From the Tennessee border, south through Madison County, NC, to Buncombe County, NC, extensive work along a 14-mi. (22.5 km) stretch of Interstate 26 has been under way for the past 10 years.
On any given day, there were between 50 and 275 workers at the job site, along with three contractors and 79 subcontractors, hired over the course of the project.
According to Randy McKinney, assistant resident engineer with the North Carolina Department of Transportation (NCDOT), Division 13, the old highway running between Buncombe County, NC, and the Tennessee border is a steep and curvy two-lane road. Constructed in the 1930s, it averages 30 to 45 accidents and one fatality per year.
“NCDOT decided it would be beneficial to the region to improve the road conditions between Mars Hill and the Tennessee state line both for ease of travel and safety,” McKinney said. “The new road will take drivers approximately 15 less minutes to travel.”
The first phase of construction began in 1993 and included a 5-mi. (8.1 km) section of highway between north Buncombe County and Mars Hill, NC. This section was divided into two projects. Construction began in 1993 on a 2-mi. (3.2 km) section and was completed in 1996. Construction on the remaining 3-mi. (4.8 km) section began in 1995 and was completed in 1998.
Both contracts, totaling $23 million, were awarded to Taylor & Murphy of Asheville, NC. This newly-paved, four-lane highway was brought up to interstate highway standards, along with the additions of bridges and widening of shoulders, which were rehabilitated. Both projects are complete and the road is open to traffic.
Construction for 9 mi. (14.5 km) of highway, from Mars Hill, NC, north to Sams’ Gap, TN, began in 1996. This new six-lane highway provides an alternative to the old two-lane U.S. 23.
“The cuts and fills were among the highest ever constructed in North Carolina, with over a 600-foot deep cut along the mountain ridges and 220-foot fills along the gaps,” McKinney said. “Over 37 million cubic yards of total excavation was done, making it one of the largest excavation projects in North Carolina.”
John Lansford, project design engineer, was responsible for the horizontal and vertical design of the grading projects, location of the bridges, general geometric design of the lanes, welcome center, scenic overlooks, escape ramps and interchanges, calculation of most of the quantities and coordination of all the different units involved in creating these massive projects. According to Lansford, the 9-mi. (14.5 km) of road was split into two grading projects.
“Because of the extent of rough grading and blasting, two grading contracts were awarded, splitting the project into six- and three-mile sections,” Lansford said. “This was done both because of the size of the job and to give opportunities to several contractors.”
Construction on the 6-mi. (9.7 km) section began at the U.S. 19/U.S. 23 intersection north of Mars Hill and continued north to Laurel Creek Road. The new six-lane highway, with approximately 5-mi. (8.1 km) built on a 6-percent grade, was designed to a 60-mph (96.5 kmh) criteria, with 8- to 10-ft. (2.4 to 3.1 m) shoulders. For truck safety the project included two truck escape ramps with a wide paved shoulder on the downhill grades. This $120-million contract was awarded to Gilbert Southern of Atlanta, GA, and took five years to complete between 1996 and 2001.
The extensive excavation required along the 6-mi. (9.7 km) section, made it necessary for Gilbert Southern to purchase $33 million of new equipment, which included a Cat 5230 excavator. This massive excavator, normally used for mining, has a 26-cu.-yd. (19.9 cu m) bucket capable of picking up 50 tons (45.4 t). The unassembled excavator, which weighs more than 800,000 lbs. (362,874 kg), was transported to the job site by 11 tractor trailers. Two Caterpillar technicians spent more than 500 hours assembling it. The excavator used 13,000 gal. (49,210 L) of diesel fuel every 24 hours and was used around the clock, six days a week for the five years.
The total amount of unclassified excavation removed was approximately 25 million cu. yds. (18.8 million cu m). This included both soil and rock removal. The total amount of undercut excavation was approximately 2 million cu. yds. (1.5 million cu m).
Off-road dump trucks with 10-ft. (3.1 m) diameter tires were used to haul materials along the job site. There was 44,000 tons (39,916 t) of erosion-control stone used to stabilize the ditches and control the runoff from the slopes. A total of $10 million was spent on erosion control.
Presplitting, which is the forming of the steep and smooth rock slopes in the big cuts, amounted to 129 sq. yds. (108 sq m). Approximately 1 million sq. yds. (836 sq m) of erosion-control matting was used on every soil slope to hold it in place and give the new grass a stable place to start growing. Four culverts were constructed along this project.
More than 84,000 linear ft. (25,603 m) of drainage pipe, including more than 11,000 linear ft. (3,352 m) of 60 in. (152.4 cm) structural steel pipe were used. Pipe was purchased from Lane Enterprises Inc., which said this was the largest single order of drainage pipe ever recorded in the United States by the company.
Four bridges, along with an animal crossing, also were constructed along the 6-mi. (9.7 km) route. Approximately 6,200 ft. (1,890 m) of concrete planters, with rock fence placed on top and behind, were installed along the project. In order to create a solid surface for the paving contractor and allow easier access to the whole project, Gilbert-Southern placed more than 200,000 tons (181,437 t) of aggregate on top of the graded soil to act as the first layer for the pavement.
