition 2, one of the conditions included in all standard 404 permits, which states: ". . . Should you wish to cease to maintain the authorized activity or should you desire to aban- don it without a good faith transfer, you must obtain a modi- fication of this permit from this office, which may require restoration of the area" (emphasis added) (Army Standard Permit). The corps takes the position that the ultimate au- thority over restoration lies with the landowner (the state for state leases, the Bureau of Land Management [BLM] for the National Petroleum Reserve-Alaska leases, and the Miner- als Management Service [MMS] for the Outer Continental Shelf [OCS] leases) (USAGE, personal communication, 12/ 12/2001~. Fewer than 1% of the permits issued contain res- toration requirements that are accompanied by specific suc- cess criteria, principally percentage cover required (USAGE, personal communication,12/12/2001~. The requirements do not define methods for estimating cover, specify whether cultivars or native species are to be used, or include specific

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92 monitoring methods to determine success (Streever et al. in press). As a result, different methods of defining percentage cover have yielded very different results (Streever et al. in press). The corps has reported that the most lenient require- ment found in a review of permits for the North Slope 30% cover in 3 years could not be met for gravel pads. Recently, the corps has included ecosystem process goals in several of its permits for new facilities. For exam- ple, the Alpine permit requires that, upon abandonment, the gravel footprint is to be rehabilitated "in a manner that maxi- mizes benefits to fish and wildlife resources, and restores the natural hydrology of the immediate project area footprint" (404 Permit #2-960874, Special Condition 9~. However, spe- cific standards for achieving those goals, criteria to measure performance, the timing of implementation, and the type and amount of monitoring required are not specified. The corps has required gravel reuse as a special condi- tion of particular permits. The Northwest Eileen permit (USACE permit 4-2000-0041) requires the permit holder to "remove and recover gravel" from 3 abandoned sites. This involves using gravel from existing pads, roads, and other unused facilities rather than mining new gravel and restoring the old sites. Gravel reuse has been required in only 6 per- mits issued by the corps (USAGE, personal communication, 12/12/2001~. If gravel reuse is added as a special condition, the permit holder must arrange to have the gravel tested for hydrocarbon contamination and cleaned (by burning hydro- carbons off) if necessary. In the event that the contamination is too severe to be removed effectively, the permit holder must identify another site of equivalent size that could serve as a source of gravel. Gravel reuse and revegetation can be expensive, particularly if decontamination is required. The nature, extent, and timing of restoration required by gravel reuse permits or upon ultimate abandonment is not specified in regulations and is subject to the discretion of the corps' Alaska District. In exercising that discretion, the corps does not appear to have made systematic use of the substan- tial research conducted by the industry and others on reveg- etation and restoration. Various experimental trials of differ- ent approaches to revegetation have been conducted by the industry at least since 1984. Those studies have yielded im- portant information about the establishment of vegetation on gravel (Streever et al. in press). Compensatory Mitigation National policy and guidelines developed by the Envi- ronment Protection Agency (EPA) and the Army Corps of Engineers in 1990 under the Section 404 program require "compensatory mitigation" for the unavoidable destruction of wetlands that can be achieved by restoring existing de- graded wetlands or by creating new, artificial wetlands. Be- cause, the corps and EPA have taken the position that the North Slope is exempt from the compensatory mitigation requirement, however, the corps is not required to oblige CUMULATIVE EFFECTS OF ALASKA NORTH SLOPE OIL AND GAS companies to restore old oil-field sites as a condition of new permits a strategy that has worked elsewhere to promote restoration. Other Fecleral Restoration Requirements In addition to the Section 404 permitting program, the federal government may impose additional restoration re- quirements in leases it awards on federal land. Under lease terms awarded in the National Petroleum Reserve-Alaska, no permanent facilities may be established in the exploration phase (BLM/MMS 1998, Stip. # 27~. To date, however, BLM has not developed specific dismantlement, removal, and restoration (DRR) requirements to meet its general goal of returning disturbed land to its original primary use (wild- life habitat and wilderness) (GAO 2002. On the federal OCS, MMS regulations, lease terms, and lease stipulations impose stringent requirements regarding removal of structures and plugging and abandoning wells. In most circumstances elsewhere in the United States, MMS has required platform removal and clearing of the ocean of obstructions to other uses (30 CFR Sec.250.700~; the agency has not specified requirements for abandonment of North Slope gravel islands. State Restoration Requirements Applicable to State Lancl The Alaska Oil and Gas Conservation Commission (AOGCC) imposes stringent well-plugging and abandon- ment procedures for all wells throughout Alaska, regardless of land ownership. The Alaska DNR oversees activities af- fecting the surface (other than spills or other contamination, which is handled by the Alaska Department of Environmen- tal Conservation [ADEC]~.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. BLM/MMS 1998, Stip. #58: "Upon field abandonment or expiration of a lease or oil- and gas-related permit, all facilities shall be removed and sites rehabilitated to the satisfaction of the AO [Authorized Officer; i.e., BLM], in consultation with appropriate federal, State, and North Slope Borough regulatory and resource agencies. The AO may deter- mine that it is in the best interest of the public to retain some or all of the facilities" (emphasis added). 2 Alaska statute AS 46.03.822 makes owners and operators liable for "damages, for the costs of response, containment, removal, or remedial ac- tion" resulting from unpermitted release of hazardous substances. AS 46.03.826 defines hazardous substances to include oil and associated prod- ucts and byproducts. The statute does not cover rehabilitation or restoration.

