The Unofficial
I-26 Construction
Madison County
North Carolina
Pages

 

This website is the unofficial location for the I-26 corridor under construction in Madison County, NC. It includes a vicinity map, photographs and information on the projects currently under construction between US 19 and the Tennessee State Line. An update is included as well detailing the latest construcion on the projects.

PROJECT A-10C

Project A-10C begins at the US 19/US 23 intersection north of Mars Hill, and runs north to Laurel Creek Road, a distance of 5.968 miles. It has been described as "the largest single construction project in the history of NCDOT", and was awarded in October 1996 to contractor Gilbert Southern for the amount of $105.6 million. This project traverses some of the most rugged terrain in North Carolina ever crossed by a major highway. Elevations range from approximately 2500' at US 19 to over 3500' near Buckner Gap, with numerous streams and tributaries needing to be crossed or diverted. Many of them are designated as trout streams, requiring extensive care in preventing silt from entering the undisturbed portions of these waterways. The existing slopes are very steep once the project crosses Jarvis Creek Road (about 1 mile north of US 19) and remain so until the northern end of the project near Laurel Creek Road. Many areas along the project have unstable soil conditions, requiring the removal of this material before actual construction of the highway can begin.

This project will involve the construction of the main highway, its drainage and any bridges needed along the route. Secondary roads needing relocation will be constructed in their entirety as well. The paving, guardrail, signing and median barrier will be added on another project once the grading is completed. Six lanes are being graded on the current project, and three will be paved on the uphill grades on a later project. On the downhill grades a wide paved shoulder will be constructed for the use of trucks if they need it. The entire corridor is designed to a 60mph criteria, and much of A-10C will be built on a 6% grade (about 5 miles of it in fact). An interchange is planned at Bear Branch Road, and a site for a Welcome Center for traffic entering North Carolina is going to be built as well. A scenic overlook will be constructed at the Welcome Center, and a separate overlook built for the northbound traffic.

To help protect trucks from endangering the public, this project will include two truck escape ramps. A truck stop at the Tennessee border on project A-10D will allow truckers to inspect their vehicles and learn information about the highway ahead of them.

Some statistics to show the sheer size of this project:
Unclassified excavation
23,400,000 cubic yards estimated to be removed
Undercut material to be removed
2,400,000 cubic yards
For visual purposes, a million cubic yards will fit into a cube 300' on a side. This project will move over 25 of those cubes!
Fill heights range up to 200' high from the existing ground
Cut depths range down to over 350' deep from existing ground
Over 84,000 linear feet of drainage pipe will be used on this project, with over 11,000 linear feet of 60" structural steel pipe alone. The order for drainage pipe on this project was the largest single order for pipe ever recorded in the United States, according to the pipe supplier.

Four culverts are planned on A-10C. One is on Higgins Branch, another is on Jarvis Creek, and two are on Bear Branch Creek. There are four bridges; two at the Higgins Branch grade separation, one on Bear Branch Road, and one on I-26 crossing over Bear Branch Road. An animal crossing is to be built between Jarvis Road and Buckner Gap to allow large mammals such as bears a safe route under the highway.

Two waste areas are included on the project to help the contractor avoid needless environmental damage created by having to dispose of over six million cubic yards of waste material. One of these sites will support the future Welcome Center; the other will be reseeded and encouraged to return to a natural state.

PROJECT A-10D

The second portion of the I-26 corridor, A-10D, was let to contract in January 1998 to Wright Brothers Construction for $48,550,000. This project runs from the north end of A-10C at Laurel Creek to the Tennessee State Line at Sams' Gap. The project is 2.832 miles long and traverses several ridges and fills on the way up to the TN State Line. Elevations along the construction range from 2880' near Laurel Creek to over 4000' at Sams' Gap. The cuts and fills are among the highest on either project, with a 600' deep cut and 200' high fills. A 220' high bridge over Laurel Creek is included in this contract, in addition to a grade separation at Sams' Gap where US 23 will pass under the new Interstate. The Appalachian Trail will also pass under the Interstate at this location.

Some more specific measurements on this project:
Unclassified excavation
8,850,000 cubic yards of material estimated
Rock Excavation
5,166,000 cubic yards estimated 
Waste material
4,160,000 cubic yards estimated
Undercut material
1,165,500 cubic yards estimated
6600' of 60"structural plate pipe, to be placed under the large fills on the project and over six miles of drainage pipe overall.

The highway is designed to 60mph speed, with a 22' median and barrier and six lanes to be graded. When the paving contract is let, three lanes will be constructed on the uphill side and a wide paved shoulder built beside the usual two lanes on the downhill side. One truck escape ramp will be constructed, as well as an inspection station near the Tennessee State Line for truckers to get information about the highway between there and US 19.

There are two large waste areas designated to dispose of the waste excavation. One is a large valley that has been isolated due to the rugged terrain and the highway location. It had been strip-logged previously and was purchased by NCDOT. The other one was a smaller valley isolated in the same manner as the first area. Both areas will be reseeded and returned to a natural condition when construction is completed.

GEOLOGY

These projects had very intensive geologic investigations conducted during the design phase. A geophysical survey was conducted in 1990, and geologic field mapping was begun in 1992. Over 6000 individual rock structure measurements were made over the 10 miles of area surveyed. Oriented rock core borings and soil overburden analysis was begun in 1993; over 5500' of oriented coring was conducted, analyzed and stored for the contractor to use during construction.

Most of the soil in the area was determined to be either colluvium or residual materials. Some of this material was over 50' deep. Soil deposits were underlain by saprolite or weathered rock in most cases. The residuum materials were red to brown medium-stiff to stiff sandy and silty clay. Maximum thickness was about 12'. The saprolite was more dominant, and was up to 10' deep in some places.

The colluvium made up the remainder of the soil material. Colluvium is ancient landslide material, and was made up of wet, silty material mixed with rocks ranging from six inches across to over 30' across. Use of this material in the highway construction is difficult; in order to use any of this material the rocks have to be separated and the remainder of it mixed with residual or saprolite. It is also very wet and exhibited good (too good!) water retaining abilities. A foot thick layer of colluvium often did not dry out even when left out in the September sun for a week. Most of this material has been disposed of in the waste sites along the project, although some is being carefully used in the actual construction.

The rock type is a Precambrian metamorphic rock of the Blue Ridge Belt, made up of biotite-granite gneiss. The borings found some instances of acid producing rock (i.e. sulfides). These rocks, if placed in areas where water could seep through them, have the potential to form weak sulfuric acid, which would be lethal to the trout streams in the region. To prevent this in the event this rock is found in significant quantities, cells will be designed with layers of crushed limestone, clay, agricultural lime and thick plastic liners around the acid rock to isolate it from the rest of the environment.

The photos I've placed on the webpage include several views of the construction along the length of the projects showing various interesting items. As work continues I will add more pictures to those already here so that viewers can see how the site changes. Photographs for project A-10D are included as well.

Anyway, hope you enjoy this website. If you have any questions, please email me.

John Lansford, PE
Project Design Engineer, A-10C and A-10D

(note: this website is my own creation and does not reflect any official position of NCDOT)


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10 April 99