Page 39 - 7166 - Rain Garden Handbook

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OPTION 1—EXCAVATE AND REPLACE SOIL

Option 1 should be used when you have poor quality soils. In
1-PLAN you examined the texture of the soil in your rain garden
area. Soils high in clay content do not drain well or support good
plant growth. If your soil forms a cohesive ball and can be shaped
like modeling clay, it has high clay content. In this case, you
should replace the soil with a new, imported rain garden soil mix.

Typically, 12 to 24 inches of rain garden soil mix is recommended.
If you have poor quality soils, consider using the 24-inch depth
for better plant growth and storing more water.

Excavation Depth Example:
6" Overflow Containment (Assuming No Berm is Constructed)
+ 6" or 12" Ponding Depth
+ 12" to 24" Rain Garden Soil Mix (Imported)

= 24" to 42" Excavation Depth

Rain Garden
Soil Mix

Kim Gridley A good rain garden soil mix typically

contains about 60% screened sand and
40% compost by volume. Contact your
local landscape and compost suppliers
for rain garden soil mixes. You can also
use an approved bioretention soil mix for
David Hymel your rain garden.