Boise & Garden City

Ada County’s yearly chipseal work: Annoying? Necessary? Here’s the deal.

Every six years, Ada County roads get a new chipseal coat.

Ada County Highway District, which maintains the roads, has divided the county into six areas. Chipseal crews rotate from one area to another each year.

This year has been the time to resurface the roads east of Orchard Street, north of Eisenman Road, south of Chinden and ParkCenter boulevards, and west of Surprise Way and Grand Forest Drive.

Before starting the chipseal work, ACHD sends out experts to assess the condition of each public road in the area in question, said Clint Heckenlively, ground crew chief for the district. If the road needs a new coat, it gets one. If not, it’s left alone.

In general, all arterial and collector streets get a new coat during their chipseal rotation, district spokeswoman Nicole Du Bois said. So do about half of the residential roads. New asphalt surfaces are good candidates, because the chipseal coat protects them and extends their lives. Other factors district experts look at include extensive asphalt patching, chip loss from the previous chipseal coat, cracking and other disintegration of the road.

Chipseal is highly unpopular with motorists and cyclists, at least while the work is going on. It’s gravelly. There are traffic delays. People complain about damage to their cars.

Every year, ACHD officials brace for the dozens of chipseal-related damage claims sure to land on their desks. The most common claim is for chipped or cracked windshields. By late July, the district had received 25 such claims, DuBois said.

Robert Boester, who lives in Southeast Boise, said he likes to ride his bike on the roads around his home, but new chipseal throws that off. While the work is underway, Boester said, he can’t tell where the bike lanes are.

Even after it’s done, he said, the new surface makes for a less pleasant ride.

“It’s rougher than a corn cob,” he said. “You take your bike out because you want to get some good exercise, and now you really have to work for it.”

Like many people, Boester complained that ACHD often resurfaces roads that are in good shape. The district maintains that it chipseals only where needed.


What is it?

It’s a hardy coating used to cover asphalt or other road surfaces that need maintenance.

Why chipseal?

It’s cheap and durable. Asphalt is smooth, but it wears more quickly. It also costs almost 10 times as much as chipseal. Within a couple of years of laying an asphalt road, Ada County Highway District tries to put a chipseal coat on top of it to preserve its integrity. A chipseal coat lasts anywhere between six and 12 years, depending on traffic, weather and other factors.

How long will this last?

The highway district started this year’s chipsealing process June 11 and expects to complete it by the end of August.

How much does it cost?

About 22 cents per square foot, compared to about two dollars per square foot for an asphalt overlay.

What about my cracked windshield?

This is a common problem. People driving over a fresh chipseal often kick up chips into their own bumpers, brakes and other car’s windshields. People sometimes complain about this happening even when they’re driving at the suggested 20 mph speed limit. If you have a complaint about damage, send an email to or call 208-387-6100. The district will forward your complaint to a third party to investigate it.

People also complain when the dips from manhole covers get deeper because the chipseal layers raise the height of the surrounding road. Ada County Highway District tries to minimize manhole dips, spokeswoman Nicole DuBois said. But the district likes to avoid adjusting the height of a manhole, which can cost up to $2,500.

Broken windshield?

If you have a complaint about damage caused by the district’s chipsealing work, send an email to or call (208) 387-6100. The district will forward your complaint to a claims expert, and a third party will investigate it.


Step 1: Preparation. This process starts in the early spring when highway district crews sweep roads and seal their cracks. Trees that will get in the way of chipsealing equipment are trimmed.

Step 2: LMCRS-2H. That’s the industry name for an oil product infused with polymers to make it extra sticky. A truck shoots the oil on each lane as the chipsealing process gets going for real.

Step 3: Put the “chip” in chipseal. A truck loaded with one-quarter or three-eighths-inch rock particles follows immediately behind the oil truck, spreading an even layer on the oil.

Step 4: Roll it in. Rubber-tire trucks, each one with nine tires in staggered alignments, drive over the rocks to set them in the layer of oil. The polymers in the oil help bind the rock to the oil. Clint Heckenlively, a ground crew chief for the district, said experts are always looking for ways to improve this process, including experimenting with steel drum rollers to push the chips into the oil. Excess rock is often left behind. Cars can push the loose rock into rows, especially at street corners, to the irritation of other motorists and especially bicyclists.

Step 5: Fogging. After allowing five to 10 days for the chip-oil bonds to set up, a truck removes the excess rocks from the roadway. After that a truck applies a thin layer of oil — similar in composition to the bottom layer — on top of the chip layer. This step, known as “fogsealing,” helps seal everything in place.

Step 6: Stripes. A few days after the fogseal is applied, crews paint lane stripes on the new, very black road.