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EFFECTS ON VEGETATION timing, and extent of restoration of gravel roads, pads, and other facilities to an undetermined future process (ADNR 2002~: At the option of the state, all improvements such as roads, pads, and wells must either be abandoned and the sites reha- bilitated by the lessee to the satisfaction of the state, or be left intact and the lessee absolved of all further responsibil- ity as to their maintenance, repair, and eventual abandon- ment and rehabilitation. Thus, as with the federal government, decisions regarding whether sites must be restored after abandonment and to what extent are largely left to future regulators. Offshore, artificial islands in state waters have been abandoned under plans approved by DNR, which typically involve removing surface hardware, and debris, providing shore protection to a specific depth, and then allowing the island to erode naturally. Under the existing unitization agreements approved by the state, nothing within a unit must be officially abandoned until the entire unit is closed. So, for example, even if the state were to decide to impose stringent restoration require- ments, the companies are not obligated to implement them on any abandoned sites within the Prudhoe Bay oil field un- til the entire unit has been closed. The Army Corps of Engi- neers, however, can require rehabilitation of individual pads within a lease or unit, although it has done so in only a few instances. Whether the oil companies have a clear, substantive obligation to remediate sites on the North Slope has been examined by a court of law on only one occasion (Exxon Mobil Corporation v. Commissioner of Internal Revenue, 114 T.C. 293 [20001~. In that case, the Internal Revenue Ser- vice challenged Exxon's deduction of expenses related to future restoration. The court held that the standard language of the leases under which Exxon and other oil companies conduct activity in the Prudhoe Bay oil field did not create a clear obligation on the part of the oil companies to undertake restoration in the oil field, with the exception of specific well-plugging and abandonment requirements imposed by the AOGCC. The almost 76,000 m3 (100,000 yd3) of solid waste gen- erated by oil-field operations every year includes scrap metal, waste insulation, tires, wrecked vehicles and air- planes, and old buildings. Although there have been im- provements in waste management, large amounts of scrap have accumulated over time, and there is no comprehensive plan for its disposition. At times, scrap is sent out on the return trips of barges that bring supplies to Prudhoe Bay, but often barges are sent back to Anchorage from the North Slope without a load of scrap. Already, the state is facing disposal of abandoned drilling rigs for which corporate dis- solution, bankruptcies, and mergers have clouded ownership, and the scrap issue is expected to become more serious as facilities age. 93 Local Government Restoration Requirements The North Slope Borough has zoning authority that ex- tends by ordinance to state, Native, and municipally owned land within the borough's boundaries. There is some debate over whether the borough' s authority extends to federal land as well. The Coastal Zone Management Act requires consul- tation with the borough before leasing and development of federal land. The borough issues permits for most activities that affect the land surface. It may exercise its authority to require restoration of existing "orphan" sites (abandoned sites where ownership is unknown), of new-construction sites, or both as a condition of new permits. The committee found no evidence that the borough has exercised its author- ity to impose specific restoration requirements separately from those of other government agencies. Local Native villages and corporations also control sur- face lands and subsurface mineral rights and can establish restoration requirements through contractual arrangements with the industry (GAO 2002~. Overlapping Authority Because few restoration requirements have been im- posed at the local, state, or federal level, overlapping juris- diction among regulatory agencies has not been a major is- sue. However, as the fields age and as decisions about restoration begin to be made in earnest, the potential exists for inconsistent or contradictory restoration requirements applying to the same piece of land. For example, the Army Corps of Engineers, the state, and the North Slope Borough all have jurisdiction over activities on state land, and each is free to impose restoration requirements. The lack of an effective, coordinated regulatory struc- ture is partly to blame for the lack of significant progress in restoring disturbed North Slope sites. Without clear and spe- cific standards, the industry faces significant uncertainty re- garding what will and will not be acceptable to