Watershed Wanderings: Permeable pavement @ EPA

Yesterday, I had the fortunate opportunity to attend a presentation at the Edison EPA office and to tour their stormwater best management practices (BMPs). I was especially intrigued by their permeable pavement parking lot. They are testing the three types of permeable pavement out there: pervious concrete, porous asphalt, and porous pavers.

Now, why are these important, and what makes them a best management practice? Traditional pavement--asphalt and concrete, what makes up roads, sidewalks, parking lots, etc--is impermeable, meaning that water is not able to pass through. Natural spaces, like forests, have pervious grounds surfaces, which means that water does pass through the soil, replenishing the groundwater supply. As development occurs, heavy machinery runs over our native soil (which may have been pervious in the past), which compacts the soil, making it impervious.

Modern stormwater practices carry water away from these impervious areas (storm drains, detention basins, etc) and do not allow water to enter the soil below, which also acts as a filter for pollutants, like sediment and motor oil. In short, permeable pavement allows water to pass through and eliminates some stormwater (and pollutants) from reaching our streams. Some flooding is caused by excess stormwater from development, which historically had been held on site and infiltrated into the ground.

So at EPA, they have a demonstration parking lot, where they are testing out these permeable pavement options. This is an active office parking lot, and they have hundreds of instruments under the parking lot to be able to measure the effectiveness of the pavement options.

The three options