RECLAMATION OF THE USIBELLI COAL MINE NEAR FAIRBANKS, ALASKA
Jason G. Bidwell
INTRODUCTION
Alaska, the fiftieth and largest state, has abundant resources available.
Alaska has abundant wildlife and resources, but it is also fragile.
Alaska has extreme environmental conditions which make for a delicate
ecosystem. A major human disturbance can easily destroy what took
thousands of years to create. The short growing season along with a layer
of permafrost in most of the interior is an area of slow recovery from
disturbances. Human intervention must be applied to insure that the
damage is reversed, however, as in other mining situations the
restoration process is challenging and experimental.
Alaska's ecological health and stability is sometimes compromised by the
need for fossil fuels. Alaska has as much coal as all the lower 48 states
together. The qualities of the coal at the Usibelli site were suitable
for strip mining, and were a desirable prospect for the mining industry.
The Usibelli Coal Mine Company started strip mining in 1943. Through the
strip mining process of scraping off the overburden, they have displaced
the native soil horizons and mixed them with tailings (Mitchell 1985)
The Reclamation Act of 1977 required the study of strip mine conditions
and implementation of restoration projects. It also set aside extra money
to do so. The job of restoring the Usibelli site was then put in the
hands of the Alaskan Forestry Service and people associated with the
University of Alaska. This purpose of this paper is to describe the
restoration attempts at Usibelli dating back to 1982 and to provide some
suggestions for increasing the success of the restoration process.
SITE DESCRIPTION
The Usibelli coal mine is the largest strip mine in Alaska. At 64
degrees northern latitude, it has an interior climate resembling
Fairbanks, which is just north of the site. It has an average air
temperature of 26 degrees F and an average yearly precipitation of 17
inches (Mitchell 1985) The original vegetation at Usibelli was boreal
forest. In a 1984 progress report (#9502587) on the reclamation project,
three test sites in the Usibelli mine were studied. Poker Flat which is
at 1500 feet above sea level, Vitro at 2000 feet, and Gold Run Pass at
2500 feet. Poker Flat has two major types of soils. Typic Cryorthods
exists in the mounded areas north of Lignite Creek. These soils are
relatively organically rich and deep and have a layer of silty loam that
covering permafrost. South of the creek, a Pergelic Cryohemist-Pergelic
Histic cryaquept complex exists in the basin area and extends southward.
This was a deep gravelly loam that exists over a frozen gravel substratum
(Mitchell 1985) Vitro which is north of Poker Flat, consisted of Typic
cryocherpts that existed on the lower gently sloping terraces that
extended to the mountains beyond. It has various stratified layers of
alluvial sediments with varied texture (Mitchell 1985) The lower area in
the mountains called Gold Run Pass consisted of a Typic Cryochrept
complex that formed steep terraced slopes that extended to the river. The
coal-covered gravelly mine spoils were left in mounds between the coal
seams. All plant growth was not prohibited even though some of the
subsoil sulfates were exposed and oxidized, which decreases the soils pH
(Dent 1992). The low sulfur content in the coal decreased the risk of
the soil becomming acidic. Leeching of the pollutants was not a problem
on this site because water capacity was low in the permafrost sub-soil
(Mitchell 1985)
RECLAMATION PROCESS
Data was collected from Usibelli for assessing its condition. USGS
topographic maps and aerial photography were used to create a basemap
which was used for reference to the site as a whole and to create a
template for natural vegetative patterns. Usibelli was largely devoid of
vegetation. Ground covers and grasses were planted first to stabilize the
soil and prevented further erosion. Amending or adding to the topsoil is
the best way to counteract the toxicity, but is not economically feasible
for large areas such as the Usibelli mine. Specific selection of tolerant
native plants helped the site by covering the exposed soil, which slowed
erosion, and held the pollutants, thereby giving less tolerant species a
chance to establish themselves (Vangronsveld 1995) Re-vegetatation is a
challenge because of low (if any) organic N in soil around a strip mine
(Nossner & Hons 1992) Continued fertilizer application was necessary to
maintain the vigor in the plantings (Mitchell 1985) Applying sewage is an
option on large sites, but it is not a long term solution and does not
release nutrients as slowly and as consistently as naturally occurring
organic N (Nossner & Hons 1992) Sewage sludge can be sprayed on the soil
from a distance, which prevents the need for excessive machine travel
across the soil and reaches the steeper areas (Bureau of Mines 1990).
Sewage for fertilization is available from facilities in nearby
Fairbanks (Mitchell 1985) Sewage application is not an environmental
problem if applied properly and if not used for agricultural crops.
(Sopper 1992) Proper application consists of sludge incorporated into
the soil. Sludge should not be applied if the ground is saturated frozen
or covered with precipitation (Sopper 1992) The short warm season in
Alaska creates a small window of time when application is appropriate. As
the ground thaws in the spring, the nutrients flow with the melted
precipitation into the root zone, where the seedlings lie (Sopper 1992)
So, fertilizer and sludge were applied in the late fall before the first
snowfall.
The soil was compacted, so imprinting was implemented. Imprinting the
ground with bulldozers greatly improved the quality and persistence of
the stands (Mitchell 1985). The seeds then have a place to enter the soil
and germinate. Raking the soil and spreading the seeds into the furrows
by use of agricultural machinery was a cost effective way of planting the
ground covers and grasses in this large area. In some places, the seeds
and seedlings were planted by drilling divots in the soil with a hoe.
Several planting method trials showed that aerial planting was effective
where adequate moisture was available. In places that it was not,
drilling was better. Drilling was especially effective and useful for
establishing plants on the sloped areas (Mitchell 1985).
