Last month I asked y’all what I should write about this month and 56% of you said you wanted to learn more about the steps that go into road construction. So here we go……
The picture of President Trump above should be striking to everyone. The process map he’s standing next to shows all the federal steps required with any new road. Since state departments of transportation (including Tennessee) receive the majority of their funding from the federal government, these requirements flow over to state projects, and in turn local projects.
High level – there are 5 steps that go into any road project.
PHASE I: Planning
A road project begins with evaluating the transportation system, taking into account city wide priorities, including its strategic plans for the system.
Spring Hill collects and maintains a vast amount of information about our roads, including:
- Road and bridge conditions,
- Traffic volumes, and
- Crash statistics.
Using this data, transportation planners, engineers, environmentalists, landscape architects, soil scientists and others identify trends that determine what and how to build. Other items to consider:
- Can the City acquire the property to build on?
- What are the environmental issues?
- What utilities will be affected by a project?
- How will we fund the project?
- How can this project be designed to be an asset to the community?
Spring Hill has a Major Thoroughfare Plan (or MTP) which captures anticipated long term roadway improvements on a more conceptual basis. Not all the projects on the MTP prove to be feasible.
Planning for individual road projects take the information already collected within the MTP and fine tunes it for the specific project being pursued.
The planning stage is both costly and time consuming, often times taking multiple years to complete for larger projects. One of the largest drivers of time is that many of the planning steps cannot be completed concurrently
and have mandatory review/comment periods.
PHASE II: Design
A detail design of the project is step two. Recently, GPS, laser surveys, and other technology have sped up the process and improved accuracy. Many factors influence designs, including:
- terrain and soil properties,
- drainage capabilities,
- traffic volume,
- the ratio of cars to trucks and buses,
- possible future development in the area,
- effects on the environment or nearby residents.
With a design in hand, the City advertises for a contractor to do the actual building. Spring Hill awards contracts based on low bid price.
The design phase can be as short as 6 months for small projects, or up to 2 years for large projects.
PHASE III: Earthwork
With a contractor on board, earthwork can begin. Earthwork is one of the most important elements in road construction because it establishes a stable foundation. A roadway with a substandard foundation will fail prematurely. That is why the road’s base layers are as important as the finished surface.
- First, the contractor builds embankments using cuts and fills.
- Next, a grader or bulldozer levels the screened dirt. Leveling bumps and filling in dips creates a surface that will support a road for decades.
- The screened dirt is sprayed with water and compacted to its maximum density.
- During this stage, the contactor installs drains and sewers. The center of the road must be higher than the edges so water will run off into the storm sewers. Drainage is a critical element because improper drainage will greatly reduce the new pavement’s life expectancy.
- All of this work must pass strict inspections before the project can continue.
- To complete the earthwork, the contractor places gravel in 12-inch layers on the road bed. Workers moisten and compact each layer. Layers are added and compacted until the road bed reaches the height called for in the design.
Earthwork can easily take 6 to 9 months. Wet weather will cause additional delays. Any time a road needs to remain open to traffic during construction (such as with Duplex) will add additional time to this phase.
PHASE IV: Paving
At last, the road bed is ready for paving. This phase moves pretty quickly, so long as the air temperature is conducive to asphalt being laid.
Paving typically only take a week or two to complete. More if the road is to remain open to traffic during construction.
PHASE V: Finishing Work and Open to Traffic
The final steps are:
- another drainage test,
- grading and landscaping around the pavement,
- applying the permanent pavement markings.
This phase can be as short as a week or two, or a couple of months depending upon the length of the project and the level of grading required.
The last three steps are the most visible steps, you can see the construction activity occurring. The last three steps are also the shortest portion of the entire project, the majority of the work occurs in the first two steps and largely out of the public eye.
Highway 31, Buckner Road, and Buckner Lane are all in the first two phases. While it may not appear as though much work is being done to move roadway infrastructure forward, that perception is wrong. Major construction is coming.