CASE STUDIES

TRACKING THE QUALITY AND LONGEVITY OF PROJECTS

Cost-Effectiveness of Double Chip Seal

Double chip seal is the most cost effective way to deal with asphalt pavements that have deteriorated too far to be saved by a single chip seal. It will hold up better than micro-surfacing or a thin overlay because it bonds to the old pavement better, it seals better, and is more flexible. To substantiate this, we continue to monitor the condition of past projects.

Before DBST

June, 2000 - "Before." Looking south from Frey Rd.

After DBST
19 years later

Doolittle Chip Seal - Bainbridge Island 2019, 19 years after DBST

October, 2019 - 19 years after double chip seal. A few cracks have started, but it is in much better condition than it was.

19-Year Study – Bainbridge Island, WA

Arrowpoint Drive NE at intersection of Frey Road NE

In 2000, a double chip seal was applied to this road. 1/2"-1/4" crushed screenings were used on the first lift and 3/8”-#10 on the second lift. Prior to applying the two lifts, the road showed signs of extreme alligator cracking in this area. The road needs to be scheduled for another chip seal; it is in fair condition with some cracks starting. The City of Bainbridge Island has done over 55 miles of double chip seal in the last 21 years; and many more miles of single chip seal, using chip seal patches beforehand where needed. The double chip seal has worked very well, staying flexible, and bridging over cracks and alligatored areas.

13-Year Study – Auburn, WA

Kersey Road SE in Auburn (SE 53rd to south city limits)

In 2006 this major arterial, between Auburn and Lake Tapps / Bonney Lake area, received chip seal patches in the wheel ruts, before applying a double chip seal using CRS-2P. The chip seal patches and first lift were installed using 1/2"-1/4" aggregate. The second lift used 3/8”-#10 aggregate, then fog sealed using CSS-1H, (mixed 60:40 with water).

Chip Seal Patching before Double Chip Seal

Using multiple layers to add body and strength

The ideal time to chip seal is before a road starts to deteriorate. The cost will be less and the road will be in better condition in the end. However, if the road has deteriorated too far for a single chip seal, multiple layers of chip seal can be used to repair poor road conditions. Multiple layers will bridge over alligator type cracking, add body and strength to the road surface, and seal the road preventing any further deterioration.

Before Chip Seal Patching and DBST

Doolitle Chip Seal - Auburn 2006, work begins

Work in progress

Doolitle Chip Seal - Auburn 2006, work underway

After Chip Seal Patching and DBST
13 years later

Doolitle Chip Seal - Auburn 2019, after Chip Seal Patching and DBST

March, 2019 - 13 years after wheel rut patching and double chip seal. The road surface looks good, considering the traffic and age. It needs a new chip seal, as a few hairline cracks have started.

14-Year Study – Port Angeles, WA

3rd Street (off US 101)

In front of a busy Safeway store and gas station we placed a double chip seal in 2005. The pavement had “block” cracking throughout the entire area. Liquid asphalt CRS-2P was applied, with 1/2"-1/4" aggregate on the bottom lift, 3/8”-#10 for the top lift, then a CSS-1h (diluted) fog seal was applied.

As of April 2019, 14 Years Later (2nd photo), the pavement has developed a few cracks, but is still much improved. Recommend another chip seal at this time, but the previous “block” cracking is not reflecting through.

Before DBST

After DBST
14 years later

Doolittle Chip Seal - Port Angeles 2019, 14 years after DBST

Before DBST

Doolittle Chip Seal - Auburn, 15th Street SW - 2006, before Chip Seal

After DBST
13 years later

Doolittle Chip Seal - Auburn, 15th Street SW - 2019, after Chip Seal

13-Year Study – Auburn, WA

15th Street SW, westbound lanes near C Street

This busy Auburn arterial (above) should have had the pavement ground off and replaced with hot mix asphalt. The funds were not available for that, so we applied a double chip seal in 2006. It has had no maintenance since then, it is a little bumpy with a few cracks, but the double chip seal is holding it together in much better condition than it was.

8-Year Study – Mukilteo, WA

5th Street, arterial going east off SR 525

2011 Double Chip Seal, 1/2”-#4 chips on the bottom layer, then 3/8”-#10 chips, with a fog seal.

Before DBST

Doolittle Chip Seal - Mukilteo, 5th Street - 2011, before Chip Seal

After DBST
8 years later

Doolittle Chip Seal - Mukilteo, 5th Street - 2019, after Chip Seal

8 years later, November 2019, no sign of any cracks.

Before DBST

Doolittle Chip Seal - Mukilteo, 47th Ave. W - 2013, before Chip Seal

After DBST
6 years later

Doolittle Chip Seal - Mukilteo, 47th Ave. W - 2019, after Chip Seal

November 2019 – 6 years later. Looks good, minor flushing because of all the truck traffic.

6-Year Study – Mukilteo, WA

47th Ave. W, just north of Chennault Beach Road

2013 Double Chip Seal, 1/2”-#4 chips on the bottom layer, then 3/8”-#10 chips, with a fog seal.

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