Page 44 - 7166 - Rain Garden Handbook

Build
38 2

Constructing the Overflow
Containment Area

The overflow containment area can be provided by following one of these two approaches:

• Either create a berm that rises a minimum of 6 inches, at a maximum 2:1 slope, from
the outside of the top surface of the ponding area (photo on bottom left).
• OR start digging down from the ground surface. Remember to start 12 inches
out from the perimeter of the top surface of the ponding area on a 2:1 slope to
Michael Carey accommodate the 6-inch overflow containment area (photo on bottom right).

• Start digging on the uphill side, measuring
down from the string to the desired depth.
• Use the soil excavated from the uphill side
to fill the downhill area, creating a flat, level
bottom and a berm on the downhill side.
• Lightly tamp down the soil on the level
bottom by walking over the fill after every few
inches is added, avoiding over compaction.

• Create a more heavily compacted berm at
the downhill side to confine water in the rain
garden. For the correct height, build the berm
up to the string. To keep the top level, the
berm will be highest at the downhill end and
then become shorter until tapering off at the
uphill end(s). The berm should have sloping
sides at 2:1 maximum and be well compacted. David Hymel David Hymel
See pages 37 and 39 for more information.