SR171/Mt. Juliet Road Interchange

SHOWCASE 3

I-40/MT. JULIET ROAD

INTERCHANGE Innovative, successful traffic engineering allows continued growth and development for booming community.

The City of Mt. Juliet and the Tennessee Department of Transportation (TDOT) sought to improve the I-40/Mt. Juliet Road interchange due to significant residential and commercial growth in the area. With an aggressive timeline and several challenging constraints, GS&P was tasked to develop improvements that would meet state and federal requirements as well as respond to the well-founded concerns of local businesses. The resulting success is a shining example of GS&P’s commitment to superior project management, problem-solving and innovative solutions to benefit an entire community.

STATE ROUTE 171 – MT. J ULIET INTERCHANGE I N T E RVI E W /

M i k e F l att , D iane R e g ens b u r g , M ar k Washin g , W es S tanton

Why did the city hire GS&P to improve the Mt. Juliet Road/I-40 interchange?

for about a third of the cost of a full-blown interchange improvement.

Mike: The Mt. Juliet Road interchange on I-40 was a miserable interchange. In the mornings and afternoons, traffic was lined up for miles—and I do mean miles— on Mt. Juliet Road. At that time it was supporting an extremely large number of commuters who lived in the area and worked in Nashville. Add to this a huge shopping complex, a neighborhood of single-family residences, and an upscale retirement community that were all being built within five miles or less of this interchange. All of this had an immediate and tremendous impact on commuter and local traffic.

With so many people involved in the decision-making, what were some of the challenges?

What involvement did GS&P have in developing the project’s financial structure, and why?

Mike: For the original plan to have been a success it would have cost much more than originally budgeted. Since the project was funded by multiple sources including the city of Mt. Juliet, TDOT and area developers, we had to help them structure the financial plan for improvements that everyone could afford. We were able to provide 15 years of time and traffic growth

Mike: This is a commercialized retail area, and getting everyone to agree on the best solutions for the project was sometimes difficult. For example, The Cracker Barrel, Mapco gas station, and Waffle House all wanted their own driveways, and we knew from experience that was a dangerous idea.

At that time, those vehicles were trying to accelerate and move across lanes of traffic to the left to make a left turn onto Belinda Parkway. While trying to do this, those vehicles were also having to slam on brakes to avoid hitting the people in front of them slowing down to turn right into these driveways. In addition to this, there were three driveways sideby-side that were allowing left turns out of them onto Mt. Juliet Road and people Northbound on Mt. Juliet Road were allowed to turn left into these driveways.

Too many movements were happening in the same location, causing an unsafe condition.

Judges' comments

Clearly a complex project showcase 3

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We had to persuade the state and the city to stand shoulder-to-shoulder with us to convince the developers and property owners that if we gave them what they wanted, the whole system would fail and they would be miserable.

In their scenario, as soon as you pull through the intersection, somebody wants to pull in and out of Mapco, Waffle House or Cracker Barrel. We had to get the existing property and business owners on board to work with us to provide their customers a safer passage of ingress and egress, while still getting the most volumes of traffic possible through the intersections and on and off the ramps.

We presented our projections and used models to demonstrate the need to limit access by building dedicated entry points to multiple properties, which allowed us to manage traffic safely.

What won them over?

Mike: A picture is worth a thousand words. Visualizing the situation helped but it was also getting key people to understand this would work. One of the first folks we brought on board was Cracker Barrel. Once we convinced them, they

TDOT required the existing bridge be maintained, so in order to build additional lanes for the slip ramp under the bridge, a retaining wall was designed to hold the slopes in place.

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Three natural gas transmission pipelines run through the northeast quadrant of the project, adding to the complexity.

A special concrete slab carries the ramp traffic and protects the gas lines from damage due to pavement settlement. Ramps were aligned to minimize impact.

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were one of the pioneers to help get the others on board.

Three natural gas pipelines ran through the northeast quadrant of the project, requiring some innovative planning.

What were some of the challenges?

Diane: One of my major responsibilities was to coordinate with the developer, the city, the state and Columbia Gulf Natural Gas. Because the pipelines carried natural gas from Texas and the Gulf Coast to the Eastern Seaboard for their heat, the timing of the construction was very critical. The gas could not be shut off or the entire eastern seaboard would not have heat. Making it even more difficult was the fact that their winters are longer than ours, so we only had a very short amount of time to work with.

Mike: Also, when the pipeline was relocated there would be about a mile’s worth of natural gas wasted into thin air, and somebody would have to pay for that.

When they turn off the valves to stop the gas from flowing, the pipes are still full of gas. They have valves placed every so often in the event of an explosion that they can cut the gas off. However, all the gas between the two sets of valves would be wasted for each of the three lines present.

Diane had to do a lot of work to bring all those parties to the table, broker the deal, and get everybody to agree on who would pay for what, which was a huge issue.

One of the more innovative aspects of your design involved crossing the pipelines under the slip ramp. Can you explain?

