(Conservation Currents,
Northern Virginia Soil and Water Conservation District, October
2004)
|
|
|
| In this engineered
rain garden, the hole was dug 4 feet deep with a 600 square
foot surface area. |
Across the bottom of the ponding area,
on top of a 6 inch base of gravel (VDOT #57), lay a perforated
drain pipe (not visible). Over the horizontal pipe is
6 more inches of gravel (VDOT #57), and then a 6 inch
layer of pea gravel. On top of the gravel layers is a
manufactured soil (Biofilter ®) with 25 percent organic
material.
|
|
|
|
| The soil is
covered with mulch. The mulch is held down by netting to
reduce the likelihood of it floating away after a storm.
The last element are the plants, all native to the area
and tolerant of moist soil. The plant roots and mulch are
responsible for pollutant removal. |
A vertical pipe
allows visual access to the underdrain, and, if necessary,
an entry point for cleaning out debris in the drain. |
|
