Arizona's General Hitchcock Highway: balancing safety and the environment.
The scenic General Hitchcock Highway in the Santa Catalina Mountains of Arizona runs through steep canyons in the sensitive Sonoran Desert, along river banks, and in high sub-alpine forest.
Not surprisingly, then, the design and construction effort to widen the highway focused on preserving and enhancing existing scenic resources and intensive landscaping with salvaged and nursery-grown native plant species. The effort was guided by an interdisciplinary team of highway engineers, geotechnical experts, landscape architects, wildlife biologists, and resource specialists. The project featured state-of-the-art rockblasting techniques, sculpting of cut-and-fill slopes, and blending the widened highway into the rugged terrain.
The 40-kilometer General Hitchcock Highway (Arizona Forest Highway 39) is an important transportation route near Tucson. The highway is the only paved route to the Santa Catalina District of the Coronado National Forest; the village of Summerhaven; about 80 research, radar, and communications sites; an Air Force facility; summer homes; and Mr. Lemmon Ski Valley and numerous other recreational facilities.
The highway was constructed between 1933 and 1951; it consists of a 6-meter paved surface with minimal foreslopes or ditch. The road is inadequate for today's traveling needs. As a result, the accident rate on this road is about five times the average in Pima County, making this road one of the most dangerous in the state.
In 1988, the Federal Highway Administration (FHWA) began a multi-phased effort to widen the General Hitchcock Highway. Another key design objective of this work is to improve deficient portions of the roadway alignment to permit motorists to travel at a more consistent speed. The reconstructed section consists of an 8.5-m paved surface with 1.2-m foreslopes and ditch.
The project involves blasting rock; constructing retaining walls; creating new picnic, trail head, and scenic-view parking areas; providing for improved drainage, erosion control, and snow removal; designing new channelized intersections with turn and auxiliary lanes; constructing turnouts for slow traffic and temporary roadside parking to improve safety and traffic operations; and ensuring environmental mitigation or enhancement.
To date, three major construction projects and one landscaping project have been completed, improving 19 of the 40 km. Depending on future funding, three or four projects are planned over the next 10 years to complete the route. The total cost of reconstruction is estimated at approximately $40 million.
The General Hitchcock Highway offers the traveler a striking and highly varied experience, due to the orderly progression of climate and vegetation types accompanying the change in elevation. The Santa Catalina mountain range is a "sky island" in the midst of the Sonoran Desert. The summit of Mt. Lemmon is almost 2,800 m. Ski Valley is the southernmost ski area in the United States. The highway rises from 870 m near Tucson to an 2,500-m crest in the Santa Catalina Mountains, passing through a sequence of nine plant zones - the Sonoran Desert upland zone at the base of the mountains, desert scrub, semi-desert grassland, evergreen-oak woodlands, pine-oak woodlands, ponderosa pine forest, and mixed conifer/aspen forest in the sub-alpine zone at the top of the range.
The highway scenery is characterized by steep, mountainous terrain; rough canyons; panoramic ridge and valley views; unique vegetation that changes with elevation, precipitation, and exposure; clear, cold-water streams; diverse wildlife; and spectacular rock formations. All of this creates some of the most attractive scenery and best recreational opportunities in the otherwise flat, arid Southwest.
The temperature variation between the two ends of the project averages 14 degrees Celsius for highs and 8 C for lows. This, combined with the changes in landform, geology, and precipitation, means that the highway provides a variety of experiences roughly equivalent to a journey at a constant elevation from Mexico to Canada.
In 1986, an environmental assessment for the project was prepared. Although it resulted in a finding of no significant impacts, the assessment did identify clearing and removal of vegetation and economic effects to local residents and businesses due to traffic delays and road closures as major concerns.
Subsequently, possible repercussions to the newly endangered Mexican spotted owl, as well as new U.S. Forest Service biological evaluation requirements, had to be addressed and re-evaluated. Because of the sensitive nature of the area and the concern of local and national environmental organizations, additional environmental studies were conducted; these studies, along with ongoing public and interagency coordination, continue as additional project phases are developed. Evaluation and mitigation details also continue to be determined on a site-by-site basis as detail design work progresses on future construction phases.