Work progressed concurrently along a 3-mi. (4.8 km) section from Laurel Creek Road to the Tennessee State Line at Sams’ Gap. This $51- million contract was awarded to Wright Brothers Construction of Charleston, TN, and took three years and eight months to complete, ending in 2001. It also was designed for a 60-mph (97 kmh) speed with a 22-ft. (6.7 m) median and concrete barrier.
One truck escape ramp was constructed, as well as an inspection station near the Tennessee State line. The contract also included a grade separation at Sams’ Gap where U.S. 23 and the Appalachian Trail pass under the new interstate.
Elevations along this 3-mi. (4.8 km) project ranged from 2,880 ft. (878 m) near Laurel Creek to more than 4,000 ft (1,219 m) at Sams’ Gap. The total amount of unclassified excavation was approximately 9 million cu. yds. (6.7 million cu m), the total rock excavation was 5 million cu. yds. (4 million cu m), the total undercut material was 1 million cu. yds. (891,000 cu m) and the total waste material was 4 million cu. yds. (3 million cu m). This project required 6,600 ft. (2012 m) of 60-in. (152.4 cm) structural plate pipe, which was placed under the large fills on the project and more than 6 mi. (9.7 km) of drainage pipe overall.
This section of the project also included construction of the 235-ft. (61 m) Laurel Creek Bridge, which is now one of the two highest bridges in North Carolina. A total of 9,700 cu. yds. (7,400 cu m) of concrete was used to build the drilled piers, stems, approach slabs, deck, median barrier and railings of the high bridge. The bridge also includes access ladders within the hollow columns and a de-icing system.
The R.R. Dawson Company, of Lexington, KY, was the subcontractor responsible for building the bridge. The designer for the bridge was the URS Corporation in Raleigh, NC.
The $34.7-million paving contract for the entire 9 mi. (14.5 km) went to APAC of Asheville, NC. This contract also included the construction of a welcome center, a scenic overlook and a parking lot for Appalachian Trail hikers.
Asphalt paving began in October 2001. Concrete paving began in June 2002 and was completed by APAC’s Ballenger Paving Division, Greenville, SC. A total of 360,000 sq. yds. (301,000 sq m) of 10-in. (25.4 cm) Portland Cement Concrete Pavement (PCCP), which was chosen because of the harsh weather conditions in this region, was placed.
According to Robert McCord, vice president of operations for Ballenger paving division, equipment used for producing and placing the PCCP was all owned by APAC and included a fleet of 28 Autocars mounted with Maxon side dump bodies, two Maxon spreaders, a Gomaco 2800 slipform paver and a CMI cure texture machine. The concrete was produced on site in a modified Rex double-drum central mix concrete plant.
“One of the most difficult challenges we faced on this job besides the 6-percent grade was the weather,” McCord explained. “Daily afternoon thunderstorms combined with the lack of sight distance in the cuts of the high mountains prevented us from seeing the incoming weather. Daily our crew would protect the newly placed concrete with plastic.”
The Asheville, NC, APAC division was responsible for laying the asphalt. A total of 148,000 tons (134,263 t) of asphalt was used for the base and shoulders, parking lots, welcome center, and scenic outlook. Additionally, 84,000 cu. yds. (64,000 cu m) of earth material was used for shoulder construction. More than 50,000 ft. (15,000 m) of guardrail and 34,000 linear ft. (10,000 linear m) of shoulder berm gutter was installed. Additionally, more than 6,200 linear ft. (1,890 m) of curb and gutter were installed for the welcome center, scenic overlook, and Appalachian Trail parking lot.
Numerous conditions along this section of I-26 made this a uniquely challenging project. Most significantly this area of I-26 includes some of the most rugged highway terrain in North Carolina. Elevations range from approximately 2,500 ft. (762 m) at U.S. 19 to more than 3,500 ft. (1,067 m) near Buckner Gap. Approximately 1 mi. (1.6 km) north of U.S. 19 the existing slopes become very steep and remain so until the northern end of the project near Laurel Creek Road.
Unstable soil conditions added to the difficulties of the project, requiring the removal of colluvium material before actual construction of the highway could began.
Additionally numerous streams and tributaries needed to be crossed or diverted. Those designated as trout streams required extensive care in order to prevent silt from entering the undisturbed portions of the waterways. A wildlife consultant was hired in 1995 to do baseline surveys of the streams, and monitoring was done every six months for turbidity, pH, siltations and fish and insect populations.
“This was one of the most heavily ecologically monitored projects in the history of NCDOT,” Lansford said. “Landscaping and beautification was also a priority on this project. This included 8 quarter acres of wildflower beds, the establishment of a monarch butterfly station above the buffer land mid way through Buckner Gap, and the planting of shrubs and trees.”
To dispose of waste excavation, four designated waste areas were established. Three of these sites were reseeded and encouraged to return to their natural states. The fourth is being used for the welcome center.
Final completion of the project is set for early August 2003. According to McKinney all that is left to do is add 1 in. (2.54 cm) of asphalt along the shoulders, install overhead signs and a few other finishing touches.