Diane: The depth of the gas lines was an issue because they require a minimum clearance of the road over the top of the pipelines plus a weight limit. By law, whenever you put traffic over a gas

line you are required by law to upgrade to a thicker pipe wall, or bury the pipes deeper—either of which involves great costs associated with moving or replacing the pipe. In this case, we did not want to have to pay to bury them deeper but we did upgrade the pipe wall. Essentially we created a third alternative: a concrete slab that also acted as the road surface and an upgraded wall to ensure we met all requirements.

Mike: It also minimized the relocation of the gas line itself, which kept costs down.

What other obstacles did you face?

Mike: During the design process, we could not close down any of the ramps to the interstate. We could temporarily close lanes on Mt. Juliet Road or SR 171, but the state was never on board to close in-ramps to the interstate. We had to always find a way to maintain access to and from I-40 east and west, which forced us to construct ramps and use more retaining wall than we normally would. The state did not want to tear out the existing bridge over I-40, so we came up with a plan to reconfigure the lanes and reuse the shoulders so that we could utilize the full width of the bridge and not have to rebuild it.

Diane: We had to add more lanes to the eight existing lanes under the bridge in order to make a slip ramp. We used retaining walls to pull the slope back underneath the bridge to add additional lanes.

Mike: The retaining walls also limited the footprint into lots that could be sold for development, which helped our client by holding down right-of-way costs.

What steps did the team take in designing new traffic signals and keeping traffic running smoothly?

Mark: The signal timing and coordinat­ ion between the various interchanges was a crucial element in this project due to the volume of traffic in this area and the limited amount of storage area between the signals. In order to prevent gridlock, special timing plans and signal phasing was used to help keep the high volume of traffic flowing.

Many other existing signals were upgraded to accommodate for the roadway widening, and a wireless communication system was added for coordination. These signals were wirelessly connected to the master controller located at the Belinda Parkway and Mt. Juliet Road intersection. The master controller is designed to communicate to the signals and, with different timing plans depending on the time of day and day of week, help traffic through the area.

How has the interchange affected the retail and business areas?

Mike: It is now one of the larger new shopping areas in Middle Tennessee, and most businesses are thriving and doing better than ever. Existing properties like Pilot and Mapco that initially told us we would put them out of business like their locations so much they have rebuilt their buildings in the same spot. All the things that locals did not believe would happen or be successful have happened, and it works. On Friday nights there is a wait at every restaurant in the area.

Wes: Mt. Juliet also did not have a hotel until the interchange was redesigned, and now they have three.

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What aspect(s) of this project did you find most gratifying?

Wes: I lived in Mt. Juliet for eight years and did all my shopping there. I am actually now moving back there and will be using the slip ramp and interchange every day. Mt. Juliet is one of the fastestgrowing cities in the state, and I am especially proud to have them as a client and enjoy our work on a daily basis.

Mike: Before, when you got off the interstate, you would have to cross over three or four lanes to get to one of the main roads. There were always accidents there, so I am really proud of the improved safety of the area.

Diane: There were so many stakeholders involved with so many demands and so little money, and we had to please everyone. I am very proud that GS&P was able to sit down and figure out the most economical way to please everyone and deliver a great project.

Mike: At the start of the project, it was clear that there were two big entities that had a stronghold that were not going to compromise. The Federal Highway Administration (FHWA) was not going to back down and give up on what they wanted for the interstate system, and they have the ultimate say over the interstate system nationwide. TDOT administers all state, local and federal funding, and since Mt. Juliet Road is a state route, TDOT had the ultimate say on the road.

Even though the city was paying our fee, we were actually working for the government, the politicians, and the business and property owners, and we needed approval from all groups. I am extremely proud we were able to come up with a plan and a design that saved the project, gave the city what it needed, and let the development happen so they could get the tax dollars they so badly needed—and we met FHWAs requirements. Our team stuck together even though we were serving multiple masters, and we ultimately found a way for our direct client to salvage a project.

Judges' comments

Successful management of community considerations

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Roa d Mt. Jul iet Traffic surrounding this booming retail and residential area continues to grow. During construction, existing traffic flow was maintained and improvements were made with minimal right-of-way impact.

g resham , smith and partners

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City of Mt. J u liet Mt. J u liet, Tennessee Hydro logic & H ydrau lic Calcu lations Survey AND Design Traffic Modeling Utility Relocation Management Services TEAM Princi pa l - in - char g e

Michael A. Flatt, P.E.

Project M ana g er

Diane Regensburg, P.E.

Project Professiona l

Lori Lange, P.E.

Project T echnician

Shawn Taylor

Geo lo g ist

R. Keith Barnhill, P.G.

C IVI L D E SIG N E R

Bruce K. Dretchen

Project E n g ineer

Chris Cowan, P.E.

A dditiona l team mem b ers

Mark H. Washing, P.E. Wes Stanton

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Gresham, Smith and Partners provides design and consulting solutions for the built environment that contribute to the success of national and international clients. For more than 40 years, GS&P has focused on enhancing quality of life and sustainability within communities. GS&P consists of industry-leading professionals practicing architecture and engineering design as well as scientists and highly specialized planning and strategic consultants in Aviation, Corporate and Urban Design, Environmental Compliance, Healthcare, Industrial, Land Planning, Transportation and Water Services. GS&P consistently ranks among the top architecture and engineering firms in the United States. For more information regarding GS&P, visit www.gspnet.com.