The primary mitigation efforts incorporated in the completed design and construction projects have been directed toward visual impacts. The project goal is to obtain complete revegetation and restoration within three years of project completion. So far, this goal has been accomplished. The mitigation effort has generally consisted of careful selection of alignment and design alternatives that minimize new visual impacts, special sculpting of new cut-and-fill slopes, and intensive landscaping and revegetation of disturbed areas.
A detailed visual resource assessment was performed early on; this led to the innovation of a more involved visual prioritization process (VPP), which was developed and first applied in 1986 to the General Hitchcock Highway project. VPP received a National Endowment for the Arts Federal Design Achievement Award in 1988.
Special techniques for the project were developed with the assistance of geotechnical and rock-blasting consultants. These techniques produced a more natural appearance of new rock cuts and protected scenic rock pinnacles. The engineering objectives were to minimize blast damage and subsequent rock fall.
The visual quality objectives were to simulate the irregularity of the existing terrain; obtain ledges, shelves, and pockets for revegetation; eliminate drill hole traces; limit damage from necessary access to the top of cut slopes; and prevent damage to the environment from uncontained blasting material and flying rocks. All blasting was carefully monitored and videotaped to document results and continually improve techniques. Special landscaping treatment of the cut-and-fill slopes - such as warping the cut face and creating ledges - were specifically detailed in the construction plans. Selective scaling, sculpting, and roughening were done to finish the cut slopes before placing topsoil and seedling.
Retaining walls were used extensively to reduce impacts of fills, minimize clearing, and preserve sensitive corridors. Retaining walls were colored and textured to blend with the environment.
At least one new major vista overlook and new trail head parking area have been included in each of the three construction phases completed so far.
Drainage improvements, particularly in the Summerhaven vicinity, were designed to improve water quality, mitigate temporary erosion during construction activities, and eliminate an existing icing problem that frequently occurred during winter.
Guardrail w-beam rails were specially treated during fabrication to obtain a texture and color similar to corrosion-resistant (self-weathering) steel beams. This is a very inexpensive way to obtain an unobtrusive, weathered appearance.
Impacts on vegetation
Fragile native trees, shrubs, and cactuses were salvaged, held, and replanted. Before the project began, the landscape architects took inventories of saguaro cactus, barrel cactus, prickly pear cactus, ocotillo, yucca, and other species. They used this information to determine the mix and density of existing plants to be salvaged and to determine new plantings. For the initial, 5-km construction phase, more than 600 saguaro cactuses, barrel cactuses, and other large plants were transplanted.
Under a separate landscaping contract, more than 3,200 nursery plants in one- and five-gallon containers were grown and established. A temporary gravity-pressure irrigation system was installed to help establish the extensive native and nursery plants; irrigation was provided for the first two years. Similar landscaping and irrigation work has been incorporated in the subsequent phases.
A large number of mature trees had to be cleared to accommodate the phase 3 reconstruction of the highway's upper section. The Forest Service gathered native ponderosa pine cones to propagate the native species, removed the seeds, and sent the seeds to a nursery to grow seedlings for replanting on the upper part of the project. More than 28,000 seedlings and 400 larger trees will be replanted when work is completed. Tubular "tree shelters" are being used to protect the sensitive seedling plants and minimize mortality. Since quaking aspen occur adjacent to the highway in only a few locations and are difficult to regenerate in this area, special measures were taken to avoid disturbing each existing stand.
A variety of native seed mixes are used in separate vegetative zones. Hydroseed mixtures included a charcoal additive to darken new cut-and-fill slopes and other disturbed areas to reduce visual impact.
