City’s paving policy keeps roads in repair, costs down

When it comes to Bellevue’s pavement management program, the guiding philosophy is that it’s better to repave now than rebuild later.

The reason? Money.

It costs up to three times more to replace a street than to repave, or overlay it. That’s why this year, the city’s contractor, Lakeside Industries, will repave 22.6 miles of roadway in 48 different segments north of Interstate 90. It’s part of Bellevue’s annual overlay effort, first started in 1982.

“It’s more cost effective to do this preventative maintenance than waiting for complete failure, which means rebuilding the entire roadway,” said Teresa Becker, who’s in charge of the overlay program. “It’s like changing the oil in your car regularly to prevent big repair bills in the future.”

In an overlay operation, the old asphalt is planed down so the new overlay will match up with the curb and gutter, which is made of concrete. Then, two inches of new, hot asphalt is put down by a large machine that creeps over the roadway at about 2 mph. That’s followed by a heavy roller that presses the asphalt into place.

If the same street required a complete rebuild, all the old asphalt would need to be removed, then 2 to 4 inches of gravel laid down and compacted, topped by about 8 inches asphalt.

What streets get the overlay treatment each year is determined by the city’s pavement management system, a detailed inventory of all city roads that was begun in 1986 and computerized in 1991.

Under this system, each street is classified according to how heavily it’s used, then rated every two years according to its condition. In the parlance of engineers, pavement distress comes from defects such as alligator cracking, rutting, raveling and flushing.

A street that scores 100 is flawless; a score of 40 or less means rehab time for sure.

Arterial roads deteriorate faster than residential roads, mainly because they are used more, but also because they accommodate heavier loads from large trucks and must endure more stops and starts, which tend to wear asphalt down faster. The freeze-and-thaw cycle of winter weather is hard on all types of streets.

Data from the pavement management system is used to identify streets in immediate need of repair and to create a six-year overlay plan. The final selection of streets to be overlaid each year is based on where in Bellevue those most in need or repair are located.