regulatory agencies. And without explicit time requirements and per- formance standards, there is little incentive for the industry to undertake expensive and complex restoration efforts. Fi- nally, the absence of standards makes monitoring and en- forcement difficult. In developing standards, flexibility must be built in to advance standards as restoration research advances. Uncertainty Regarcling Future Neecl for Sites One obstacle to restoration and rehabilitation is uncer- tainty about whether old gravel roads, pads, airstrips, and other facilities might be needed in the future. As technology advances and the economics of production change, aban- doned pads could become economically profitable to oper- ate. Thus, there is some reluctance on the part of the industry to commit to restoring currently unused sites.

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94 Contaminatecl Sites The ADEC maintains a database of contaminated sites throughout the state. The database lists more than 90 con- taminated sites associated with oil and gas activities on the North Slope. The extent and nature of contamination on those sites varies considerably. As part of the charter agreement governing BP' s acqui- sition of ARCO, the two companies agreed to assess and clean up 43 of their sites by the end of 2007 (Charter Agree- ment, II.A.3. and Exhibit Did. BP and ARCO agreed to spend $10 million to assess and clean up another 14 orphan sites (Charter Agreement, II.A.1. and Exhibit Did. ADEC confirmed that the 14 are the only known orphan sites, but that others are likely to be found (Judd Peterson, ADEC, personal communication, 11/13/2001~. The companies also agreed to work with ADEC to develop a database of con- taminated and solid-waste orphan sites to identify the nature and location of the sites, the responsible parties, and the rela- tive priority for cleanup of each based on an evaluation of risk to human health and the environment (State of Alaska, BP, and ARCO; Charter for Development of the Alaskan North Slope; Sec. II.A.1 [19991~. Finally, as part of the charter agreement, ARCO and BP agreed to clean up 170 exploration and production reserve pits (Charter Agreement, Exhibit D.3.A. and D.3.B). This includes pits being cleaned out and closed pursuant to a 1993 consent agreement between environmental groups and ARCO. Another 158 pits in the area from the Canning River to Point Lay are being closed under the state's closeout regu- lations (J. Peterson, ADEC, personal communication, 2001~. The contents of all production pits, and some exploration pits, are being ground and injected. The rest of the explora- tion pits are being closed using "freezeback," whereby be- low-grade pits are capped and allowed to freeze in place. One-hundred-eighty-four of the 328 reserve pits on the North Slope are now officially closed (ADEC 2002), but this does not necessarily mean that the sites have been restored. The fate of those sites, some of which could be affected by shore- line erosion, and of 5 "regional" drilling-waste disposal sites on the North Slope that used freezeback as the closure method is uncertain. Between 115,000 and 183,000 m3 (150,000 and 240,000 yd3) of waste was buried at each re- gional site (ADEC, unpublished material, 9/6/2001; ADEC, memo to NRC staff, 12/10/2001 ~ . In addition to sites and reserve pits that are known to be contaminated, industry is concerned about the potential li- ability and expense associated with recycling possibly con- taminated gravel from roads and pads. 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 kilome- ters of tundra habitat affected by development (GAO 2002~. Estimates for different projects indicate that the total cost will run into the billions of dollars. Phillips Petroleum has estimated that it would cost be- tween $50 million and $100 million to remove facilities and restore the Alpine area (R. Lance, Phillips Alaska, unpub- lished material, 7/10/2001~. With 30 million bbl (4.77 bil- lion L, 1.26 billion gal) of oil produced to date, that cost is equivalent to $1.67-$3.33 per barrel. Alpine covers an area of 39 ha (97 acres) (MMS 2001b), yielding an average resto- ration cost of between $1.2 million and $2.5 million per hect- are ($500,000 and $1 million per acre). Assuming roughly similar costs to remove facilities and restore the estimated 3,600 ha (9,000 acres) of gravel-covered tundra on the North Slope, the overall cost of restoration could range from $4.5 billion to $9 billion. In the context of litigation brought in 1989 and 1990, Exxon estimated that fieldwide costs to plug and abandon wells, dismantle and remove facilities, and close reserve pits using the freezeback method would be $928 million for the Prudhoe Bay field (not including gravel removal, revegeta- tion, or grind-and-inject costs) (Exxon Mobil Corporation v. Commissioner of Internal Revenue, 114 T.C. 293 [20001~. The company calculated