Special traffic control measures were developed to mitigate the economic effect of reduced or inconvenienced traffic during the construction. The major portion of the reconstruction and heavy excavation work took place from 11:00 p.m. Sunday night through 6:30 a.m. Friday morning. The highway remained open to all traffic from 6:30 a.m. on Fridays through 11:00 p.m. Sundays and on all national holidays. Numerous other measures were taken to ensure minimal inconvenience to the traveling public:
* Several Forest Service development roads were improved with grading and gravel surfacing to function as temporary detours, facilitate heavy grading and retaining wall construction, and further reduce traffic delays.
* A public awareness campaign was developed to keep the traveling public advised of the construction schedule and anticipated delays: (1) FHWA maintained two telephone hotlines to provide general project information and the exact closure schedule. (2) A variable-message electronic sign was installed at the beginning of the route to keep the public informed of changing conditions on the project. (3) Brochures - in both English and Spanish - were prepared and widely distributed throughout Tucson; these contained a map of the construction areas, detours, and the traffic control schedule. (4) Flaggers also distributed the brochures to motorists waiting to pass through the construction. Flaggers were well-prepared to answer motorists' questions about both the construction project and about travel destinations. (5) Project information was provided to the local media with interview and photo opportunities, and public service announcements and paid informational commercials were broadcast on local television and radio during critical construction periods.
* Delays and road closures were analyzed and scheduled with input and close cooperation from area residents and businesses.
To reduce heavy truck hauling and to efficiently use the excavated material, 25 percent of the excavated rock was crushed for aggregate materials and 25 percent was used to backfill retaining walls.
Impacts on wildlife
Surveys were made to determine the presence and habitat of special-status wildlife species. Special construction requirements were developed to minimize repercussions on threatened species, including the Mexican spotted owl, desert tortoise, lesser long-nosed bat, and long-tongued bat. Biologists conducted an inventory of sensitive plant species to avoid encroachment and to facilitate salvaging and transplanting native plants to protect the habitat. They particularly noted agave plants, which are a primary food resource for the lesser long-nosed bat.
A number of Mexican spotted owl management areas border or cross the highway. Construction, drilling, and blasting activities were scheduled to avoid the reproductive period of the Mexican spotted owl from Feb. 1 through July 31. Since the owls hunt at night and are dependent on their keen hearing and night vision to capture prey, noise and disturbance had to be limited at night. Dozers, excavators, backhoes, loaders, rock trucks, and track drills were not permitted to operate at night for roadway excavation or hauling of excavated material. Only light construction of retaining walls, installation of culvert pipes, aggregate placement, and road maintenance were permitted at night. Lighting equipment could only be used to illuminate limited work areas (maximum of 75 m in length) and was restricted to a maximum of four individual units less than 9.5 m in height. If an active Mexican spotted owl nest had been found within 0.4 km of the project area, work activities restricted at night would have been suspended entirely in that vicinity until after July 31.
A 7.5-m wildlife underpass structure was constructed at an existing through-fill to provide a wildlife passage. The reinforced-concrete collar was designed to minimize the structure length and the "tunnel effect" and to increase sunlight in the underpass.
Additional phases of the General Hitchcock Highway reconstruction effort are currently being developed; the next will begin in January 1996. The environmental mitigation efforts have been successful so far. The initial phase of this project received an FHWA Biennial Design Excellence Award in 1990 and also a national award from the American Society of Landscape Architects in 1993.
Nevertheless, concerns have been expressed regarding how the highway design will be implemented in future phases, particularly in the most sensitive areas of rock pinnacles and river banks. Successful completion of this vital safety project will entail an ongoing process of addressing resource protection through design and mitigation planning and a continuing willingness to respond to interagency and public concerns.
Mark B. Taylor is a design project manager with FHWA's Central Federal Lands Highway Division (CFLHD) in Denver, Colo. He has been involved with the General Hitchcock Highway Project since its inception in 1983. Although his area of responsibility has changed recently to cover other states, he remains responsible for this project's development to ensure design continuity. He has been with FHWA since 1974 and with CFLHD since 1978.
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|Author:||Taylor, Mark B.|
|Date:||Mar 22, 1995|
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