Slurry seal program

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What is a slurry seal?

Slurry seal is a mixture of asphalt emulsion, mineral aggregates, water and additives. It is a cost-effective preventative maintenance treatment that extends the life of the road surface while causing the least amount of inconvenience to travelers and residents. Slurry seal treatments fill cracks and voids, seal the surface to prevent water from penetrating roadway surfaces and improve skid resistance.

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Why is the treatment important?

Preventive road maintenance saves tax dollars. Over the long term, it is less expensive to maintain the road surface than to reconstruct it when it fails.

The average life of an asphalt road surface is 20 to 30 years. However they start to show signs of distress and deterioration much earlier. The sun's rays beating down on the pavement during hot summer months bakes the road surface and causes drying and cracking. Rain can seep into the road base and cause premature failures such as potholes. When the road surface has been properly maintained by sealing the surface every seven to 10 years, then the more expensive overlay repaving is necessary only every 20 to 30 years.

Who pays for the work?

Property owners in the voter-approved Urban Road Maintenance District (inside the Urban Growth Boundary, outside of cities) pay $0.25 per $1,000 assessed value on their property taxes for maintenance of local streets.

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Who does the work?

A private, professional paving contractor is selected to do the road work based on a competitive bidding process. The contractor is required to comply with Oregon specifications and with Washington County contract requirements. A Washington County inspector is on-site, ensuring work is performed in compliance with the contract.

What can residents expect?

In the weeks before the slurry seal treatment, some minor patching, street cleaning, crack sealing and other work may be done to prepare the street for surface treatment.

Before slurry seal work is scheduled to begin, residents will receive two postcards in the mail. The first postcard briefly explains the treatment and requests adjacent property owner's trim vegetation encroaching the roadway. The second postcard explains what residents can expect on the day of the treatment.

At least 24 hours before the slurry seal is scheduled to begin the contractor will deliver a notice to affected property owner's front doors. No parking signs will be posted on the streets to be treated. Residents will be asked to park vehicles off affected streets by 7 a.m. on the day work is scheduled to occur. Vehicles will be towed to an adjacent street if necessary.

The contractor will notify garbage haulers and other service providers of their planned schedule.

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What do residents need to know?

Slurry seal is applied as a liquid and requires several hours to solidify before the surface is ready for traffic. The slurry material, in liquid form, is messy, sticky and very hard to clean up.

  • Do not park, drive, walk or bike on the roadway while the slurry is curing.
  • Keep children and pets off the road.
  • Keep water off the street the night before scheduled work.

The first few days after the treatment is applied it may look like the surface color is changing and turning darker. This is all part of the normal process. Vehicles driving over the slurry seal help roll and smooth the surface. While this is happening, some rocks may loosen from the mixture and minor, cosmetic defects may appear.

A few weeks after the treatment is applied crews will perform an inspection, sweep up loose gravel, make necessary surface repairs and replace any pavement markings.

Learn more

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