City of Newcastle
Pavement Maintenance Program – 2022 Slurry Seal

Update:  October 18 City Council Meeting
Below are updates regarding the slurry seal project that were announced during the City Manager Update portion of the October 18 City Council meeting.

1)  City staff are continuing to hold the contractor responsible for addressing punch list items including, removing large aggregates, spot patching, and resealing the pock marks along 125th Pl SE near Donegal Park (this last item will occur in 2023 because the weather window has past). Staff met with the president of Doolittle Construction last Wednesday to discuss the poor-quality workmanship. The contractor expressed their commitment to working with the City to address our concerns.

2) City staff still believe the use of slurry seal on local streets is an appropriate and prudent maintenance technique. Unless directed otherwise by the City Council, staff intend to continue to use this method in the future taking lessons learned with this initial project.

3) It is acknowledged that there are many locations of poor workmanship with this project, and City staff will continue to work with the contractor to address those concerns. The work performance is not, however, to the level of a failed project. The City, at this point, again, unless otherwise directed by the City Council, does not intend to repave the slurry sealed streets.
concerns.

What is a Slurry Seal?

Slurry sealing is a thin seal coat made up of aggregates, asphalt emulsion, and mineral filler that fills in small cracks and surface imperfections to give the roadway a uniform color and texture. It's one of many effective tools in the City’s preventative maintenance program and is typically applied to residential streets that are in fair-to-good condition. Slurry seal application can extend a street’s good conditions for five to ten years by protecting the underlying surface from the effects of wear and weather. Many cities locally and nationally use this cost-effective strategy to renew the road surface and to seal minor cracks and other irregularities. This preventive maintenance process protects the pavement from moisture penetration and oxidation.

Like painting a house, slurry seal creates a protective layer that preserves the underlying structure and prevents the need for more expensive repairs in the future. This short YouTube video from the City of Los Angeles explains how slurry seal treatment helps protect and preserve local streets today and for the future.

Why Did the City Perform a Slurry Seal?
The slurry seal work was selected because it's a proven and cost-effective technique to maintain existing pavement. The cost to perform the 2022 slurry seal work was $8.08 per square yard. For comparison, the average cost of the 2021 pavement overlay work was $41.40 per square yard, over five times more expensive. Lower cost isn't the only reason that a slurry seal was chosen: The slurry seal will defer the need for a costly pavement overlay, thereby lengthening the lifespan of City streets while reducing the cost to maintain them, and use of slurry seal will improve the citywide pavement condition at a lower overall cost. The use of slurry seal on local roads was a recommendation included in the 2019 and 2021 Pavement Management System Update Reports (link).

Why Was My Street Chosen for Slurry Seal?
Streets included in the 2022 slurry seal project were determined based on the current pavement conditions, pavement age, and locations with recent crack-sealing work.

Remaining Work to be Performed
The City’s contractor, Doolittle Construction, is continuing work on punch list-items, and the City is withholding a portion of the contractor’s payment until all punch-list work is complete. Remaining items to be addressed include:

- Complete removal of all large aggregates (the larger pieces of rock in the seal)

- Address voids in the pavement surface (the small holes in the seal) resulting from large aggregate removal on 125th Pl. SE

- Remove remaining stockpiled aggregates at the SE 95th Way site

Resident Feedback

Complaints received by the City from residents are largely summarized into the three categories described below.

Dissatisfaction of the Road Surface – Slurry seal is quite a bit different than an asphalt overly. Slurry seal is a pavement-maintenance technique, whereas an asphalt overlay is considered rehabilitation work. With a slurry seal, the new surface is rougher and sheds some of the aggregate, creating gravel deposits on top of the new slurry seal. The contractor’s crews sweep the streets, typically one week after application and then again three weeks after application. As time progresses, traffic smooths the surface by dislodging the larger aggregate and pushing smaller aggregate into the underlying pavement. Sweepings and rain also help. Below are photos from the City of Kirkland that show how the roadway surface smooths out over time:

Much of the feedback about the appearance and roughness of the slurry seal are the result of an unfamiliarity with this type of maintenance work. The contractor distributed a notification flyer in advance of the work. The flyer included a “What Can I expect From the Slurry Seal” (link) that described the difference between the slurry seal work and asphalt overlay. Going forward, city staff will consider additional outreach efforts to educate and prepare residents for planned roadway resurfacing work.

The latest sweeping work performed on Friday, September 30, has removed much of the remaining loose gravel from the roadway.

Larger Aggregates in the Street  – The Contractor’s aggregate stockpile contained a small number of larger aggregate contaminates. Examples of these larger aggregates are included in the photos below. This work is out of specification, meaning it's outside of our acceptable range, and is being addressed. Removal of all the larger aggregate contaminates is included on the contractor’s punch list, and the contractor is in the process of performing this work. The largest aggregate contamination, along 125th Pl. SE adjacent to Donegal Park, have been removed. Smaller (yet also out of specification) rocks are also present in other locations of the project. The City is withholding a portion of the contractor’s payment until this work is complete. A specific timeline for this work is not available, however, it is expected to be completed within a matter of weeks.

"Not an Appropriate Technique for Urban Roads" - Slurry seal is commonly used by surrounding cities on local urban streets. Recently completed slurry seal projects are listed below.

- Redmond (2022)

- Seattle (2022)

- Kirkland (2021)

- Bothell (2021)

- Kenmore (2020)

- Shoreline (2020)

- Burien (2018)

- Mukilteo (2018)

In contrast, chip seal is a maintenance technique commonly used on rural roads. Chip seal is different from slurry seal in that the aggregate size in chip seal is larger, resulting in a considerable rougher surface. A photo from a recently completed chip seal project in Kittitas County is shown below.

     

What to Expect Next
As the contractor continues to work through their punch list, the condition of the slurry seal will smooth out. The road will also continue to smooth over time. Thank you for your patience as this process comes to completion.