Gone are the days (if they were ever here) of “Who do you gotta know to get this street fixed?” In Mt. Lebanon, a computer selects streets slated to go under the knife.
This year’s street reconstruction budget of $2.1 million will cover complete reconstruction of nine sections of streets. Another $254,000 is budgeted for major repair of another six (see table).
For the past five years, Mt. Lebanon has used Pavement View Plus software to assist help make decisions about which roads to repair or reconstruct. To get the system going required a lot of legwork—literally. Gateway Engineers, Mt. Lebanon’s engineering consultant, sent their employees out to assess the condition of every stretch of road in town, collecting extensive data on all pavement defects and using a numerical system called the Overall Condition Index (OCI) to give each section of street a baseline rating.
The rating system takes into consideration the type of street, which is determined by the amount of traffic it receives. Streets are categorized as arterial. or main roads; collectors, which connect residential and arterial streets, and residential. The history of the road, when it was last repaired or reconstructed is factored in also, along with the type of material the road is made of—concrete, asphalt or brick—and the severity of damage. For example, says Tom Kelley, Mt. Lebanon public works director, an “alligator” cracking that radiates outward from a central point—is more serious than longitudinal cracks, which run in parallel lines.
Each defect in the pavement is given a numerical value, which is subtracted from 100 to arrive at the OCI number. A score of 85 to 100 indicates a street that doesn’t need repair; 60 to 84 calls for minor repairs; 45 to 59 requires major repairs, and an OCI below 45 means that section of street needs major repairs or reconstruction.
The majority of streets in Mt. Lebanon are either asphalt or an asphalt-over-concrete mix. Asphalt is the easiest material to repair. “Asphalt is almost self-healing,” Kelley says. “You can repair it all the way down to the base.”
Last year, the OCI rating average for all the streets in Mt. Lebanon was 72. About 20 percent of our roads fall into the top category, meaning they’re in very good shape; almost 60 percent are in the next highest, meaning they need minor repair, and only about 1 percent are rated at the bottom. Previous commissions debated the possibility of saving money by doing just maintenance on roads that merited reconstruction. Fortunately, that idea never grew to fruition. In a presentation to the commission in 2011, Municipal Engineer Dan Deiseroth projected that putting off serious reconstruction projects would result in a communitywide OCI rating of 40 in 20 years time.
Maintenance means replacing a portion of the road to extend its useful life. Maintenance includes spot curb repair and removing and replacing 3 inches of bituminous material. Reconstruction is reserved for that bottom 1 percent of streets that have exceeded their useful life and cannot be maintained further. Reconstructing a street means excavating all of the layers of the road and rebuilding it with two 1 ½-inch layers of asphalt and binder, a 5- to 8-inch base of aggregate rock and another six inches of stone. Curbs are replaced as necessary. Cost of reconstruction versus maintenance is roughly 6 to 1, and the results mirror the cost. Kelley says a street that is completely reconstructed should last 50 years, while streets that get maintenance repairs will have to be worked on again in about 10 years.
In general, it costs about $1.67 million per mile to rebuild a street, as opposed to $282,000 for resurfacing. But because resurfacing is a short-term solution, in the long run it’s not as cost-effective as biting the bullet and rebuilding a failing street.
“In the city of Pittsburgh, they used to call [resurfacing] ‘painting the street black,’” Kelley says. “You’re not addressing the reason the street is failing, which is usually poor drainage, and it’s more of a band-aid approach. The real way to address the issue is to put money into drainage and eliminate the water problem.”