The 133-mile Sterling
Highway and 38-mile Spur Highway are the only designated state highways
on the western side of the Kenai Peninsula.
Less than 22 miles of this highway system actually pass through the
Kenai National Wildlife Refuge, from the Russian River (MP 55) to the Sterling development
corridor (MP 76), so why is the refuge so concerned about the cumulative
effects of highway traffic and highway projects?
Vehicle traffic: In 2009, ~1.4 million vehicles traveled
through the refuge, averaging 2.7 vehicles per minute. This traffic volume exceeds (by 60%) the
hypothesized threshold of 100 vehicles per hour beyond which highways become
significant barriers to grizzly bear movement (Waller and Servheen 2005). Traffic volume of this magnitude also helps
translate to an average of ~225 moose killed annually over the last decade by
vehicles on the Kenai Peninsula.
Peninsula-wide wildlife movement: The Sterling and Spur Highways have the
potential to segregate some wildlife species on the Kenai Peninsula into two
subpopulations due to mortality by vehicles and/or avoidance of vehicles. The total linear distance from the mouth of
the Kenai River to the Seward Highway (along the eastern most edge of Kenai
Lake) is 65 miles. After eliminating
Kenai Lake and Skilak Lake as natural barriers to wildlife movement, the
remaining potential segment for north-south movement is 38.5 miles. However, the continuing urbanization in the
Kenai-Soldotna-Sterling area and in Cooper Landing has severely bottlenecked passage
for landscape-level wildlife movement.
Only two corridors remain that allow unrestricted (except for the
highway) wildlife movement between the northern and southern parts of the
refuge: a 3.5-mile wide segment
immediately west of the mouth of Skilak Lake and a 4-mile wide segment from the
headwaters of Skilak Lake to the west end of the MP45-60 project. These two corridors combined represent <
20% of the historical area available for north-south movement by wildlife. The refuge is clearly concerned about this
gradual severing of the Kenai Peninsula into two distinct parts. In our 2010 Comprehensive Conservation Plan,
an 0.5-mile wide travel corridor for wildlife was established along the north
shore of Skilak Lake in which no new Refuge trails, boat launches or campgrounds)
Stream hydrology and salmon populations: Although the headwaters of most streams on
the western side of the Kenai Peninsula are within refuge boundaries, many of
these streams are vulnerable because they flow under the highway system to
reach the Cook Inlet. Twelve of these
streams are listed in the Anadromous Waters Catalog: the Kenai River, Ninilchick River, Kasilof
River, Moose River, Deep Creek, Crooked Creek, Slikok Creek, Soldotna Creek and
Jean Creek flow under the Sterling Highway; the Swanson River, Beaver Creek and
Bishop Creek flow under the Spur Highway.
In addition, the Resurrection River, which includes refuge lands within
the upper reaches of its watershed, flows under the Seward Highway before reaching
Resurrection Bay. Within these 13
watersheds, there were 13 bridges and 27 culverts on the highway system in 2011;
19 of these crossings are catalogued by the Kenai Watershed Forum as providing
inadequate or marginal passage for anadromous fish.
Invasive species: Vehicles and the highway corridor are not only
vectors for invasive plants onto the Kenai Peninsula, they are also significant
conduits for invasives being introduced into Refuge watersheds that intersect
the highway system. Data from the Alaska
Exotic Plant Information Clearinghouse in 2011 indicates that 11% of 13,896 infestations
of more than 110 exotic plant species on the Kenai Peninsula are within 150m of
either the Sterling or Spur Highways. Of
706 records of reed canary grass, a highly invasive species that has the
potential to compromise the integrity of stream hydrology and anadromous
fisheries, 12% are along the highway system.
In fact, the Kenai Peninsula Cooperative Weed Management Area recently
developed a spatially-explicit strategic plan for managing reed canary grass
that is based, in part, on the nexus of highways and streams (http://www.kenaiweeds.org/pdfs/PHAR_Watershed_Strategic_Plan_FINAL.pdf).
Noise: Traffic sounds can both disturb wildlife and degrade
the experience of visitors to Kenai Wilderness. Vehicle noise was measured on and adjacent to the Sterling Highway in
July 2004, a period of peak vehicle traffic. Highway noise averaged 72 dB (SE = 0.26, n =
180) immediately on the highway, about the equivalent of typical construction
equipment, although values as high as 120 dB were recorded for short periods.
Where the Sterling Highway passes through forested areas, most
vehicle-generated noise was reduced to background levels in the first 100–200
meters from the highway. However, vehicles continued to be heard above
background noise levels more than 500 meters from the highway where the highway
passed through open areas (primarily muskegs).
An interagency group consisting of representatives from the Alaska
Department of Fish & Game, Alaska Department of Transportation & Public
Facilities, Alaska Department of Public Safety, Alaska Moose Federation, Federal
Highway Administration, and the Kenai National Wildlife Refuge jointly conducted
a study in 2005-2007 entitled “Wildlife
Mitigation and Human Safety for Sterling Highway Milepost 58–79 Project”. The purpose
of this cooperative effort was to improve human safety by reducing
wildlife-vehicle collisions (WVC) along the Sterling Highway corridor through
the Kenai National Wildlife Refuge while maintaining permeability and allowing
wildlife to freely move across the Refuge landscape.
Female moose were tagged with GPS collars in Oct-Nov 2005 (n = 31)
and 2006 (n = 32). Female caribou was
also collared in 2006 (n = 5) and 2007 (n = 7). Of the 59 moose and 9 caribou collars
retrieved, 558,239 locations were downloaded, resulting in 1,107 crossings of
the Sterling Highway within the project area. Between Nov 2005 and Jan 2009, 232 hotline
phone calls from the motoring public reported 389 animals within the study area
including 24 black bears, 11 brown bears, 117 caribou, 9 lynx and 230
moose. There were also 174 WVCs
documented within the study area during 2000–2007, including collisions with 24
black bear, 3 brown bear, 5 caribou and 142 moose. The area of highest concern was between MP 69 –
75, a 6-mile section in which 48% of WVCs, 68% of wildlife hotline sightings,
and 83% of GPS moose and caribou crossings occurred.
of this study can be found in Wildlife Mitigationand Human Safety for Sterling Highway MP58–79 Project. This
report presents sound scientific information on moose crossings, limited
caribou crossings as well as transportation infrastructure impacts on wildlife
and habitat, and how to best address and minimize those impacts.
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