its share as $204 million. Exxon also estimated that well-plugging costs alone amounted to $132,000 per well (Exxon Mobil Corporation v. Commis- sioner of Internal Revenue, 114 T.C. 293 [2000]~. The Phillips 2000 Annual Report indicates that the esti- mated total future DRR costs stemming from its acquisition of ARCO Alaska amounted to more than $1.5 billion (Phillips 2000~. Virtually all of Phillips holdings acquired from ARCO in Alaska are on the North Slope. About 80 wells drilled on federal land in what is now the National Petroleum Reserve-Alaska were improperly plugged and abandoned, and some are leaking oil and other substances. The BLM estimates the cost to restore the sites at upwards of $100 million (GAO 2002~. The estimated cost to abandon two platforms in Cook Inlet is $31 million (VanDyke and Zobrist 2001~. The Army Corps of Engineers estimates that the aver- age cost of gravel decontamination, reuse, and revegetation on the North Slope is approximately $2.5 million per hectare ($1 million per acre) of gravel picked up. With a total gravel footprint of 3,755 ha (9,225 acres) (see Chapter 4), the total cost is slightly more than $9 billion. However, that assumes that all the gravel would need decontamination, which is not the case. The anticipated high cost of restoration on the North Slope raises concerns about whether adequate funds will be available to undertake restoration when production ceases. Most North Slope leases are now held by large, multinational, integrated oil and gas companies that clearly have the wherewithal to pay for abandonment and restora-

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EFFECTS ON VEGETATION tion.3 However, if the North Slope follows the pattern ex- hibited by the rest of the industry in the United States, own- ership is likely to change over time as production declines. As large companies no longer find it economical to maintain leases, they could sell out to smaller companies with fewer expenses that can operate these leases profitably. A shift in ownership from large to small companies as fields age has already begun at Cook Inlet, where 14 of the 16 current offshore platforms began operations before 1969 (Van Dyke and Zobrist 2001~. As production declined from 83 million bbl (13.2 billion L, 3.5 billion gal) per year in 1970 to 11 million bbl (2.75 million L, 462 million gal) per year in 1999, one large multinational company offered all of its Cook Inlet infrastructure for sale, and another sold 2 plat- forms to a much smaller independent business. A third sold its oil production facility to a smaller independent firm, al- though it retains its gas interest (Van Dyke and Zobrist 2001~. A recent oil discovery in Cook Inlet has revived inter- est in the region. If leases on the North Slope are transferred from the large multinational companies to smaller independent firms, the smaller concerns are less likely to have the resources to pay for restoration when production ceases. Existing state and federal bonding requirements are not remotely sufficient to cover the costs of restoration. The state DNR requires bonds of $500,000 per company statewide, whereas restora- tion of the Alpine oil field alone is estimated as $50 million to $100 million. The BLM requires bonds of $300,000 for the National Petroleum Reserve-Alaska, but the Army Corps of Engineers requires no bonding for activities conducted under section 404 permits. Existing bond requirements also are intended to serve several purposes (among them to en- sure royalty payments), further diluting the amount that would be available if needed for restoration. The MMS bonding requirements are much higher: each company must have a $3 million statewide production bond. However, even this amount is sufficient to cover only a small fraction of estimated restoration costs. The MMS may re- quire companies to post supplemental bonds equal to the es- timated abandonment costs at the facility, but it has not yet done so on the North Slope. The BLM, MMS, and DNR all specify that original les- sees retain liability arising from activities that occurred be- fore any lease transfer to other entities. In theory, this means original lessees would retain responsibility for restoration expenses.4 However, it is not clear whether this will occur in 3 Following conventional accounting practices, the major companies that operate on the North Slope report amounts on their books that will be used for DRR. However, there is no actual money set aside for those purposes. DRR funds are, like depreciation, an accounting procedure, not actual cash accessible by subsequent leaseholders or government agencies. 4 Transfer of Section 404 permits does not require Army Corps of Engi- neers approval. The new owner assumes the permit obligations of the per- mit holder upon transfer. 