Emily Simnitt
The Idaho Statesman
The Ada County Highway District won’t be paving the 8th Street Extension in Boise — it will be coating it in brown stuff.

It’s called Soil-Sement, and it basically works like a glue that binds all the dust particles together to form a hard surface, Terry Little, ACHD traffic services manager, told the Boise City Council on Tuesday.

That means if you drive your car or ride your bike up 8th Street after it’s treated with the stuff, you won’t be kicking up a bunch of dust or doing much damage to the road.

And, if it looks anything like its picture, you won’t feel like you’re in a concrete jungle.

You can expect to see the stuff on the first 1.1 miles of the road by the end of September.

If it doesn’t pass muster with the new multi-agency 8th Street Task Force, ACHD says it will scrape the stuff off and start over.

Soil-Sement has been used extensively in Arizona and California on similar roads, but it still needs to prove it can withstand an Idaho winter.

The plan replaces an earlier proposal to put pavement on about 3 miles of the extension. That plan drew a firestorm of criticism from the city, Foothills users and others, who said paving the road would lead to more cars going faster up the stretch.

So far, the new plan has had a better reception.

It’s a good compromise, ACHD officials say, because it does what ACHD set out to do — reduce safety hazards, maintenance costs, air pollution and erosion — and it creates a middle ground between paving and keeping the road as loose dirt.

In fact, it was a concerned citizen who tipped ACHD off to Soil-Sement in the first place after the district sent out more than 100 letters and more than 150 e-mails asking for suggestions from the people who spoke up about surfacing 8th Street at earlier hearings.

“It’s not pavement, but it’s not status quo,” ACHD spokesman Craig Quintana said.

It’s also relatively cheap. The first coat will cost about $13,000, and subsequent coats, which will be needed about once a year, will cost about $4,000.

That’s oodles less than the almost $30,000 a year ACHD says it costs to maintain the dirt road as it has in the past.

The city embraces the plan.

“This shows that reasonable people can come to reasonable solutions once you get the dialogue going,”

Councilwoman Paula Forney said. “We could have saved our community some trauma if we had come to this earlier.”

The dialogue will continue. The task force — which includes representatives from ACHD, the city, the Bureau of Land Management, the U.S. Forest Service and other agencies — will meet in early September and also will talk about ways to fix the road’s drainage problem. So, what is this brown stuff?

It’s called Soil-Sement, and it’s supposed to be a lot more like dirt than cement. Technically, it’s comprised of polymer emulsion glues that bind loose particles together into a harder surface that inhibits erosion and dust creation.
In a small sample ACHD brought to City Hall on Tuesday, it basically looks like hard dirt.

Wisconsin State Parks have used it to fight erosion on mountain bike trails. It’s been approved by the U.S. Environmental Protection Agency and the California Air Resources Board, but it hasn’t yet been tested by a Boise winter or by the Foothills enthusiasts who will use it the most. That’s what will happen this fall and next spring.