Native plants were used when reseeding because of their natural
adaptations to the weather conditions. At the Usibelli site, a complex
mixture of native ground covers and grasses were selected for their
hardiness and tolerance to pollutants. Several introduced, but northern
species along with some legumes with similar traits were also included.
Most native species are not available commercially. Seeds must be
gathered and grown in controlled conditions to provide the seeds and
seedlings needed (Mitchell, 1985). The following plants were tested:
|
| Alopecurus pratnsis | Meadow foxtail |
| Alopecurus arundinaceus | Creeping foxtail |
| Agropyron desertorum `Nordan' | Crested wheatgrass |
| Agropyron riparium `Sodar' | Streambank wheatgrass |
| Agropyron spicatum | Bluebunch wheatgrass |
| Agropyron subsecondum | Bearded wheatgrass |
| Agropyron trachycaulum | Slender wheatgrass |
| Arctagrostis latifolia | Polargrass |
| Bromus inermus `Polar' | Smooth bromegrass |
| Bromus biebersteinii | Meadow bromegrass |
| Calamagrostis canadensis | Bluejoint reedgrass |
| Calamagrostis purpurascens | Purple pinegrass |
| Deschampsia beringensis | Bering hairgrass |
| Deschampsia caespitosav | Tufted hairgrass |
| Elymus sibericus | Siberian Wildrye |
| Festuca rubra `Arctared' | Red Fescue |
| Festuca longifolia `Scaldis' | Hard fescue |
| Festuca arundinacea `Alta' | Tall fescue |
| Medicago media | Varigated alfalfa |
| Modicago falcata | Yellow-flowered alfalfa |
| Paccinellia sp. | Alkaligrass |
| Panucum clandestinum | Deertongue |
| Phalaris arundinascea | Reed canarygrass |
| Phelum pretense `Engmo' | Timothy |
| Poa pratensis `Nugget' | Alaskan Bluegrass |
| Poa compressa | Canada bluegrass |
| Poa glauca `Tundra' | Glaucous bluegrass |
| Trifolium hybridum | Alsike clover |
| Trifolium repens | White clover |
|
* bold plants are native to the site
At the test sites, the seedlings responded well to fertilizer
application. Without the continued application of fertilizer, plantings
loose their vigor and die off within 3 to 4 years (Mitchell 1985).
Intensive an repeated intervention is required to get the plants to
become established. The soil conditions at the Usibelli site were too
severe for most of the plantings. Most did not survive their second
winter. The red fescue, smooth bromegrass, foxtail and timothy persisted
throughout the site. As expected, different plants were more apt than
others to survive in the extreme situations in the site. For example,
plants like alsike clover and some sainfoin preferred areas that were
protected from the winter winds, such as roadsides that were covered with
heavy snow from plows. Red fescue and smooth bromegrass were the only
survivors of the winter winds at Gold Run Pass. Plants like foxtails and
timothy both favored swales and gullies. The introduced Nordan crested
wheatgrass, tufted grass, and Sodar streambank wheagrass initially grew
throughout the sites, but never established. Bromegrass grew in clumps
when it normally is a vigorous spreader (Mitchell 1985).
DISCUSSION
Aerial planting produced high mortality rates for the seeds. Places
where laborers hand planted seedlings produced higher survival rates
(Mitchell 1985). Random hand planting of the most vigorous grasses chosen
improved the success rates of the other seedlings (Mitchell 1985) The
sterility caused by the pollutants also had an effect on the soil
microbes, mainly the mycorrizae. Mycorrhizae is found naturally in soil
but not in coal polluted soil. (Bureau of Mines 1990). Mycorrhizae
increases the survival rate of the seedlings by increasing the exchange
rate of nutrients between the roots and the soil. Seedlings infected with
mycorrhizae had a better chance of survival (Miller 1987). When and if the
soil can eventually become stabilized and established with grasses, trees
could be planted in various areas. A selection of trees were made to
accommodate the conditions at the site. The following trees are native and
hardy to the site: Abies balsamea, Balsam Fir, Alnus incana,
Lodgepole pine, Populus deltoides, Cottonwood, Populus tremuloides,
Quaking aspen. These trees tolerate poor, gravelly moist and polluted
soils. Abies balsamea is especially suitable for the higher elevations
because of its tolerance to wind. Alnus incana is valuable because of
its nitrogen fixing properties (Dirr 1990). In places where trees would be planted, the site should
be disked to incorporate the grass organic material. The soil will be
prepared and easy to plant. In places where aerial seeding was
unsuccessful, hand planting of seedlings should be implemented to insure
some vegetative establishment. In places where the public will observe
the restoration project, denser plantings and larger seedlings should be
planted so the public can see that there is progress being made. Besides
educating people on a restoration efforts importance, their opinion of it
is essential for continuing the project and future reclamation efforts.
BIBLIOGRAPHY
Dent, D. 1992. Reclamation of Acidic Sulfate Soils. Advances in Soil Science p331-50
Department of Alaskan Coal Mining. 1982. Alaskan Coal: Resources and Developmental Constraints. 139p.
Dirr,MA. 1990. Manual of Woody Landscape Plants. Stipes Publishing Company.
Mitchel, WW. 1985. Revegetation of Alaskan Mine Spoils. Alaska University. 98p.
Nossner, LR and Hons, FM. 1992. Reclamation of Mine Tailings Soils. Advances in Soil Science. p351-431
Sopper,WE. 1992. Reclamation of Mineland Using Sewage Sludge Soils. Advances in Soil Science. p351-431.
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