Pavement Preservation

Annual Arterial Overlay Program

Asphalt pavement deteriorates over time. Tiny cracks appear on the surface. Light rutting appears in the wheel paths and cracks grow larger. The roadway doesn’t drive as well. Rainwater doesn’t shed as freely. Water seeps into cracks and erodes the gravel supporting the asphalt. Potholes appear, and driving is rough. At this stage, only extensive and expensive repaving can repair the roadway. The annual budget varies depending on grants awarded. The estimated annual budget for this program is $900,000 in City funds which may be supplemented with additional grant funds.

Where does the money come from?

The City pays for its Annual Arterial Overlay Program with money from the Capital Fund.

What is included in this work?

The Annual Arterial Overlay Program monitors pavement condition, pursues grant funding, and designs and manages the construction projects.

Bothell conducts field surveys every year. Typically, half of the city is evaluated each year. We measure the size and type of cracking, the surface condition (weathering and raveling), ruts, and patching. Based on the survey data, the roadways are assigned a Pavement Condition Index (PCI).

PCI Ratings

85 - 100 Excellent 61%
70 - 85 Very Good
55 - 70 Good 29%
40 - 55 Fair 10%
25 - 40 Poor
10 - 25 Very Poor
0 - 10 Failed 0%

Each street’s PCI rating is entered into asset management software that predicts the roadway’s future condition, based on historical PCI data, pavement preservation techniques, and spending levels. Based on the PCI, roadway classification, budget, and other factors, staff determines which streets will be paved each year.

Preventive treatments are substantially less expensive than repaving, so more roads can be treated each year for the same cost. Preventive treatments, applied at the right time, extend pavement life by preventing rainwater from seeping into and undermining the pavement.

Pavement preservation techniques: Added pavement life expectancy by roadway condition

Treatment Comparative Cost Very Good Good Poor
Slurry Seal Low 7 - 10 years 3 - 5 years 1 - 3 years
Chip Seal Low 7 - 10 years 3 - 5 years 1 - 3 years
Microsurfacing Moderate 8 - 12 years 5 - 7 years 2 - 4 years
Overlay High 10 - 12 years 5 - 7 years 2 - 40 years
Reconstruction Highest 15 - 20 years 15 - 20 years 15 - 20 years

Cost of Deferred Maintenance

Pavement Condition Index