Low Impact Development Manual for Michigan - OSEH - University ...

Native vegetation should be used in contained planter
boxes (Appendix C). They are hardy and self-sustaining
with little need for fertilizers or pesticides. Irrigation
needs to be monitored, since plants will need to
be watered during dry periods. Sensors can help to
regulate moisture in the planter box, ensuring consistent
moisture. Smaller trees are highly encouraged
because of the canopy and shade they will provide,
reducing the urban heat island effect. Planters should
be constructed of stone, concrete, brick, wood, or any
other suitable material.
This type of planter box can be installed to retrofit an
existing urban streetscape or large area of pavement,
such as at an entryway to a building.
Infiltration
An infiltration planter box (Figure 7.43) is designed
to allow runoff to filter through the planter soils (thus
capturing pollutants) and then infiltrate into native
soils below the planter. These planters are generally
constructed to be flush with surrounding paved areas.
The planter is sized to accept runoff and temporarily
store the water in a reservoir on top of the soil. Different
design variations are encouraged, but should allow
a minimum delay in stormwater runoff capture of three
to four hours after a wet weather event.
Recommended vegetation includes native rushes, reeds,
sedges, irises, dogwoods, and currants. Also, the dimensions
of the sand/gravel area used in these designs should
be determined by an engineer and designed to receive
less than approximately 15,000 square feet of impervious
area runoff. The minimum planter width is typically
30 inches with no minimum length or required shape.
Suggested structural elements of infiltration planter boxes
are stone, concrete, brick, or pressure-treated wood. In
general, infiltration facilities should be greater than 10
feet from structures and at least five feet from an adjoining
property line or as required by local ordinances.
Figure 7.43
Schematic of Infiltration Planter Box
Protect the subgrade
from heavy
machinery and
over-compaction
Rainwater enters the
planter box and soaks
into the soil
Soil/Compost
Mix
Infiltration bed (optional) containing
clean, uniformly graded stone
Stormwater infiltrates and
recharges the groundwater
Schematic of Infiltration Planter Box
Example of Infiltration Planter Box
Rainwater flows off
the rooftop and into
the downspout...
...and across the
pavement...
LID Manual for Michigan – Chapter 7 Page 260