Pavers, Gravel, and Concrete? Oh, My!

Some of you may have noticed the construction in the library parking lot over the winter. As the spring approaches and brings with it the Farmers’ Market on Wednesday mornings, I wanted to share some neighborhood news. 

There are signs posted in the soil by the corner with Parkers’ Lane that ask we not walk in the seeded area. You might ask: “What seeded area?” Some seven years ago, the county’s Stormwater Management Division designed a system to treat and capture the stormwater runoff from the library’s site. According to Christopher J. Mueller of the division, while there are many methods of doing so (see http://www.fairfaxcounty.gov/dpwes/stormwater/whatis_swm.htm) the project at Sherwood Library uses three. 

First, let’s talk about the tree box filters you’ll find on this corner. These are concrete boxes filled with filter material such as stone or sand and a tree, something like a sidewalk inlet with a tree growing inside. Stormwater, with its various kinds of debris carried along, is filtered by the tree and the material within the box. The water gets cleaned and absorbed in an environmentally friendly fashion, and the tree gets needed nutrients.

The signs on the corner will signal the second method of filtration. Called a bioretention garden, it’s made up of permeable material in an open depression with a selection of trees, shrubs, grasses, and flowers. It functions like the box described above, but in a different size and with a different look. At the moment, the area doesn’t look finished because the plants aren’t yet installed. They will be in a few weeks.

As you walk around the Farmers’ Market, you may not notice the third feature of the corner. You might see the permeable pavers that consist of filter materials underneath porous stone blocks. The smaller gravel between the pavers allows water to filter between the pavers to the underground filter system. On the surface, the pavers are strong enough to use as a parking lot surface.

Whitman Middle School also participates in this project. Those who walk between the school and the library may have noticed what appears to be a ditch between the buildings. Technically, it’s called a swale, and it also slows down stormwater to prevent silt and nutrients from being carried to the Chesapeake Bay.

And speaking of gardening and growing plants, please stop by the library for forms to send samples of soil, bugs, and plants for identification by Virginia Tech and Fairfax County specialists, as well as books of tips for making your gardens grow!