SDOT’s preventative maintenance programs extend the life of streets which are in good condition and postpone the day when we need to rebuild them.
This year SDOT conducted a pilot project using microsurfacing, a preservation treatment that is seeing growing use by transportation agencies.
Microsurfacing is a thin layer of emulsified asphalt mixed with crushed stone for traction.
It renews the surface and seals fine cracks. This prevents oxidation and keeps out water – two forces which damage pavement.
It’s a lot like painting a house. The paint is a protective layer which keeps out moisture and prevents the wood siding from rotting and needing to be replaced.
Microsurfacing is an alternative to chip sealing. Both are seal coats, but chip sealing includes a layer of rock chips which must be swept up several weeks after the project. Compared to chip sealing, microsurfacing looks more like a conventional asphalt surface.
SDOT traditionally chip sealed about one fourth of Seattle’s residential streets over multiple years.
In 2013, SDOT chip sealed streets in Greenwood / Crown Hill and microsurfaced streets in Wedgwood. Based on the results, SDOT plans to microsurface additional streets in Arbor Heights and Fauntleroy in 2014.
Microsurfacing and chip sealing are good investments. They last about 5 to 10 years and keep the streets from needing to be rebuilt, which costs at least ten times as much as preventative maintenance.