Breathing Pavement: Surface offers flood protection

Kali Katerberg/Daily Mining Gazette Shown here is traditional pavement on Scott Street in Hancock, one of the many steep roads in the area but one that escaped flash flood destruction in June.

HOUGHTON — When precipitation falls to the ground, some materials like sand allow it to seep in quickly, but for traditional pavement that’s not the case.

Enter permeable pavement. With traditional asphalt or cement paving, the materials are not porous, which often results in pooling on the pavement or runoff.

In the case of the June flooding, large volumes of rain led to washed-out roads, as large volumes of water carved new pathways for themselves.

Permeable pavement, or porous asphalt, is one method of reducing runoff, mimicking how soil absorbs rainfall by allowing the water to pass through to the soils below. The process is initially higher cost, but by reducing stormwater infrastructure, it saves money in the long run.

According to the Federal Highway Administration (FHWA), permeable pavement can reduce runoff volume, help with contaminants by filtering soil and recharge groundwater.

The method has been used around the country.

Snow research in Minnesota has shown the surface melts materials faster, causing a decrease in salt usage, but winter road maintenance on porous road materials can clog the pores, so the pavement requires occasional cleaning.

So could it be used in the Copper Country?

The short answer is yes, but the method comes with many considerations and would require research, said Michigan Tech Civil and Environmental Engineering assistant professor Zhen Liu.

In the case of flooding, using porous pavement has the potential to help.

“We can have a lot of water moving on the top surface of the pavement, and it needs to go somewhere. Maybe if we use porous pavement, the water would get into the soil below the pavement,” Liu said.

However, in cases like the June 17 flood, Liu suspects the storm would have still been too strong. Water could accumulate under the pavement, and if that built up, eventually things would wash away.

“For a relatively small precipitation event‚ porous material can possibly handle that. If we have a very bad storm I’m not sure,” he said.

Permeable pavement has some limitations other than how much water it can handle, namely the level of traffic.

Though fairly common, porous pavement is typically restricted to parking lots, driveways and small volume roads. Handling heavy traffic like trucks can pose a challenge.

“(When) we introduce more pores into the pavement that will impact the mechanical property of the pavement, it will make it weaker,” Liu explained.

Porous pavement also requires a relatively flat site to work optimally, which might not work on the area’s steeper hills.