How was the rain garden constructed?


(Conservation Currents, Northern Virginia Soil and Water Conservation District)

Elements of a Rain Garden

 

hole for rain garden
In this engineered rain garden, the hole was dug 4 feet deep with a 600 square foot surface area.
gravel and soil layers
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.
mulch and plant layer
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.
man inspecting vertical pipe
A vertical pipe allows visual access to the underdrain, and, if necessary, an entry point for cleaning out debris in the drain.

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