Boulders on a highway? For US 89A repairs, ADOT called Boulder Busters

Boulders on a highway? For US 89A repairs, ADOT called Boulder Busters

August 4, 2016

Mudslide Aerial View

By Tom Herrmann / ADOT Communications

If there’s something strange sitting in your road
Who you gonna call? (Boulder Busters)
15 feet tall
In the northbound lane
Who you gonna call? (Boulder Busters)

I ain’t afraid of no rocks



On Aug. 9, 2015, a monsoon storm dropped more than 1.5 inches of rain in just 15 minutes onto House Rock Valley in northern Arizona. The mudslides that covered sections of US 89A across 24 miles weren’t unexpected. What surprised Arizona Department of Transportation crews were the boulders, as large as 15 feet in diameter, that came to rest on the highway between Marble Canyon and Jacob Lake. That's bigger than the equipment that ADOT had available could move.


Boulder buster

Who you gonna call?

To break up the boulders and reopen US 89A in just 20 hours, albeit with just one usable lane in areas, ADOT used Boulder Busters. These are explosive cartridges that look like 12-gauge shotgun shells but have a thicker rim that would prevent them from being used in a shotgun. Crews drill a hole in a boulder, fill it with fluid, insert one to three shells and trigger an explosion.

Rock-bustin’ makes me feel good…

The Federal Highway Administration says the Boulder Busters cartridge has several advantages over traditional explosives. Blasts send minimal rock flying, avoiding costly road closures and job delays. Large equipment doesn't have to be moved away from the blast. The operator triggers the explosion by pulling on a lanyard from about 30 yards away.


Moving the mudslide rubble.

With the help of Boulder Busters, ADOT reopened US 89A quickly, safely and without having to battle the Stay Puft Marshmallow Man.

Tons of stone blocking your path
Who you gonna call? (Boulder Busters)
Can’t make your way
To Jacob Lake
Who you gonna call? (Boulder Busters)

I ain’t afraid of no rocks.


ADOT North Central District

We hope you saw our announcement that ADOT and contractor The S.J. Anderson Co. of Mesa have received the 2015 Harry H. Mellon Award of Excellence Winner in Job Order Contracting for the US 89A House Rock Flash Flood Project. That's the work that made permanent repairs to US 89A in just 53 days following ADOT's emergency response to reopen the highway.

Here's a photo from the ceremony showing representatives of ADOT and its North Central District, the contractor, the Federal Highway Administration and the Gordian Group, which presented the award.

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