95 practice. To date, there has been only one such transfer in Alaska, involving an offshore lease in Cook Inlet from a large multinational corporation to a smaller company. Be- cause the multinational did not guarantee liability, the state raised the bond required of the new owner as a condition of the transfer (Van Dyke and Zobrist 2001~. There are no for- mal criteria governing when additional financial assurances should be required (GAO 2002~. FINDINGS Effects on Vegetation Effects of contaminant spills on North Slope vegeta- tion have not accumulated because the spills have been small and cleanup and rehabilitation efforts at spill sites generally have been successful. Some 1,540 km (956 mi) of roads, 350 gravel pads, and the extensive gravel mining have combined to result in 7,011 ha (17,324 acres) of tundra and floodplains being di- rectly covered by oil development. The total does not in- clude the Trans-Alaska Pipeline and the Dalton Highway. 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, thermo- karst, and roadside snow accumulation. The effects accumu- late and interact with effects of parallel pipelines and with off-road vehicle trails. The measurable direct effects cov- ered approximately 4,300 ha (10,500 acres) in the developed fields, not including indirect effects of the Dalton Highway. The indirect effects associated with roads, reducing roadside flooding, dust-killed tundra, and thermokarst are estimated to cover at least 4,300 ha (10,500 acres). This does not include areas affected by off-road vehicle trails, includ- ing seismic trails. Dramatic progress has been made in minimizing the effects of new gravel fill by reducing the size of the gravel footprint required for many types of facilities and by substi- tuting ice for gravel in some roads and pads. Roadside dust has resulted in the loss of mosses and in earlier snow melt along many roads. Acidic tundra areas along the Dalton Highway with abundant Sphagnum moss are particularly sensitive to dust. Chip-seal treatment of roads could dramatically reduce generation of roadside dust. Impoundments next to raised roadbeds and pads have caused extensive habitat changes in flat portions of the Arc- tic Coastal Plain. Higher summer soil temperatures near roads and pads results in thermokarst, which is continuing to expand out- ward from roads. Some nonnative species were introduced in seed mix- tures and mulches, but most have not persisted and have not spread beyond the sites where they were introduced.

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96 Networks of seismic trails (as well as ice roads and pads) cover extensive areas of the tundra. The proprietary nature of industry-obtained seismic data made it impossible for the committee to determine the total line kilometers and location of seismic trails for the full period of oil exploration on the North Slope. According to the committee's best esti- mate, more than 52,000 km (32,000 mi) of seismic trails, receiver trails, and camp-move trails were created between 1990 and 2001, an annual average of 4,700 km (2,900 ml). The committee views seismic trails as producing a serious accumulating visual effect. 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 explo- ration of the Arctic National Wildlife Refuge were not no- ticeable on the ground after 8 years of recovery. An esti- mated 15% of those trails are still visible from the air after 16 years of recovery. This would be a major concern for proposed future exploration in areas of high wilderness value if similar effects occurred.m Data from the FWS provide good information regard- ing the long-term recovery from 2-D seismic exploration on trails that were created 15 years ago. However, the results might not be applicable to the high spatial density of the newer trails and larger camps associated with 3-D surveys. It is open to conjecture whether the continuing evolution in the technology of seismic-data acquisition would reduce effects. Current regulations require minimum average snow depth and frost penetration of 15 cm (6 in.) and 30 cm (12 in.), respectively, before seismic activities are permitted on the tundra. Those requirements are not based on scientific evidence. The variations in snow depth and density across the North Slope are not considered in the establishment of opening dates for seismic exploration each year, and 15 cm (6 in.) of snow is not sufficient to protect the tundra in many areas of the North Slope. The use of ice roads and ice pads has increased and will continue, but little information is available on how long effects will persist after one or more seasons pass. Because the hundreds of onshore spills that occur annually are well reported, they have been the subject of a great deal of concern among North Slope residents and oth- ers. However, because most spills have been small, have occurred on gravel pads, and have been cleaned up, the eco- logical effects of onshore spills have been small and local- ized and hence have