Project Case Study: Green shoulders preserve corridors character

October 2007 » Feature Articles
Geotextile helps achieve a context-sensitive road design through Kentucky’s picturesque horse country.
Brian Baker

Project
Central Kentucky’s Paris Pike

Civil engineer
Lochner, Inc., Lexington, Ky.

Product application
High performance turf reinforcement mat from Propex Geosynthetics provides long-term strength, dimensional stability, durability, and functional longevity to a scenic highway’s soft shoulder.


Geotextile helps achieve a context-sensitive road design through Kentucky’s picturesque horse country.

In an area of the country known for its rolling hills of bluegrass and horse farms, there is a short stretch of pavement that is considered one of the nation’s most scenic roadways. U.S. 27/68—or Paris Pike as it is called by the locals—stretches 12.5 miles from Paris, Ky., to Lexington, Ky. The route dates back to the 1830s when it became a major thoroughfare for stagecoach travelers and U.S. mail distribution. Today, winding its way though a 10,000-acre historic district, the scenic corridor has seen little change since the 1920s, and the land owners situated on either side of the road wanted it to stay that way.

But in 1966, the Kentucky Transportation Cabinet (KYTC) initiated a planning study to identify needed road improvements and submitted its findings to the U.S. Department of Transportation for approval. After roughly 12 years of planning, the project was brought to a halt after a citizen’s group, Bluegrass Land and Nature Trust, filed a civil suit in Federal District Court to stop the project, which originally called for the newly constructed road to be a straight shot between Paris and Lexington. Opponents of the road project feared it would destroy many historical landmarks and do irreparable damage to the area’s horse farms. As a result, the project was cancelled in 1980.

In 1986, after seeing the road become increasingly congested and even more dangerous to travelers, proponents for the road widening and the citizen’s group opposed to it decided the time was right to work together and reopen the project. For the good of the community, they established a goal to find a solution that would not only improve driving conditions but also conserve the area’s rich history.

Lochner, Inc., was contracted to address a number of issues that needed to be resolved and to ensure the overall success of the project. A national leader in transportation engineering, Lochner is known for providing innovative and environmentally sensitive solutions to the communities they serve, which was evident in their approach to this project.

To gather as much information as possible, Lochner’s staff held numerous community meetings and went door-to-door in an effort to make sure every resident along the corridor was heard from. What started as an information-gathering exercise evolved into the formation of the Paris Pike Task Force, made up of local governments, citizens, civil engineers, landscape architects, local nature and historic preservation trusts, and other organizations and professionals.

"When Lochner got the contract for this project, we knew it would be a huge challenge," explained the firm’s Senior Vice President Charles Craycraft, P.E. "There were so many issues we had to address. Not only did we have to make the road safer for motorists, we had to create a context-sensitive design that would really maintain and enhance the historic character of the corridor. That’s why we felt it was so important to get the opinions of as many people as possible—to really get a sense of the community’s vision and expectation for this project."

The information obtained by Lochner engineers and the Paris Pike Task Force was crucial to the success of the project. The primary concern of the KYTC and area residents—keeping the impact on the natural and human environments to a minimum—would have to be addressed in every phase of the project.

That meant 223 acres of Maury silt loam top soil—only found in Central Kentucky horse farms, critical to the horse racing industry, and unavailable for purchase—was stripped, stockpiled, and returned to its original thickness. It also meant the road was aligned to avoid or minimize impact to historical structures and properties, such as 3 miles of dry-laid stone fences and signature entrances to horse farms common in the area. The mortar-less rock fences were dismantled by hand and rebuilt to the exact specification of the original wall. Any entrance ways impacted by the construction were rebuilt to match the original entrances as part of the contract cost. Additionally, an aesthetically pleasing timber guardrail, with steel backing for support, was used in place of the more traditional steel guardrails common to the national highway system.

To reduce the amount of paved surface, a unique design criterion was established for the new roadbed. The new Paris Pike roadbed uses the existing roadway where possible. The existing road cross-section of 22 feet of pavement was expanded to 56 feet (two 12-foot-wide travel lanes and 2-foot-wide paved shoulders in each direction). This was to accommodate faster design speeds as well as comply with AASHTO Green Book safety standards. The shoulders on the highway were developed with 2 feet of asphalt pavement that includes rumble strips, bordered by 6 feet of reinforced grass.

It was important for the KYTC and area residents to have green shoulders and a green median, but they needed reinforced surfaces that could meet tough performance standards. The reinforcements specified by Lochner engineers to meet those standards included crushed rock, clay, and a woven high-performance turf reinforcement mat (HPTRM) called Pyramat, manufactured by Propex, Inc., which increased the loading capacity of the shoulder.

"We used a geotextile for the grass shoulders and ditches to ensure durability under load," explained Craycraft. "In particular, we specified the Pyramat product because of its performance in ditch situations and the 3-D structural matrix that reduces rutting under wet shoulder conditions."

According to Propex, the HPTRM’s 3-D woven construction provides long-term strength, dimensional stability, durability, and functional longevity not available in other permanent or degradable erosion control solutions. Additionally, its X3 fiber technology provides the fastest way to permanently anchor vegetation. The HPTRM reinforces the shoulders to withstand occasional vehicle traffic and weather extremes, while providing an aesthetically pleasing alternative to rock or pavement. In addition, a reinforced "soft" shoulder is a stormwater best management practice that removes pollutants from highway runoff to improve water quality.

Pyramat high performance turf reinforcement mat is installed along Paris Pike to ensure the shoulders withstand occasional vehicle traffic and weather extremes.


To prepare the shoulders for installation, the silt loam soil was dragged and, in places, hand graded to create a relatively smooth surface. After the area was graded, six-man crews installed 75,000 square yards of Pyramat parallel to the roadbed and then covered it with 3/4 inch of soil in preparation for seeding and, in some portions of the shoulder, covering with sod. In all, the installation took approximately two weeks. Twelve to 16 weeks after installation, the shoulders were already experiencing heavy growth.

Coming in at $70 million for the entire cost of the project, Paris Pike was opened to four-lane traffic in late November 2003, and an official dedication ceremony took place on Dec. 2, 2003. Since the opening, the high tensile strength of the HPTRM has protected the roadside during the area’s wet seasons and successfully reinforced the shoulders with an aesthetically pleasing solution—in line with the context-sensitive design parameters of the overall project.

"The Paris Pike project was successful because the Kentucky Transportation Cabinet and the FHWA recognized that the road’s design must be sensitive to the cultural, historic, and environmental aspects of the area," said Craycraft. "Their partnership with the Lochner team enabled the project’s design and construction to reflect the beauty of Central Kentucky’s horse country."

Brian Baker is an account executive for The Johnson Group. He can be contacted at bbaker@johngroup.com.


Upcoming Events

See All Upcoming Events