Kirstin Davis

Managing Street Health with Micro-surfacing

Kirstin Davis, Communications Manager – Public Works, 509.625.7773

Tuesday, August 23, 2022 at 3:40 p.m.

Managing Street Health with Micro-surfacing

Successfully maintaining conditions of City of Spokane streets calls for the right treatment at the right time. Maintaining 2,200 lane miles of streets is more complicated and costly than one thinks, especially when those streets are located 47.8 degrees north of the equator where freezing and thawing cycles are an annual event. The maintenance treatment of the street depends on various conditions.

Micro-surfacing is used as a preventive maintenance tool to repair slight to moderate pavement surface defects by filling small cracks, fix light rutting or treat raveling asphalt surfaces. The materials used in the process are emulsified asphalt, water, well-graded, fine aggregate and mineral filler. The average cost with installation is six to nine dollars per square yard. For comparison, a grind and overlay rehabilitation project average cost is 30 dollars per square yard installed.

In 2019, three micro-surfacing projects covered four miles of arterial streets and brought mixed performance results. Cracks were filled well, leading in less water freezing and thawing and causing significant potholes that lead to more damage. At the same time, surfaces didn't hold up as expected. Both freezing temperatures and extreme heat can cause a breakdown in micro-surfaced streets. Micro-surfacing is the most cost-effective solution in the right environment.

Based on what the street department learned from 2019 projects, adjustments were made, and 2022 projects include 7.2 residential street miles and 5.5 lane miles of arterials. You can watch Streets Department Director Clint Harris provide an update to City Council at the Aug. 22 Public Infrastructure and Environmental Sustainability committee meeting (54:00-1:06:00).

City streets are rated on a scale from 0 to 100 using a "pavement condition index" (PCI). New streets begin at a PCI of 100 and gradually deteriorate over time. Oftentimes "fair" streets can become "good" streets again with routine maintenance. Eventually maintenance becomes ineffective, and reconstruction is necessary. The City conducts inspections on a rotating basis, every two years for arterials and every four years for residential streets. 

To learn more about Street Maintenance, visit our website.

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