An initiative to protect wildlife along Arizona’s State Route 260 corridor project has been designated as one of three new Exemplary Ecosystem initiatives by the Federal Highway Administration (FHWA).
The other two initiatives recognized are Nevada’s Washoe Lake Wetland Mitigation Area; and New Hampshire Route 101’s ecological protection and enhancement features.
The Arizona initiative represents a coordinated planning effort among the Arizona Department of Transportation (ADOT), the FHWA, United States Department of Agriculture (USDA) Forest Service, Tonto National Forest, the Arizona Game and Fish Department (AGFD); and others.
The project involved major construction upgrades to address increased traffic and safety concerns along the Payson to Show Low Highway, State Route 260.
Over 10 to 15 years, ADOT will upgrade 17 mi. (27 km) of two-lane highway to four-lane divided highway from Payson to the Mogollon Rim. This corridor lies within the Tonto National Forest and passes through some of the most scenic country in the state.
Moderate to high densities of elk occur along the corridor throughout the year and increas eseasonally during fall and spring. Statistics of wildlife-vehicle collisions along this section of SR 260 are some of the highest in Arizona.
As travel on Arizona’s rural highways increases, these collisions, especially involving large animals such as elk and mule deer, are a growing concern.Wildlife-vehicle collisions cause millions of dollars of damage to vehicles each year and may result in serious injury or death of humans and wildlife.
Arizona’s diverse wildlife resources also are impacted by loss or fragmentation of habitat due to highways, which can reduce or eliminate access to important habitat components ranging from critical winter range to key watering sites. Populationsmay be divided into smaller and smaller subpopulations, decreasing genetic interchange, increasing the chance of localized extinctions, and ultimately reducing viability.
As part of the SR 260 upgrade, ADOT has made a significant commitment to reduce the risk of wildlife-vehicle collisions and maintain or enhance wildlife permeability across the highway. ADOT will employ measures including 11 sets of bridged wildlife underpasses, six sets of larger bridges over streams, wildlife-proof fencing, innovative fencing alternatives, such as steep cut and fill slopes and “elk rock” (closely placed rip-rap) to encourage use of underpasses, and escape structures to prevent wildlife from getting trapped within fencing.
Because ADOT had not previously employed any of these measures, it is funding AGFD to study their effectiveness for future construction along SR 260 as well as other highways across the state. The AGFD, USFS, and FHWA also have funded this research.
Construction on SR 260 from Payson to the Mogollon Rim will be completed in six phases. The first, Preacher Canyon, is already complete and includes two sets of wildlife underpasses and a set of large bridges. Given this phased construction schedule, the research program includes both short- and longer-term goals.
The primary goal is to assess the effectiveness of wildlife-vehicle collision reduction and safety measures. at Preacher Canyon. The longer-term goal is to use the canyon section as a pilot study of techniques to evaluate elk movement patterns and safety measures.
The AGFD is using several research methods on the SR 260 project. Integrated infrared video camera systems allow researchers to assess passage rates, animal behavior, use of escape structures, traffic levels, andwildlife movement around the ends of the fencing. Global positioning system (GPS) data from collared elk willprovide information on daily and seasonal movements during various stages of construction and will help determine the number and location of crossings and the potential for wildlife underpasses and associated fencing to “intercept” crossing elk.
In addition, a standardized wildlife-vehicle collision form in place since August 2000 provides consistent data on the overall effectiveness of collision-reduction measures.
Since the field phase of this research began in February 2002, considerable progress has been made in reaching its goals. Monitoring shows significant use of the Preacher Canyon underpass structures by elk.
At the east underpass, in operation the longest, 976 elk have been recorded, with 700 crossing through the underpass (passage rate of 73.9 percent). At the west underpass, 393 elk have been recorded with 187 elk using the west underpass (passage rate of 50.7 percent).
Despite the use of underpasses by elk, wildlife-vehicle collisions have not decreased significantly in the Preacher Canyon section, most likely due to insufficient fencing. The AGFD has proposed landscaping and fencing retrofits to increase effectiveness. Monitoring has already begun on the next section of highway nearing completion, Christopher Creek (four underpasses and three bridges), applying insights from the first phase of research.
Monitoring of the first construction phase has provided valuable information to help reduce wildlife-vehicle collisions in future phases.
For example, researchers from AGFD have worked closely with ADOT and the project contractor to modify designs for an upcoming construction phase — the Kohls Ranch Indian Gardens wildlife underpass. Monitoring data suggest that using mechanically stabilized earth (MSE) walls adversely affects elk behavior and use of the west underpass at the Preacher Canyon Section. Revised plans call for limiting MSE walls on the Indian Gardens underpass, relying on other options to stabilize fill material.
In addition, plans include limited elk-proof fencing to funnel wildlife through the underpass. Using GPS data from collared elk on the location of highway crossings, various fencing scenarios will be evaluated.
While the planned underpass and fencing are projected to intercept only 7 percent of crossings, fencing a higher proportion of the highway (1.1 mi.) is projected to intercept nearly 75 percent.
The SR 260 project will represents one of the most comprehensive efforts in North America to reduce the risk of wildlife-vehicle collisions and enhance wildlife’s ability to roam.