Crestwood is planning far in advance for its future street projects, repairs and needs. 

At the Feb. 13 Board of Aldermen meeting, City Administrator Kris Simpson gave a presentation on residential street projects and repairs. 

He explained that streets are designed with several layers: the subbase course, the base course – usually crushed gravel – and the surface course. The surface course is the top layer of the street and is typically made of either asphalt or concrete. 

Asphalt streets, on average, have a lifespan of seven to 10 years. When it is time to repair them, a process called “mill and overlay” is done by grinding up – or “milling” – the surface course of asphalt, removing it, and then overlaying a fresh course of asphalt atop the base. This costs on average $13 per square yard. 

Due to the short lifespan of this type of street, Crestwood began applying asphalt rejuvenator, a coating applied to the asphalt surface after the mill and overlay process, extending the lifespan by three to five years. 

Concrete streets, on the other hand, require a completely different method when it comes to repairs. 

“We call (it) selective slab replacement,” Simpson said to the board. “The city identifies the concrete slabs that need replacement – if they have cracks or some other deficiencies – and (then) we hire a contractor who replaces just those slabs by breaking them up, and then pour(ing) in new concrete. The slabs that are in good condition are left in place, they’re not touched.”

This process is much more costly than the mill and overlay procedure, sitting anywhere from $63 to $69 per square yard. Concrete streets do, however, typically have a lifespan of 30-50 years, so this process should not have to be done very often. 

In Crestwood, roughly 32% of streets are asphalt and 31% are concrete. The remaining 35% are a combination of the two, called asphalt-overlaid concrete streets. 

“In the early 2000s, Crestwood faced the challenge of deteriorating residential pavement conditions, as well as dwindling revenues. Instead of incurring the cost of performing selective concrete slab replacements, the city elected to pour a top course of asphalt on top of the concrete slabs. Again, you’re in that $13 per square yard range rather than the $60+ per square yard range,” Simpson said. 

This practice only went on for about 10 years, though a large percentage of streets in the city are still asphalt-overlaid concrete. Not known at the time of construction is that asphalt-overlaid concrete streets are problematic due to a multitude of issues. 

“With any street, water penetration is the enemy,” Simpson said. “But, it’s a particular problem with asphalt over concrete streets as that water freezes and thaws. When it freezes, it contracts, and then when it thaws, it expands. That creates gaps, which creates surface issues. Sometimes it’s potholes, sometimes it’s displacement, sometimes it’s other things. This freeze-thaw cycle is occurring at the concrete course beneath the asphalt course as well as at the top layer asphalt course, and so you’re having compounding issues there.”

“Concrete streets also have expansion joints, which shift with the freeze-thaw cycle,” he added.

Asphalt-overlaid concrete streets are repaired the same way typical asphalt streets are: with the mill and overlay process. The top course of asphalt is milled down, minor repairs are done to the concrete underneath, and fresh asphalt is poured. These repairs are not necessarily ideal, though, as issues with the concrete layer cannot be dealt with adequately, and the subbase can’t be addressed at all. Additionally, nothing is done to repair the old curbs of the concrete streets, and as time goes by, they continue to degrade and become nonfunctional. 

Though there is no dedicated funding source for this work currently, the city has begun to convert these asphalt-overlaid concrete streets back to regular concrete streets, or asphalt streets with concrete curbs. 

“We’re getting rid of the old concrete subbase, restoring the base beneath the road surface and then pouring a fresh full-depth asphalt street with a new concrete curb so that the curbing is repaired,” Simpson said. “We started doing this last year with the reconstruction of Del Vista (Drive), and Del Vista was reconstructed as a full concrete street. When we performed that, that eliminated 2% of the asphalt over concrete streets in our network.”

This year, the city plans on reducing another 2% of asphalt-overlaid concrete streets by replacing Banbury Court, Coffey Court and Coffey Drive. In 2025, a portion of Pardee Spur will be replaced.

Because these projects have to fit within the city’s existing capital dollars, it will take decades to finish every street. It is also costly, with the total cost of converting all streets sitting between $10 and $20 million in today’s dollars. The city will continue to decide yearly which streets to repair depending on resources. 

“This is going to be something that’s going to take a consistent application of will over an extended period of time to be completed. Obviously, 2% per year means that it’s going to take 50 years,” Simpson said. “ But the good news is the end result is going to be a better street network for Crestwood at the end of the day… we’re going to have a better driving surface for longer (and) it’s going to be in a more sustainable position.”