I f the pavement on the new entrance to the Lake Wilderness trail across from the library looks a bit bumpy, that’s no accident.
It is the city’s first use of “pervious concrete,” a type of pavement that allows rainwater to pass straight through. The access walkway was completed last spring during the upgrades and roundabout construction on Witte Road near the Maple Valley Library.
“If you look at the concrete, it looks like rice cakes,” says David Casey, city engineer for Maple Valley. “You can go out there with a cup of water and dump it on that, and it will disappear into the ground.”
The idea is to use nature’s filtration system — soil and ground cover — to keep stormwater runoff out of Lake Wilderness and other waterways even as development continues.
“When you start taking that (natural) surface area away you have to mitigate it somehow,” says City Manager David Johnston. “It was kind of a hard lesson to learn over 100 years because people would just build, build and build without thinking about the implications.”
Pervious concrete has been around for a few years, but the city had shied away from it because it was expensive to maintain, Casey says. Recent improvements in materials have changed that.
The Fred Meyer parking lot will be the first commercial use in Maple Valley of pervious asphalt, which works the same way, allowing water to sink straight into the ground, Casey says.