A plan by the city of Nolensville to widen Sunset Road from the Benington subdivision to Nolensville Road has hit a couple of speed bumps.
Poor existing road quality and a waterline replacement issues were revealed at a meeting at City Hall Thursday night. Both may slow the project down.
Engineers at the consulting firm of Ragan-Smith Associates have been working with the city on the project since 2014. They had come up with an initial design for the plan that involved turning Sunset Road into a road with two 12-feet-wide travel lanes, a 12-foot wide turn lane, two four-foot-wide bike paths on either side of the road, a 10-foot-wide expanse of grass and a 10-foot-wide multi-use path on one side of the road.
Since that design was drawn up, however, engineers were confronted with several challenging developments that called into question certain elements of the plan.
For starters, engineers were arranging to cover the existing road with one-and-a-half inches of overlay as part of the road widening. They hired the geotechnical consulting firm TTL to take some samples of the asphalt to test its condition. The results, to put it mildly, were not great.
“Twenty-two years I’ve been working on roadway jobs, I’ve never had Leann come to me and wave a flag and say, This is weird,” Ragan-Smith Vice President Scott Niesen said about the results. Leann Whitwell was one of the consultants from TTL who did the core samples.
It’s not that Sunset was the worst quality road Niesen had ever tested, but the depth of pavement measured along the road was remarkably inconsistent.
Whitwell and her team took about 12 borings on this stretch of Sunset Road and in each spot detected wildly different amounts of asphalt versus stone. There “was not a tremendous amount of rhyme or reason” to the results, Niesen said. As a result, the asphalt was graded “very poor” in many places, raising serious questions about its integrity.
Another issue the engineers have faced recently has to do with waterline placement, which the Nolensville College Grove Utility District estimated to cost around a $220,000. When engineers actually looked at the plans NCGUD drew up, though, they saw some problems with the waterline placement.
Further inspection revealed that there was actually about 4,000 feet of waterline that would need to be relocated at a cost of $700,000 due to the location of the project’s multi-use path. Niesen described this as “not just devastating news but its gonna take some looking at.” The engineers decided they needed to redesign the route the path takes to avoid impacting the waterline.
Finally, in 2016 the U.S. Army Corps of Engineers came up with firmer rules for how developers would have to deal with the endangered Nashville crayfish during construction. Those rules, and the associated monitoring and mitigation costs that come with them, convinced engineers that they needed to amend their plans to avoid doing work on streams in the area as much as possible.
These considerations led the Ragan-Smith engineers to come up with three different plans for the widening project’s future.
Option A was something of the status quo plan. The multi-use path would still be diverted at places to avoid impacts with the waterlines, but engineers would stick with the one-and-a-half inch overlay over the road.
The downside to that, of course, has to do with the poor condition of the pavement.
“If we were to keep the plans as we got it, with just this overlay, we’re probably a year, two years, three years [from] where that road will start to deteriorate and show the same signs of failure and become a maintenance challenge,” Niesen said. He projected that the full cost of this option was about $4.6 million.
“We can just move off of Option A,” Alderman Jason Patrick said, after Niesen presented it. “It’s Option Zero.”
Mayor Jimmy Alexander was similarly unimpressed.
“We’ve spent too much time on Option A,” he said, dismissing the thought of paying so much money for a project that would only last a couple of years.
When trying to come up with an Option B, the engineers had one question on their mind.
“We talked to Leann and we said, What can we do to beef up this pavement to get some more life out of it?” Niesen said.
The result they came up with was pretty similar to Option A in many ways, although different in some important respects.
“It’s essentially the same option with the exception also that we would look at really repairing maybe 30 to 40 percent of the spots that are visually problematic and really cut it out and patch it and do it right,” Niesen said.
Part of this option would involve using a protective surface called a petromat on the road, as well as additional overlay totaling about three-and-a-half rather than one-and-a-half inches. Whitwell said you could expect to get about an extra year or two of use out of each additional half-inch of overlay.
“Again, five to seven years is what we’re talking about” with this option, Niesen said, before the city started running into problems. He expected that this option would cost a bit more than option A—around $4.9 million total.
Option C differed the most from the original plan.
“We always thought this would be an overlay job when we started it a couple of years ago,” Niesen said.
The problems with the condition of the current asphalt, however, led engineers to wonder if maybe a full reconstruction of this stretch of Sunset Road weren’t the best option.
Niesen said there were two options for a full reconstruction plan.
“We’re gonna take the existing road and we’re either gonna take it out entirely and import new rock material and build it up, or there’s another technique where you can rubble up the road and add cement to that rubbled up road and perhaps shorten your time,” he said.
Which of those two full reconstruction paths to take, though, would wait. At Thursday’s meeting, Niesen thought the main question was whether reconstruction was even a consideration for the mayor and aldermen.
“It’s really more of a question of are A and B acceptable or are we talking about a reconstruction? If we’re talking about a reconstruction, we’re gonna try and find out what is the [most] cost effective and provides the longest life to the road,” Niesen said.
A full reconstruction would cost around $5.2 million, Niesen estimated. He said the life span of the road, though, could be up to 20 years with this plan.
Alderman Patrick viewed Option C as obviously the best choice.
“You’re talking about Option B, five to seven years versus C, 15 to 20 years and you’re talking about a cost differential of $300,000…what’s the conversation exactly?” Patrick said.
As he sees it, Nolensville can’t afford not to go with the option that will most improve the road.
“Listen, we’ve got three main arterial roads that feed Nolensville—Rocky Fork, Clovercroft and Sunset. We’ve got to provide the very best possible product,” Patrick said.
Mayor Alexander agreed and cut right to the next point.
“We’re down to where we all agree that Option C is what we would prefer. Now we have to start thinking about where we can get the funds,” he said.
Indeed, funding is one of several obstacles to getting the road project going, alongside the effort of getting the right of way from residents along the construction path.
Town Administrator Kenneth McLawhon said funding could potentially come from a number of sources, some perhaps from elements of Governor Bill Haslam’s new transportation proposal. It’s too early to see exactly how that proposal will shake out, though.
Once construction does get underway, Niesen said he thinks the project could be completed in nine to 12 months.
Of course, this is just phase one of the widening project. The second phase will eventually see Sunset Road widened from the Benington subdivision to the Brentwood city limits at Waller Road.
