I-5 north and south of Seattle has many lane miles of old concrete pavement that have been approaching the end of their effective service lives. In 2011 the Washington State Department of Transportation (WSDOT) designed its first crack & seat and asphalt overlay on the I-5 corridor. Antigo completed 120,000 square yards of crack & seat of I-5 northbound lanes north of Burlington (Skagit County) in 13 workdays over 6 weeks in June and July. The success of this project, and two others on rural areas of I-90, positioned WSDOT to consider the use of crack & seat on I-5 in the Seattle metro area.
In 2016, 68,000 square yards of I-5 southbound lanes in the area between Tukwila and Federal Way (King County) were cracked & seated and covered with an initial leveling lift of asphalt during two 55-hour partial freeway closures (10 p.m. Friday to 5 a.m. Monday). Additional lifts of asphalt were placed during subsequent closures.
In 2017, 120,000 square yards of I-5 northbound lanes in the same area were cracked & seated and covered with an initial leveling lift of asphalt during four weekend closures.
Not only did the construction process proceed smoothly for these three projects, but the new asphalt pavement had excellent initial smoothness and is providing continuing smoothness. WSDOT provided the following Mean Roughness Index (MRI) data. MRI is the average of International Roughness Index (IRI) from both wheel paths.
|Location||Pre-Construction MRI||Post-Construction MRI||Most Recent MRI|
|Skagit||95 in/mile||50 in/mile||51 in/mile (2019)|
|King SB||182 in/mile||43 in/mile||43 in/mile (2019)|
|King NB||178 in/mile||48 in/mile||51 in/mile (2019)|
In 2020 the WSDOT Skagit County project was the inaugural winner of the Perpetual Pavement by Conversion Award presented by the Asphalt Pavement Alliance. The award recognizes new asphalt roads constructed over an existing road that meet Perpetual Pavement criteria.
These projects highlight the effectiveness of crack & seat and asphalt overlay as a reconstruction process that gets in and gets out quickly while minimizing traffic disruption, that is very cost effective, and provides a long lasting and smooth pavement.
I-5 NB, n/o Burlington (MP 231.79 to 243.39), Skagit County
I-5 SB, Tukwila (MP 142.76 to 156.71), King County
I-5 NB, Tukwila (MP 147.64 to 156.51), King County
Cracked & seated 308,000 square yards
9" thick jointed plain concrete pavement (JPCP)
8.4" thick asphalt overlay
Skagit County: June & July, 2011
King County SB: July, 2016
King County NB: June, 2017
Washington State Department of Transportation, Contracts 8016, 8816 & 8992
Skagit County: Granite Construction Co., Bellingham, WA
King County SB: MidMountain Contractors, Inc., Kirkland, WA
King County NB: Gary Merlino Construction Co, Inc., Seattle, WA