not accumulated. However, such spills contaminate gravel, which impedes its reuse for environmen- tal reasons (and adds liability and financial issues). There have been no documented negative effects of air quality to vegetation in the Prudhoe Bay region, but the potential exists for local long-term, effects of air pol- lutants on some types of vegetation, particularly lichens, to accumulate. CUMULATIVE EFFECTS OF ALASKA NORTH SLOPE OIL AND GAS Areas of Special Concern Several North Slope landscape features are focal points of plant and animal diversity, including pingos, ripar- ian corridors, salt marshes, and small groves of trees. The role of the coastal nonacidic tundra regions for wildlife has not been adequately studied. None of the three rare plant species found on the North Slope is threatened by current oil-field activities, al- though all occur in habitats that could be mined for gravel. Facility Removal and Restoration Tundra sensitivity to disturbance, recovery from dis- turbance, and the effectiveness of rehabilitation techniques are all affected by local variations in climate, soils, and topography. The oil industry and the regulatory agencies have made strides in developing techniques for rehabilitating some disturbed habitats. The most difficult areas to reclaim include the 3,736 ha (9,225 acres) covered by gravel roads and pads, some of which are still in use. Only about 1% of that area has been rehabilitated. Liability for contaminated sites poses an obstacle to the reuse of gravel. State, federal, and local government agencies have largely deferred decisions regarding the nature and extent of restoration (with the exception of well-plugging and aban- donment procedures). The lack of clear state or federal per- formance criteria, standards, and monitoring methods gov- erning restoration is partly to blame for the lack of significant progress in restoring disturbed sites on the North Slope. Because the obligation to restore abandoned sites is unclear and because the financial capacity to do so uncer- tain, the committee judges it unlikely that most disturbed habitat on the North Slope will actually be restored unless those constraints change. Comprehensive restoration and land-use planning for the post-oil-and-gas era on the North Slope is lacking. No funds have been set aside for dismantling and removing the estimated $50 billion worth of existing infra- structure on the North Slope or for restoring the thousands of hectares of tundra affected by industrial activities. Total costs are likely to be billions of dollars. RECOMMENDATIONS Effects on Vegetation Long-term studies of the response of tundra plant communities to a variety of contaminants, including oil, die- sel fuel, and saltwater, would promote the development of contaminant sensitivity and recovery potential maps. Changes in roadside thermokarst over time should be

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EFFECTS ON VEGETATION documented and monitored to determine long-term trends in the expansion of those areas. Studies are needed to determine the amount of snow and frost penetration required to protect tundra from the ef- fects of seismic exploration. Some plant species are particu- larly sensitive to seismic trails, so the studies should con- sider effects at the plant-species level. Monitoring of the long- and short-term effects of off- road ice roads and other off-road trails is needed. An inexpensive monitoring program focused on li- chens should document trends in the accumulation and ef- fects of sulfur and other air pollutants on vegetation. Areas of Special Concern ~7 Ecosystem and wildlife studies on the North Slope would benefit from spatial databases that include more detailed information on substrate chemistry, climate, and topography. A multiple-scale planning procedure is needed to identify areas of special botanical and wildlife concern, 97 such as riparian systems, nonacidic tundra, coastal wet- lands, and pingos, at regional, landscape, and plot-specific scales. Facility Removal and Restoration A comprehensive, slopewide plan should be devel- oped to identify land-use goals after the oil industry leaves. The plan should specify the rehabilitation and restoration objectives needed to achieve the goals, identify specific per- formance criteria and monitoring requirements tied to reha- bilitation and restoration objectives, provide an inventory of facilities on the North Slope and information on ownership, identify contamination status and former habitat type, and discuss whether portions of the site might be likely to have future uses. It should include a mechanism to ensure that adequate financial resources will be available to restore pub- lic lands in accordance with the plan. Site-specific plans for eventual revegetation should be developed for each developed site, taking into account regional climate, substrate, and topographic setting.