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

Playgrounds/basketball/tennis
Porous asphalt street in Portland, OR
Streets and alleys
Permeable paver street in Dowagiac, MI
Source: Pokagon Band of Potawatomi Indians
Rooftop/impervious area connections
Pervious pavement systems are often used to provide
total site stormwater management where rooftops and
other impervious surfaces are tied into the infiltration
bed below the pavement surface. This can be an effective
means to manage stormwater for a development site,
while reducing land disturbance for stormwater BMPs.
If pervious pavement systems receive runoff from adjacent
areas, proper sediment pretreatment for that runoff
must be considered to prevent clogging of the storage
bed. Typical pretreatment can be achieved by the use of
properly maintained cleanouts, inlet sediment traps, and
water quality inserts or filter devices.
It is recommended that direct surface sheet flow conveyance
of large impervious areas to the pervious pavement
surface be avoided. High sheet flow loading to pervious
pavement surfaces can lead to premature clogging of
the pavement surface. To avoid this, it is recommended
that adjacent impervious areas be drained and conveyed
to the infiltration bed via inlets and trench drains with
proper sediment pretreatment.
Design Considerations
While evaluating the following design considerations,
there are also several additional resources to consider
when implementing pervious pavement. These include
the Site Design Process for LID (Chapter 5), Soil
Infiltration Testing Protocol (Appendix E), the Recommendations
for Materials are specific to porous asphalt
and porous concrete (Appendix D), and additional steps
set forth in the introduction to this chapter.
Siting
1. The overall site should be evaluated for potential
pervious pavement/infiltration areas early in the
design process because effective pervious pavement
design requires consideration of grading.
2. A four foot clearance above the seasonally high
water table and bedrock is recommended. A two
foot clearance can be used but may reduce the
performance of the infiltration BMP used.
3. Orientation of the parking bays along the existing
contours will significantly reduce the need for cut
and fill.
LID Manual for Michigan – Chapter 7 Page 247