Good Question: Does A Rock Coating Really Help Streets?

MINNEAPOLIS (WCCO) — It’s is the time of year many of us are arriving home to see a sign reading, “LOOSE GRAVEL.” The summertime dump of rock on our residential and busy streets is an irritation to many, but what’s going on with all those rocks?

“There’s actually a lot of good happening here,” said Mike Kennedy, Director of Public Works for the city of Minneapolis.

The process is called chip seal-coating. It’s chips of aggregate that are forming a new surface for the road.

“It’s one of those things you hate while it’s happening, but it does a lot of good for your streets,” said Kennedy. “This is pothole prevention work.”

City crews put down a layer of hot liquid asphalt first.

“This seals up the pavement and keeps water out. Water is the enemy. Water is what freezes up and causes the potholes,” said Kennedy.

That’s followed by another truck, dumping an even layer of rock onto the hot asphalt. The asphalt seals the road, and acts as a glue for the rocks.

“It’s specially engineered to be the perfect shape and size. It’s a crush granite we use,” said Kennedy.

Those rocks become the new surface for the road.

“It’s a new surface, a very thin surface,” he said.

Then three heavy machines with rollers try to pack down the aggregate, before cars do the real work. By driving on the rock for several days, the rock gets crushed into a new surface. After a week, a street sweeper comes back and cleans up the extra.

“It can be done several times. Typically, you’ll build a street, and than maybe one, two, or three times you can put a seal-coat on it. Then you’ll need to do something more aggressive,” said Kennedy, like grinding off the top layer and put down a new pavement.

“On an arterial, or a downtown, heavy-trafficked street, a good 7 to 10 years it extends that life cycle. On a residential street, it might give more than that,” he said.

So, if you do it several times, it can extend a road with a 20-year life into a road with a 50-year life.

The cost is the main benefit. According to Kennedy, it costs about $60,000 to do a mile of seal-coated pavement.

“To reconstruct the street would be like 60 times as much,” he said. “It’s really very cheap.”

Cities and suburbs throughout Minnesota do the same process, because it’s a cost-effective form of maintenance for the roads.

More from Jason DeRusha
  • Bigbill

    Why is Jason putting such a negative spin on this. I thought saving tax payers money is a good thing.

  • kim

    How is he putting a negative spin on it? He had the people explain why it is done. The single comment about how motorists find the loose gravel signs irritating is very mild.

    • idiocracy

      Right. Jason tends to present the questions the way they are asked. Rocking a road is irritating and can seem pointless, so of course people will ask this Good Question with a negative tone.

  • Not a good repair procedure

    This method of road maintenance/repair is ridiculous and causes more problems than it solves. That doesn’t even count the damage the rocks do to your vehicle’s paint job and all the rocks and tar your kids end up dragging into your house.

    You DO NOT get another 30 years of life out of a road by doing this.

    It is simply a “repair on the cheap.”

    • Get it straght

      Not a good repair procedure

      You really should do some research. While the article uses averages they are relatively correct when looking at engineering standards in Minnesota. If you have been a life-long resident of Minnesota and can remember back into the 80’s when cities having budgetary problems delayed or eliminated sealcoating programs they were not only milling and overlaying but doing complete reconstructs years earlier than necessary. It works like putting a clear coat on paint . . . helps protect it from Minensota’s weather. Sealcoating is most often funded as part of a city’s operating budget . . . overlays and reconstructs are paid for by the property owners abutting the project area. A cheap overlay will cost a residential unit upwards of $1,500 or more right now. IF you still feel it is a waste make sure you DON’T complain when you receive that notice in the mail that your street needs be replaced and you will be paying for it.

  • Ted

    Another benefit of the loose gravel on the roads is it keeps bicyclists away

    • Tony

      Have another cheeseburger Ted. Your 7 o’clock shows are coming on.

      • Mel

        Wow, arrogant much, Tony? Ted made a light comment about bicyclists not being in the way as much (use the dang sidewalks!) and you jump to the conclusion that he is fat and watches too much TV? You MUST suffer from cacomorphobia. See? We can all jump to irrational conclusions…

        • Nice Ride

          Ted and Mel. Did you know that bicyclists are entitled to a lane on the road? If not, go back and relearn to share the roads. If any of you two every bicycled before, the sidewalks are not as flat and pleasant as the roads. Start bicycling around town and you’ll know what I mean.

          • Ted

            Of course I know that. Thats why its nice when there is loose gravel on the roads – vehicles travel over it just fine, bicycles not so much so they leave the road to the cars.

            Very simple

  • I hate the loose rock

    I hate when they do this our neighborhood roads. The neighborhood kids have had some fantastically nasty wipeouts on their bikes and the scars to prove it. It wrecks the whole summer for rip sticking as well. The biggest culprit I see in the neighborhood is plow damage digging into the roads leaving long gouges.

  • idiocracy

    One bad thing about this method of upkeep is that cities can make extra money in their budgets disappear quickly. I’ve seen streets done and redone in a couple years when there are worse streets that go neglected for years.

    • Concrete guy

      Cheaper way to buy time and hate to inform you but it’s pretty damn effective. This coming from a concrete guy …. maybe I need to not post it.
      Pour concrete pour concrete pour concrete …. get me back to work!
      It may cost 20x more but concrete is good and purty

  • Chase

    “a good 7 to 10 years it extends that life cycle. On a residential street, it might give more than that,”

    Yeah right, they do this cheap seal coating in my mild trafficked neighborhood every three years because it starts to fall apart.

    I’m sure part of longevity is the process but the fact is, no one can afford to have this process done multiple times. The average project will have a single coating.

    Not only that, as an automotive detailer I hate seal coating with a passion. Dust, rock chips, paint marring; just a few problems I have with seal coating.

  • Rocks!

    Leave the rocks alone.

  • Seal Coating Really Help Streets with pothole prevention? | Firemanscontractors

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